On Mean-Square Decision Feedback Equalization and Timing Phase

We analyze the effect of timing phase on the performance of digital data receivers which employ decision feedback equalization. It has long been conjectured, and verified by computer simulations, that decision feedback equalizers are considerably less sensitive to the choice of timing phase than are conventional transversal linear equalizers. We develop the theoretical machinery which provides a rationale for these observations. It follows from our results that for typical operating conditions a 1-2 dB penalty can be incurred by choosing a bad timing phase in decision feedback, while the penalty can be an order of magnitude greater than this (in dB) in conventional linear equalizers.