The impact of imperfect channel estimations on the performance of optimum combining in decode-and-forward relaying in the presence of Co-channel interference

Optimum combining (OC) in cooperative relaying enables achieving a diversity gain of M in the presence of co-channel interference (CCI), where M is the number of relay nodes. The additional performance overhead of OC is the need for estimation of interferer channels. The impact of imperfect channel estimation on the performance of OC with decode-and-forward relaying is analyzed. When the source-destination and relay-destination channel estimations are imperfect, the diversity gains of OC deteriorate and the performance further degrades with increase of the error variance. When the destination node accurately estimates the variances of the interferer channel state information (CSI), instead of instantaneous CSI, no performance loss is observed. Thus, the overhead associated with the interferer channel estimation in OC can be significantly reduced.