Compound reconfigurable symmetric slotted MIMO antenna with ABS enclosure for indoor wireless applications
Thangarasu D., Thipparaju R.R., Palaniswamy S.K.
Article, AEU - International Journal of Electronics and Communications, 2024, DOI Link
View abstract ⏷
This research work reports the Compound Reconfigurable MIMO Antenna (CRMA) utilizing RF PIN diodes for indoor wireless communication applications. The proposed CRMA comprises a quad-symmetric slotted radiator with a common ground structure. It can perform frequency, polarization and pattern switching at frequency standards such as IEEE 802.11a/b/g/n (2.4/5.5 GHz), IEEE 802.11ax (6 GHz) and 5G/n78 (3.5 GHz). A parasitic element of a modified U-shaped stub is utilized to achieve polarization reconfiguration. Further, to achieve pattern reconfiguration two crossed-shaped slots are implemented. The proposed antenna achieves a bandwidth of 320 MHz at 2.4 GHz, 950 MHz at 3.5 GHz and 1870 MHz at 5.5 GHz. At these resonant frequencies, the antenna is capable of producing both circular and linear polarization with a pattern tilt towards different angular directions such as 30°, 120°, 210°, 300°, 330°, 240°, 150°, 60°. The designed CRMA follows orthogonal orientation and exhibits better diversity performance with ECC < 0.1, DG > 9 dB, TARC < −13 dB and CCL < 0.27 bps/Hz. Also, an Acrylonitrile Butadiene Styrene (ABS) enclosure is designed and fabricated to validate the performance of the antenna with casing, further to analyze the suitability of the antenna for indoor wireless applications.
Graphene based waveguide fed hybrid plasmonic terahertz patch antenna
Mahankali P., Mondal S., Thipparaju R.R., Mohandoss S.
Article, Frequenz, 2024, DOI Link
View abstract ⏷
The terahertz (THz) technology has fascinated lot of attention due to its enormous potential for a wide range of applications in the public, private and enterprise domains. This research work demonstrates the design structure and analysis of graphene based waveguide fed hybrid plasmonic THz patch antenna (HPTPA) constructed at around 3 THz. Hybrid plasmonic THz waveguide (HPTW) as a feeding line for the proposed THz patch antenna can increases antenna efficiency. The graphene is sandwiched between gallium arsenide (GaAs) and silver (Ag) to confine THz waves efficiently. Using mode analysis in finite element method for the proposed HPTW the propagation length, effective refractive index has been thoroughly examined. Based on the finite element method (FEM) approach, the results of the designed graphene-based waveguide fed HPTPA shows a high effective refractive index of 2.9, large propagation length of 230 µm, gain of 2.29 dBi, bandwidth of 200 GHz and efficiency of 85 % has obtained. The proposed graphene-based waveguide fed HPTPA could be beneficial to enable several photonic integrated circuit applications in next-generation wireless communication.
Multifunctional twelve port frequency agile diversity antenna for indoor wireless applications
Thangarasu D., Palaniswamy S.K., Thipparaju R.R., Alzaidi M.S., Kumar S., Elkamchouchi D.H.
Article, Scientific Reports, 2023, DOI Link
View abstract ⏷
The recent resurgence of new-generation reconfigurable technologies delivers a plethora of various applications in all public, private and enterprise solutions over the globe. In this paper, a frequency reconfigurable polarization and pattern diverse Multiple-Input-Multiple-Output (MIMO) antenna is presented for indoor scenarios. The MIMO antenna is comprised of twelve radiating elements, and polarization and pattern diversity is obtained by arranging them in three different planes: Horizontal Plane (HP), Vertical Plane-I (VP-I), and Vertical Plane-II (VP-II). The proposed antenna operates in mode I (wideband) and mode II (multiband), by combining two different radiators using PIN diodes. The antenna dynamically switches between Mode I (wideband) and mode II (multiband). Mode, I cover the ultra-wideband (UWB) range from 2.3 to 12 GHz, while mode II covers GSM (1.85–1.9 GHz), Wi-Fi and LTE-7 (2.419–2.96 GHz), 5G (3.15–3.28 GHz and 3.45–3.57 GHz), public safety WLAN (4.817–4.94 GHz), and WLAN (5.11–5.4 GHz) frequency bands. The peak gain and efficiency of the MIMO antenna are 5.2 dBi and 80%, respectively.
Graphene based quad port terahertz MIMO antenna for wireless indoor communications
Article, Optical and Quantum Electronics, 2023, DOI Link
View abstract ⏷
This research paper presents, an octagonal shaped graphene based terahertz patch antenna is designed for indoor communications. For a unit cell, a single graphene layer with a thickness of 10 nm has been layered over a quartz (SiO4) substrate with a thickness of 100 µm to increase the effectiveness of the multiple-input and multiple-output (MIMO) antenna. The MIMO antenna is chosen to operate at a frequency of 0.3 THz. For a quad-port MIMO configuration, the element cells have been arranged orthogonally. The total cross-sectional area of the terahertz (THz) MIMO antenna is 1325 × 1325 µm2. The suggested MIMO antenna device achieves a bandwidth of 113 GHz over a frequency range of 0.257–0.370 THz. Moreover, the mutual coupling coefficient is less than − 15 dB. The designed THz MIMO antenna’s diversity performance is analyzed and the obtained diversity matrices are the diversity gain (DG) (< 9.96 dB), envelope correlation coefficient (ECC) (< 0.01), channel capacity loss (CCL) (< 0.35 bps/Hz), and total active reflection coefficient (TARC) (< − 10 dB), respectively.
Optimization of strip-based hybrid plasmonic terahertz waveguide with distributed Bragg reflector layers
Pallavi M., Thipparaju R.R., Mondal S., Mohandoss S.
Article, Optical Engineering, 2023, DOI Link
View abstract ⏷
In view of recent developments in the utilization of terahertz (THz) communications technology for the increasing demands of high speed and data rates for various wireless applications, this research work targets the design and analysis of distributed Bragg reflector (DBR)-based hybrid plasmonic THz waveguide. This THz waveguide operates at a frequency range from 2.5 to 3.5 THz. The proposed DBR-based hybrid plasmonic THz waveguide consists of DBR layers of gallium arsenide (GaAs) and aluminum arsenide, high-density polyethylene (HDPE) as substrate, a GaAs stripe for wave-guidance, and few layers of graphene layers in HDPE for better confinement. To increase the light confinement between DBR and graphene, a GaAs strip is placed into HDPE. By altering the width and height of the GaAs strip, the parameters birefringence, mode field diameter (MFD), confinement loss, effective mode area, beat length, and dispersion have been fully examined. The obtained simulation results shows high birefringence of 0.6276, maximum MFD of 45 mm, low confinement loss of 7.5 × 10 - 9 mm - 1, high effective mode area of 16.5 mm2, and low anomalous dispersion of 0.0023 (ps/THz/cm) in the range of 2.5 to 3.5 THz. This optimized THz waveguide may helps to enable in guided THz applications for photonic integrated circuits.
Quad Element Reconfigurable Radiation Pattern MIMO Antenna for Indoor Wireless Communication
Article, Progress in Electromagnetics Research Letters, 2023, DOI Link
View abstract ⏷
A quad-element reconfigurable radiation pattern Multiple Input Multiple Output (MIMO) antenna is designed for WLAN and 5G applications suitable for indoor wireless communications. It consists of four radiating elements that operate over triband frequencies 2.4, 3.5, and 5.5 GHz. Moreover, the pattern diversity is obtained by introducing two diagonally crossed slots in the radiator to steer the main beams of the antenna in 8 different angular directions using eight PIN diodes. The overall physical dimension of the proposed antenna is about 0.55 × 0.55λ0. In addition, an Acrylonitrile Butadiene Styrene (ABS) enclosure is designed, and the performance of the proposed antenna is evaluated. The measurement results show that the proposed antenna has an impedance bandwidth of 4.18%, 14.13%, and 28.5% at the said frequencies, respectively.
Quad Port Multipolarized Reconfigurable MIMO Antenna for Sub 6 GHz Applications
Thangarasu D., Palaniswamy S.K., Thipparaju R.R.
Article, International Journal of Antennas and Propagation, 2023, DOI Link
View abstract ⏷
Recent reconfigurable technological advancements for wireless communication systems provide various global solutions. This research work presents a quad port multipolarized switchable multiple input multiple output (MIMO) antenna for sub 6 GHz applications. It covers the frequency range from 3.1 to 5.1 GHz, including the 5G NR band n78 (3.3 to 3.8 GHz) and 5G NR band n79 (4.4 to 5 GHz). The proposed antenna comprises four offset-fed monopole antenna elements with an overall dimension of 60 mm × 65 mm. To achieve circular polarization (CP), a parasitic meandering resonator is integrated with antenna elements using four PIN diodes. The polarization diversity is obtained by controlling the bias states of four PIN diodes. The radiating element -1/-3 offers left hand circular polarization (LHCP), while element -2/-4 procures right hand circular polarization (RHCP) when all diodes are ON. Consequently, the proposed antenna provides linear polarization (LP) under reverse bias conditions. Moreover, the designed antenna acquires a wide axial ratio bandwidth (ARBW) of 36.1%. In addition, the developed MIMO antenna exhibits isolation greater than 15 dB using the common ground plane, and the obtained ECC is less than 0.13. The prototype is fabricated, and the simulated responses are in good correlation with the measured results.
Quad Port Pattern Reconfigurable Antenna for Indoor Applications
Thangarasu D., Rao T.R., Palaniswamy S.K.
Conference paper, WiSPNET 2023 - International Conference on Wireless Communications, Signal Processing and Networking, 2023, DOI Link
View abstract ⏷
A quad port pattern reconfigurable Multiple Input Multiple Output (MIMO) antenna is presented for Indoor wireless communication. The reconfigurability is achieved by integrating eight PIN diodes. The designed antenna operates over 5 to 7 GHz frequency, which supports the WLAN (5.15-5.35) GHz and Wi-Fi 6E (5.925-7.125) GHz frequency bands. Moreover, the developed antenna achieves the gain and efficiency of about 5.9 dBi and 85 % respectively. The designed antenna also achieves an ECC of less than 0.02 and a diversity gain of around 9.9 dB. The antenna is modelled using Finite Difference Time Domain (FDTD) technique.
Terahertz Imaging for Aerospace Applications
Karthikeya Sharma M., Rao A., Kumar K., Rao T.R.
Conference paper, WiSPNET 2023 - International Conference on Wireless Communications, Signal Processing and Networking, 2023, DOI Link
View abstract ⏷
Terahertz (THz) Imaging has gained significant importance in the past few decades owing to the unique properties of THz radiation. In this paper, we use image processing algorithms on THz images to automate the process of manually analyzing the image for the detection of faults in aircraft composites as we intend to simplify the non-destructive evaluation of samples under inspection. THz images of a propagating crack in a concrete block taken at different frequencies are analyzed to measure the intensity of deformation. Further, THz image samples of aircraft panels are used to investigate common faults such as air cavities (voids), debonding, delamination, mechanical damage, and burn effects. The proposed algorithm's prediction on the intensity of deformation is compared with the actual values to demonstrate the potential of image processing in non-destructive evaluation. We also discuss a few methods to manipulate the THz image for the accurate detection of faults.
Well-to-wheel performance of internal combustion engine vehicles and electric vehicles–study for future Indian market
Saini H., Rama Rao T., Saini S., Anbazhagan G., Sharma V.
Article, Energy Sources, Part A: Recovery, Utilization and Environmental Effects, 2023, DOI Link
View abstract ⏷
Thanks to top-notch vehicle testing and internationally standardized inspections, the modes of transportation are cleaner and more efficient today. Though the development for conventional internal combustion engine vehicles (ICEVs) has almost saturated today, yet it retains the commercial/heavy-duty (trucks and buses) automobile market. Thus, it becomes of utmost importance to analyze the well-to-wheel efficiency for determining the overall energy consumption and greenhouse gas (GHG) emissions while transitioning toward sustainable transportation. Electric vehicles (EVs) do have environmental impacts that are directly related to the country’s electricity generation, as they may involve fossil burning where other alternative sources of energy are not adequately present. This paper presents the overall energy efficiencies and GHG emissions from commercial/heavy-duty ICEVs and EVs. The study also briefly compares the other vehicle segments like 2 Wheeler, 3 Wheeler, and cars. Finally, the results show that commercial/heavy-duty ICEVs are advantageous over heavy-duty EVs when the GHG emissions are considered as of today. The commercial/heavy-duty ICEVs emit over 405 g CO2e/km, and counter EVs produce 706 g CO2e/km. The GHG emissions from 2 Wheeler ICEV were 46 g CO2e/km and by the same segment, EV is 13 g CO2e/km. Moving toward the car segment, an ICEV car produces around 158 g CO2e/km and an EV of a similar model emits 67 g CO2e/km. Furthermore, the 3 Wheeler ICEV emits around 99 g CO2e/km and a 3 Wheeler EV produces lesser at 24 g CO2e/km. Moving further on well-to-wheel energy efficiency, ICEVs have a maximum overall energy efficiency of 28%. Since EVs use various sources of energy for charging the battery, the overall efficiency was found to be at least 21% and maximum up to 39%. Thus, on an average EVs presently have a well-to-wheel efficiency of 32% when electricity generation mix is used for charging.
Compact dual-band MIMO cubical antenna for automotive applications
Kannappan L., Palaniswamy S.K., Kanagasabai M., Sachin Kumar, Alsath M.G.N., Rao T.R.
Article, International Journal of Electronics, 2023, DOI Link
View abstract ⏷
There is a strong demand for compact and multiband antennas as wireless technologies become more integrated into automobiles. These antennas must be able to serve multiple services without compromising the size and installation space. In addition, the antenna incorporated should not affect the aesthetic appearance of the vehicle. This paper presents a compact multiple-input-multiple-output (MIMO) antenna working at 2.45 GHz (Wi-Fi/Bluetooth/RFID) and ultra-wideband (UWB) frequencies. A basic rectangular monopole with a self-complementary structure is used to design the antenna element. The size of the antenna element is 20 × 22 mm2. The proposed MIMO cube is developed with four antenna elements in cubical orientation to achieve compactness and better isolation. The overall dimension of the MIMO antenna is 35 × 22 mm2. The diversity antenna shows impedance bandwidth of 2.4–11.5 GHz and isolation of more than 20 dB. The envelope correlation coefficient (ECC) of the MIMO antenna is less than 0.2, diversity gain (DG) is greater than 9 dB, and total active reflection coefficient (TARC) and channel capacity loss (CCL) are less than −10 dB and 0.4 bits/s/Hz, respectively. The gain and efficiency are found to be greater than 1 dBi and 72%, respectively.
Interdigitated photoconductive terahertz antenna for future wireless communications
Rathinasamy V., Thipparaju R.R., Edwin N.F.B., Mondal S.
Article, Microwave and Optical Technology Letters, 2022, DOI Link
View abstract ⏷
Recently, the technology buzz on utilization of terahertz (THz) technology in beyond 5G and 6G communication is growing due to the demands for large network capacity, bandwidth, and ultrahigh data rates. The THz frequencies are prudent for short-range future wireless communication systems as they provide extraordinary channel capacity with data rates from few Gb/s to Tb/s due to its ultra-wide spectrum bandwidth. However, there exists many challenges in designing devices that operate under THz frequencies. The photo-conductive antenna (PCA) is one of the crucial components that support realization of ultrafast wireless THz communications. In this paper, investigations on photoconductive antennas with interdigitated electrodes (IDEs) have been presented for THz communications with an equivalent circuit model for IPCA with corresponding solved expressions. The results show that the maximum THz field strength of 4.41 × 105 V/m is achievable by a 10 μm interdigitated teeth length IPCA with larger spectrum bandwidth of about ~8 THz. The antenna module makes the possibility of miniaturization of the THz sources and detectors for the emerging variety of wireless THz applications.
6G and beyond: Investigation of broadband terahertz interdigitated photoconductive antenna by exploiting laser parameters
Boby E.N.F., Prajapati J., Rathinasamy V., Rao T.R., Mondal S.
Article, Microwave and Optical Technology Letters, 2022, DOI Link
View abstract ⏷
Photoconductive Antennas (PCA) are widely used for terahertz (THz) generation and detection. These PCAs build the basis for future 6G communication as they provide a high data rate and broad bandwidth. In this work, interdigitated photoconductive antenna (IPCA) has been designed and optimized for better performance in terms of THz radiation. The proposed IPCA is made of LT-GaAs substrate material deposited on SI-GaAs. Silver material has been assumed for the IPCA electrode structure. Moreover, the dependence of IPCA on the incident laser parameters such as its wavelength (λ = 800, 1060, and 1550 nm) and pulse duration (100–500 fs) has been investigated theoretically for different teeth widths (We = 500, 100, 50, and 20 nm). The performance of the IPCA with various parameters such as average carrier density, conductance, total photocurrent, THz radiated power, and electric field strength, has been analyzed. The results show maximum THz electric field strength of 20.85 V/m for a photo-generated current of 1.887 A and enormous bandwidth beyond 14.9 THz with 20 nm teeth-width-based IPCA when illuminated with 100 fs 800 nm laser pulses. The proposed IPCA structure provides enhanced THz radiation compared to conventional PCA. This investigation helps the researchers to develop and integrate IPCA for future wireless communications as well as for a variety of applications, such as time-domain spectroscopy (THz-TDS), medical imaging, sensing, and security-related applications.
3-D twelve-port multi-service diversity antenna for automotive communications
Kannappan L., Palaniswamy S.K., Kanagasabai M., Kumar P., Alsath M.G.N., Kumar S., Rao T.R., Marey M., Aggarwal A., Pakkathillam J.K.
Article, Scientific Reports, 2022, DOI Link
View abstract ⏷
This paper presents a twelve-port ultra-wideband multiple-input-multiple-output (MIMO)/diversity antenna integrated with GSM and Bluetooth bands. The twelve-port antenna is constructed by arranging four elements in the horizontal plane and eight elements in the vertical plane. The antenna element, which is created using a simple rectangular monopole, exhibits a frequency range of 3.1 to 12 GHz. The additional Bluetooth and GSM bands are achieved by introducing stubs into the ground plane. The size of the MIMO antenna is 100 × 100 mm2. The antenna offers polarization diversity, with vertical and horizontal polarization in each plane. The diversity antenna has a bandwidth of 1.7–1.9 GHz, 2.35–2.55 GHz, and 3–12 GHz, the radiation efficiency of 90%, and peak gain of 2.19 dBi. The proposed antenna offers an envelope correlation coefficient of < 0.12, apparent diversity gain of > 9.9 dB, effective diversity gain of > 8.9 dB, mean effective gain of < 1 dB, and channel capacity loss of < 0.35 bits/s/Hz. Also, the MIMO antenna is tested for housing effects in order to determine its suitability for automotive applications.
Quad-port electromagnetic band gap (EBG)—backed non-isomorphic multiple-input-multiple-output (MIMO) antenna for wearable applications
Govindan T., Palaniswamy S.K., Kanagasabai M., Velan S., Kumar S., Rao T.R.
Article, Flexible and Printed Electronics, 2022, DOI Link
View abstract ⏷
This paper presents the design of a quad-port orthogonal ultra-wideband (UWB) monopole antenna backed with an electromagnetic band gap (EBG) structure. The EBG structure provides band stop/band reject characteristics in the entire UWB range. The overall dimension of the diversity antenna is 70 × 70 × 1 m m 3 ( 0.68 λ 0 × 0.68 λ 0 × 0.01 λ 0 ), where λ 0 corresponds to the lowest resonating frequency. The proposed monopole antenna offers good impedance bandwidth of 8.67 GHz (2.93-11.6 GHz). The estimated diversity characterization metrics observed over the obtained frequency range are envelope correlation coefficient < 0.11, mean effective gain (MEG) < 1 dB, effective diversity gain < 9.88 dB, apparent diversity gain < 9.99 dB, channel capacity loss < 0.19 bits (s Hz)−1, and total active reflection coefficient < −20.95 dB. Also, specific absorption rate analysis is realized for the antenna in seven different tissues of the body (forehead, forearm, upper arm, chest, abdomen, thigh and lower leg) to check radiation exposure towards the human body.
Numerical investigation and circuit analysis of interdigitated photoconductive antenna for terahertz applications
Rathinasamy V., Thipparaju R.R., Boby E.N.F., Mondal S.
Article, Optical and Quantum Electronics, 2022, DOI Link
View abstract ⏷
Terahertz generation through photoconductive antenna (PCA) is quite popular mainly due to the advancement of nanotechnology and material research. An extensive investigation of the interdigitated photoconductive antenna (IPCA) in the terahertz (THz) frequency band has been carried out based on numerical modeling. An equivalent circuit model for IPCA based on its electrical perspective with corresponding expressions has been solved to understand the capacitive behavior of the gap between the interdigitated electrodes. This work explores the performance of IPCA with variation in structural parameters of their interdigitated electrode geometry in the active region. The interdigitated elemental periodicity, width and length of the IPCA are varied by keeping the interdigitated gap constant between the elements. The temporal behavior of generated electric field and its corresponding spectral response of the IPCAs with variation in the interdigitated electrode geometry has been compared. Moreover, the coupling behavior of the elements has been observed in the generated radiation. Finally, the results prove that the THz amplitude, frequency and efficiency can be enhanced by optimizing the structural parameters of the interdigitated electrode elements in the active region. This analysis is very useful while doing the practical experiments in spectroscopy, imaging and communication applications.
Design and Analysis of Graphene based Octagonal Short-angular Circular Patch MIMO Antenna for Terahertz Communications
Pandey G.K., Rao T.R., Mondal S.
Conference paper, 2022 2nd International Conference on Intelligent Technologies, CONIT 2022, 2022, DOI Link
View abstract ⏷
In this research, a Graphene based octagonal short-angular circular patch (OSACP) 2x2 multi-input-multi-output (MIMO) antenna is designed for Terahertz (THz) short-range communications. Graphene, as a 2D material, has gained momentum for the realisation of the plasmonic THz antennas due to its unique electromagnetic properties, can fetch the property of surface plasmon polariton (SPP) at THz regime. The graphene layers of thickness 0.01 um have been placed on a Silicon Nitride (Si3N4) substrate of thickness 15 um to increase the efficiency of MIMO antenna. The radiation characteristics of the proposed antenna model are compared to those of a Si3N4 substrate structure based microstrip patch antennas using FDTD technique with a cross-sectional area of 1232 × 1232 um2. It exhibits the return loss (S11) better than -10 dB over the frequency range of 0.259 - 0.324 THz.
