Comparison of Relaying Strategies for Cooperative Diversity Systems with Adaptive Modulation

In this paper, we propose several relay selection schemes for cooperative diversity systems with adaptive transmission. The proposed schemes are based on dual-hop relaying with multiple relays. We analyze the performance of the proposed schemes by quantifying the average spectral efficiency and the outage probability. We also investigate the tradeoff of performance and complexity among proposed schemes by evaluating the average number of active relays, path estimations, and signal- to-noise ratio comparisons. Our proposed schemes and analysis are also applicable to single relay systems with multiple antennas.