Energy efficiency optimization for full-duplex relaying with hybrid self-interference cancellation in 60 GHz indoor wireless systems

An intensive analysis of energy efficiency (EE) is presented for full-duplex (FD) relay-assisted 60 GHz indoor wireless systems. It is proved that the EE of FD relaying systems is strictly quasi-concave or mono-increasing with respect to transmission power at source node, under a maximum transmission power constraint. We develop a hybrid self-interference cancellation scheme for the full-duplex relay, where one-stage interference cancellation (passive suppression) or two-stage interference cancellation scheme (passive suppression + analog cancellation) is opportunistically selected, together with transmission power adaptation, to maximize the instantaneous EE with given channel gains. A low-complexity optimization algorithm is proposed. We show a counter-intuitive finding that, with a relatively loose maximum transmission power constraint, the two-stage self-interference cancellation scheme is preferable to the one-stage solution, resulting in a higher optimized EE. Simulation results also show that FD relaying is much more energy efficient than half-duplex (HD) relaying.