An Integrated Frequency Tunable MIMO Antenna for IOT Applications
Thangarasu D., Palaniswamy S.K., Rao T.R., Kanagasabai M., Kumar S.
Conference paper, 2022 International Conference on Wireless Communications, Signal Processing and Networking, WiSPNET 2022, 2022, DOI Link
View abstract ⏷
This paper presents a dual-polarized reconfigurable MIMO antenna for IoT applications using pin diodes. The proposed antenna covers a wideband from 3.3 GHz to 6 GHz (5G band) and also switches between two resonating frequencies 2.4 GHz - Zigbee and 5.8 GHz - WLAN. However, the developed antenna achieves the gain and efficiency of about 4 dBi and 80 % respectively. The designed antenna also achieves ECC less than 0.08 and a diversity gain of around 9 dB. The antenna is modeled in Computer Simulation Tool (CST).
CPW-Fed Quad-Band Dual Port Meandered Monopole Automotive Antenna
Kannappan L., Palaniswamy S.K., Kanagasabai M., Kumar S., Rao T.R., Govindan T.
Conference paper, 2022 International Conference on Communication, Computing and Internet of Things, IC3IoT 2022 - Proceedings, 2022, DOI Link
View abstract ⏷
A dual-port MIMO antenna is presented in this paper. It operates at multiple frequencies like 0.9, 2.45, 3.3 and 5.5 GHz. The overall dimension of the presented MIMO is 38×16 mm2 and it is developed on FR-4 substrate. The orthogonal placement of antenna offers dual polarization and good isolation of greater than 15 dB is achieved without any decoupling structures. The antenna is fabricated and required measurements are conducted. The peak gain is found to be 4.34 dBi and maximum efficiency is 97%. The diversity parameter study shows that ECC<0.1, DG>9.88, TARC<-10 dB and CCL<0.1 bits/s/Hz. The antenna is studied for antenna housing effect to know the stability of the antenna in the vehicular environment.
Sub-6 GHz Eight-Port 3-D Vehicular Antenna
Kannappan L., Palaniswamy S.K., Kanagasabai M., Kumar S., Rao R.T., Govindan T.
Conference paper, 2022 International Conference on Wireless Communications, Signal Processing and Networking, WiSPNET 2022, 2022, DOI Link
View abstract ⏷
This paper presents an 8-port 3-D MIMO diversity antenna designed for sub-6 GHz band. It shows -10dB impedance bandwidth over the frequency of 3.2-6 GHz. The size of the unit cell is 30 × 30× 0.76×3 and it is developed on Rogers 5880 substrate. The unit element is augmented into 8 port MIMO antenna. The MIMO antenna's footprint is 66× 66 mm 2. The elements are placed right-angled to each other for better isolation. It also helps in achieving polarization diversity with six polarization vectors. The isolation is found to be greater than 20 dB. The peak efficiency and gain are respectively 98 % and 3.3 dBi. The MIMO characteristic study results in TARC value less than -10 dB, CCL value less than 0.15 bits/s/Hz, ECC < 0.003, and DG > 9.85. The stability of the antenna in automotive environment is checked using housing effects.
On the Design and Performance Analysis of Flexible Planar Monopole Ultra-Wideband Antennas for Wearable Wireless Applications
Thangarasu D., Thipparaju R.R., Palaniswamy S.K., Kanagasabai M., Alsath M.G.N., Potti D., Kumar S.
Article, International Journal of Antennas and Propagation, 2022, DOI Link
View abstract ⏷
With the promising developments in wearable communication technology, attention towards flexible electronics is increasing day-by-day. This study presents flexible low-profile ultra-wideband (UWB) antennas for wearable applications. The antenna comprised of a modified dewdrop-inspired radiator and a defected ground plane and has an impedance bandwidth of 3.1-10.6 GHz. The antenna flexibility is investigated using four different substrates (polyester, polyamide, denim, and Teslin) and tested on a cotton shirt and a high-end Res-Q jacket to evaluate their performance stability for body-worn applications. The fabricated planar dewdrop-shaped radiator (PDSR) antennas have a radiation efficiency of >90%, a gain of >4 dBi, and a group delay variation of fewer than 0.5 ns. The antenna conformability is measured by placing the fabricated antennas on various curved and nonplanar parts of the human body. The aforementioned antennas offer better flexibility for different bent conditions. The specific absorption rate (SAR) of the designed antennas is investigated to determine their wearability, and values are found to be less than 0.2 W/Kg. Also, the received signal strength (RSS) is discussed in order to analyze signal attenuation, and the performance analysis of the antennas is compared.
Quad-port multiservice diversity antenna for automotive applications
Kannappan L., Palaniswamy S.K., Wang L., Kanagasabai M., Kumar S., Alsath M.G.N., Rao T.R.
Article, Sensors, 2021, DOI Link
View abstract ⏷
A quad-element multiple-input-multiple-output (MIMO) antenna with ultra-wideband (UWB) performance is presented in this paper. The MIMO antenna consists of four orthogonally arranged microstrip line-fed hexagonal monopole radiators and a modified ground plane. In addition, E-shaped and G-shaped stubs are added to the radiator to achieve additional resonances at 1.5 GHz and 2.45 GHz. The reliability of the antenna in the automotive environment is investigated, with housing effects taken into account. The housing effects show that the antenna performs consistently even in the presence of a large metal object. The proposed MIMO antenna has potential for various automotive applications, including vehicle-to-vehicle (V2V), vehicle-to-infrastructure (V2I), vehicle-to-everything (V2X), intelligent transport system (ITS), automatic vehicle identifier, and RFID-based electronic toll collection.
On the design and performance analysis of wristband MIMO/diversity antenna for smart wearable communication applications
Govindan T., Palaniswamy S.K., Kanagasabai M., Rao T.R., Alsath M.G.N., Kumar S., Velan S., Marey M., Aggarwal A.
Article, Scientific Reports, 2021, DOI Link
View abstract ⏷
The design of a silicone rubber-based wristband wearable antenna exploiting pattern diversity is presented in this paper. The wristband diversity antenna consists of four identical antenna elements with an inter-element spacing of 0.68λ0, where λ0 is the lower cut-off wavelength. A modified trapezoidal-shaped radiator with a rectangular ground structure is used to achieve ultra-wide bandwidth. The proposed multiple-input-multiple-output (MIMO)/diversity antenna covers a frequency range of 2.75–12 GHz. The antenna element offers a radiation efficiency of 89.3% and a gain of 3.41 dBi. The size of the wristband diversity antenna is 1.1λ0 × 18.4λ0 × 0.18λ0. The diversity performance characteristics of the prototype antenna are examined, with the envelope correlation coefficient (ECC) < 0.18, apparent diversity gain (ADG) > 9.5, effective diversity gain (EDG) > 9.5, mean effective gain (MEG) < 1 dB, total active reflection coefficient (TARC) < − 10 dB, and channel capacity loss (CCL) < 0.1 bits/s/Hz over the entire operating band. The specific absorption rate (SAR) of the proposed wristband antenna is analyzed to determine its radiation exposure on the human body, and the results show that the values are less than 0.02 W/kg.
Compact dual-band bandpass filter with high-passband isolation using coupled lines and open stub
Kishore S., Arora A., V. Phani Kumar K., Velidi V.K., Nayak C., Rao T.R., Rajkumar R.
Article, Microwave and Optical Technology Letters, 2021, DOI Link
View abstract ⏷
This article presents the design and analysis of a compact dual-band bandpass filter employing coupled lines and open circuit stub. The filter frequency response contains two passbands with good isolation between them and five transmission zeros in the stopband. The analytical design equations for transmission zero frequencies are obtained based on lossless transmission line theory and the even and odd mode analysis method. A dual-band bandpass filter operating at GSM (0.9 GHz) and Wi-Fi (2.4 GHz) frequencies is designed, fabricated, and tested. The proposed design method is verified by the excellent agreement between the simulated and measured results.
Performance investigations of a quad-band microstrip antenna for body wearable wireless devices
Article, Applied Computational Electromagnetics Society Journal, 2021, DOI Link
View abstract ⏷
This research work proposes a microstrip-based quad-band monopole antenna for body Wearable Wireless Devices (WWD) for Wireless Body Area Network (WBAN) applications. Ultra high frequency (UHF) and Ultra wide band (UWB) technology have been known for their efficiency to meet power, size and distance considerations for WBANs. The designed antenna resonates at four frequencies, 1.8, 2.4, 5.0 and 8.9 GHz covering licensed and license-free wireless technologies. The antenna design considers the electromagnetic (EM) effects due to the interaction of body tissues with the radio frequency (RF) waves, which are very different when compared to their interaction with free space. The performance of the antenna is investigated in terms of radiation efficiency, total gain, specific absorption rate (SAR), and thermal effects (short and long term). A simplified, human body tissue layer model is used for simulations utilizing EM computations. Simulated and experimental results are paralleled and are found to be in good agreement.
Analysis on the Effects of Materials on Propagation Path in an Indoor Office Environment at 60 GHz
Shehade K., Susila M., Sreedevi A.G., Rama Rao T.
Conference paper, Journal of Physics: Conference Series, 2021, DOI Link
View abstract ⏷
Recently, 60 GHz have been logged as a virtuous choice for high data rate indoor communications. This paper presents a millimeter-wave propagation analysis at 60 GHz and measurements in an indoor office environment of a multi-storied building. The main factors for multipath propagation in millimeter waves are delay spread, path loss, and received power. Being an indoor environment, building materials and frequency sensitivity materials (permittivity, conductivity, roughness) plays a significant role in propagation analysis. The model is compared with the International Telecommunication Union's recommendations (ITU), including material attenuation. 20 dBi horn antenna as transmitter and 20 dBi omnidirectional antenna as the receiver, an office environment is modeled in Wireless Insite, and the effects are studied.
Microstrip Dual-Band Bandpass Filter with Wide Bandwidth Using Paper Substrate
Phani Kumar K.V., Velidi V.K., Althuwayb A.A., Rama Rao T.
Article, IEEE Microwave and Wireless Components Letters, 2021, DOI Link
View abstract ⏷
This work presents the design and analysis of a novel dual-wideband bandpass filter (BPF) using the transversal filtering section (TFS), coupled lines (CLs), and stepped impedance stubs (SISs). Initially, a dual-band BPF employing TFS and CLs is designed. To enhance the bandwidth and selectivity, SIS units and quarter wavelength transmission lines are attached at the input and output ports. This novel filter's frequency response has six transmission zeros in the stopband and four transmission poles in each passband. A prototype with center frequencies of 1.17 and 2.4 GHz is realized on a biodegradable substrate and tested. The tested and simulated results are in high congruence, validating the proposed design circuit and theory.
Truncated elliptical Self-Complementary antenna with Quad-Band notches for SWB MIMO systems
Kumar Raheja D., Kumar S., Kumar Kanaujia B., Kumar Palaniswamy S., Rao Thipparaju R., Kanagasabai M.
Article, AEU - International Journal of Electronics and Communications, 2021, DOI Link
View abstract ⏷
In this work, a compact four-element super-wideband (SWB) multiple-input-multiple-output (MIMO) antenna with four notched bands is designed. The unit resonating element of the MIMO antenna consists of a semi-elliptical monopole patch with high eccentricity. The elliptical patch of the antenna element is truncated from the top to develop a polarization diversity-based compact MIMO configuration. In the coplanar ground surface, a flipped-slot of matched geometry is introduced, which complements the truncated antenna element. Also, four slit-resonators are introduced in the radiating patch of the antenna element to eliminate Wi-Fi, WLAN, Wi-MAX, and X-band signals (2.4, 3.5, 5.5, and 8.5 GHz, respectively) from the SWB. In the proposed quad-port SWB-MIMO configuration, the truncated elliptical self-complementary antenna (TESCA) elements are arranged in rotational symmetry and mutually orthogonal to each other. The diversity antenna exhibits impedance bandwidth (for |S11| < −10 dB) from 1.15 to 40 GHz (bandwidth ratio ~35:1), inter-element isolation greater than 18 dB, and ECC < 0.005. The proposed four-element diversity antenna may be a good candidate for cognitive radio and ubiquitous applications.
L-RPL: RPL powered by laplacian energy for stable path selection during link failures in an Internet of Things network
Pushpalatha M., Anusha T., Rama Rao T., Venkataraman R.
Article, Computer Networks, 2021, DOI Link
View abstract ⏷
The routing protocol RPL for low power and lossy networks (LLNs) suffers from reduced reliability, increase in control overhead, longer latency and higher energy utilization on experiencing high node density, link or node failures in the network. This paper aims to elaborately study the behaviour of RPL's expected transmissions count (ETX) based path selection for lengthier routes and the impact of node density and link or node failures on them. Our study finds that the path selection along long routes suffers due to the lack of decisive information on the neighbourhood links. As an alternate, a laplacian energy based path selection is proposed to enrich RPL by bringing in additional neighbourhood connection information into the path selection process to provide stable paths. Laplacian energy drop, a two-walk neighbourhood connectivity measure that is incorporated in L-RPL helps a node to pick the most resilient path. By simulation and testbed experiment results, it is shown that the proposed L-RPL improves path selection and reduces control overhead (29.05% and 39.68% reduction in (Destination Advertisement Object) control data when 9% of nodes fail and during normal conditions respectively), latency and also improves energy utilization.
Parametric Analysis of Inter-combed Photoconductive Antenna for Terahertz Communication
Flora Boby E.N., Rathinasamy V., Rao T.R., Mondal S.
Conference paper, Proceedings - International Conference on Communication, Information and Computing Technology, ICCICT 2021, 2021, DOI Link
View abstract ⏷
The parametric analysis of inter-combed photoconductive antenna (IcPCA) has been explored for the efficient terahertz (THz) generation and detection. A comparison of structural parameters has been analyzed in terms of the total photocurrent, THz radiated power and optical to THz conversion efficiency which is very useful in practical experiments like imaging, spectroscopy and communication applications. As the geometry of the antenna also plays a major role, the innovative inter-combed structure has been used to increase the radiation efficiency of PCA. The proposed IcPCA design provides high THz photocurrent compared to the conventional dipole photoconductive antenna. There are many input parameters such as laser repetition rate, laser pulse duration, bias voltage, carrier lifetime which also affects the power and efficiency of PCA. Moreover, the simulation on IcPCA shows better performance of three orders of magnitude higher than any other conventional dipole PCA. The design, simulation and optimization of IcPCA is an absolute need for efficient THz source and detection which is the key component of future generation (beyond 5G and 6G) communication system.
RFID-Band Integrated UWB MIMO Antenna for Wearable Applications
Govindan T., Palaniswamy S.K., Kanagasabai M., Kumar S., Rao T.R., Kannappan L.
Conference paper, 2021 IEEE International Conference on RFID Technology and Applications, RFID-TA 2021, 2021, DOI Link
View abstract ⏷
This manuscript prescribes the design of a four-port ultra-wideband (UWB) diversity antenna combined with 2.4 GHz ISM radio band. The denim-based wearable antenna is intended for use as a radio frequency identification (RFID) tag for tracking and security applications. The unit cells of the antenna are arranged orthogonally to each other to achieve isolation $gt15$ dB. The bending analysis of the proposed antenna is performed to ensure its stability. The dimensions of the unit cell and four-port MIMO antenna are $30 times 17 times 1$ cubic millimeter and $55 times 53 times 1$ cubic millimeter, respectively. The proposed antenna's specific absorption rate (SAR) is researched in order to determine the safer SAR limit set by the Federal Communications Commission (FCC).
SINR based association algorithm for indoor device-to-device communication networks
Article, Peer-to-Peer Networking and Applications, 2020, DOI Link
View abstract ⏷
The new generation telecommunications is growing at a spectacular pace and Device-to-Device (D2D) communication networks plays major role to meet the growing demands by billions of connected devices over the globe. Generally, indoor based D2D communication networks relays on distributed small cell solutions for better connectivity. This research proposes Signal-to-Interference-plus-Noise Ratio (SINR) based – Device Association Vector Algorithm (S-DAVA) for maximum network connectivity by efficiently discovering the neighbors and its D2D link based on network sum rate and SINR. The algorithm uses Rician model for Line-of-Sight (LoS) component to investigate the D2D network performance. The algorithm when evaluated with other conventional methods showed an improvement of 18.85% in throughput, and 10% of efficiency in energy with reduced network delay of 19%. This paper also checks its performance over traffic load, outage probability and network sum rate.
Compact Frequency and Bandwidth Reconfigurable Microwave Filter
Kingsly S., Kanagasabai M., Alsath M.G.N., Kumar P.S., Rao T.R., Indhumathi K., Subbaraj S., Panneer Selvam Y.
Article, Wireless Personal Communications, 2020, DOI Link
View abstract ⏷
This paper details the construction and working of a compound reconfigurable filter capable of frequency and bandwidth reconfiguration in the frequency range from 2 to 3 GHz. The switching between frequency and bandwidth reconfiguration is inherited by two PIN diodes. Bandwidth tuning is facilitated by tuning two transmission zeros individually using varactor diodes, giving flexibility in reconfiguring the upper and lower pass edges. The two transmission zeros are obtained using simple concentric square loop resonators. The maximum bandwidth obtained is 1.5 times the minimum bandwidth offered by the filter. Hence the filter can be used for dynamic bandwidth allocation. This prototype is fabricated and validated in real-time. The simulated and measured results are analogous to each other.
Interdigitated Photoconductive Antenna Design and Analysis for Terahertz Wireless Applications
Mondal S., Rathinasamy V., Kapoor S., Mukherjee S., Rama Rao T.
Conference paper, 2020 IEEE 3rd 5G World Forum, 5GWF 2020 - Conference Proceedings, 2020, DOI Link
View abstract ⏷
Terahertz (THz) frequencies span over a range of 0.1-10 THz within the electromagnetic spectrum and seeking technologically and commercial development for various applications, particularly in wireless domain. This research paper proposes a variety of designs for the inter-digitated photoconductive antenna (IPCA) and examines their performance for efficient generation and detection of THz radiation. The design parameters like inter-digitated element dimensions, number of digitated elements and dielectric gap have been varied and a comparison of the gain bandwidth is presented using finite difference time domain solver.
Enhancing machine learning aptitude using significant cluster identification for augmented image refining
Samiappan D., Latha S., Rao T.R., Verma D., Sriharsha C.S.A.
Article, International Journal of Pattern Recognition and Artificial Intelligence, 2020, DOI Link
View abstract ⏷
Enhancing the image to remove noise, preserving the useful features and edges are the most important tasks in image analysis. In this paper, Significant Cluster Identification for Maximum Edge Preservation (SCI-MEP), which works in parallel with clustering algorithms and improved efficiency of the machine learning aptitude, is proposed. Affinity propagation (AP) is a base method to obtain clusters from a learnt dictionary, with an adaptive window selection, which are then refined using SCI-MEP to preserve the semantic components of the image. Since only the significant clusters are worked upon, the computational time drastically reduces. The flexibility of SCI-MEP allows it to be integrated with any clustering algorithm to improve its efficiency. The method is tested and verified to remove Gaussian noise, rain noise and speckle noise from images. Our results have shown that SCI-MEP considerably optimizes the existing algorithms in terms of performance evaluation metrics.
Implementation of a compact dual-band bandpass filter using signal interference technique on paper substrate
Arora A., Madan A., Sarika, Bhattacharjee M., Nayak C., V. Phani Kumar K., Thipparaju R.R.
Article, AEU - International Journal of Electronics and Communications, 2020, DOI Link
View abstract ⏷
This paper exhibits the design and implementation of a compact dual-band bandpass filter on paper substrate. The proposed filter which works on the principle of signal interference technique has a parallel combination of short-circuited coupled line and an H-shaped network of transmission lines with open stubs. Due to the superposition of signals of the two transmission paths, a second order dual-band bandpass response with four transmission zeroes is achieved. To validate the proposed design, theoretical analysis using the lossless transmission line model is carried out and acknowledged. The developed dual-band filter prototype with center frequencies 1.17 GHz and 4.06 GHz has 3-dB fractional bandwidths of 82.56% (0.69–1.656 GHz) and 20.59% (3.645–4.481 GHz), respectively. The simulated and experimental results are in good congruence with each other. The proposed dual-band bandpass filter can be used in various wireless applications, for example, Global System for Mobile Communications (880–915 MHz), Aircraft surveillance (960–1215 MHz), Indian Regional Navigation Satellite System (1.164–1.188 GHz), Amateur radio (1.24–1.30 GHz), Global Positioning System (1.559–1.61 GHz), Satellite phones (1.616–1.626 GHz), and Satellite communication (3.7–4.2 GHz).
Security and privacy attacks during data communication in Software Defined Mobile Clouds
Moorthy V., Venkataraman R., Rama Rao T.
Article, Computer Communications, 2020, DOI Link
View abstract ⏷
There has been an enormous growth in networking and data communication between the wireless devices. Cloud computation has taken a giant leap into the mobile domain to cater to the on-going communication demands. The latest programming techniques have also paved the way for incorporating Software Defined Networking techniques in Mobile Cloud environment. The growth of networking infrastructure with many such technological innovations, has led to the parallel increase in security and privacy of data at different levels of communication. The communication links and interfaces have become targeted platform for various security attacks causing denial of services. This survey comprehends an in-depth analysis of the possible data privacy attacks and threats in the proposed Software Defined Mobile Cloud. The possibilities of the attacks which are enlisted focus on various ways of spoofing and flooding of data packets, mis-interpretation and aggregation of the flow rules for communication, packet dropping and traffic flow enrouting at different cross-layered architectural levels built over the heterogeneous networks. An overview of the mechanisms to encounter the various vulnerabilities in the suggested framework is recommended. This article further identifies research directions and challenges to incorporate the possible techniques and preventive solutions, to overcome the malicious attacks in the software defined mobile cloud.
Interdigitated-slot photoconductive antenna for terahertz applications
Rathinasamy V., Kapoor S., Rout A., Rao T.R., Mondal S.
