Two-Way MIMO Relaying Systems Employing Layered Relay-and-Antenna Selection Strategies

In this paper, a variety of layered relay-and-antenna selection (LRAS) strategies are developed for the two-way multiple-input multiple-output (MIMO) amplify-and-forward (AF) relaying systems in the presence of spatial correlation between antennas over fading channels. On the basis of the achievable sum-rate (ASR) maximization, the condition number (CN), adaptive discrete stochastic approximation (A-DSA), Gram-Schmidt (GS), and squared Frobenius norm (SFN)-based LRAS algorithms are investigated under an equal power allocation. To reduce the computational complexity of the relay-and-antenna selection (RAS) selection strategies, the best single relay and the subset of transmit-and-receive (Tx/Rx) antenna pairs are selected and separated into a two-stage manner. Remarkably, the LRAS techniques enable to alleviate substantially the computational complexity incurred by an exhaustive-mode RAS search algorithm. Finally, simulation results demonstrate the excellent sum-rate capacity of the proposed LRAS methods over other existing selection ones for MIMO two-way multiple-AF-relay systems.