Joint power and rate adaptation aided network-coded PSK for two-way relaying over fading channels

Advanced downlink (DL) decode-and-forward two-way relaying (DF-TWR) is developed for the sake of maximizing the attainable spectral efficiency. Network-coded phase-shift keying (NC-PSK) holds the potential of significantly increasing the data rate of the network, while adaptive modulation is a powerful technique of improving both the energy and spectral efficiency. Hence power-controlled adaptive NC-PSK has the potential of achieving performance enhancements over fading channels. Given this framework, based on the bit-error-ratio (BER) bounds developed, we derive the closed-form spectral efficiency for a continuous-rate, continuous-power adaptive NC-PSK scheme, where both the transmit power and the transmit rate are optimized subject to specific power- and BER- constraints. We then conceive and investigate a discrete-rate scheme relying on a pair of solutions proposed for maximizing the throughput of the network. Our simulation results reveal that the proposed schemes are capable of achieving a higher spectral efficiency than their fixed-power counterparts.