Conference paper, 2019 IEEE Indian Conference on Antennas and Propagation, InCAP 2019, 2019, DOI Link
View abstract ⏷
GaAs based Photoconductive antenna (PCA) have widespread industrial uses as terahertz (THz) emitters for next generation wireless applications. It is well known, that a periodic-metallic structure at the edges of the antenna electrodes, similar to plasmonic PCAs, can extraordinarily increase the antenna performance. In this research, we have described the greater efficiency of Interdigitated-Slot Photoconductive Antenna (IPCA) as THz generators, than no-slot IPCA because of their higher screening electric field. Having a teeth length of 20 μm, width of 8 μm and a slot of 2 μm in the center, the reflection coefficient of -33 dB at 4.65 THz with a bandwidth of 0.515 THz has been achieved, whereas, with two slots around the center, the reflection coefficient is -17 dB at 2.835 THz with a bandwidth of 1.29 THz. The results show how frequency tunability and dual band radiation can be achieved by optimization of antenna parameters.
Measurements at 2.4, 3.4, 5.2, 28 and 60 GHz for Device-to-Device Wireless Communications
Sreedevi A.G., Rao T.R., Susila M.
Article, Wireless Personal Communications, 2019, DOI Link
View abstract ⏷
Wireless communication networks with increased demand for higher speed in data transfer have paved way for device-to-device (D2D) wireless communications. This paper, investigates the radio link characteristics of D2D communication network in an indoor environment utilizing radio frequency experiments and ray-tracing based simulations at frequencies of 2.4, 3.4, 5.2, 28 and 60 GHz. The path loss exponent and standard deviation are estimated and compared with free space path loss, log normal shadowing, International Telecommunication Union model and compared with other research works. This work also studied the impact of indoor environments on D2D communications.
Reinforcement learning algorithm for 5G indoor device-to-device communications
Article, Transactions on Emerging Telecommunications Technologies, 2019, DOI Link
View abstract ⏷
Fifth generation (5G), the next generation telecommunications will be striking the markets in near future. Device-to-device (D2D) communication would be a part of 5G to serve communication needs for billions of connected devices to support high data rate ultrareliable low latency communications. Indoor 5G will be relying on distributed small cell solutions and D2D along with machine-to-machine connections. Machine learning is one of the most promising tools for providing the best set of solutions to learn the influential scenarios and certain parameters of the communication networks. This research proposes reinforcement-learning-based latency controlled D2D connectivity (RL-LCDC) algorithm and its Q-learning approach in an indoor D2D communication network for strong 5G connectivity with minimum latency. The proposed approach, RL-LCDC efficiently discovers the neighbors, decides the D2D link, and adaptively controls the communication range for maximum network connectivity. The results show that RL-LCDC optimizes the connectivity with lower end-to-end delay and better energy efficiency with efficient convergence time when compared with other conventional schemes.
Tunable band-notched high selective UWB filtering monopole antenna
Kingsly S., Thangarasu D., Kanagasabai M., Alsath M.G.N., Palaniswamy S.K., Rao T.R., Subbaraj S., Selvam Y.P., Sambandam P., Ganesan G.
Article, IEEE Transactions on Antennas and Propagation, 2019, DOI Link
View abstract ⏷
This communication presents the design, fabrication, and testing of a tunable band-notched UWB filtering antenna. The proposed filtering antenna comprises a semiellipsoid radiator and a microstrip transmission line to cover the UWB communication bandwidth from 3.1 to 10.6 GHz. It also comprises two J-shaped open-ended stubs and an asymmetric T-shaped open-ended stub to create notch bands at 3.5 GHz (WiMAX), 5.2 GHz, and 5.8 GHz (WLAN) in the UWB spectrum. The center frequencies of the notch band are tuned continuously using varactors with percentage tuning of 7.5%, 5.38%, and 3.54%. The prototype is fabricated and experimentally validated.
Device-to-Device Radio Link Analysis at 2.4, 3.4, 5.2, 28 and 60GHz in Indoor Communication Environments
Sreedevi A.G., Rao T.R., Susila M.
Article, Frequenz, 2019, DOI Link
View abstract ⏷
Device-to-device (D2D) communication has become one of the major areas of research ever since the industry was advancing to LTE and 5G. In this nascent stage of transformation, this research work characterizes the radio link behavior of D2D communication network in an indoor environment utilizing licensed and unlicensed band experiments and ray-tracing based simulations at frequencies of 2.4, 3.4, 5.2, 28 and 60GHz. The path loss exponent (PLE) and standard deviation are estimated and compared with free space path loss (FSPL), log normal shadowing (LNS), International Telecommunication Union (ITU) model and also, compared with other research works. This work also studied the impact of indoor environments on D2D communications along with link budget, channel capacities and required performance improvements.
Heart shaped bow-tie antenna for tera hertz communication applications
Rathinasamy V., Kapoor S., Thangarasu D., Rao T.R., Kumar P.S.
Conference paper, 2019 International Conference on Wireless Communications, Signal Processing and Networking, WiSPNET 2019, 2019, DOI Link
View abstract ⏷
Terahertz (THz) radiations constitute a comparatively less explored region between microwave and infrared field in the electromagnetic (EM) spectrum. This research presents the design, construction and simulation of an antenna which can be suitably used for THz communications, with ultrahigh speed wireless links for biomedical imaging; identification, sensing, and tracking (IST) applications utilizing 1.3 to 5.0 THz band frequencies. The heart shaped bow-tie structure is preferred to enhance the bandwidth and other performance specifications with compact size of about 6 × 6 mm. The low cost silver coating is used as conducting material and the antenna module is a reliable solution for the emerging THz wireless applications.
On the bending and time domain analysis of compact wideband flexible monopole antennas
Mohandoss S., Palaniswamy S.K., Thipparaju R.R., Kanagasabai M., Bobbili Naga B.R., Kumar S.
Article, AEU - International Journal of Electronics and Communications, 2019, DOI Link
View abstract ⏷
In this paper, flexible, low profile and robust planar monopole antennas are designed and analyzed for its performance over conformal surfaces, intended for Ultra-Wideband (UWB) and Body Centric Wireless Communications (BCWC). By the aid of alike shape (modified rectangular shaped) radiator and truncated ground plane, two compact microstrip fed antennas are designed and fabricated on flexible substrates – Polyamide and Teslin (environmentally friendly, flexible and green-electronics). The proposed polyamide antenna with a size of 50 mm × 40 mm × 0.8 mm, radiates over frequency range from 1.8 to 13.3 GHz and teslin antenna with a dimension of 50 mm × 40 mm × 0.712 mm, covers the frequency range from 1.4 to 13.4 GHz. To validate the designed prototypes, the antennas are fabricated and the impact performance are analyzed, while flexing the antenna from its nominal straight arrangement (bending through its length, width, different bending radius and angles). Further, time domain analysis is carried out in free space and in various bent scenarios with pulse excitation to validate the antennas for UWB applications. The transmission coefficient characteristics (S21) and group delay for various bending conditions are measured and the fidelity factor for all the scenarios are greater than 0.82, which make the antennas good candidate for UWB-BCWC.
Investigations of specific absorption rate and temperature variations for an uwb antenna for wireless applications
Susila M., Rao T.R., Varshini K., Kumar P.S., Pushpalatha M.
Article, Progress In Electromagnetics Research M, 2019, DOI Link
View abstract ⏷
This paper portrays a compact planar ultra-wideband (UWB) antenna design and development for wireless applications. The proposed antenna is influenced by fractal geometry design, where a pentagon slot is introduced inside a circular metallic patch, and iterations were carried out to achieve needed wide bandwidth. The antenna is deployed over an FR4 substrate with relative permittivity of 4.4 and thickness of 0.16 cm, to achieve wider impedance bandwidth. The proposed antenna is of low profile with dimensions of 32×32mm, and it operates over bandwidth of 12.1GHz (2.9- 15 GHz). Specific Absorption Rate (SAR), the measure of exposure of electromagnetic (EM) energy on human tissues, is observed when proposed antenna is placed in close proximity to the dispersive phantom model. Also, the time domain analysis is done on human tissue model to observe the performance of the antenna and to validate its capability with wireless devices which are in near vicinity to the human all the time. Further, in this research, the temperature variation on human tissue is examined using Infrared (IR) thermal camera. Investigation on these parameters and validation with Radio Frequency (RF) equipment helps to prove that the proposed antenna is a suitable candidate for UWB wireless communication applications.
A digitized universal filtered orthogonal frequency division multiplexing for next generation communication applications
Article, Computers and Electrical Engineering, 2018, DOI Link
View abstract ⏷
Universal filtered orthogonal frequency division multiplexing (UF-OFDM) is an alluring next generation 5G waveform for communication with small bursts transmission. Moreover, there are arising applications in which short data packet transmissions are awaited to carry fault-finding messages that must be obtained with low latency and high reliability. Visible light communication (VLC) acts as an ideal technology to accomplish these requirements. VLC uses intensity modulation and direct detection techniques and hence they require the signals to certainly be real valued positive sequences. In this paper, a digitized UF-OFDM based on delta sigma modulation (DSM) is proposed. The implementation of the proposed digital UF-OFDM is analyzed in comparison with continuous-time domain representation of UF-OFDM (CT-UF-OFDM). The simulation result exhibits that the system which is projected has better SNR performance than the digitized OFDM. It is found that around 15.8 dB of SNR is improved using the proposed scheme as compared to digital OFDM.
SAR investigations on the exposure compliance of wearable wireless devices using infrared thermography
Article, Bioelectromagnetics, 2018, DOI Link
View abstract ⏷
Wearable electronics have become the norm over the last few years. Extensive use of wearable wireless devices (WWD) in greater proximity to the body has increased concern about potential biological effects due to the interaction of human tissues with electromagnetic (EM) fields. Human tissues absorb radiofrequency (RF) waves that are capable of affecting energy states at a molecular level, leading to unsafe effects. Remarkably, thermal effect due to the absorption of RF waves is a better biological manifestation than traditional specific absorption rate (SAR) values. In this study, we investigated the application of infrared thermography (IRT) to obtain temperature dynamics and reconstructed average SAR to evaluate the exposure compliance of WWDs. A microstrip-based monopole antenna was used to determine the biological effects of the interaction of EM waves with the body. SAR was obtained using EM field simulations and through reconstruction from thermal measurements with the use of bio-heat equations. The maximum average SAR on the skin was 50 mWkg−1 for the simulations and 54 mWkg−1 from reconstruction after IRT experiments. The maximum temperature change in both cases was observed to be less than 1 °C. The difference between the average SAR obtained through IRT and simulation tools was 8.9% on average. SAR determination from the information acquired using IR temperature dynamics can assess bio-compliance of modern wearable devices for various wireless applications. Bioelectromagnetics. 39:451–459, 2018. © 2018 Wiley Periodicals, Inc.
Fractal based ultra-wideband antenna development for wireless personal area communication applications
Mohandoss S., Thipparaju R.R., Balarami Reddy B.N., Palaniswamy S.K., Marudappa P.
Article, AEU - International Journal of Electronics and Communications, 2018, DOI Link
View abstract ⏷
This paper presents a bandwidth enhanced, compact planar ultra-wideband antenna design for wireless personal area communication (WPAN) applications. The proposed antenna has fractal based geometry and is constructed using several iterations of a pentagon slot inside a circular metallic structure. The partial ground plane of the basic radiator is tapered, defected and a U slit is etched out from the microstrip feed to improve the −10 dB |S11| bandwidth. The proposed fractal based antenna has an impedance bandwidth from 2.9 GHz to 15 GHz with low profile configuration and is fabricated on FR4 substrate with dimensions of 32 mm × 32 mm × 1.6 mm. To authenticate the designed prototype, the antenna is fabricated and tested for impedance and radiation characteristics. The designed antenna has stable radiation characteristics in the operating band. Furthermore, the antenna is validated for its applicability in WPAN, by calculating fidelity factor through time domain analysis along with the transmission coefficient and group delay measurements.
Multiband reconfigurable filtering monopole antenna for cognitive radio applications
Kingsly S., Thangarasu D., Kanagasabai M., Alsath M.G.N., Thipparaju R.R., Palaniswamy S.K., Sambandam P.
Article, IEEE Antennas and Wireless Propagation Letters, 2018, DOI Link
View abstract ⏷
A compact frequency-agile multiband filtenna is presented in this letter. The proposed reconfigurable filtering antenna performs independent switching between four operating bands viz. 1.8 GHz (GSM), 2.4 GHz (Bluetooth), 3.5 GHz (WiMAX), and 5.2 GHz (WLAN). This switching allows the unused bands to be utilized by the secondary user, making the antenna suitable for cognitive radio applications. An elliptical wideband monopole antenna is excited through a reconfigurable bandpass filter (BPF) integrated onto the 50 Ω transmission line. The BPF comprises four distinct structures to tune to four different frequencies using p-i-n diodes. The proposed filtenna has the reflection coefficient less than -20 dB for all the desired operating bands. Furthermore, this multiband filtenna offers gain of about 1.1, 2.6, 3, and 3.4 dBi at the four frequency bands. The prototype filtenna is fabricated, and the simulation results are verified experimentally.
Design of X Band ALTSA
Rao T.R., Tiwari N., Phani Kumar K.V., Kumar S.
Conference paper, International Symposium on Wireless Personal Multimedia Communications, WPMC, 2018, DOI Link
View abstract ⏷
A X band antenna for wireless communication applications is presented. The single element ALTSA has peak gain of 13.8 dB whereas 16.1 dB was attained with two elements. Both of the designed antennas have good radiation efficiency of above 80%. Rogers 6002 material having ϵr of 2.94 and 0.254 mm thick is utilized for antenna designs.
Design of penta-band antenna with integrated LNA circuit for vehicular communications
Article, IET Circuits, Devices and Systems, 2018, DOI Link
View abstract ⏷
In this study, the design of concurrent penta-band capable antenna with integrated low-noise amplifier (LNA) for vehicular wireless communication applications is presented. Spiral structured penta-band-based planar monopole antenna is designed to cover navigational frequencies 1.2 and 1.5 GHz, wireless communication frequencies 2.4 and 3.3 GHz and dedicated short range communication frequency 5.8 GHz. LNA was designed and developed with pseudomorphic high electron mobility transistor technology, frequency transformation technique, and load-pull methodology that operates simultaneously at all desired frequencies. The designed antenna with integrated LNA helps better return loss and improved impedance bandwidth compared with passive antenna designs. The developed antenna module operates simultaneously at 1.2, 1.5, 2.4, 3.3, and 5.8 GHz with a gain > 10 dB and noise figure < 2 dB. More than 150 MHz impedance bandwidth achieved at all the desired bands with this proposed integrated antenna module with LNA.
Compact and flexible monopole antenna for ultra-wideband applications deploying fractal geometry
Geetha G., Palaniswamy S.K., Gulam Nabi Alsath M., Kanagasabai M., Rama Rao T.
Article, Journal of Electrical Engineering and Technology, 2018, DOI Link
View abstract ⏷
This paper presents a compact ultra-wideband (UWB) flexible monopole antenna design on a paper substrate. The proposed antenna is made of iterations of a circular slot inside an octagonal metallic patch. This fractal-based geometry has been deployed to achieve compactness along with improved bandwidth, measured reflection coefficient -10 dB bandwidth ranging from 2.7 to 15.8 GHz. The overall size of the antenna is 26 mm×19 mm×0.5 mm, which makes it a compact one. The substrate used is paper and the main features like environment friendly, flexibility, green electronics applications and low cost of fabrication are the key factors for the proposed antenna. The aforementioned UWB prototype is suitable for many wireless communication systems such as WiMAX, WiFi, RFID and WSN applications. Antenna has been tested for the effect of bending by placing it over a curved surface of a very small radius of 10 mm.
Optical Channel Analysis of Turbo Coded MIMO-OFDM System for Visible Light Communication
Gauni S., Manimegalai C.T., Kalimuthu K., Kaushik V.C.S., Rama Rao T.
Conference paper, Lecture Notes in Electrical Engineering, 2018, DOI Link
View abstract ⏷
Optical wireless communication (OWC) system uses intensity modulation with direct detection (IMDD) to modulate the intensity of the signal in order to transmit information. There is an increase in the exploration of the modulation techniques used in visible light communications (VLC) in recent times. This paper deals with the comparison of power efficient modulation techniques such as dual-header pulse interval modulation (DH-PIM) and digital pulse interval modulation (DPIM) for VLC systems. Further, power allocation is studied under AWGN and Rayleigh channel. It is seen that the results prove to be spectrally efficient in the analysis of MIMO-OFDM VLC systems.
Specific absorption rate distributions of a tapered slot antenna at 60 GHz in personal wireless devices
Article, IEEE Antennas and Propagation Magazine, 2017, DOI Link
Substrate Integrated Waveguide Based High Gain Planar Antipodal Linear Tapered Slot Antenna with Dielectric Loading for 60 GHz Communications
Article, Wireless Personal Communications, 2017, DOI Link
View abstract ⏷
The 60 GHz band has the potential to provide high speed wireless communication. Substrate integrated waveguide (SIW) fed millimeter wave high gain antipodal linear tapered slot antenna (ALTSA) is presented in this paper. To obtain high gain the dielectric loading in addition to the corrugation structure is applied to the ALTSA. The use of SIW technology allows a highly efficient, compact and low cost planar design. The antenna is designed and simulated in an electromagnetic field simulation tool. A single element ALTSA is designed first. Then SIW power divider is used for designing 1 × 4 ALTSA array. To validate the proposed design, prototypes have been fabricated and measured. The simulated results agree well with the measured values which validates the proposed design. The measured return loss of single-element ALTSA and 1 × 4 ALTSA array is better than 12 dB over the entire 60 GHz band (57–64 GHz). The measured gain for single-element ALTSA and 1 × 4 ALTSA array is 18.7 ± 0.4 dBi and 22.9 ± 0.6 dBi respectively over the 60 GHz band.
Design of penta-band low noise amplifier with integrated active antenna for vehicular communications
Vijay R., Rama Rao T., Venkataraman R., Vasanthi M.S.
Article, International Journal of Microwave and Wireless Technologies, 2017, DOI Link
View abstract ⏷
The design and integration of penta-band planar antenna with a low noise amplifier (LNA) for vehicular wireless applications is discussed in this research. By integrating antenna with a LNA, the return loss can be kept low with the increased bandwidth compared with a passive antenna with the same design. The performance of the passive antenna, LNA, and integrated active antenna (IAA) are individually validated with the aid of vector network analyzer. The designed IAA covers navigational frequencies 1.2 and 1.5 GHz, wireless communication frequencies 2.4, 3.3 GHz and dedicated short range communication frequency 5.8 GHz, with LNA gain (>10 dB) and noise figure (<2 dB). The proposed design gives room for simultaneous reception of all the desired frequency bands with better performance for vehicular communications.
Device-to-device network performance at 28 GHz and 60 GHz using device association vector algorithm
Conference paper, 2017 IEEE International Conference on Signal Processing, Informatics, Communication and Energy Systems, SPICES 2017, 2017, DOI Link
View abstract ⏷
Device-to-device (D2D) will be the future of wireless technology with low power, high data rate and low latency for information exchange between wireless devices. However it may not be always feasible because of mobility and influence of surroundings on the devices. This paper presents an approach to model and investigate D2D network at two millimeter wave (mmW) frequencies of 28 and 60 GHz, by calculating the received signal strength (RSS) and signal-to-interference-plus-noise-ratio (SINR). A generalized joint optimization problem to maximize the overall rate of the D2D network with regard to a device association vector algorithm (DAVA) is presented. Simulation results show network performance under different indoor scenarios using DAVA.
Integrated bandpass-filter with planar UWB antenna for wireless communications
Susila M., Rama Rao T., Pushpalatha M.
Conference paper, 2017 IEEE International Conference on Signal Processing, Informatics, Communication and Energy Systems, SPICES 2017, 2017, DOI Link
View abstract ⏷
A planar antenna integrated with bandpass filter (BPF) which operates over the ultra-wideband (UWB) frequency of 3.1 to 10.6 GHz is proposed in this research for wireless communication applications. The antenna is designed with slotted circular patch to cover the desired band and a filter is designed using distributed components to ease the integration and compactness utilizing a shunt stub resonator. The antenna and integrated BPF is made on FR4 substrate with relative permittivity of 4.4 and 1.6 mm thickness. An insertion loss less than 2 dB, Quality factor of 0.9133 and an efficiency of 80% is observed. A return loss less than 10 dB is realized over the entire band with the integrated BPF module.
Design and Performance Analysis of a Penta-band Spiral Antenna for Vehicular Communications
Article, Wireless Personal Communications, 2017, DOI Link
View abstract ⏷
Developments in automotive industries are increasing to deliver secured and pleasant journey by exchange of information among the vehicles, inside vehicles, between vehicle and with infrastructure utilizing wireless communication networks (WCN). To meet the requirements for various wireless applications, a new printed planar based circularly polarized penta-band spiral antenna with tapered feed is designed to cover the navigational frequencies viz., 1.2, 1.5 GHz and WCN frequencies viz., 2.4, 3.3 GHz and Dedicated Short Range Communication frequency 5.8 GHz for vehicular mobile communications. A 3D Electromagnetic (EM) tool is used for design and is validated via field measurements with Radio Frequency (RF) equipment. In order to validate the performance of the designed antenna, Received Signal Strength (RSS) experiments were conducted between two vehicles at 2.4 and 5.8 GHz in an open area and on road with a vehicle moving speed of 15 km/h. Further, path loss analysis is done for vehicular environments with line of sight condition are simulated using EM propagation tool and simulated results are compared with empirical model viz., ITU, Two-ray reflection, dual-slope model and COST 231 Walfisch Ikegami model.
Investigations on SAR and Thermal Effects of a Body Wearable Microstrip Antenna
Article, Wireless Personal Communications, 2017, DOI Link
View abstract ⏷
Wearable technology has emerged as a hot topic in contemporary years around the globe and the interest in this sector continues to develop and will dominate in the future as well. This research work presents a microstrip-based multi-band monopole antenna for body wearable wireless devices (WWD) used for various body centric wireless communication applications. The designed antenna works at multi bands resonating at 1.8, 2.4, 5.0 and 8.9 GHz covering wireless and UWB based communication technologies. The electromagnetic (EM) effects of radiation absorption are investigated in terms of specific absorption rate and its biological manifestation as heating effect. EM computations and measurements are used to analyze the biological effects when placed on different sites on the body. Thermal effects for short term exposures and steady state conditions are evaluated using analytical methods. Experimental techniques using infrared thermography has been used for finding out the temperature elevation at three specific regions of the body. Simulated, analytical and experimental results of the heating effect are compared and are in good agreement. Further, the rise in temperature is found to be compliant with international safety regulations.
