Complementary sequences–based channel estimation for diffuse wireless optical communications

Abstract

Since wireless optical communication (WOC) systems can offer several potential advantages over their radio frequency counterparts, there has been a growing interest in WOC systems. Influenced by the complicated optical propagation environment, there exists diffuse propagation phenomena. In order to eliminate the effect of multipath propagation caused by diffuse reflection, much attention should be concentrated on the channel estimation in diffuse WOC systems. This paper focuses on the complementary sequences (CSs) for estimating a channel impulse response in WOC systems. Based on the training sequences (a preamble and a postamble sequence are included in the data frame), this paper studies the channel estimation in WOC systems. Further, a simple expression for Cramer-Rao bound (CRB) is proposed to evaluate the two-sided channel estimation errors. By minimizing the CRB, the CS-based channel estimation method is proposed. Moreover, the sequence detection performance measured by a bit error ratio is also investigated. Simulation results show that the channel estimation and sequence detection performance can be significantly improved by employing the CS-based channel estimation.