Robust equalization for spread-response precoding systems

The problem of equalization for spread-response precoding systems based on minimum mean-square error (MMSE) estimates of the fading channel coefficients is considered. These systems are attractive, low complexity alternatives to the combination of interleaving and error-control coding for achieving time diversity in fading environments. To make the performance of these systems robust to channel estimation errors, we derive the linear equalizer at the receiver that maximizes the effective signal-to-noise-and-interference ratio (SNIR) subject to uncertainty in the channel measurements. We examine the bit-error rate performance and develop fixed and dynamic solutions to the associated problem of optimal power allocation between the data transmissions and channel measurements. The effectiveness of these algorithms is demonstrated through measurements obtained from an indoor wireless setting.