The two-way relay (TWR) channel is a practical framework to facilitate bidirectional communication. Using network coding concepts, the spectrum efficiency has been highly enhanced. Two main ideas underlying the new coding methods are that firstly, forwarding the messages does not require relay to decode the messages; secondly, two transmitters in the uplink are also receivers in the downlink and hence their self-transmitting messages can be exploited in decoding the desired information.

In this thesis, we study the data rate optimization for TWR channel with physical-layer network coding (PNC). First, we investigate a general TWR channel with flexible durations of uplink and downlink. The results obtained can be applied in more general channel model. In the process of optimizin...[ Read more ]

The two-way relay (TWR) channel is a practical framework to facilitate bidirectional communication. Using network coding concepts, the spectrum efficiency has been highly enhanced. Two main ideas underlying the new coding methods are that firstly, forwarding the messages does not require relay to decode the messages; secondly, two transmitters in the uplink are also receivers in the downlink and hence their self-transmitting messages can be exploited in decoding the desired information.

In this thesis, we study the data rate optimization for TWR channel with physical-layer network coding (PNC). First, we investigate a general TWR channel with flexible durations of uplink and downlink. The results obtained can be applied in more general channel model. In the process of optimizing weighted sum-rate of TWR channel with decode-and-forward (DF), we observe that maximizing the uplink data rates may not always increase the sum-rate and thus a criterion for uplink data rate selection is proposed for TWR channel. We also extend the results to N-way relay channel and to TWR channel with PNC.

We then extend the results to consider the power allocation for a two-way multi-antenna relay channel to further increase the spectrum efficiency. The investigations on the uplink transmission and the downlink transmission are done separately. In the uplink channel, to maximize the symmetric data rate, we propose an optimal receive beamforming method at the relay and an optimal power allocation scheme between users. According to the power allocation scheme, users’ power should be allocated inversely proportional to channel gains. In the downlink channel, the relay multicasts a common message to both users. A heuristic design of the transmitted signal covariance at relay is presented and the design is applied to multicast channel with multi-antenna users. Simulation results show that the proposed multicast data rate is very close to the optimal multicast data rate.