Sum rate maximization antenna selection via discrete stochastic approximation in MIMO two-way AF relay with imperfect CSI

Recently, the MIMO two-way AF relaying, a promising spectral efficient transmission technique, has attracted a great deal of attention. Meanwhile, it has been shown that it is possible to improve the performance of MEMO systems by employing antenna selection technology. Existing antenna selection algorithms in MEMO two-way AF relay assume perfect channel state information(CSI). However, as a matter of fact, it is difficult to obtain perfect CSI. In this paper, considering the antenna correlation and channel estimation error, we derive the lower bound on sum rate utilizing worst case uncorrelated additive noise theorem in MIMO two-way AF relaying system, and analyze the effect of antenna correlation and channel estimation error on the sum rate. Then, an optimal relay antenna selection algorithm based on discrete stochastic optimization is proposed to maximize the sum rate under the assumption of imperfect CSI. We also prove the convergence of the proposed algorithm through theoretical analysis. Through extensive numerical simulation, we observe that the proposed relay antenna selection algorithm converges to the best antenna set obtained by exhaustive search when only imperfect CSI is available.