Performance Evaluation of Full Duplex Communications in 5G Networks: The Impact of Interference and Traffic Asymmetry

Full-duplex communications (FDC) is one of the enabling technologies for 5G systems and its true impact on performance needs to be evaluated by taking into account the new sources of interference inherent to this technology. We focus on the realistic scenario where FDC is only enabled at the base-stations (BS). The coexistence of uplink and downlink transmissions calls for a joint uplink and downlink scheduling problem and to take all interference into account, a multi-cell system needs to be considered. We also argue that traffic asymmetry (TA), i.e., the fact that the downlink traffic is much larger than uplink traffic, cannot be ignored. Specifically, we formulate a system-wide joint scheduling problem that incorporates all sources of interference and TA, and show how to solve it. The main engineering insights are that in a realistic setting, i) FDC does not double capacity as often mentioned; ii) TA has the largest (negative) impact on the FDC performance; iii) imperfect self interference cancellation has the second largest impact and iv) inter-base station interference, i.e., the interference caused by co-channel BSs, has the third. FDC cannot double the performance of a TDD (time division duplex) system. The gain is rarely above 50% even though it is higher in rural or heterogeneous networks.