Precoder Design for Unknown Frequency Flat Fading Channels

This paper introduces a precoder design for wireless receivers with imperfect fading channel state information (CSI). Imperfect CSI arises from inaccurate channel modelling or suboptimum channel estimation procedure. Precoders at transmitters are considered here as the means to reduce detection error. To that end, a new lower bound for pairwise error probability (PEP) is introduced. Using the proposed lower bound, precoders are optimized to improve the bit error rate (BER) performance of a receiver which uses basis expansion models (BEM) to estimate time varying channel coefficients without statistical information about the channel. Two precoder design criteria, namely pairwise coding and diversity gain are introduced through the proposed lower bound. Experimentation and theoretical analysis reported here indicate significant improvement in the BER performance of the BEM based receiver when it is used with the precoder in fading channels.