SIW Based Antipodal Linear Tapered Slot Antenna for Inter-Satellite Communication Links at 60 GHz
Article, Wireless Personal Communications, 2017, DOI Link
View abstract ⏷
Future space exploration demands inter-satellite links (ISL) that allow high speed communication between two or more satellites. This paper is concerned with the antenna system capable of establishing and maintaining ISL at 60 GHz. A high gain corrugated and hat shaped dielectric loaded antipodal linear tapered slot antenna (ALTSA) based on substrate integrated waveguide technology for inter-satellite communications at 60 GHz is proposed in this paper. A gain of 16.2 dBi achieved with a single element corrugated ALTSA and the 1 × 2 corrugated ALTSA array has a gain of 18.5 dBi with return loss below −10 dB at 60 GHz band. Similarly, the hat shaped dielectric loaded ALTSA has gain of 17.29 dB with single element and 19.22 dB was achieved with two elements ALTSA. Both have good radiation efficiency of above 92%. Electromagnetic field simulation tools have been utilized for the design and simulation of the proposed antennas.
Penta-band linear tapered feed planar spiral antenna for vehicular communications
Article, International Journal of Microwave and Wireless Technologies, 2017, DOI Link
View abstract ⏷
Owing to dynamic nature of vehicular environments, it becomes essential to achieve effective communication via vehicle-to-vehicle and infrastructure-to-vehicle. This leads to the need for an antenna system that supports multiple frequency bands, high gain, broadside radiation pattern, and circular polarization. We propose single-arm penta-band-based spiral antenna with dimensions of 51 × 35 × 1.574 mm3 resonating at navigational wireless frequencies 1.2 GHz for IRNSS and 1.5 GHz for GPS; wireless communication frequencies 2.45 and 3.3 GHz and dedicated short range communication frequency 5.8 GHz. Linear taper feed has been introduced to achieve good impedance matching and the outer edge feed of the spiral on the same plane helps to achieve circular polarization. The measurement result proves the betterment in impedance of the spiral antenna that varies from 50 -55 Ω across the desired operating frequencies.
Penta-band Linear Tapered Feed Spiral Antenna Design and Radio Link Characterization for Vehicular Communications
Article, Wireless Personal Communications, 2017, DOI Link
View abstract ⏷
Increasing mobility, safety and passenger comfort are very strong motivations for implementation of Intelligent Transportation Systems (ITS) in practice. The role of wireless communications in ITS has become compelling, both for industry and research community. Wireless communications technologies provide a platform for the exchange of data among the vehicles. A penta-band printed spiral antenna with tapered feed is proposed for vehicular communication system, facilitating vehicle-to-vehicle (V2V) and infrastructure to vehicle (I2V) communication. The antenna covers the navigational frequencies viz., 1.2, 1.5 GHz and Wireless Communication frequencies viz., 2.45, 3.3 GHz and Dedicated Short Range Communication frequency, 5.8 GHz for vehicular communications. Further, radio link characterization of I2V and V2V propagation channel is carried out using Electromagnetic propagation tool, and compared with empirical path loss models of ITU, two-ray reflection and inter-vehicle models.
D2D communications performance analysis for LOS and NLOS scenarios with DAV algorithm
Conference paper, IEEE International Conference on Circuits and Systems, ICCS 2017, 2017, DOI Link
View abstract ⏷
Massive growth of connected devices, network traffic and wide range of application requirements have paved way for Device-to-device (D2D) network communication. This paper offers a D2D network model at 28 and 60 GHz, and methods to calculate the received-signal-strength (RSS) and signal-to-interference-plus-noise-ratio (SINR). The propagation analysis of two scenarios, Line of Sight (LOS) and Non-Line of Sight (NLOS) communication is modelled, and analyzed using network sum rate. A generalized joint optimization problem which maximizes the whole rate of the D2D network using an association vector algorithm is also presented. Simulation results show network performance and its dependency over distance and frequency using Device Association Vector Algorithm (DAVA).
Beamforming investigation for wireless communication at 60 GHz
Conference paper, Proceedings of the 2017 International Conference on Wireless Communications, Signal Processing and Networking, WiSPNET 2017, 2017, DOI Link
View abstract ⏷
With the current scenario of increasing number of cell phone users, wireless communication technology is certain to demand more channel capacity and higher data rates with less interference. Increased number of users using various applications and use of pre-existing congested bandwidth is primary reason for this scenario. With emerging wireless technology, Space Division Multiple Access in unlicensed millimeter wave spectrum can be suitable approach for capacity improvement and interference minimization in future. Beamforming is considered as space division multiple access (SDMA) technique. In Beamforming, an antenna array selects signals spatially on the basis of their time of capture at each element. Capture time varies on each element based on the direction of arrival (DOA) with exception of signal arriving orthogonally at an array. Basics on beamforming, selection of factors impacting the issues in beamforming like sensor elements of an array, spacing between array, number of elements in an array, operating frequency and its range etc. are discussed in this paper. Contrast between the Conventional and Adaptive beamforming is brought with MATLAB simulation at 60 GHz.
Analysis of human body temperature elevation at 60 GHz with antipodal linear tapered slot antenna
Shrivstava P., Rao T.R., Abe B.T.
Conference paper, 2017 Global Wireless Summit, GWS 2017, 2017, DOI Link
View abstract ⏷
In the near future, new generation wireless network communications are expected to provide new paradigms over the existing networks with rich multimedia features and performance. In this perspective, progress in computational electromagnetics (EM) and advances in millimeter-wave (MmW) frequency bands propelling for ultra-high-resolution and ultra-high-speed wireless systems/applications. With the deployment of MmW wireless technologies, brinks of potential MmW induced biological and health effects should be carefully considered. Due to the short wavelength and low penetration depth, energy absorption is confined to the skin surface, and it is difficult to evaluate a significant volume for Specific Absorption Rate (SAR) at MmWs. The purpose of this study is to observe the temperature elevations from Antipodal Linear Tapered Slot Antenna at 60 GHz on three different body parts for the use of personal wireless devices (PWD) for various wireless applications, utilizing EM tool and Infrared Thermal Camera.
Investigations on suitable modulation techniques for visible light communications
Manimegalai C.T., Gauni S., Raghavan N., Rao T.R.
Conference paper, Proceedings of the 2017 International Conference on Wireless Communications, Signal Processing and Networking, WiSPNET 2017, 2017, DOI Link
View abstract ⏷
Optical Wireless Communication (OWC) is widely used in current broadband access markets. This is due to the usage of optical radiation through free space for transmission. OWC employs Intensity Modulation with Direct Detection (IMDD) to modulate the intensity of the signal in order to transmit information. This offers a flexible networking solution. OWC systems that operate in the visible band region (390-750 nm) are referred to as Visible Light Communication. VLC has a dual purpose of illumination and communication system. VLC uses On-Off Keying (OOK) and Pulse Position Modulation (PPM). But recently, a noticeable increase in the use of a number of other modulation techniques such as Digital Pulse Interval Modulation (DPIM) and Dual-header Pulse Interval Modulation (DH-PIM) to improve the efficiency in terms of both the bandwidth and power has been observed. This paper concentrates on baseband pulse time modulation techniques that are used to modulate data for OWC and compares OOK, PPM, DH-PIM and DPIM techniques with respect to their spectral efficiency, optical power, bandwidth, transmission capacity, packet transmission rates and peak average power ratio (PAPR).
Performance analysis of digitized multicarrier system for optical wireless communication
Deepa T., Rao T.R., Mathur H., Srivstava P., Abe B.T.
Conference paper, 2017 Global Wireless Summit, GWS 2017, 2017, DOI Link
View abstract ⏷
Optical wireless communication (OWC) in the infrared and visible range is an appealing technology, principally in environment arenas where radio communication encounters difficulties. One o f the most important subdivisions of OWC technology is the visible light communication (VLC) that uses visible light (VL) between the range 400 and 800 THz. VLC uses intensity modulation/direct detection (IM/DD). Hence the signals ought to be strictly real valued positive sequence. The fundamental modulation techniques such as on-off keying (OOK) and Pulse Position Modulation (PPM) are in accordance with existing constara current tight emitting diode (LED) drivers, however it comes with one drawback of having low spectral efficiency and restricted feasible data rates of VLC. Orthogonalfrequency-division multiplexing (OFDM) is one of the superior techniques that encode digital data on to multiple carrier frequencies and is widely known for providing high spectral efficiency. Despite of these advantages it comes with the disadvantage of high peak to average power ratio (PAPR) besides complicated Digital-to-Analog converter (DAC) and modification of LED drivers of VLC system being pre-requisite. Ln this paper, we present Delta-Sigma modulation (DSM) based OFDM which offers excellent robustness against noises and nonlinear distortions in VLC systems. The digital OFDM has been analyzed in terms of complementary cumulative distribution function (CCDF), error vector magnitude (EVM), bit error rate (BER) and received constellation diagram by means of MATLAB simulation to characterize the waveforms. Simulation results show that the DSM considerably enhances the system performance of digitized OFDM.
Wideband wearable antenna for body wireless communications
Rao T.R., Reddy B.N.B., Tiwari N., Srivastava P., Balachary M.
Conference paper, 2017 Global Wireless Summit, GWS 2017, 2017, DOI Link
View abstract ⏷
A wideband wearable monopole patch antenna is presented in this paper. The antenna design has a defected ground. Rectangular slots are created on top patch and also on the defected ground surface. The antenna is designed and simulated on different substrates. Simulations are also performed by placing the antennas on phantom model. The antenna designed on FR4 substrate is fabricated. The return loss of the fabricated antenna is measured and found to be similar to the simulated return loss. Simulated peak gain of the antenna is 6.8 dB on FR4 substrate.
Concurrent Multi-Band Low-Noise Amplifier
Ramya, Rama Rao T., Venkataraman R.
Article, Journal of Circuits, Systems and Computers, 2017, DOI Link
View abstract ⏷
With rapid expansions of wireless communications, requirements for transceivers that support concurrent multiple services are continuously increasing and demanding design of a concurrent low-noise amplifier (LNA) with low noise figure (NF), high gain, and high linearity over a wide frequency range for various wireless applications. The proposed work focuses on a concurrent multi-band LNA that works at navigational frequencies, namely, of 1.2GHz and 1.5GHz, wireless communication frequencies, namely, of 2.45GHz and 3.3GHz, dedicated short range communication (DSRC) frequency of 5.8GHz for the vehicular communication applications. This circuit has a distinct input matching network which resonates at all desired five frequency bands and is achieved by adapting frequency transformation method. To accomplish simultaneous reception of the desired penta-band, the output matching is designed with simple LC matching network with the aid of load-pull methodology.
Antipodal linear tapered slot antenna with dielectric loading using substrate integrated waveguide technology for 60 GHz communications
Article, Applied Computational Electromagnetics Society Journal, 2017,
View abstract ⏷
The 60 GHz band is capable of providing high speed communication. In this paper a substrate integrated waveguide (SIW) fed high gain antipodal linear tapered slot antenna (ALTSA) is presented. In order obtain high gain the dielectric loading is applied to the ALTSA in addition to the corrugation structure. Using SIW technology, a highly efficient, compact and low cost planar design is realized. An electromagnetic field simulation tool is used for design and simulation of the antenna. SIW power divider is used for designing 1x4 ALTSA array. To validate the proposed design, prototype is fabricated and measured. The simulated results agree well with the measured values which validates the proposed design. The measured return loss of 1x4 ALTSA array is better than 12 dB over the entire 60 GHz band (57 GHz - 64 GHz). The measured gain of 1x4 ALTSA array is 23.1 ± 0.5 dBi over the 60 GHz band.
Design of SIW fed antipodal linearly tapered slot antenna array with hat-shaped dielectric loading for 60 GHz wireless communications
Rao T.R., Sarath C., Tiwari N., Jyoti R.
Conference paper, Proceedings - 7th IEEE Indian Antenna Week 2016: A Workshop on Advanced Antenna Technology, IAW 2016, 2017, DOI Link
View abstract ⏷
Substrate integrated waveguide (SIW) based antipodal linear tapered slot antenna (ALTSA) with dielectric loading at 60 GHz for wireless communication applications are presented. The hat shaped dielectric loaded ALTSA has gain of 17.29 dB with single element and 19.22 dB was achieved with two elements ALTSA. Both got good radiation efficiency of above 92%. The antennas are designed using Rogers RT/Duroid 6002 material with dielectric constant 2.94 and thickness of 0.254 mm. Ansys HFSS and CST MWS were used for the EM computations.
Penta-band active integrated spiral antenna
Vijay R., Rao T.R., Venkataraman R.
Conference paper, APCAP 2016 - 2016 IEEE 5th Asia-Pacific Conference on Antennas and Propagation, Conference Proceedings, 2017, DOI Link
View abstract ⏷
This paper describes the design of novel penta-band active integrated spiral antenna for vehicular wireless applications. Frequency transformation method is adopted for the input matching network of the penta band low noise amplifier (LNA) and by using load-pull methodology; the output matching circuit is designed with simple LC matching network. The designed active integrated spiral antenna operates at navigational frequencies 1.32/1.5 GHz, wireless communication frequencies 2.4/3.3 GHz and Dedicated short range communication frequency 5.8 GHz.
Design of SIW fed antipodal linearly tapered slot antennas with curved and hat shaped dielectric loadings at 60 GHz for wireless communications
Rao T.R., Sarath C., Tiwari N., Jyoti R.
Conference paper, APCAP 2016 - 2016 IEEE 5th Asia-Pacific Conference on Antennas and Propagation, Conference Proceedings, 2017, DOI Link
View abstract ⏷
A substrate integrated waveguide (SIW) based antipodal linear tapered slot antenna (ALTSA) with dielectric loading at 60 GHz for wireless communication applications are presented. The antenna ALTSA 1 with hat-shaped dielectric loading has gain of 17.29 dB. The gain of another antenna ALTSA 2 is 18.18 dB which is constructed by adding a curved dielectric slab loading on top of ALTSA 1 and showed good efficiency of about 95%. The ALTSA 1 designed using Rogers RT/Duroid 6002 material with dielectric constant 2.94 and thickness of 0.254 mm. And, Rogers Ultralam 1217 with dielectric constant 2.17 and thickness of 1 mm is used for ALTSA 2. Ansys HFSS and CST MWS were used for the electromagnetic (EM) simulation and computation of antennas.
Investigations on the biological effects of wearable antennas at UHF and UWB frequencies: A thermal perspective
Conference paper, 2016 IEEE Annual India Conference, INDICON 2016, 2017, DOI Link
View abstract ⏷
With increasing interest in the usage of wearable wireless communication technologies at UHF (0.3-3 GHz) and UWB (3.1-10.6 GHz) frequencies, investigations on the human body interaction with these devices is becoming important. This paper provides a Microstrip based multi-band monopole antenna for Body Wearable Wireless Devices (BWWD), resonating at 1.8 GHz, 2.4 GHz, UWB frequencies, covering licensed and license-free wireless technologies when placed on human tissues. Five body parts are considered to evaluate the biological effects of the radiations on the body. Specific Absorption Rate (SAR) values were found to range from 0.09-0.25 W/kg on the skin, by using numerical modeling. The thermal effects were analyzed and compared between numerical, simulated and experimental results. Experimental investigations were carried out using Infra-red thermography. Temperature rise was observed to be less than 1° C in all the approaches. Analyses show that Infrared thermography, a temperature-based technique can be used to evaluate the compliance of wearable devices with safety exposure guidelines for various wireless applications.
Design of Penta-Band Low Noise Amplifier
Vijay R., Rama Rao T., Venkataraman R.
Conference paper, 2016 IEEE Annual India Conference, INDICON 2016, 2017, DOI Link
View abstract ⏷
A new Penta-Band Low Noise Amplifier (PB-LNA) for vehicular communication applications that works simultaneously at navigational frequencies viz., 1.2 GHz, 1.5 GHz and wireless Communication frequencies viz., 2.4 GHz, 3.3 GHz and Dedicated Short Range Communication frequency (DSRC), 5.8 GHz is designed and analysed. Frequency transformation method is adopted for the input matching network of the designed PB-LNA. The output matching circuit is designed with a LC matching network by applying load-pull methodology. The LNA is unconditionally stable for the desired frequency bands. The power gain of PB-LNA is in the range of 10 dB to 12 dB. Noise figure (NF) below 2dB is achieved in the band of interest.
Mach-Zehnder Interferometer based high sensitive water salinity sensor for oceanographic applications
Uma Kumari C.R., Samiappan D., Rama Rao T.R., Sudhakar T.
Conference paper, 2016 IEEE Annual India Conference, INDICON 2016, 2017, DOI Link
View abstract ⏷
A high sensitive Mach-Zehnder Interferometer (MZI) based fiber optic sensor for the measurement of sea water salinity has been demonstrated in this research. At first, femtosecond laser is used as the source and its performance in sensing salinity of sea water is analyzed. Secondly, a Carbon monoxide (CO) laser operating in the spectrum of 4.8 to 8.3 pm is used to excite the arms of MZI. It has been observed that wavelength shifts related to attenuation dips are highly sensitive to salinity of sea water when CO laser is used as the source. Using simple and robust schematic design, sensitivity of 0.01pm/ppt is achieved for salinity range of 31 to 37 ppt at a constant temperature of 27°C. The all-optical MZI salinity sensor indicated here is easy to fabricate, low cost, highly sensitive and finds application in the field of oceanography.
Investigations of SAR distributions and temperature elevation on human body at 60GHz with corrugated antipodal linear tapered slot antenna
Article, Progress In Electromagnetics Research M, 2017, DOI Link
View abstract ⏷
New generation wireless communications are expected to provide new services over the existing variety of wireless applications in the coming years. In this perspective, advances in utilization of computational electromagnetics (EM) and millimeter-waves (mmW) frequency bands make them as candidates for ultra-high-resolution and ultra-high-speed wireless communications. With the deployment of mmW wireless technologies, brinks of potential mmW induced biological and health effects should be evaluated carefully. The EM exposure is usually measured in terms of absorbed power from any user operating wireless devices. The exposure varies with the part of the body and location of the source that is exposed to the radio frequency waves. The purpose of this study is to observe EM exposure in terms of Specific Absorption Rate (SAR) and temperature elevations at mmWs from the designed Antipodal Linear Tapered Slot Antenna (ALTSA) at 60GHz on different body parts utilizing EM computations and experiments with Infrared Thermal Camera.
Estimation of specific absorption rate using infrared thermography for the biocompatibility of wearable wireless devices
Article, Progress In Electromagnetics Research M, 2017, DOI Link
View abstract ⏷
Wearable wireless technology has developed as an exciting topic over the last couple of years. With the extensive use of Wearable Wireless Devices (WWD) in greater proximity to the body for various wireless applications, the concern about biological effects due to the interaction of human tissues with the radiations is growing. In this research, we investigate the application of Infrared Thermography (IRT) to obtain temperature dynamics and reconstruct Specific Absorption Rate (SAR) to evaluate the exposure amenability of WWDs. A microstrip monopole antenna on a wearable substrate is used to determine the biological effects of the interaction of electromagnetic (EM) waves on the body. SAR is obtained using EM field simulations and by reconstruction from thermal measurements with the use of bio-heat equations for a continuous exposure of 300 s. Validation of IRT to reconstruct SAR is demonstrated by comparison with EM computations. The maximum SAR was 32 mW/kg, for simulations and 35 mW/kg, from reconstruction after IRT experiments. The maximum temperature change in both cases was always less than 1◦C. The difference between the SAR obtained through IRT and simulation tools accounted for an average of 8.7%. Information acquired using IR temperature dynamics can yield SAR values which can assess radio frequency exposure compliance for WWD at frequencies used for modern wireless technologies, with reliability.
Design and analysis of wideband monopole antennas for flexible/wearable wireless device applications
Balarami Reddy B.N., Sandeep Kumar P., Rao T.R., Tiwari N., Balachary M.
Article, Progress In Electromagnetics Research M, 2017, DOI Link
View abstract ⏷
Compact wideband flexible monopole antennas are designed and analyzed for its performance for Body Centric Wireless Communications (BCWC). Two antennas with identical radiators on different substrates are designed and fabricated on polyamide and teslin paper substrates, deploying a modified rectangle-shaped radiator. With the aid of modifications in the radiating plane and defecting the ground plane, the polyamide based antenna is designed to operate between 1.8 and 13.3GHz, and teslin paper based antenna is designed to operate between 1.45 and 13.4GHz to cover the wireless communication technology frequencies and ultra-wideband range for various wireless applications. The reflection coefficient characteristics of the fabricated antennas on free space and on various sites of the body are measured and match reasonably well with the simulated reflection coefficient characteristics. The specific absorption rate (SAR) analysis is also carried out by placing the antennas on tissue layered model.
Indoor channel characterization studies for V-band gigabit wireless communications using dielectric-loaded exponentially tapered slot antenna
Article, International Journal of Microwave and Wireless Technologies, 2016, DOI Link
View abstract ⏷
Demands for very high-speed wireless communication access is rapidly growing with respect to the increasing data rates for the use of rich multimedia content in various applications of defense, enterprise, industrial, and public domains. To serve these gigabit fidelity (Gi-Fi) uses for various wireless applications, millimeter wave (MmW) wireless technology with huge bandwidth in licensed/unlicensed bands is triggering boundless avenues. In this research, the concept of substrate-integrated waveguide (SIW) and exponentially tapered slot (ETS) antenna are used together design a high-gain, efficient planar dielectric-loaded antenna for MmW-based Gi-Fi wireless communications using unlicensed 60 GHz band in the MmW family. The SIW is used to feed the antenna and a dielectric is utilized increasing the gain. The dielectric-loaded ETS antenna and compact SIW feed are fabricated on a single substrate, resulting in low cost and easy fabrication utilizing printed circuit board process. The measured gain of single-element antenna is 11.4 dB, with radiation efficiency of 96.84% at 60 GHz. Then indoor radio wave propagation studies are carried out using elliptically dielectric-loaded ETS antenna with radio frequency measurement equipment to measure and model propagation channels at 60 GHz. The attained simulations are compared with the experimental results.
