Robust transceiver design for multi‐user multiple‐input multiple‐output amplify‐and‐forward relay systems

In this study, the authors consider the robust transceiver design in a dual‐hop multi‐user multiple‐input multiple‐output amplify‐and‐forward relay system. By incorporating the antenna correlation at both ends of the channel and taking the channel estimation errors into account, the authors propose two robust design approaches under the minimum sum mean‐square‐error criterion. Specifically, they decouple the original problem into three convex sub‐problems in the first approach and develop an iterative algorithm with guaranteed convergence. The second approach converts the original problem into simple power allocation problems utilising a certain relaying structure, and the approximate closed‐form solutions are derived. Some practical implementation issues are also discussed. Simulation results are provided to demonstrate the effectiveness of the proposed approaches.