Single and Multiple Relay Selection Schemes and their Diversity Orders

This paper is on relay selection (RS) schemes for wireless relay networks. First, we derive the diversity of many single RS schemes in the literature. Then, we generalize the idea of RS by allowing more than one relay to cooperate. Several multiple RS schemes are proposed, which are proved to achieve full diversity. Simulation results show that they perform much better than the corresponding single RS methods and very close to the optimal multiple RS scheme. However, the computational complexity of the suboptimal schemes are linear in the number of relays, far superior to the optimal selection, which has exponential complexity. In addition, when the number of relays is large, the multiple RS schemes require the same amount of feedback bits from the receiver as single RS schemes.