Diversity Analysis of Distributed Space-Time Codes in Relay Networks with Multiple Transmit/Receive Antennas

The idea of space-time coding devised for multiple-antenna systems is applied to the problem of communication over a wireless relay network, a strategy called distributed space-time coding, to achieve the cooperative diversity provided by antennas of the relay nodes. In this paper, we extend the idea of distributed space-time coding to wireless relay networks with multiple-antenna nodes and fading channels. We show that for a wireless relay network with M antennas at the transmit node, N antennas at the receive node, and a total of ℛ antennas at all the relay nodes, provided that the coherence interval is long enough, the high SNR pairwise error probability (PEP) behaves as (1/P)min{M,N}ℛ if M≠N and (log1/MP/P)ℳℛ if M=N, where P is the total power consumed by the network. Therefore, for the case of M≠N, distributed space-time coding achieves the maximal diversity. For the case of M=N, the penalty is a factor of log1/MP which, compared to P, becomes negligible when P is very high.