Finite-SNR Diversity-Multiplexing Tradeoff Analysis of Relay Network with two Antennas at the Source in Rayleigh Fading Channels

In this paper, we analyze the diversity-multiplexing tradeoff (DMT) of a simple relay network model in cellular system. The relay network model consists of a two-antenna base station and single-antenna mobile terminals. Compared with most prior work, we put emphasis on DMT analysis at finite signal-to-noise ratio (SNR) in Rayleigh Fading Channels. Specifically, we first derive the closed-form expressions of the outage performance and the finite-SNR DMT for the system model. Then, we investigate the effect of time allocation among the source and the relay on the outage and DMT performance. Our results reveal that the conventional asymptotic SNR DMT significantly overestimates finite-SNR DMT in the practical SNRs. We also demonstrate that the finite-SNR DMT is equivalent to the conventional asymptotic DMT when the SNR approach infinity.