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.