Increasing throughput in multi-way three-user MIMO networks using successive relaying and IRI cancellation

This paper considers multi-way communications among three users equipped with multiple-input multiple-output (MIMO) transceivers that exchange massages between each other via two amplify-and-forward (AF) co-located relays. In this network with half-duplex MIMO relays, the wireless medium is simultaneously utilized for time-slotted transmissions by one of the users and one of the relays in order to increase the network capacity. The relays successively relay the signals creating inter-relay interference (IRI), which limits the bit error rate (BER) performance. To mitigate the IRI, this paper develops a cancellation technique at the receiving side of the users through specialized signal processing and scheduling of transmissions with opportunistic listening. The full IRI cancellation is possible assuming that every transceiver knows its receiving channel state information (CSI) and the inter-relay CSI. When all nodes - users and relays - are equipped with M antennas, the proposed scheme allows to exchange M messages per time slot which doubles the capacity of the network over the conventional AF system operating with a single relay in one-way setup. Simulation results document the effectiveness of the developed scheme in terms of channel capacity and the BER performance.