Abstract
In this thesis, we present two suboptimal joint power allocation (PA) and relay selection (RS) schemes with different design objectives for two-way amplify-and-forward relay systems with nonreciprocal channels, where multiple single-antenna relays are considered and only one relay is selected for cooperation with two sources. The first approach is to maximize the smaller received signal-to-noise ratios (SNRs) at the two sources under a total transmit power constraint, where closed-form PA expressions are derived to make the received SNRs at the two sources equal for each relay, and the relay resulting in the largest balanced received SNR at the two sources is selected for cooperation. The second approach is to minimize the total transmit power under received SNR constraints at the two sources, where closed-from PA expressions are obtained based on a standard convex optimization procedure for each relay, and the relay resulting in the minimum total transmit power is selected for cooperation. It is shown that earlier works relating to these two approaches for reciprocal channels are special cases of the proposed joint PA-RS schemes. Moreover, computer simulation results show that both the proposed PA schemes without RS provide better performance than the equal PA scheme, and that using the proposed RS schemes with their own corresponding proposed PA schemes further enhances the system performance.