Low-complexity SNR-based channel pairing in multichannel MABC-based two-way relaying

We consider two-way amplify-and-forward relaying in a multichannel system with two end users and a single relay. A two-slot multi-access broadcast (MABC) relaying strategy is considered. For given power allocation, we investigate into the problem of subchannel pairing at the relay to maximize the achievable sum rate in the network. Unlike in the oneway relaying case, our result shows that there exists no explicit SNR-based subchannel pairing strategy that is optimal for sum-rate maximization for two-way relaying. Nonetheless, we propose a low-complexity SNR-based suboptimal pairing scheme, SNR^eff-Greedy algorithm, using an effective SNR as the metric for pairing. For N subchannels, the proposed scheme has O(N² log N) complexity, as opposed to O(N³) complexity in obtaining the optimal solution. Simulations demonstrate the effectiveness of the proposed scheme in performance as compared to the optimal pairing and other suboptimal schemes.