Design of concurrent penta – Band based low noise amplifier for vehicular communications
Ramya R., Rao T.R., Vasanthi M.S.
Conference paper, Proceedings of the 2016 IEEE International Conference on Wireless Communications, Signal Processing and Networking, WiSPNET 2016, 2016, DOI Link
View abstract ⏷
In this work, a new concurrent penta-band low noise amplifier (CPB-LNA) that works at navigational frequencies viz., 1.2 GHz, 1.5 GHz and wireless Communication frequencies viz., 2.45 GHz, 3.3 GHz and Dedicated Short Range Communication frequency (DSRC), 5.8 GHz for vehicle to vehicle communications is designed and analysed. This circuit has a distinct input matching network which resonates at all desired five frequency bands simultaneously and is achieved by adapting frequency transformation method. The output matching circuit comprises of simple LC matching network designed by using load-pull methodology. The CPB- LNA is simulated using Advance Design System (ADS). The power gain of CPB- LNA is 15.09 dB at 1.2 GHz, 14.368 dB at 1.5 GHz and 14.945 dB at 2.4 GHz, 14.302 dB at 3.3 GHz and 12.075 dB at 5.8 GHz. Noise figure (NF) of 0.48 dB at 1.2 GHz, 1.7 dB at 1.5 GHz and 1.07 dB at 2.4GHz, 0.572 dB at 3.3 GHz and 1.201 dB at 5.8GHz are achieved. Input and output return loss is below -12 dB for all desired frequency bands.
Performance evaluation of RF based Inter Satellite communication Link at 60 GHz
Chinmayi A.V., Vasanthi M.S., Rao T.R.
Conference paper, Proceedings of the 2016 IEEE International Conference on Wireless Communications, Signal Processing and Networking, WiSPNET 2016, 2016, DOI Link
View abstract ⏷
Inter-satellite links provide direct connectivity between two or more satellites, thus eliminating the need for intermediate ground stations while sending data for various wireless applications. This paper proposes the investigations on performance evaluation of Radio Frequency (RF) signal at 60 GHz utilizing Matlab/Scilab computation. A block level model is designed at 60 GHz for estimation of satellite RF link along with the link budget calculator. The operation of the link budget calculator features the calculation of effective noise temperature, noise power, Effective Isotropic Radiative Power(EIRP), Free Space Loss(FSL) and received power of the RF Inter-Satellite Link which further provides an important ground for the Inter-Satellite Link block level design. The power spectrum, constellation diagram and eye-diagram at both transmitter and receiver side for the RF link is evaluated with a separation distance of 500 km and 1000 km.
Design of SIW fed antipodal linearly tapered slot antenna with hat-shaped dielectric loading at 60 GHz for inter-satellite communication
Sarath C., Tiwari N., Rao T.R., Jyoti R.
Conference paper, Proceedings of the 2016 IEEE International Conference on Wireless Communications, Signal Processing and Networking, WiSPNET 2016, 2016, DOI Link
View abstract ⏷
A substrate integrated waveguide(SIW) based antipodal linear tapered slot antenna (ALTSA) with dielectric loading at 60 GHz for inter-satellite communication applications is presented. The antenna gain is 17.29 dB at the frequency of interest with good efficiency of 95.1%. The antenna is designed using Rogers RT/Duroid 6002 material with dielectric constant 2.94 and thickness 0.254 mm. A hat-shaped dielectric loading is added to the antenna to form a dielectric guiding structure, which narrows the beamwidth. To reduce the cross-polarization levels and relative side-lobe levels, rectangular shaped corrugation is used in the antenna design. Ansys HFSS software is used for the simulation of antenna.
Antipodal Linear Tapered Slot Antenna Based Radio Link Characterization in Narrow Hallway Environment at 60 GHz
Article, Journal of Infrared, Millimeter, and Terahertz Waves, 2016, DOI Link
View abstract ⏷
The performance of wireless communication systems is predominantly dependent on propagation environment and respective radiating antennas. Due to the shorter wavelength at millimeter wave (MmW) frequencies, the propagation loss through the objects in indoor environments is typically very high. To improve the channel capacity and to reduce inter-user interference, a high gain directional antenna is desired at MmW frequencies. Traditional antennas used in MmW devices are not suitable for low-cost commercial devices due to their heavy and bulky configurations. This paper focuses on design and development of a very compact (44.61 × 9.93 × 0.381 mm) high gain antipodal linear tapered slot antenna (ALTSA) utilizing substrate integrated waveguide (SIW) technology at 60 GHz. Received signal strength (RSS), path loss, and capacity are studied for MmW indoor applications utilizing ALTSA with radio frequency (RF) measurement equipment in narrow hallway environment.
A switched beam antenna array with butler matrix network using substrate integrated waveguide technology for 60 GHz wireless communications
Article, AEU - International Journal of Electronics and Communications, 2016, DOI Link
View abstract ⏷
The 60 GHz band has a lot of potential for high speed multi-gigabit wireless communications. In this paper, a switched beam antenna array based on substrate integrated waveguide (SIW) technology is designed and simulated at 60 GHz band. The antenna array is fed by 4 × 4 planar butler matrix network in order to achieve the switched beam characteristic. The use of SIW technology offers a low cost and a planar design. Each of the components is designed and simulated in the electromagnetic simulation tool CST MWS. The components are integrated later to form the switched beam antenna. Then the designed switched beam antenna is fabricated for measurement. The simulated results agree well with the measured values which validates the proposed design. The return losses and isolations are lower than -10 dB from 57 GHz to 64 GHz for all of the input ports. The peak gain for the switched beam antenna array is 17.5 dBi at 60 GHz.
A switched beam antenna array with butler matrix network using substrate integrated waveguide technology for 60 GHz radio
Article, Applied Computational Electromagnetics Society Journal, 2016,
View abstract ⏷
A switched beam antenna array based on substrate integrated waveguide (SIW) technology is designed and simulated for 60 GHz communications. The antenna array is fed by 4x4 planar butler matrix network in order to achieve the switched beam characteristic. Each of the components is designed and verified through simulations in electromagnetic field simulation tools, CST MWS and HFSS. The components are integrated later to form the switched beam antenna array. The return losses and isolations are better than 10 dB from 57 GHz to 64 GHz for all of the input ports. The peak gain for the switched beam antenna array is 18 dBi at 60 GHz.
Performance investigations and SAR analysis of a dual-band microstrip antenna for body wearable wireless devices at UWB channel frequencies
Article, International Journal of Microwave and Optical Technology, 2016,
View abstract ⏷
A microstrip based dual-band monopole antenna for body Wearable Wireless Devices (WWD) is proposed utilizing channels in the Ultra Wide Band (UWB) spectrum. The designed dual-band antenna targets lower band (4.7-5.3 GHz) and upper band (7.3-8.5 GHz) of the unlicensed UWB spectrum to meet low, high data rates. The antenna design considers the difference in the interaction of body tissues with the electromagnetic (EM) fields, when compared to free space. The performance of the antenna on different wearable substrates, the robustness of the antenna to work with varying skin thickness and on different sites on the body along with the thermal effects on the skin are analyzed. A simplified, human tissue layer model that is frequency dependent in its properties is used for simulations and computations. Simulated and experimental results were compared and found to be in agreement favouring the use of the antenna for wearable devices for various WBAN applications.
Circularly polarized penta-band based planar tapered feed spiral antenna design and radio link analysis for vehicular communications
Ramya, Rama Rao T., Venkataraman R.
Article, International Journal of Microwave and Optical Technology, 2016,
View abstract ⏷
Intelligent transportation systems (ITS) aims at adding information and communication technologies to transportation infrastructures and vehicles to improve safety and efficiency. Wireless communications play the inevitable role in ITS and provide a platform for the exchange of data among the vehicles. Circularly polarized penta-band planar spiral antenna with tapered feed is presented to aid vehicular communications. The antenna covers navigational frequencies viz., 1.2 GHz, 1.5 GHz and Wireless Communication frequencies viz., 2.45 GHz, 3.3 GHz and Dedicated Short Range Communication frequency 5.8 GHz for the Vehicle-Vehicle communications. The Antenna is designed and simulated with Electromagnetic (EM) simulation tool and validated with Radio Frequency equipment. The suitability of the proposed antenna for vehicular communications is validated through the radio link analysis on the line of sight, and the non-line of sight scenarios utilizing EM computations and path loss models.
Thermal distribution based investigations on electromagnetic interactions with the human body for wearable wireless devices
Article, Progress In Electromagnetics Research M, 2016, DOI Link
View abstract ⏷
With increasing interest in the usage of wearable wireless communication technologies at 1.8 & 2.4GHz and 5 & 8.9GHz band of frequencies, investigations on the human body interaction with these devices are becoming important. This paper provides a microstrip-based multi-band monopole antenna for body Wearable Wireless Devices (WWD), covering licensed and license-free wireless technologies at UHF/UWB when placed on human body. Five parts of the body were considered to evaluate the electromagnetic (EM) effects on the body. Specific Absorption Rate (SAR) values were found to range from 0.09-0.25 W/kg by using numerical modeling. The thermal effects were investigated experimentally using infrared thermography, and temperature changes not exceeding 1°C were noticed. Analyses of numerical, simulated and experimental results show that infrared thermography, a temperature-based technique, can be used to evaluate the compliance of WWDs with safety exposure limits for various wireless applications.
60 GHz radio link characteristic studies in hallway environment using antipodal linear tapered slot antenna
Article, IET Microwaves, Antennas and Propagation, 2015, DOI Link
View abstract ⏷
Millimetre-wave (MmW) frequencies offer large bandwidth with which gigabit data rates can be easily achieved with simple radio architectures. At MmW frequencies, the short wavelength enables integration of the antenna on the same chip as the microwave monolithic integrated circuits. This research work emphasises on the design and development of antipodal linear tapered slot antenna (ALTSA) using substrate integrated waveguide (SIW) technique and its radio link characteristics at 60 GHz for wireless local area network and wireless personal area network applications. SIW feeding technique is used to eliminate the unwanted radiations from feed. The proposed antenna is designed and simulated using three-dimensional (3D) electromagnetic tools. Radio propagation is profoundly site specific and depends on frequency of operation, interference from surroundings and other dynamic factors. To predict signal strength, delay and achievable data rates, it is important to characterise the radio channel. The radio link study is carried out using ALTSA with radio frequency measurement equipment to measure and characterise propagation channels in narrow hallway environment at 60 GHz.
Design of a Quad Band Microstrip Antenna for Wearable Wireless Devices and investigations on substrate types and performance at various body sites
Conference paper, Proceedings of the International Conference on Computing and Communications Technologies, ICCCT 2015, 2015, DOI Link
View abstract ⏷
This work proposes a novel Quad Band Microstrip Antenna for Body Wearable Wireless Devices (BWWD). The designed antenna finds immense applications in general health monitoring utilizing wearable devices, sports health monitoring and observing military personnel in war field where monitoring bio-signals is the prime objective. Ultra high frequency (UHF) and Ultra wide band (UWB) technology adequately meet power, size and distance considerations for WBANs. The antenna designed operates at quad bands, resonating at 1.8 GHz, 2.4 GHz, 5.0 GHz and 8.9 GHz when placed on human body. They are the de-licensed, GSM, Wi-Fi and UWB. The antenna design considers the interaction of body tissues with the electromagnetic (EM) fields, which is different when compared to free space. The performance of the antenna is investigated at different places on the body and for different type of substrates. Most common and comfortable sites on body are chosen as anatomical sites for placement of WWD. A simplified, human body tissue layer model that is frequency dependent in its properties is used for simulations. Simulations are carried out using EM analysis tools.
Millimeter wave dielectric loaded exponentially tapered slot antenna array using substrate integrated waveguide for gigabit wireless communications
Article, Hongwai Yu Haomibo Xuebao/Journal of Infrared and Millimeter Waves, 2015, DOI Link
View abstract ⏷
A new and upcoming application is the use of 60 GHz antennas for high date rate point-to-point connections to serve Gigabit (Gi-Fi) wireless communications. The design of Millimeter wave (MmW) antennas has to cope with the unadorned influences of manufacturing tolerances and losses at 60 GHz. In this paper, the concept of Substrate Integrated Waveguide (SIW) and Exponentially Tapered Slot (ETS) antenna were used together to design a high gain, efficient planar dielectric loaded antenna for MmW Gi-Fi wireless communications at 60 GHz. The SIW is used to feed the antenna and a dielectric is utilized in front of the antenna to increase the gain. The dielectric loaded ETS antenna and compact SIW feed were fabricated on a single substrate, resulting in low cost and easy fabrication. The antenna with elliptical shaped dielectric loaded was fabricated using printed circuit board process. The measured gain of the single element antenna is 10.2 dB, while the radiation efficiency of 96.84% is obtained at 60 GHz. The Y-junction SIW power divider is used to form a 1×4 array structure. Measured gain of the 1 × 4 array antenna is 13.3 dB, while the measured radiation pattern and gain are almost constant within the wide bandwidth of the antenna.
Planar High Gain Dielectric Loaded Exponentially Tapered Slot Antenna for Millimeter Wave Wireless Communications
Article, Wireless Personal Communications, 2015, DOI Link
View abstract ⏷
A new and upcoming application is the use of millimeter wave (MmW) antennas for high date rate point-to-point connections to serve gigabit (Gi-Fi) wireless communications. The concept of substrate integrated waveguide (SIW) and exponentially tapered slot (ETS) antenna are used together design a high gain, efficient planar dielectric loaded antenna for MmW Gi-Fi wireless communications at 60 GHz. The SIW is used to feed the antenna and a dielectric loading is utilized in front of the antenna to increase the gain. The dielectric loaded ETS antenna and compact SIW feed are fabricated on a single substrate, resulting in low cost and easy fabrication. The antenna with elliptical shaped dielectric loaded is fabricated using printed circuit board process. The measured gain of the antenna is 11.4 dB, while the radiation efficiency of 96.84 % is obtained at 60 GHz. The measurement results are compared with simulated results.
A switched beam antenna array with butler matrix network using substrate integrated waveguide technology for 60 GHz communications
Conference paper, 2015 International Conference on Advances in Computing, Communications and Informatics, ICACCI 2015, 2015, DOI Link
View abstract ⏷
A switched beam antenna array based on substrate integrated waveguide (SIW) technology is designed and simulated for 60 GHz communications. The antenna array is fed by 4×4 planar butler matrix network in order to achieve the switched beam characteristic. The use of SIW technology offers a low cost and a planar design. Each of the components is designed and verified through simulations in electromagnetic field simulation tool, CST MWS. The components are integrated later to form the switched beam antenna array. The return losses and isolations are lower than -10 dB from 57 GHz to 64 GHz for all of the input ports. The peak gain for the switched beam antenna array is 16 dBi at 60 GHz.
Design of a novel microstrip-fed UWB fractal antenna for Wireless Personal Area communications
Conference paper, 2015 International Conference on Advances in Computing, Communications and Informatics, ICACCI 2015, 2015, DOI Link
View abstract ⏷
A novel microstrip-fed fractal antenna is designed and fabricated to achieve the desired Ultra Wideband (UWB) features for Wireless Personal Area Network (WPAN) communication applications. The proposed antenna comes with a compact size of 34×32×1.6 mm3 and design simulations executed utilizing 3D Electromagnetic (EM) tool and its prototype is validated using Radio Frequency (RF) equipment. The antenna operates over the entire UWB band with nearly omnidirectional radiation patterns and observed a maximum gain of 4.83 dB with an impedance bandwidth of 7.90 GHz. Further, simulations have also done for 1 × 2 antenna array for better gain and performance.
Indoor radio link characterization studies for millimeter wave wireless communications utilizing dielectric-loaded exponentially tapered slot antenna
Article, Journal of Electromagnetic Waves and Applications, 2015, DOI Link
View abstract ⏷
A trend that is pragmatic in todays wireless communications is the demand for the supportof increasing data rates over short distances. Through the last decade, ample knowledge about the 60 GHz millimeter wave (MmW) channel has been gathered and different architectures have been analyzed to develop MmW communication systems for commercial applications. The usage of MmW frequencies is perceived as a resilient entrant for realizing future, gigabit wireless communications as it offer vast bandwidths for short-range indoor communications. In this work, the MmW antenna solutions for exponentially tapered slot (ETS) antenna using substrate integrated waveguide (SIW) technology and indoor radio wave propagations are studied at 60 GHz for wireless communications. The SIW is used to feed the antenna, and a dielectric loading is utilized in front of the antenna to increase the gain. The antenna with elliptical-shaped dielectric loaded is fabricated using printed circuit board process. The measurement results are compared with simulated results. Then, the indoor short-range radio wave propagation study is carried out using ETS antenna with RF measurement equipment to measure and model propagation channels at 60 GHz. The attained simulations are compared to the experimental results.
Radio frequency transceiver architecture energy efficiency analysis for wireless sensor communications
Vasanthi M.S., Rao T.R., Prasad M.A.
Article, Journal of Circuits, Systems and Computers, 2015, DOI Link
View abstract ⏷
Wireless Sensor Network (WSN) Communications technology enables the sensor nodes to observe, identify, understand and respond to changes in surrounding environment. Many of the communication devices for WSN have power constraints, due to their small size and the requirement to operate off small batteries for long periods of time. Thus energy efficiency is an important design criterion. Since energy consumption in the transceiver front ends is dominant, the focus is on reducing the energy consumption on the system level. In this research article the energy model for the alternating quadrature differential binary phase shift keying (AQ-DBPSK) modulation-based transceiver is developed and compared with the energy models for various transceiver architectures, popularly used in WSN nodes. Its suitability for energy efficient operations in WSN applications is investigated in this research article. Through theoretical analysis and simulated results, we discuss how to select the energy efficient transceiver front end for various WSN application scenarios.
High gain dielectric loaded exponentially tapered slot antenna array based on substrate integrated waveguide for V-band wireless communications
Article, AEU - International Journal of Electronics and Communications, 2015, DOI Link
View abstract ⏷
The conception of substrate integrated waveguide (SIW) technology and exponentially tapered slot (ETS) antenna are together used to design a high gain, and efficient planar dielectric loaded antenna for V-band wireless communications. SIW is used to feed the proposed antenna. To increase the gain of the antenna, a dielectric loaded portion is used in front of the antenna and works as a dielectric guiding structure. The dielectric loaded ETS antenna and compact SIW feed are fabricated on a single substrate, resulting in low cost and easy fabrication. The antenna with elliptical shaped dielectric loaded is fabricated using printed circuit board process. The measured gain of the single element antenna is 10.2 dB, while the radiation efficiency of 96.84% is obtained at 60 GHz. The Y-junction SIW power divider is used to form a 1×2 array structure. Measured gain of the 1×2 array antenna is 11.2 dB, while the measured radiation pattern and gain are almost constant within the wide bandwidth of the antenna.
Performance investigations with antipodal linear tapered slot antenna on 60ghz radio link in a narrow hallway environment
Article, Progress In Electromagnetics Research C, 2015, DOI Link
View abstract ⏷
The performance of wireless communication systems is predominantly dependent on propagation environment and respective radiating antennas. Due to the shorter wavelength atMillimeter Wave (MmW) frequencies, the propagation loss through surroundings in indoor environments is typically very high. To improve the channel capacity and to reduce inter-user interference, a high gain directional antenna is desired at MmW frequencies. Traditional antennas used in MmW devices are not suitable for low-cost commercial devices due to their heavy, bulky and expensive configurations. This paper focuses on design and development of a very compact (44.61mm × 9.93mm × 0.381mm) high gain Antipodal Linear Tapered Slot Antenna (ALTSA) utilizing Substrate Integrated Waveguide (SIW) technology at 60 GHz. Received signal strength (RSS), path loss (PL) and capacity are studied for MmW based wireless applications utilizing electromagnetic (EM) computations and Radio Frequency (RF) experiments in narrow hallway environment.
Near-floor short-range radio link measurements and modelling at 915/2400 MHz in indoor corridors for wireless sensor networks
Dhanavanthan B., Rama Rao T., Dhanavanthan P.
Article, International Journal of Sensor Networks, 2015, DOI Link
View abstract ⏷
The advancement in wireless communication and sensor technologies has made it necessary to understand and predict the radio frequency (RF) propagation losses at near-floor and short-range for low powered, randomly deployable wireless sensor communications/networks. Very few models exist for planning and deployment of randomly deployable wireless sensor networks (WSNs). Most of them require extensive mathematical calculations and an in-depth knowledge of the environment. A simple linear regression (LR) based model for near-floor, short-range in indoor corridor environments in a high raised building for Wireless Sensor Communication is proposed using received signal strength (RSS) measurements at 915 and 2400 MHz utilising RF equipment and Matlab simulations. On the basis of the results of repeated measurements and modelling, the proposed LR model is observed to be suitable for prediction of short-range, near-floor path loss (PL) in line-of-sight (LoS) conditions at very low antenna heights in indoor corridors.
Trust-based backpressure routing in wireless sensor networks
Venkataraman R., Moeller S., Krishnamachari B., Rao T.R.
Article, International Journal of Sensor Networks, 2015, DOI Link
View abstract ⏷
In this paper, we apply a vector autoregression (VAR) based trust model over the backpressure collection protocol (BCP), a collection mechanism based on dynamic backpressure routing in wireless sensor networks (WSNs). The backpressure scheduling is known for being throughputoptimal. In the presence of malicious nodes, the throughput optimality no longer holds. This affects the network performance in collection tree applications of sensor networks.We apply an autoregression based scheme to embed trust into the link weights, so that the trusted links are scheduled. We have evaluated our work in a real sensor network testbed and shown that by carefully setting the trust parameters, substantial benefit in terms of throughput can be obtained with minimal overheads. Our results show that even when 50% of network nodes are malicious, VAR trust offers approximately 73% throughput and ensures reliable routing, with a small trade-off in the end-to-end packet delay and energy consumptions.
