Outage Probability of X-Duplex AF Relay-Aided mmWave MIMO Systems with Relay Selection in B5G and 6G

We consider a millimeter wave (mmWave) multiple input multiple output (MIMO) multiple-relay aided system in beyond 5G (B5G) and 6G with a multiple antennas source, multiple amplify-and-forward (AF) X-duplex (XD) relays with single transmit and single receive antenna, and one multiple antennas destination. XD relays can switch adaptively between half-duplex (HD) relaying and full-duplex (FD) relaying modes to improve the system performance. We derive an expression for the outage probability of the system by assuming a relay selection scheme based on the maximum end-to-end (E2E) signal to interference plus noise ratio (SINR). Moreover, both Rician small scale fading and large scale fading includes blockage effect and path-loss are considered in source to relay and relay to destination mmWave channels, in addition, a realistic model for residual self-interference is studied. Simulation results present the accuracy of the theoretical expression of the outage probability of XD relaying in the mmWave MIMO system and show that it has superior outage performance compared with both HD and FD relaying.