Error-rate performance of uplink cooperative communications with decode-and-forward protocol

For cooperative communications, the decode-and-forward (DF) protocol can give promising error-rate performance provided that the relay node has the decoding capability. In this study, the authors consider the DF cooperation for cellular uplink communications, in which the source node is equipped with a single antenna, and both the relay and destination nodes are equipped with multiple antennas. For this case, the authors analyse the exact symbol-error-rate (SER) for M-quadrature amplitude modulation (QAM) signals over Nakagami-m fading channels. To avoid the cumbersome integral calculation, the authors derive an asymptotic approximation for the SER, which lets them not only gain fast understanding of the improvement from cooperative diversity, but also have more insight into how the channel characteristics and the number of antennas affect the SER performance. Specifically, to reduce the SER, the authors find that: first, good condition of the relay-destination channels is more critical than good condition of the source-relay channels; second, large number of antennas at the relay node is more critical than large number of antennas at the destination node. All these results are not exploited and discussed before. Simulations are finally presented to demonstrate the correctness of the authors- analysis and perception for the considered cooperation scenario.