High gain dielectric loaded exponentially tapered slot antenna based on substrate integrated waveguide for V-Band wireless communications
Article, Applied Computational Electromagnetics Society Journal, 2014,
View abstract ⏷
The conception of Substrate Integrated Waveguide (SIW) technology and Exponentially Tapered Slot (ETS) antenna are together used to design a high gain, and efficient planar dielectric loaded antenna for V-band wireless communications. To increase the gain of the antenna, a dielectric loaded portion is used in front of the antenna which works as a dielectric guiding structure and SIW is used to feed the proposed antenna. The dielectric loaded ETS antenna and compact SIW feed are fabricated on a single substrate, resulting in low cost and easy fabrication. The antenna with elliptical shaped dielectric loaded is fabricated using printed circuit board process. The measured gain of the single element antenna is 10.2 dB, while the radiation efficiency of 96.84% is obtained at 60 GHz. The Y-junction SIW power divider is used to form a 1×2 array structure. Measured gain of the 1×2 array antenna is 11.2 dB, while the measured radiation pattern and gain are almost constant within the wide bandwidth of the antenna.
Toward a smart, fully connected society: An overview of the 32nd meeting of the Wireless World Research Forum
Friderikos V., Helard M., Porras J., Rao T.R.
Editorial, IEEE Vehicular Technology Magazine, 2014, DOI Link
Circularly polarized dual band micro strip patch antenna for vehicular wireless network communications
Conference paper, 2014 IEEE International Conference on Advanced Networks and Telecommunication Systems, ANTS 2014, 2014, DOI Link
View abstract ⏷
A circularly polarized dual band micro strip patch antenna for vehicular wireless communication at 2.45 GHz and 5.5 GHz is designed and studied its performance. To obtain the circular polarization, slots have been introduced at the sides of the rectangular patch. Axial Ratio bandwidth of 700 MHz and 230 MHz at lower (1.9 GHz-2.6 GHz) and higher (5.4 GHz-5.63 GHz) frequency bands are observed using electromagnetic (EM) simulation tools. The proposed antenna gives 2.24 dB at 2.45 GHz and 4.97 dB gain at 5.5 GHz and impedance bandwidth of 320 MHZ at 2.4 GHz band and 450 MHz at 5 GHz band. Omnidirectional radiation pattern, improved Circular polarization, small dimensions and low cross polarization at both bands make this antenna particularly suitable for vehicular wireless communication networks.
A microstrip antenna at UWB frequencies for body wearable wireless devices
Conference paper, 2014 IEEE International Conference on Advanced Networks and Telecommunication Systems, ANTS 2014, 2014, DOI Link
View abstract ⏷
This paper proposes a novel Microstrip Antenna for body Wearable Wireless Devices (WWD) used for monitoring bio signals in human body. The antenna finds immense application in health monitoring utilizing WWD in Sports, Medicine and monitoring military personnel where monitoring bio- signals is the prime objective. Ultra wide band (UWB) technology adequately meets power, size and distance considerations for WBANs. The antenna designed operates at dual bands, 4.2-4.9 GHz and at 7.6-8.4 GHz within the unlicensed UWB spectrum (3.1-10.6 GHz). The antenna design also considers the difference in interaction of body tissues with the electromagnetic (EM) fields. The performance of the antenna is studied and analyzed at different places on the body in terms of radiation efficiency, total gain and Specific Absorption Rate (SAR). The anatomical positions for WWD are chosen considering the most common and comfortable sites on body. A simplified, human body tissue layer model that is frequency dependent in its properties is used for simulations. Simulations are carried out using EM simulation analysis tools.
Analysis of planning and deployment issues for short-range gigabit wireless communications at 60 GHz
Article, International Journal of Microwave and Optical Technology, 2014,
View abstract ⏷
This research work targets to address the needs of next generation wireless technology for Wireless Local Area Networks (WLAN) and Wireless Personal Area Networks (WPAN) including multimedia equipment, utilizing short-range Gigabit Radios at 60 GHz. The issues involved in planning and deployment of wireless communications operating at 60 GHz are examined in this paper by analyzing the radio channel propagation characteristics in typical indoor environments such as Narrow Straight Corridor (NSC) and Class Room (CR). This study includes several onsite measurements using 60 GHz transmitter/receiver modules and modeling of similar environments using full 3-D Ray-tracing simulations of Remcom's Wireless InSite and XGtd. It is observed from the performed analysis that the architectural design and dimensions of the indoor environments play a vital role in the Received Signal Strength (RSS) where the observed Path Loss Exponent (PLE) value is found to be 2.11 to 2.25 for NSC and 1.92 to 2.13 for CR within an operating space of 10 m. It is also witnessed that the maximum Specific Absorption Rate (SAR) value at the receiver is 0.2*10-05 W/kg for 1 gm of brain tissue for WLAN/WPANs at 60 GHz. © 2014 IAMOT.
AQ-DBPSK modulation performance analysis for wireless sensor communications
Vasanthi M.S., Kumar D., Rama Rao T.
Article, WSEAS Transactions on Communications, 2014,
View abstract ⏷
Wireless sensor nodes have a limited amount of energy resource that determines their lifetime. So, Energy efficient modulation techniques are of paramount importance for wireless sensor communication (WSC). Also the type and behavior of the pulse shaping filters used, influences the performance of the modulation scheme. The Alternating Quadratures Differential Binary Phase Shift Keying (AQ-DBPSK) modulation scheme which is a variation of the Differential Binary Phase Shift Keying (DBPSK) scheme is simulated and a comparative study of communication performance metrics like Magnitude Error, Phase Error, Bandwidth Efficiency and Bit Error Rate (BER) for Binary Phase Shift Keying (BPSK), DBPSK and AQ-DBPSK using Raised Cosine and Root Raised Cosine filters are presented and analyzed. The results obtained show that tradeoffs can be made between spectral efficiency and energy efficiency by selecting the proper modulation scheme and using the appropriate value of excess bandwidth for the pulse shaping filter.
A novel energy metric for optimal energy efficient sensor communications
Vasanthi M.S., Rama Rao T., Swetha K.
Article, International Review on Computers and Software, 2014,
View abstract ⏷
As low powered, battery operated nodes are used in wireless sensor networks, conservation of energy at all levels of system design is very essential. In this paper, we focus on the efficient transmission of data over a noisy channel by selecting optimal energy efficient values for the physical layer parameters. We introduce an energy metric called "Effectually Received bit Energy" (ERE) which is the amount of energy spent in a successful transmission over a given channel. By minimizing this metric, we find the optimum hop distance and optimal transmit energy for different modulation schemes. The results which are obtained in this paper can be useful to the network designers for selecting the suitable hop distance, transmit energy and the modulation scheme that will help in maximizing the lifetime of the network. © 2014 Praise Worthy Prize S.r.l. - All rights reserved.
A novel smiley fractal antenna (SFA) design and development for UWB wireless applications
Article, Progress In Electromagnetics Research C, 2014, DOI Link
View abstract ⏷
Ultra Wideband (UWB) has been deliberated as a promising technology for short-range wireless communication with large unlicensed frequency band for commercial, enterprise private and public uses. Designing an antenna of compact size for portable wireless devices is one of the challenges especially for UWB based wireless communication technologies. In this paper, a novel Smiley Fractal Antenna (SFA), employed with N-notch feed and modified ground plane, is designed and developed to achieve the desired characteristics. The proposed antenna is of compact size with dimensions of 34×32×1.6mm3, fabricated on an FR-4 substrate with εr = 4.4. The radiation pattern of the proposed antenna is omnidirectional with a maximum gain of 4.83 dB and efficiency of 93.55% obtained through 3D electromagnetic simulation software tools. The simulated results are compared with measured ones using RF equipment. The results obtained show that the proposed SFA is a suitable candidate for variety of UWB wireless communication applications.
A novel fractal antenna design for UWB wireless communications
Susila M., Rao T.R., Gupta A.
Conference paper, IEEE MTT-S International Microwave and RF Conference 2014, IMaRC 2014 - Collocated with Intemational Symposium on Microwaves, ISM 2014, 2014, DOI Link
View abstract ⏷
Ultra Wideband (UWB) has been pondered as a promising technology for short-range wireless communication with large unlicensed frequency band for commercial, military, medical, enterprise private and public uses. A novel fractal antenna is designed to achieve the desired UWB characteristics. The proposed antenna is of compact size with dimension 34×32×1.6 mm3. Analysis of this antenna is done utilizing the 3D Electromagnetic tools. The simulated radiation pattern of the proposed antenna is nearly of Omni-directional with a maximum gain of 4.83dB and efficiency of 93.55%, with impedance bandwidth of 7.90 GHz (3.24 GHz to 11.14GHz). The proposed fractal antenna is well suited for Ultra Wideband (UWB) Wireless Communication Applications.
Near ground path gain measurements at 433/868/915/2400 MHz in indoor corridor for wireless sensor networks
Rama Rao T., Balachander D., Nishesh T., Prasad M.V.S.N.
Conference paper, Telecommunication Systems, 2014, DOI Link
View abstract ⏷
Near to ground radio frequency (RF) propagation path gain (PG) measurements at short distances at antenna height of 50 cm from the ground/floor were made in typical narrow and wide straight indoor corridors at 433/868/915/2400 MHz in a modern multi-storied building. The measurement was performed utilizing RF equipment and comparisons were made with Matlab simulations of ray tracing technique, free space model and ITU-R model along with Full-3D ray tracing model of Wireless Insite (WI) software. Measured PG values showed good agreement with WI in all cases. Path loss exponent (PE) values ranging from 1.22 to 2.13 were observed from the measured data. The research work reported in this paper is predominately geared towards characterizing radio link for wireless sensor networks in typical indoor corridor environments. © 2013 Springer Science+Business Media New York.
Concave lens integrated conical horn at 60 GHz for energy efficient wireless applications
Conference paper, Proceedings of the 2013 International Conference on Advances in Computing, Communications and Informatics, ICACCI 2013, 2013, DOI Link
View abstract ⏷
This paper investigates the development of a concave lens integration concept in a conical horn antenna, and its considerate use in the Received Signal Strength (RSS) enhancement of outdoor based (60 GHz) mm mesh networks. A conical horn antenna is developed in High Frequency Structural Simulator (HFSS) with a gain of 12 dB and Half Power Beam Width (HPBW) of 10° to model the RSS in a street. Ray tracing based model shows that there are only limited paths which are significant for a highly directional link under consideration. The results obtained are modeled in matlab software. Further, when a concave lens is integrated into the same horn antenna an increase of 5 dB in gain is obtained there by increasing the efficiency. With the incorporation of concave lens, gain has increased resulting in a better RSS of mm wave links at similar transmitted power. An analogous street model is developed in Wireless Insite (WI) with similar concave lens antenna dimensions, gain and transmitted power. The simulated result also shows an increment in RSS whose values are comparable with modeled matlab values. The analysis of this approach can be an alternative to the concept of multiple antenna technique and also the energy efficient antenna for WPAN applications. © 2013 IEEE.
In-vehicle RF propagation measurements for electronic infotainment applications at 433/868/915/2400 MHz
Conference paper, Proceedings of the 2013 International Conference on Advances in Computing, Communications and Informatics, ICACCI 2013, 2013, DOI Link
View abstract ⏷
Received Signal Strength (RSS) propagation measurements were made in a vehicular environment (In-Car) at 433/868/915/2400 MHz utilizing RF equipment and Matlab simulations. Path loss and Path loss Exponent values were deduced from the measured RSS from various positions in a Multi Utility Vehicle (MUV). The research work presented in this paper predominately targets characterizing radio link for Wireless Sensor Communications/Networks for in-vehicle electronic infotainment applications at very short-ranges. © 2013 IEEE.
Performance comparison study of AQ-DBPSK modulation scheme for energy efficient wireless sensor communications
Vasanthi M.S., Kumar D., Rama Rao T.
Conference paper, Proceedings of the 2013 International Conference on Advances in Computing, Communications and Informatics, ICACCI 2013, 2013, DOI Link
View abstract ⏷
Transceivers with low energy consumption are indispensable components for wireless sensor networks. Energy efficient modulation techniques are of paramount importance for wireless sensor communication (WSC) where energy efficiency directly affects the lifetime of the sensor nodes. Also the type and behavior of pulse shaping filters influences the performance of the modulation scheme. In this paper an energy efficient modulation scheme, AQ-DBPSK for WSC in indoor environments is simulated and its performance is analyzed for Additive White Gaussian Noise (AWGN) and Rayleigh fading conditions. A comparative study of communication performance metrics like Magnitude Error, Phase Error, Bandwidth Efficiency and Bit Error Rate (BER) for BPSK, DBPSK and AQ-DBPSK using Raised Cosine and Root Raised Cosine filters are presented and analyzed. © 2013 IEEE.
Investigations on AQ-DBPSK modulation based RF transceiver for wireless sensor communication networks
Article, WSEAS Transactions on Circuits and Systems, 2013,
View abstract ⏷
This research work demonstrates the simulation results of a Radio Frequency (RF) transceiver with Alternate Quadrature Differential Binary Phase Shift Keying (AQ-DBPSK) modulation at 2.4GHz. The RF transmitter consists of an AQ-DBPSK modulator, an up conversion mixer, a 2.4 GHz Band pass filter and a power amplifier. At the receiver RF front end, the Low Noise Amplifier (LNA), mixer with down conversion to Intermediate Frequency (IF), a Low Pass Filter (LPF) and an AQ-DBPSK demodulator is used. The block level parameters of the transmitter and receiver RF front end like Noise Figure (NF) and Gain are optimized to meet the transceiver specifications for the applications in Wireless Sensor Communication Networks.
Trust management and modeling techniques in wireless communications
Venkataraman R., Pushpalatha M., Rama Rao T.
Book chapter, Security, Privacy, Trust, and Resource Management in Mobile and Wireless Communications, 2013, DOI Link
View abstract ⏷
Trust management is an emerging technology to facilitate secure interactions between two communicating entities in distributed environments where the traditional security mechanisms are insufficient due to incomplete knowledge about the remote entities. With the development of ubiquitous computing and smart embedded systems, new challenges and threats come up in a heterogeneous environment. Trust management techniques that depend on a centralized server are not feasible in wireless peer-to-peer communication networks. Hence, the trust management and modeling strategies are becoming increasingly complex to cope with the system vulnerabilities in a distributed environment. The aim of this chapter is to have a thorough understanding of the trust formation process and the statistical techniques that are used at different stages of the trust computation process. The functional components of a trust management framework are identified and some of the existing statistical techniques used in different phases of the trust management framework are analyzed.
Implementation of a trust model over OLSR in a wireless Ad Hoc testbed
Gaurav C., Chandramouleeswaran D., Khanam R., Venkataraman R., Pushpalatha M., Rao T.R.
Conference paper, Proceedings of the 2013 2nd International Conference on Information Management in the Knowledge Economy, IMKE 2013, 2013,
View abstract ⏷
The concept of a customized Optimized Link State Routing (OLSR) protocol with focus on augmented security protecting a node against blackhole and flooding attacks launched by its neighbor nodes in the network by implementing a trust model is described in this paper. This trust model is a computational variable that dictates the behavior of the node to protect itself against malicious attack in a robust and intelligent manner. We have also developed a testbed that evaluates the resultant deportment of the node in real time and generates user friendly analysis reports. Through real time test runs, we have concluded results favoring our proposal in the following network measures of throughput, end to end delay and overhead. The throughput was found to be 70% better in real time ad hoc testbed which has been designed to have 25% blackhole and flooding nodes respectively. The overhead encountered was minimal despite the end to end delay of packets being higher than the traditional OLSR by 30 msec. Our work is also the first ever implementation of a trust model over an ad hoc routing protocol in a real ad hoc testbed.
Analysis of planning and deployment issues for short range Gigabit radio’s at 60 GHz
Conference paper, International Conference on Communication and Signal Processing, ICCSP 2013 - Proceedings, 2013, DOI Link
View abstract ⏷
This research work targets to address the needs of new generation wireless technology for Wireless Local Area Networks (WLAN) and Wireless Personal Area Networks (WPAN) including high-performance personal computers (pes) and multimedia equipment, utilizing short-range Gigabit Radios at 60 GHz. The issues involved in planning & deployment of wireless communications system functional at 60 GHz were analyzed in this paper by analyzing radio channel propagation characteristics in typical indoor environments. This study includes several onsite measurements using 60 GHz transmitter/receiver modules and modeling of similar environments using full 3-D Ray-tracing simulations of Remcom's Wireless InSite and XGtd. Values of the Received Signal Strength (RSS) and path loss using horn antennas are presented along with the values of path loss exponent, channel capacity and number of access points inferred from the measurements/simulations to support high quality wireless multimedia data transmissions. This study also attempts to present the amount of attenuation in the indoor environment and to infer the values of Specific Absorption Rate (SAR) for brain tissues based on the RSS at 60 GHz. © 2013 IEEE.
Dielectric loaded exponentially tapered slot antenna for 60GHz wireless networks
Conference paper, International Conference on Communication and Signal Processing, ICCSP 2013 - Proceedings, 2013, DOI Link
View abstract ⏷
This paper deals with the dielectric loaded Exponentially Tapered Slot (ETS) antenna needed for ultra-high-speed, ultra high-capacity wireless communication systems which work at 60 GHz for wireless communication networks applications and illustrates its specifications and requirements. The antenna in such systems requires high gain, high-efficient and high performance design specifications. The ETS antenna and the loaded dielectric are integrated by using the same single substrate resulting in easy fabrication and low cost. The ETS antenna with rectangular and elliptical shaped loaded dielectrics were designed and fabricated. These antennas have high gain and narrow beamwidths both in the E-plane and in the H-plane. The designed antenna is simulated using 3D electromagnetic software CST Microwave Studio and made comparison with Ansys HFSS to validate the design procedure. The results from the simulations and those from the measurements are in good agreement. © 2013 IEEE.
In-vehicle RF propagation measurements for Wireless Sensor Networks at 433/868/915/2400MHz
Balachander D., Rao T.R., Tiwari N.
Conference paper, International Conference on Communication and Signal Processing, ICCSP 2013 - Proceedings, 2013, DOI Link
View abstract ⏷
Received Signal Strength (RSS) propagation measurements were made in a vehicular environment (In-Car) at 433/868/915/2400 MHz utilizing RF equipment and Matlab simulations. Path loss and Path loss Exponent values were deduced from the measured RSS from various positions in a Multi Utility Vehicle (MUV). The research work presented in this paper predominately targets characterizing radio link for Wireless Sensor Communications/Networks for vehicular environments at very short-ranges. © 2013 IEEE.
Design & simulation of energy efficient AQ-DBPSK based RF transmitter for wireless sensor networks
Dash S., Vasanthi M.S., Rao T.R.
Conference paper, International Conference on Communication and Signal Processing, ICCSP 2013 - Proceedings, 2013, DOI Link
View abstract ⏷
The system level design and simulation results of an energy efficient 2.4 GHz Radio Frequency (RF) transmitter is being presented in this research paper. RF transmitter consisting of an Alternating Quadrature Differential Binary Phase Shift Keying (AQ-DBPSK) modulator, an up conversion mixer, band pass filter and a power amplifier are proposed in this work. The AQ-DBPSK technique is used as it increases the efficiency of the transmitter power utilization. In the transmitter the AQ-DBPSK signal is converted to 2.4 GHz by using a direct conversion I/Q up converter. The design presented focuses on the determination of optimum performance of transmitter by considering factors such as power consumption, output power and noise factor. © 2013 IEEE.
Design of Antipodal Linear Tapered Slot Antenna using SIW at 60GHz for Gigabit Wireless communications
Chandra D., Shrivastava P., Rao T.R.
Conference paper, International Conference on Communication and Signal Processing, ICCSP 2013 - Proceedings, 2013, DOI Link
View abstract ⏷
The family of tapered slot antennas (TSA), has good electrical performance including gain, relatively low side lobes, a circular symmetric main beam and practically constant impedance over a broad frequency band. Fabrication on thin, flexible substrates allows the TSA to be conformed over a given body, such as an aircraft wing or a piece of clothing for wearable network. Impedance matching is a major issue in this type of antenna and to surmount the impedance matching difficulty, a TSA with antipodal geometry is introduced in this present work. One of the advantages of the antipodal geometry is that the designer does not need to layout any stubs on the Printed Circuit Board (PCB) to achieve impedance matching. Substrate Integrated Waveguide (SIW) feeding technique allows us to design all the attributes of antenna system upon a common substrate and provides a high Q-factor. Therefore, this study focuses on the design of Antipodal Linear Taper Slot Antenna (ALTSA) with SIW technique using CST Microwave Studio (CST MWS) simulation tool to provide a detailed simulations operating at 60 GHz. The size of the proposed antenna is very compact (44.61mm × 9.93mm × 0.381mm) and the substrate used is RT/DUROID 5880. © 2013 IEEE.
Ultra wide band Twin Eleven slot patch antenna for bandwidth enhancement
Vidya J.S., Shrivastava P., Susila M., Rao T.R.
Conference paper, International Conference on Communication and Signal Processing, ICCSP 2013 - Proceedings, 2013, DOI Link
View abstract ⏷
New design of a microstrip patch antenna with Twin Eleven shaped slot is presented that achieves a minimum impedance bandwidth of 37.931%. The Twin Eleven shaped slot increases the bandwidth and reduces the complication of design to a very high extent while compared to other slot geometries due to the similarity in the shape of slots that are made on the patch. The proposed antenna is designed for the 5 GHz ISM band and is designed and simulated by the electromagnetic simulation software HFSS. The VSWR curve and the radiation patterns are also demonstrated in this paper in which the importance is given to the antenna bandwidth. © 2013 IEEE.
RF propagation investigations in agricultural fields and gardens for wireless sensor communications
Balachander D., Rao T.R., Mahesh G.
Conference paper, 2013 IEEE Conference on Information and Communication Technologies, ICT 2013, 2013, DOI Link
View abstract ⏷
This work reports Received Signal Strength (RSS) at ISM band 2.4 GHz using RF equipment in Agricultural (Corn, Paddy and Groundnut) fields and Gardens (Coconut garden with green grass, open lawn with dry green grass and wet green grass) targeting short-range, near ground RF propagation measurements for planning and deployment of Wireless Sensor Communications in agriculture fields and gardens for precision agriculture and plantation management applications. Path Loss (PL), Path Loss Exponent (PLE) and corresponding Root Mean Square Error (RMSE) values were deduced from the measured RSS from various positions in these environments. Empirical foliage loss prediction models such as COST 235, Early ITU Vegetation and Weissberger models were compared with the experimental results. © 2013 IEEE.
