Training-Based Joint Antenna and Relay Selection in Multiuser Downlink Cellular Network with RF Impairments

We analyze the performance of a dual-hop downlink cellular amplify-and-forward cooperative system in the presence of both channel estimation errors and radio frequency (RF) impairments, where multiple antennas are deployed only at the base station (BS) and single-antenna at relays and mobile stations (MS). Specifically, we derive approximate as well as exact closed-form expressions for the outage probability and expected spectral efficiency. In addition, simple asymptotic expressions at the high signal-to-noise ratio (SNR) regime are obtained, which facilitate the characterization of the achievable diversity order of the system. To validate the derived analytical expressions, we presented simulation results which are sufficiently tight across the entire range of SNRs. Findings of the paper suggest that full diversity order can be achieved only when the RF front-end hardware is assumed to be perfect, while in practice the imperfections in hardware are inevitable and reduce diversity order of the system. Moreover, the influence of key parameters such as the number of antennas, users, and relays on the system performance has been presented with the influence of the level of RF impairments.