Transceiver design for multi-user MIMO AF relay systems with bounded channel uncertainties

In this paper, we investigate the transceiver design in a dual-hop multi-user multiple-input multiple-output amplify-and-forward relay system. By taking the bounded channel uncertainties into account, we propose two robust design methods under the minimum sum mean-square-error (SMSE) criterion. The original problem is first transformed into a tractable one applying the generalized sign-definiteness lemma, and then the transceiver is achieved by employing an iterative algorithm based on alternating optimization. Moreover, in order to reduce the complexity, a novel cutting-set method is developed to solve the considered problem efficiently by solving an alternating sequence of SMSE minimization and worst-case analysis problems. Simulation results are provided to demonstrate the effectiveness of the proposed methods.