Short-range near-floor RF propagation experiments in indoor corridors for Wireless Sensor Communications
Conference paper, 2013 7th European Conference on Antennas and Propagation, EuCAP 2013, 2013,
View abstract ⏷
Short-range, near-floor Radio Frequency (RF) propagation path loss (PL) measurements at antenna height of 2 cm and 50 cm from the floor were made on Porcelain, Green granite and Plywood covered floors of typical narrow and wide straight indoor corridors at 915/2400 MHz in a modern multi-storied building utilizing RF equipment. Comparisons between measured and simulated PL values were deduced utilizing Matlab simulations of Ray-tracing technique, free space and ITU-R models. Mean path loss exponent (PLE) values were deduced from the measured data. The research work made in this paper is predominately targets characterizing radio link for Wireless Sensor Communications/Networks in typical indoor corridor environments. © 2013 EurAAP.
Investigations of corrugation issues in SIW based Antipodal Linear Tapered Slot Antenna at 60 GHz
Rao T.R., Shrivastava P., Tiwari N.
Conference paper, 2013 7th European Conference on Antennas and Propagation, EuCAP 2013, 2013,
View abstract ⏷
In recent days, Substrate Integrated Waveguide (SIW) technology is attracting a lot of interest in the development of Millimeter-wave (MmW) based circuits due to its inherent advantages. This paper focuses on the design of Antipodal Linear Tapered Slot Antenna (ALTSA) using SIW technique for Wireless Local Area Network (WLAN) and Wireless Personal Area Network (WPAN) applications. The feeding is based on SIW structure which provides high Q-factors and allows planar printed circuit board fabrication process. In this paper ALTSA at 60 GHz without corrugation and with inner and outer rectangular corrugation have been discussed and compared with traditional structure with the new corrugated structures. It is noticed that, the proposed ALTSA designs are having better front to back ratio (F/B) and radiation patterns. Though, such developments have been reported earlier in other frequency bands, rarely any literature have reported of such developments at 60 GHz band. © 2013 EurAAP.
RF propagation measurements in agricultural fields for Wireless Sensor Communications
Mahesh G., Balachander D., Rao T.R.
Article, Proceedings of IEEE International Conference on Circuit, Power and Computing Technologies, ICCPCT 2013, 2013, DOI Link
View abstract ⏷
This work reports Received Signal Strength (RSS) at ISM band 2.4 GHz using Digi's XBee-PRO ZB S2B transceiver modules with integrated whip antenna in Agricultural (Corn, Paddy and Groundnut) fields targeting short-range, near ground RF propagation measurements for planning and deployment of Wireless Sensor Communications/Networks in agriculture fields for precision agriculture and plantation management applications. Path Loss (PL), Path Loss Exponent (PLE) and corresponding Root Mean Square Error (RMSE) values were deduced from the measured RSS from various positions in these environments during crop growth and maturity stages. Empirical foliage loss prediction models such as COST 235, Early ITU Vegetation and Weissberger models were compared with the experimental results. © 2013 IEEE.
Analysis of AQ-DBPSK modulation for WSN transceivers in indoor environments
Vasanthi M.S., Kumar D., Rama Rao T.
Conference paper, 2013 International Conference on Information Communication and Embedded Systems, ICICES 2013, 2013, DOI Link
View abstract ⏷
Energy efficient modulation techniques are of paramount importance for wireless sensor communication where energy efficiency directly affects the lifetime of the networks. Transceivers with low energy consumption are indispensable components for wireless sensor networks. The main objective of this paper is to simulate AQ-DBPSK modulation scheme and analyze its performance for wireless sensor communication in indoor environments under Additive White Gaussian Noise channel and Raleigh fading conditions. Also a direct conversion transmitter architecture using AQ-DBPSK modulation at 2.4GHz is simulated. © 2013 IEEE.
RF propagation investigations at 915/2400MHz in indoor corridor environments for wire-less sensor communications
Article, Progress In Electromagnetics Research B, 2013, DOI Link
View abstract ⏷
Propagation of Radio Frequency (RF) waves in indoor corridors is very complex and diverse as the propagation effects in the indoor scenarios are those that change over fractions of wavelength. Therefore, understanding of RF propagation characteristics is vital for the design of air interface and estimation of propagation losses is very much needed especially for wireless networks such as randomly deplorable Wireless Sensor Communications. In this research work, short-range, near floor/ground RF propagation path loss measurements at low antenna heights of 2 cm and 50 cm from the floor were made in typical narrow and wide straight indoor corridors at 915/2400MHz in a modern multi-storied building utilizing RF equipment. Comparisons between measured and simulated path loss values were made utilizing Matlab simulations of Ray-tracing technique, free space and ITU-R models. Mean path loss exponent values were deduced from the measured data. The research work reported in this paper is predominately geared towards characterizing radio link for Wireless Sensor Communications/Networks in typical indoor corridor environments.
Ultra-high frequency near-ground short-range propagation measurements in forest and plantation environments for wireless sensor networks
Rao T.R., Balachander D., Tiwari N., Prasad M.V.S.N.
Article, IET Wireless Sensor Systems, 2013, DOI Link
View abstract ⏷
The growing interest in applications of wireless sensor networks (WSNs) in vegetation environment has made it important to understand and predict the impact of vegetation on coverage and signal quality. As most of the proposed vegetation attenuation models are mainly based on measurements in temperate climate their prediction accuracy needs to be tested in tropical climate. With the presence of high humidity and high temperature in the tropical climate the attenuation because of vegetation is bound to increase. Very few researches have been reported about the attenuation because of vegetation related to WSN applications in scrub forest and plantation environments from the regions having tropical climate in Indian subcontinent. This study focuses on short-range, near to ground received signal strength measurements at 915 and 2400 MHz to evaluate vegetation attenuation models for planning and deployment of wireless sensor communications/ networks in tropical climate for precision agriculture and plantation management applications. The measurements have been done in scrub forest, mango and guava plantation environment. It is found that International Telecommunication Union (ITU) Recommendation (ITU-R) and Weissberger models under predict vegetation because of attenuation, whereas the Cost 235 model has high prediction accuracy in the scrub forest and plantation environments in tropical climate. © The Institution of Engineering and Technology 2013.
Dielectric loaded exponentially tapered slot antenna utilizing substrate integrated waveguide technology for millimeter wave applications
Article, Progress In Electromagnetics Research C, 2013, DOI Link
View abstract ⏷
A novel compact dielectric loaded Exponentially Tapered Slot (ETS) antenna using Substrate Integrated Waveguide (SIW) technology is presented in this paper for Millimeter (Mm) wave wireless communication applications. The dielectric loaded ETS antenna and compact SIW feed are fabricated on a single substrate. The compact SIW feeding structure results in a considerable reduction in size and eliminates the unwanted radiations from feed. The proposed antenna is designed, fabricated, and investigated at 60 GHz. Furthermore, the proposed antenna design is simulated using electromagnetic software CST Microwave Studio and the comparison is made with Ansys HFSS to validate the design procedure. The measurement results are compared with simulated results.
Energy efficient AQ-DBPSK based RF transceiver for wireless sensor networks
Conference paper, 2013 IEEE International Conference on Advanced Networks and Telecommunications Systems, ANTS 2013, 2013, DOI Link
View abstract ⏷
This research work addresses simulation results of a 2.4GHz Radio Frequency (RF) transceiver with Alternate Quadrature Differential Phase Shift Keying (AQ-DBPSK) modulation at 1 Mbps. The RF transmitter consists of an AQ-DBPSK modulator, an up conversion mixer, a 2.4 GHz Band pass filter and a power amplifier. At the receiver RF front end, the Low Noise Amplifier (LNA), mixer with down conversion to Intermediate Frequency (IF), a Low Pass Filter (LPF) and an AQ-DBPSK demodulator is used. The block parameters of the transmitter and receiver RF front end like Noise Figure (NF) and gain are simulated and optimized to meet the transceiver specifications targeting wireless sensor networks. © 2013 IEEE.
Dielectric loaded exponentially tapered slot antenna for wireless communications at 60GHz
Article, Progress In Electromagnetics Research C, 2013, DOI Link
View abstract ⏷
This paper deals with the dielectric loaded Exponentially Tapered Slot (ETS) antenna needed for ultra-high-speed, high- capacity wireless communication systems which work at 60 GHz and illustrates its specifications and requirements. The antenna in such system requires high gain, high-efficient and high performance design specifications. The ETS antenna and the loaded dielectric are integrated using the same single substrate resulting in easy fabrication and low cost. The ETS antenna with rectangular and elliptical shaped loaded dielectrics were designed and fabricated. These antennas have high gain and wider beamwidth in both E-plane and H-plane. The proposed antenna design is simulated using 3D electromagnetic software CST Microwave Studio and the comparison is made with Ansys HFSS to validate the design procedure. The results obtained from the simulations and the measurements are in good agreement. © 2010 EMW Publishing. All Rights Reserved.
RF propagation experiments in agricultural fields and gardens for wireless sensor communications
Balachander D., Rao T.R., Mahesh G.
Article, Progress In Electromagnetics Research C, 2013, DOI Link
View abstract ⏷
This work presents results for the path loss due to foliage at 2.4 GHz using RF equipment and XBee-Pro ZB S2B transceiver modules in Agricultural fields (Corn, Paddy and Groundnut) and Gardens (Coconut garden with green grass, open lawn with dry green grass and wet green grass) targeting short-range, near ground RF propagation measurements for planning and deployment of Wireless Sensor Communications for precise agriculture and plantation management applications. Path Loss (PL), Path Loss Exponent (PLE) and corresponding Root Mean Square Error (RMSE) values were deduced from the measured RSS from various positions in these environments. Empirical foliage loss prediction models such as COST 235, Early ITU Vegetation and Weissberger models were compared with the experimental results.
Investigations on corrugation issues in SIW based antipodal linear tapered slot antenna for wireless networks at 60 GHZ
Shrivastava P., Chandra D., Tiwari N., Rao T.R.
Article, Applied Computational Electromagnetics Society Journal, 2013,
View abstract ⏷
In recent days, substrate integrated waveguide (SIW) technology is attracting a lot of interest in the development of millimeter-wave (MmW) based circuits due to its inherent advantages. Tapered slot antenna (TSA) with antipodal geometry is used to surmount the impedance matching constraint and to enhance electrical performance including gain, side lobes levels, and main beam pattern. This paper focuses on the design of antipodal linear tapered slot antenna (ALTSA) using SIW technique at 60 GHz for wireless local area network (WLAN) and wireless personal area network (WPAN) applications. The size of the proposed antenna is very compact (43.29 mm × 9.93 mm × 0.381 mm) and the substrate used is RT/ Duroid 5880. Corrugations have been investigated on both the edges to improve antenna gain, front-to-back ratio, and radiation patterns. Numerical simulations are performed using 3D-EM tools, high frequency structure simulator (HFSS) and CST microwave studio (CST MWS). The obtained results reveal that when corrugation is introduced in the antenna there is a significant improvement of 3 dB in gain, respectively. This study has been reported earlier in other frequency bands but rarely any literature has been reported of such development at 60 GHz. © 2013 ACES.
Security issues and models in mobile ad hoc networks
Book chapter, Technological Advancements and Applications in Mobile Ad-Hoc Networks: Research Trends, 2012, DOI Link
View abstract ⏷
This chapter covers issues related to security in mobile ad hoc networks. It acts as a comprehensive survey material covering the cryptographic schemes and trust modeling techniques traditionally found in mobile ad hoc network (MANET) survey articles. The need for hybrid security techniques, involving both cryptographic approach and trust based model, in a resource constrained ad hoc network, is also emphasized in this work. Additionally, the lack of realism in the research works related to ad hoc network security is also pointed out. The state of the art in ad hoc security should employ hybrid techniques that can be easily implemented in an ad hoc network. This will lead to the large scale deployment of mobile ad hoc networks in various context-aware applications. © 2012, IGI Global.
RF transceiver design and simulation for indoor wireless applications
Conference paper, 2012 3rd International Conference on Computing, Communication and Networking Technologies, ICCCNT 2012, 2012, DOI Link
View abstract ⏷
Wireless networks of sensor nodes are envisioned to be deployed in the physical environment to monitor a wide variety of real-world phenomena. Wireless sensor networksare becoming popular in military and civilian applications such as surveillance, monitoring, disaster recovery, home automation and many others. These networks demand low power and low cost transceiver design. The power consumed by node transceiver electronics is non-negligible and has a major impact on battery life. The main objective of this paper is to design a low power transceiver for indoor wireless applications. This transceiver operates at 2.4GHzwith data rates up to 1.0Mbit/s with QPSK modulation. The required transmitter power is -5.0 dBm. The design exhibits a noise figure of 4.2 dB at transmitter side and 4.225 dB at receiver side.The error vector magnitude (EVM) is 9.7% and receiver sensitivity is -95dBm for bit error rate of 10 -3. Agilent Advanced Design System (ADS) is used for design and performance evaluation of our system. © 2012 IEEE.
Indoor corridor radio propagation characteristics at 60 GHz for wireless communications
Conference paper, 2012 3rd International Conference on Computing, Communication and Networking Technologies, ICCCNT 2012, 2012, DOI Link
View abstract ⏷
For the next generation wireless local area networks (WLAN) and wireless personal area networks (WPAN), 60 GHz radio channel propagation characteristics in typical indoor corridor environments are addressed in this paper using Matlab simulations of ray-tracing, ITU-R model and full-3D ray-tracing model of Wireless Insite. Pathloss and rms delay spreadobtained through simulations of models foromnidirectional and horn antennasare presented. © 2012 IEEE.
Microstrip, slotted rectangular waveguide array and Patch-fed rod antenna design and simulation for Gigabit wireless communications at 60 GHz
Conference paper, 2012 3rd International Conference on Computing, Communication and Networking Technologies, ICCCNT 2012, 2012, DOI Link
View abstract ⏷
This paper deals with the design of 2×2 Microstrip, Slotted rectangular waveguide antenna array and Patch-fed rod antennas needed for ultra high-speed, ultra high-capacity wireless communication systems which work at Millimeter waves at 60 GHz for different multimedia applications in indoor environments and illustrates its specifications and requirements. The antenna in such systems requires high gain, high-efficient, wider beamwidth and high performance design specifications. The designed antennas were simulated using electromagnetic software Agilent's EMPro and Ansys HFSS. © 2012 IEEE.
UHF short-range pathloss measurements in forest & plantation environments for wireless sensor networks
Rama Rao T., Balachander D., Tiwari N.
Conference paper, 2012 IEEE International Conference on Communication Systems, ICCS 2012, 2012, DOI Link
View abstract ⏷
This work presents received signal strength at UHF, 868/915/2400 MHz utilizing radio frequency equipment and Matlab simulations in forest and plantation (Mango & Guava) environments. Path loss, path loss exponent, root mean square error and corresponding cumulative distribution function values were deduced from the measured data at various positions in foliage environments using omnidirectional antennas at 1.0 m height from the ground. Empirical foliage loss prediction models such as COST 235, ITU-R and Weissberger models were compared with the experimental results. The research work reported in this paper is predominately targeted towards characterizing short-range near ground radio link for wireless sensor communications/networks in vegetation environments. © 2012 IEEE.
Investigations of indoor radio propagation characteristics at 60 GHz for wireless communications
Rao T.R., Murugesan D., Labay V.A.
Article, International Journal of Microwave and Optical Technology, 2012,
View abstract ⏷
For the next generation Wireless Local Area Networks and Wireless Personal Area Networks, 60 GHz radio channel propagation characteristics in typical indoor environments are addressed in this paper using Matlab simulations of Ray-tracing, ITU-R model and full-3D Ray-tracing model of Wireless InSite. Values of the Pathloss, rms mni-directional and horn antennas are presented along with the values of Pathloss Exponent and Channel Capacity deduced from our simulations. It is observed that Architectural design and dimension considerations of indoor environments were playing major role on Received Signal Strength. © 2012 ISRAMT.
Short-range near floor path gain measurements in indoor corridors at UHF for wireless sensor communications
Rama Rao T., Balachander D., Tiwari N.
Conference paper, 2012 IEEE International Conference on Communication Systems, ICCS 2012, 2012, DOI Link
View abstract ⏷
Near to floor/ground radio frequency propagation path gain measurements at short distances at antenna height of 50 cm from the ground were made in typical narrow and wide straight indoor corridors at 433/868/915/2400 MHz in a modern multi-storied building. The measurement was performed utilizing RF equipment and comparisons were made with Matlab simulations of ray tracing technique, free space model and ITU-R model along with Full-3D ray tracing model of Wireless Insite software. Measured PG values showed good agreement with Wireless Insite model in all cases. Path loss exponent values ranging from 1.22 to 2.13 were deduced from the measured data. The research work reported in this paper is predominately geared towards characterizing radio link for wireless sensor communications / networks in typical indoor corridor environments. © 2012 IEEE.
60 GHz radio wave propagation studies in an indoor office environment
Rama Rao T., Murugesan D., Tiwari N., Labay V.A.
Conference paper, 2012 IEEE International Conference on Communication Systems, ICCS 2012, 2012, DOI Link
View abstract ⏷
60 GHz radio channel propagation characteristics in indoor office environment are addressed in this paper using full 3-Dimensional ray tracing of Wireless InSite and a simple deterministic 2-Dimensional model utilizing Ray-tracing technique. The comparisons are made with free space model and site-general prediction model of ITU-R. Values of the path gain, rms delay spread for sectoral horn and omni-directional antennas are presented. Also, path loss exponent and channel capacity values deduced from the simulation investigations. © 2012 IEEE.
Implementation of a trust model over AODV in a wireless ad hoc testbed
Gaurav C., Chandramouleeswaran D., Khanam R., Venkataraman R., Pushpalatha M., Rao T.R.
Conference paper, 2012 3rd International Conference on Computing, Communication and Networking Technologies, ICCCNT 2012, 2012, DOI Link
View abstract ⏷
We have customized Ad hoc On demand Distance Vector (AODV) protocol and augmented security aspect in real time scenario using numeric step values called Trust assigned to finite number of neighbor nodes to evaluate network behavior, subsequently secure the network by barricading the network from malicious nodes in Blackhole and flooding attack modes. Experiments were carried out using a custom-made testbed built on wxPython that supports various characteristics of nodes like variable data rates, node positions and malicious behavior for testing and display results in a graphical format. The results have favored aforementioned proposal showing a 70% increase in throughput obtained from trust implemented experimentation as compared to standard one without the trust parameter. The overhead in trusted scenario encountered was minimal despite the end to end delay of packets being higher than the traditional AODV by 30 msec. Hence, we have concluded that our method of using trust has resulted in a secured reactive protocol with applications suited for wireless attack prone environment when applied to a network consisting of four nodes. Our work is also the first ever implementation of a trust model over an adhoc routing protocol in a real adhoc testbed. © 2012 IEEE.
Regression-based trust model for mobile ad hoc networks
Venkataraman R., Pushpalatha M., Rama Rao T.
Article, IET Information Security, 2012, DOI Link
View abstract ⏷
The focus of this study is to propose a generalised trust-model over routing protocols in mobile ad hoc networks (MANETs). It is observed that the presence of malicious nodes is a critical factor affecting the network performance in an ad hoc network. The novelty in the approach is that the notion of trust can be easily incorporated into any routing protocol in MANETs. The vector auto regression based trust model is introduced to identify malicious nodes that launch multiple attacks in the network. The proposed trust model is incorporated over ad hoc on-demand distance vector (AODV) routing protocol and optimised link state routing (OLSR) protocol in MANETs. The performance evaluations show that by carefully setting the trust parameters, substantial benefit in terms of throughput can be obtained with minimal overheads. The computed trust and confidence values are introduced into the path computation process of the ad hoc routing protocols. It was observed that the nodes in the network were able to learn the malicious activities of their neighbours and hence, alternate trustworthy paths are taken to avoid data loss in the network, with trade-offs in end-to-end packet delay and routing traffic. © 2012 The Institution of Engineering and Technology.
Intra-vehicular RF propagation measurements at UHF for Wireless Sensor Networks
Rao T.R., Balachander D., Sathish P., Tiwari N.
Conference paper, Proceedings of the 2012 International Conference on Recent Advances in Computing and Software Systems, RACSS 2012, 2012, DOI Link
View abstract ⏷
Received Signal Strength (RSS) propagation measurements were made in a vehicular environment (Intra-Car) atUHF range (433/868/915/2400 MHz)utilizing RF equipment and Matlab simulations. Pathloss and Pathloss Exponentvalues were deduced from the measuredRSS from various positions in a Multi Utility Vehicle (MUV). The research work reported in this paper is predominately focuseson characterizing radio link for Wireless Sensor Communications/Networks forvehicular environments at very short-range. © 2012 IEEE.
System level analysis of energy efficient transceiver at 2.4 GHz for wireless sensor networks
Vasanthi M.S., Rama Rao T., Posnet Priyadarshan G.
Conference paper, 2012 International Conference on Computing, Electronics and Electrical Technologies, ICCEET 2012, 2012, DOI Link
View abstract ⏷
Recent advances have resulted in the ability to integrate sensors, wireless communications and digital electronics into a single integrated circuit package. This capability is enabling networks comprised of very low cost sensors nodes that are able to communicate with each other. Energy efficient wireless communications is an essential requirement for Wireless Sensor Networks (WSN) in many environmental monitoring applications and there is a growing need to improve the lifetime of wireless sensor nodes. The power consumed by node transceiver electronics is non-negligible and has a major impact on battery life. This paper describes a system level methodology to analyze a complete RF transceiver architecture for short-range energy limited applications requiring high data rates. The overall system specifications are derived using system level simulations utilizing Matlab programming and Agilent's Advanced Design System. The obtained specifications can be used for implementing an energy efficient transceiver at 2.4GHz for WSN applications. © 2012 IEEE.
RF propagation measurements in forest & plantation environments for Wireless Sensor Networks
Rama Rao T., Balachander D., Nanda Kiran A., Oscar S.
