Hop-by-hop Beamforming for Dual-hop MIMO AF Relay Networks

This paper presents a comprehensive performance analysis of dual-hop multiple-input multiple-output amplify-and-forward relay networks with hop-by-hop beamforming. The impact of practical transmission impairments; (i) feedback delays, (ii) channel estimation errors and (iii) spatially-correlated fading on the system performance is studied. Specifically, the amount of performance degradation due to these impairments are quantified analytically. To this end, a general closed-form expression for the cumulative distribution function of the end-to-end signal-to-noise ratio is derived and used to obtain the outage probability, and the average symbol error rate (SER). Further, the asymptotic outage probability and average SER are derived to obtain valuable system-design insights such as the diversity order and array gain. Numerical results are presented to show the detrimental effect of imperfect channel state information on the system performance. Further, our analyses are validated through Monte-Carlo simulations.