On the Achievable Rates of Memoryless Two-Way Relay Channels

Amplify-and-forward (AF) and demodulate-and-forward (DMF) can be effectively used in memoryless two-way relay channels (TWRCs) to enhance the spectral efficiency. In this paper, we study AF and DMF, in terms of their achievable data exchange rate, for a memoryless TWRC. Our results show that unlike memoryless one-way relaying, increasing users´ SNR benefits AF more than DMF. Another interesting observation is that while with DMF a higher data rate is provided for the user whose channel condition is better, with AF the situation is the reverse. That is, the user with worse channel condition can receive at a higher data rate. Further, we find that for a TWRC with asymmetric users´ channels, AF can take advantage of power back-off at the users, without degrading the data rate, to improve the energy efficiency while power back-off is not beneficial for DMF.