Optimal User Pairing for Asymmetric Multi-Way Relay Channels with Pairwise Relaying

We study an asymmetric multi-way relay channel where users have different channel conditions. To enable data exchange between the users, an existing practical approach, where users transmit their data to the relay in pairs, is considered. For pairwise transmission, we consider two different scenarios at the relay, called functional-decode-forward (FDF) and decode-and-forward (DF). For both FDF and DF, we first show that due to unequal channel conditions, the achievable common rate of the pairwise strategy depends on the order in which the users are paired. This motivates us to find the pairing strategy maximizing the achievable rate. This rate is then compared with the capacity upper bound and the achievable rate of a random user pairing.