Optimum HDAF Relay-Assisted Combining Scheme with Relay Decision Information

For single-input multiple-output (SIMO) systems, Maximum Ratio Combining (MRC), employed at the receiver, achieves the best performance compared to other combining schemes in the literature, such as Selection Combining (SC) and Equal Gain Combining (EGC). However, for cooperative relay-based systems, MRC has limited performance due to the lack of relay decision information awareness at the destination combiner. To overcome this limitation, this paper proposes a new optimum combining scheme, which is being demonstrated for Hybrid-Decode-Amplify-Forward (HDAF) cooperative system. This scheme utilizes relay decision information in the form of the number of errors per received packet over the source-relay link. The derivation of the optimum combining scheme is based on a mathematical model that utilizes conditional error probability. The improved performance of the proposed optimum combining scheme is demonstrated through analytical results and Monte Carlo simulations.