Optimal training and redundant precoding for block transmissions with application to wireless OFDM

The adoption of orthogonal frequency-division multiplexing by wireless local area networks and audio/video broadcasting standards testifies to the importance of recovering block precoded transmissions propagating through frequency-selective finite-impulse response (FIR) channels. Existing block transmission standards invoke bandwidth-consuming error control codes to mitigate channel fades, and training sequences to identify the FIR channels. To enable block-by-block receiver processing, we design redundant precoders with cyclic prefix and superimposed training sequences for optimal channel estimation and guaranteed symbol detectability, regardless of the underlying frequency-selective FIR channels. Numerical results are presented to access the performance of the designed training and precoding schemes.

I. Introduction

Block transmissions relying on linear redundant filterbank precoding with cyclic prefixed (CP) or zero-padded (ZP) blocks have gained increasing interest recently for mitigating frequency-selective multipath effects (see, e.g., [2], [11], [17], [19] and references therein). Redundancy removes interblock interference (IBI), and facilitates (even blind) acquisition of channel state information (CSI) at the receiver. It also leads to data efficient, low-complexity linear equalizers [zero-forcing (ZF) or minimum mean-squared error (MMSE)] with guaranteed symbol detectability regardless of the zero locations of the underlying finite-impulse response (FIR) channel [17].