In this paper we consider first price auction (FPA) model for 5G wireless networks. FPA is credible auction and yields higher expected revenue compared to second price auction (SPA) with budget constraints users. We first describe the model of wireless communications and then present the equilibrium analysis for FPA. We next consider budget constraint FPA and also analyze FPA with the number of user increasing to infinity. With large number of users, FPA tend to be truthful and credible auction. Finally, we study budget constrained repeated first price auctions using mean field fluid approximations. We also analyze the equilibrium behavior of the user with mean field approximations.