Self-interference cancellation for two-way amplify-and-forward relaying systems

This study proposes implementation of two-way amplify-and-forward relaying systems in practical environments where signals from two source nodes arrive at a relay with different propagation delays. The authors develop a self-interference delay and channel estimation technique applicable for practical environments. Whereas receiver processing in conventional schemes is performed in the baud rate domain, in this work, oversampling (or Nyquist sampling) is introduced at the receiver to avoid any energy loss in the desired signal. They derive the proposed estimator in the oversampled domain on the basis of the least square criterion and also provide a design guide for the oversampling ratio and the application of a self-interference canceller. They observe from the author´s analysis and simulation results that an oversampling of 2 is sufficient, and it is not preferable to use a self-interference canceller when L/(N·ISNR) is greater than 1, where the interference-to-signal-plus-noise ratio (ISNR) denotes the power ratio of the self-interference to the desired signal plus noise, L is the channel length and N is the number of symbols in one time slot.