Secrecy Sum Rate Maximization in Multi-Antenna Two Way Relay Networks

This study investigates the achievable secrecy rate of two-way relay-assisted networks. It is assumed that there is no direct link between transceiver ends and the communication is carried out in two hops through the use of multi-antenna relays in the middle of transmission, where the relays employ amplify-and-forward strategies. To increase the bandwidth efficiency, intending nodes exchange their confidential messages in two hops. First, both nodes simultaneously send their messages to the relay nodes. Then, throughout the second hop, the relays make use of cooperative beamforming to send their incoming information in such a way that the achievable secrecy sum rate is maximised, considering each node is subject to a minimum secrecy rate constraint. Accordingly, two beamforming strategies, named as null-space beamforming and information leakage alignment beamforming are proposed, where their achievable secrecy sum rates are investigated and compared to existing works addressed in the literature.