Conference paper, International Conference on Recent Trends in Information Technology, ICRTIT 2012, 2012, DOI Link
View abstract ⏷
This work reports Received Signal Strength (RSS) at 868/915/2400 MHz utilizing RF equipment and Matlab simulations in Forest and Plantation (Mango & Guava) Environments. Path loss, Vegetation water content and corresponding Cumulative Distribution Function (CDF) values were deduced from the measured RSS from various positions in foliage environments using unit gain omnidirectional antennas at 1m height from the ground. Empirical foliage loss prediction models such as Cost 235, ITU-R and Weissberger models were compared with the experimental results. The research work presented in this paper is predominately targets characterizing short-range near ground radio link for Wireless Sensor Communications/Networks in vegetation environments. © 2012 IEEE.
Near ground/floor RF path gain measurements in indoor corridors at 2400 MHz for wireless sensor communications
Rao T.R., Balachander D., Murugesan D., Ramesh S., Prasad M.V.S.N.
Conference paper, Procedia Engineering, 2012, DOI Link
View abstract ⏷
Radio frequency (RF) propagation path gain (PG) measurements were made in typical narrow straight and wide straight indoor corridors at 2400 MHz in a modern multi-storied building utilizing RF equipment and Matlab simulations of Ray-tracing technique, free space model, ITU-R model and full-3D Ray-tracing model of Wireless Insite. Measured PG values showed similar patterns with simulated values in most of the scenarios. The research work presented in this paper is predominately geared towards characterizing radio link for Wireless Sensor Communications/Networks in typical indoor corridor environments.
Implementation of a Regression-based Trust Model in a Wireless Ad hoc Testbed
Venkataraman R., Pushpalatha M., Rao T.R.
Article, Defence Science Journal, 2012, DOI Link
View abstract ⏷
Wireless ad hoc networks are resource constraint and vulnerable to various security attacks. Trust based security modelling go hand in hand with cryptographic services to offer good security services. We have implemented a vector auto regression (VAR) based trust model over ad hoc on demand distance vector protocol and optimised link state routing protocol. The novelty in this model lies in capturing individual functional behaviours of a neighbour in an ad hoc network and modeling them as regression parameters. The experimental results show the feasibility of implementing trust models over real ad hoc network deployments. The simulations results show that the proposed VAR trust model offers better performance compared to the existing trust models. © 2012, DESIDOC.
Path gain measurements at 868/915 MHz for Wireless Sensor Communications in indoor corridors
Rao T.R., Balachander D., Chamberlin K.
Conference paper, International Symposium on Advanced Networks and Telecommunication Systems, ANTS, 2011, DOI Link
View abstract ⏷
Radio frequency (RF) propagation path gain (PG) measurements were made in typical narrow straight and wide straight indoor corridors at 868/915 MHz in a modern multi-storied building utilizing RF equipment and Matlab simulations of Ray-tracing technique, free space model, ITU-R model and full-3D Ray-tracing model of Wireless Insite. Measured PG values showed similar patterns with simulated/modeled values in most of the cases. The research work presented in this paper is predominately geared towards characterizing radio link for Wireless Sensor Communications/Networks in typical indoor corridor environments. © 2011 IEEE.
Radio channel characteristics in an indoor corridor environment at 60 GHz for wireless networks
Rao T.R., Murugesan D., Ramesh S., Labay V.A.
Conference paper, International Symposium on Advanced Networks and Telecommunication Systems, ANTS, 2011, DOI Link
View abstract ⏷
For the next generation wireless local area networks (WLANs) and wireless personal area networks (WPANs), 60 GHz radio channel propagation characteristics in typical indoor corridor environments are addressed in this paper using Matlab simulations of Ray-tracing, ITU-R model and full-3D Ray-tracing model of Wireless Insite. Values of the path gain (PG), rms delay spread (DS) and power delay profile (PDP) for omnidirectional and horn antennas are presented. © 2011 IEEE.
Microstrip-to-substrate integrated waveguide aperture couplers
Conference paper, 2011 2nd International Conference on Wireless Communication, Vehicular Technology, Information Theory and Aerospace and Electronic Systems Technology, Wireless VITAE 2011, 2011, DOI Link
View abstract ⏷
Multi-aperture couplers between microstrip circuitry and substrate-integrated waveguides are presented. The design procedure is described, and couplers formed by single-aperture and dual-aperture configurations are presented. It is demonstrated that the coupling can be as tight as 1 dB but that weaker coupling leads to more broadband and flatter coupler performance. Designs are carried out in an HFSS environment; comparison with CST validate the design procedure. Dimensions and parameters of all couplers are presented as guidelines for general design purpose. © 2011 IEEE.
FPGA based FFT algorithm implementation in WiMAX communications system
Conference paper, 2011 2nd International Conference on Wireless Communication, Vehicular Technology, Information Theory and Aerospace and Electronic Systems Technology, Wireless VITAE 2011, 2011, DOI Link
View abstract ⏷
Increasing the performance is the best criterion for developing any communication system. The work presented here is aimed at increasing the speed & performance of the OFDMA (Orthogonal Frequency-Division Multiple Access) modulator and demodulator. This paper presents a high level implementation of a high performance FFT for OFDM Modulator and Demodulator. The design has been coded in Verilog and targeted into Xilinx Spartan 3 FPGAs. The developed OFDMA communication structure is then targeted to the OFDMA based WiMAX communication modules, for increasing their efficiency by utilizing FPGA based FFT algorithm. © 2011 IEEE.
60 GHz radio channel characteristics in an indoor environment for home entertainment networks
Rao T.R., Ramesh S., Murugesan D.
Conference paper, Communications in Computer and Information Science, 2011, DOI Link
View abstract ⏷
60 GHz radio channel propagation characteristics in a typical indoor environment are addressed in this paper using a simple deterministic 2-Dimensional model utilizing ray-tracing technique based on geometrical optics (GO) and image principle. Values of the received power, rms delay spread (DS) and power delay profile (PDP) for horn, omni-directional and isotropic antennas are presented. © 2011 Springer-Verlag.
A generalized trust framework for mobile ad hoc networks
Venkataraman R., Pushpalatha M., Rama Rao T.
Conference paper, Communications in Computer and Information Science, 2010, DOI Link
View abstract ⏷
Mobile ad hoc networks (MANET) are formed when two or more nodes come within the communication range of each other. Since the wireless range is very short, all the nodes in the network have to extend their complete co-operation for efficient functioning of the network. This paper proposes a generalized trust framework for any ad hoc routing protocol to curb selfish and malicious nodes in a MANET. The trust relationships existing between the nodes determine the routing path to be taken for data transfer. The trust framework is combined with any MANET routing algorithm. The performance analysis of this framework is currently done with two reactive protocols. Jointly, they form a trusted network to curb various attacks originating in the ad hoc network. This type of a trusted framework established in a MANET, would be most suited for tactical environments. © 2010 Springer-Verlag Berlin Heidelberg.
An FFT approach for efficient OFDM communication systems
Harikrishna K., Rao T.R., Labay V.A.
Conference paper, 2010 International Conference on Signal Acquisition and Processing, ICSAP 2010, 2010, DOI Link
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In the widely used OFDM (Orthogonal Frequency Division Multiplexing) systems, the FFT and IFFT pair are used to modulate and demodulate the data constellation on the subcarriers. This paper presents a high level implementation of a high performance FFT for OFDM Modulator and Demodulator. The design has been coded in Verilog and targeted into Xilinx Spartan3 FPGAs. Radix-22 Algorithm is proposed and used for the OFDM communication system. This algorithm has the same multiplicative complexity as the radix-4 algorithm, but retains the butterfly structure of radix-2 algorithm. The design is parameterizable in terms of input word length, output word length, twiddle factor word length, and processing word length. Also, it is scalable in terms of number of stages. © 2010 IEEE.
An efficient FFT architecture for OFDM communication systems
Conference paper, ARTCom 2009 - International Conference on Advances in Recent Technologies in Communication and Computing, 2009, DOI Link
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This paper presents a high level implementation of a high performance FFT for Modulator and Demodulator in OFDM. The design has been coded in VHDL and targeted into Xilinx Virtex-E XCV3200E FPGAs. The hardware requirement comparison shows that our implementation outperforms other implementations of FFT on the same series of FPGAs. Radix-22 algorithm has the same multiplicative complexity as the radix-4 algorithm, but retains the butterfly structure of radix-2 algorithm. © 2009 IEEE.
Capacity & performance issues in a MIMO based MB-OFDM ultra wide band communication system
Affum Ampoma E.K., Rama Rao T., Labay V.A.
Conference paper, ICAST 2009 - 2nd International Conference on Adaptive Science and Technology, 2009, DOI Link
View abstract ⏷
Ultra wideband (UWB) technology is one of the promising solutions for future short-range communication which has recently received a great attention by many researchers. However, interest in UWB devices prior to 2001 was primarily limited to radar systems, mainly for military applications, due to bandwidth resources becoming increasingly scarce and also its interference with other commutation networks. This research work provides performance analysis of multiband orthogonal frequency division multiplexing (MB-OFDM) UWB MIMO system in the presence of binary phase-shift keying time-hopping (BPSK-TH) UWB or BPSK-DS UWB interfering transmissions under Nakagami-m and Lognormal fading channels employing various modulation schemes using MATLAB simulations. Also, provides capacity analysis showing variation of channel capacity with respect to distance well as signal-to-noise ratio. ©2009 IEEE.
Design of multilayered substrate-integrated waveguide cross-slot couplers
Labay V.A., Bornemann J., Rao T.R.
Conference paper, European Microwave Week 2009, EuMW 2009: Science, Progress and Quality at Radiofrequencies, Conference Proceedings - 39th European Microwave Conference, EuMC 2009, 2009, DOI Link
View abstract ⏷
This paper introduces multilayered cross-guide crosss-slot directional coupler designs in substrate-integrated waveguide (SIW) technology. Interface ports are modeled by dielectric-filled waveguides which allow for a higher dynamic range in scattering parameters than conventionally used microstrip-to-SIW transitions. It is demonstrated that in double-or triple-layered configurations, coupling values between 10 dB and 25 dB can be achieved over almost an entire waveguide band. Several Ka-band double- or triple-layered cross-guide coupler designs are presented using an Ansoft's HFSS design environment. CST's Microwave Studio is used for performance verification. © 2009 EuMA.
An efficient FFT architecture for OFDM communication systems
Harikrishna K., Rama Rao T., Labay V.A.
Conference paper, APMC 2009 - Asia Pacific Microwave Conference 2009, 2009, DOI Link
View abstract ⏷
The FFT (Fast Fourier Transform) processor plays a critical part in speed and power consumption of the Orthogonal Frequency Division Multiplexing (OFDM) communication system. This paper presents a high level implementation of a high performance FFT for OFDM Modulator and Demodulator. The design has been coded in VHDL and targeted into Xilinx Virtex-E XCV3200E FPGAs. The hardware requirement comparison shows that our implementation outperforms other implementations of FFT on the same series of FPGAs. Radix-22 algorithm has the same multiplicative complexity as the radix-4 algorithm, but retains the butterfly structure of radix-2 algorithm. The design is parameterizable in terms of input word length, output word length, twiddle factor word length, and processing word length. Also, it is scalable in terms of number of stages. ©2009 IEEE.
Prevention of flooding attacks in mobile ad hoc networks
Venkataraman R., Pushpalatha M., Khemka R., Rao T.R.
Conference paper, Proceedings of the International Conference on Advances in Computing, Communication and Control, ICAC3'09, 2009, DOI Link
View abstract ⏷
The lack of any centralized infrastructure in mobile ad hoc networks (MANET) is one of the greatest security concerns in the deployment of wireless networks. Thus communication in MANET functions properly only if the participating nodes cooperate in routing without any malicious intention. However, some of the nodes may be malicious in their behavior, by indulging in flooding attacks on their neighbors. Some others may act malicious by launching active security attacks like denial of service. This paper addresses few related works done on trust evaluation and establishment in ad hoc networks. Related works on flooding attack prevention are reviewed. A new trust approach based on the extent of friendship between the nodes is proposed which makes the nodes to co-operate and prevent flooding attacks in an ad hoc environment. The performance of the trust algorithm is tested in an ad hoc network implementing the Dynamic Source Routing (DSR) protocol. Copyright 2009 ACM.
Fault tolerant and dynamic file sharing ability in mobile ad hoc networks
Pushpalatha M., Venkataraman R., Khemka R., Rao T.R.
Conference paper, Proceedings of the International Conference on Advances in Computing, Communication and Control, ICAC3'09, 2009, DOI Link
View abstract ⏷
This paper proposes a new method for replication of files within a mobile adhoc network based on the prediction of the drift of the mobile nodes. The main feature of mobile ad hoc network is the dynamic topology. That is the nodes in the network are in mobile. To facilitate file sharing in mobile networks the only technique is file replication. Shared files are available at all times even if the owner of the file drifts away. The goal is to ensure that files autonomously maintain replica levels over time in a potentially dynamic and hostile environment. Also the proposed algorithm ensures that only those files are to be replicated which are about to exit from the network ensuring better efficiency and fewer overheads. Existing algorithms are simulated in Netlogo simulation environment and observations are compared with the proposed technique to check the efficiency of all algorithms. Copyright 2009 ACM.
Performance analysis of flooding attack prevention algorithm in MANETs
Venkataraman R., Pushpalatha M., Rama Rao T.
Article, World Academy of Science, Engineering and Technology, 2009,
View abstract ⏷
The lack of any centralized infrastructure in mobile ad hoc networks (MANET) is one of the greatest security concerns in the deployment of wireless networks. Thus communication in MANET functions properly only if the participating nodes cooperate in routing without any malicious intention. However, some of the nodes may be malicious in their behavior, by indulging in flooding attacks on their neighbors. Some others may act malicious by launching active security attacks like denial of service. This paper addresses few related works done on trust evaluation and establishment in ad hoc networks. Related works on flooding attack prevention are reviewed. A new trust approach based on the extent of friendship between the nodes is proposed which makes the nodes to co-operate and prevent flooding attacks in an ad hoc environment. The performance of the trust algorithm is tested in an ad hoc network implementing the Ad hoc On-demand Distance Vector (AODV) protocol.
Trust based Energy aware reliable reactive protocol in mobile ad hoc networks
Pushpalatha M., Venkataraman R., Ramarao T.
Article, World Academy of Science, Engineering and Technology, 2009,
View abstract ⏷
Trust and Energy consumption is the most challenging issue in routing protocol design for Mobile ad hoc networks (MANETs), since mobile nodes are battery powered and nodes behaviour are unpredictable. Furthermore replacing and recharging batteries and making nodes co-operative is often impossible in critical environments like military applications. In this paper, we propose a trust based energy aware routing model in MANET. During route discovery, node with more trust and maximum energy capacity is selected as a router based on a parameter called 'Reliability'. Route request from the source is accepted by a node only if its reliability is high. Otherwise, the route request is discarded. This approach forms a reliable route from source to destination thus increasing network life time, improving energy utilization and decreasing number of packet loss during transmission.
Investigation of VHF signals in bands i and II in southern India and model comparisons
Prasad M.V.S.N., Rama Rao T., Ahmad I., Paul K.M.
Article, Indian Journal of Radio and Space Physics, 2006,
View abstract ⏷
In order to achieve a highly reliable communication with a simple and small receiver, one requires the knowledge of the spatial and temporal variability of field strength. This assumes greater significance in broadcasting applications where the user expects a very high quality signal. The performance of any communication circuit depends on the models employed to calculate the coverage area and interference problems. The development and identification of models is a continuing and ongoing process and there is always scope for refinement. With this objective some field strength measurements were conducted using Chennai TV and FM stations in several radiais. The variability of the path loss as a function of distance has been studied and path loss exponents deduced from the observed values were compared with the model available in literature. The agreement and deviations of the model with the observed results are presented and discussed and two approaches have been proposed to compare the observed results.
Coverage and capacity calculations for a CDMA cell in different radio environments
Conference paper, EUROCON 2005 - The International Conference on Computer as a Tool, 2005,
View abstract ⏷
Coverage and capacity are important issues in the planning process for mobile cellular networks. In this article, we focus on calculations for capacity and coverage for a Code Division Multiple Access (CDMA) cell for Universal Mobile Telecommunication System (UMTS) network in different radio propagation environments, based on propagation prediction models. © 2005 IEEE.
A performance study on the 802.11g WLAN OFDM system
Conference paper, EUROCON 2005 - The International Conference on Computer as a Tool, 2005,
View abstract ⏷
In the recent years, WLAN (Wireless Local Area Network) standards have been evolving rapidly. The IEEE 802.11g standard was set in 2003 as a new wireless protocol aimed at enhancing existing data rates. This paper focuses on the performance of IEEE 802.11g system based on OFDM (Orthogonal Frequency Division Multiplexing) using modeled transmitter and receiver. We investigate the performance analysis through computer simulations over the JTC (Joint Technical Committee) realistic channel model for various modulations like BPSK, QJPSK, 16-QAM and 64-QAM. © 2005 IEEE.
Double knife edge diffraction propagation studies over irregular terrain
Prasad M.V.S.N., Bhaskara Rao S.V., Rama Rao T., Sarkar S.K., Sharma S.
Article, Indian Journal of Radio and Space Physics, 2004,
View abstract ⏷
Mountain cliffs constituting knife edges influence radio wave propagating from VHF to microwave frequencies. The diffraction phenomena caused by these single or multiple knife edges are a dominant propagation mechanism that has to be taken into account in planning TV, FM networks, cellular radio, microwave network, etc., in mountainous regions. In order to investigate the above mechanism field strength measurements were conducted over five double knife edge paths and the measured signal levels are compared with several prediction techniques. The deviations of the prediction techniques and their suitability are presented in this paper. It is seen that out of all the prediction methods Giovanelli's method gives best agreement with the observed results.
Rain attenuation studies at 11.7GHz over southern India
Rao S.V.B., Rao T.R., Reddy I.V.S., Prasad M.V.S.N., Reddy V.G., Reddy B.M.
Article, Indian Journal of Radio and Space Physics, 2002,
View abstract ⏷
Rain attenuation studies were made at 11.7 GHz utilizing INSAT-2C satellite signals over southern India during rain events. The observed cumulative distribution of rain attenuation is compared with prominent prediction models. These are the first results observed on an operational earth-satellite path in India.
HF radio signal fading and atmospheric radio noise measurements at low latitudes
Vijaya Bhaskara Rao S., Rama Rao T., Gunasekhara Reddy V., Lakshmi D.R., Veenadhari B., Dabas R.S., Ahmed I., Gupta M.M., Reddy B.M.
Article, Radio Science, 2002,
View abstract ⏷
Two HF broadcast transmissions, one originating from Sri Lanka (7.1°N, 79.9°E) at 11.800 MHz around the geomagnetic equator and the other from BBC, Masirah (20.6°N, 58.9°E), at 15.310 MHz several degrees north of the geomagnetic equator were monitored at Tirupati (13.5°N, 79.5°E) in southern India to compare the fading characteristics of the links. It is found that the link over the geomagnetic equator exhibits much higher fade rates as compared to the other link. The fade ranges also are, in general, higher for Sri Lanka. Fade allowances derived from these data do indicate that margins higher than those recommended by the International Telecommunication Union Radiocommunication Sector (ITU-R) need to be provided at these latitudes. The diurnal variation in the atmospheric radio noise (ARN), which sets a lower limit to the satisfactory reception of signal, over the Indian subcontinent is in total disagreement with the variations obtained at higher latitudes. This rather puzzling phenomenon has been interpreted as being due to path attenuation differentials between the LOS mode and the ionospheric mode from the lightning source because of significantly greater cloud height in the Indian region.
Mobile radio propagation path loss studies at vhp/uhf bands in southern India
Rama Rao T., Vijaya Bhaskara Rao S., Prasad M.V.S.N., Sain M., Iqbal A., Lakshmi D.R.
Article, IEEE Transactions on Broadcasting, 2000, DOI Link
View abstract ⏷
Field strength measurements at 200, 400 and 450 MHz (VHF/UHF band) were conducted with the field strength meter placed on board of a vehicle in Southern India. Observed field strength values were converted into path losses and are compared with different path loss prediction methods like Hata, Egli, Blomquist-Ladell, COST 231 Walfisch-Ikegami, Walfisch-Bertoni and ITU-R. These path loss studies are carried out in urban, suburban and open areas in this region. The results showed that Hata's method gave better agreement with observed values in urban, suburban and open regions. COST 231 Walfisch-Ikegami model is also in good agreement with the observed values in urban and suburban regions. Egli and Blomquist-Ladell methods showed moderate agreement in open region only. The agreement of Walfisch-Bertoni and ITU-R methods with observed values is not good. © 2000 IEEE.
Effect of sea breeze on propagation characteristics over a LOS microwave link located in Indian south-east coast
Rama Rao T., Vijaya Bhaskara Rao S., Prasad M.V.S.N., Sarkar S.K., Lakshmi D.R.
Article, Indian Journal of Radio and Space Physics, 1999,
View abstract ⏷
Studies on microwave signal propagation provide an opportunity to investigate the variable nature of the atmosphere. The present study deals with the effect of sea breeze on the propagation characteristics observed over a line-of-sight (LOS) microwave link operating at 6 GHz and situated in the south-east coast of India. It has been found that the amplitude of the received microwave signal suffers appreciably during the onset of sea breeze. The correlation between the cases of onset of sea breeze observed from microwave amplitude measurements and those from meteorological observations has been found to be good. The large change in refractivity has been observed during the onset of sea breeze. Such change in refractivity profile causes fading in microwave radio signals.
Single knife edge diffraction propagation studies over a hilly terrain
Rama Rao T., Vijaya Bhaskara Rao S., Prasad M.V.S.N., Sarkar S.K.
Article, IEEE Transactions on Broadcasting, 1999, DOI Link
View abstract ⏷
Field strength measurements are made to study the Single knife edge diffraction propagation in the hilly terrain of Tirupati, Southern India. TV signals originating from Narayana Giri Hill in VHF band are monitored at 4 different locations of Tirupati for this purpose. The observed values are converted into path loss values and are compared with prediction techniques. An attempt is made to study the adaptability of these techniques and found that ITU-R, Epstein - Peterson, Deygout and Edward - Durkins methods are in closer agreement with the observed path loss where as Blomquist - Ladell over estimates the observed path loss.
