Achievable performance and limiting factors of echo cancellation in wireless communications

Self-interference cancellation for wireless communications, similar to its wireline counterpart echo cancellation, is considered in this paper. We analyze the factors that impacts echo/self-interference canceller performance. It is shown that the main factors limiting its performance are the excess MSE, echo-channel estimation error, and various nonlinear effects. By establishing a linearized model of the channel estimator, we derive expressions of the errors at the echo canceller output as functions of the estimator's time constant, the bandwidth of channel variation, the receiver SNR and the echo level. The optimal adaptation time constant are derived. Non-linearities in the transmitter and receiver are shown to be the main limiting factor. Finally, implementations considerations of echo cancellers are discussed.