Optimal training sequences for indoor wireless optical communications

Abstract

Since indoor wireless optical communication (WOC) systems can offer several potential advantages over their radio frequency counterparts, there has been a growing interest in indoor WOC systems. Influenced by the complicated optical propagation environment, there exist multipath propagation phenomena. In order to eliminate the effect of multipath propagation, much attention should be concentrated on the channel estimation in indoor WOC systems. This paper investigates optimal training sequences (TSs) for estimating a channel impulse response in indoor WOC systems. Based on the Cramer–Rao bound (CRB) theorem, an explicit form of search criterion is found. Optimum TSs are obtained and tabulated by computer search for different channel responses and TS lengths. Measured by mean square error (MSE) performance, channel estimation errors are also investigated. Simulation results show that the MSE of the channel estimator at the receiver can be reduced significantly by using the optimized TS set. Moreover, the longer the TS, the better the MSE performance that can be obtained when the channel order is fixed.

Training sequence based frequency-domain channel estimation for indoor diffuse wireless optical communications

“…For simplicity, only major computational block of the proposed FD search strategy and TD search strategy are considered to evaluate the time complexity. Comparing the search strategies described in [12] for TD channel estimation method with the FD method described in (35), we can see from the table that the optimal TSs search strategy in FD can significantly reduces the complexity of the search. In other words, the procedure of searching for optimum sequences in FD is time consuming than that of TD method.…”

“…As a typical channel estimation method, TD channel estimation has been discussed extensively for conventional radio communications [9,10]. However, http://jwcn.eurasipjournals.com/content/2012/1/326 LED LED only a few works have been done for the channel estimation for diffused WOC systems [11][12][13]. In [11], TS-based channel estimation for WOC systems has been investigated, and the optimal TSs for a better channel estimation performance have been found by computer search in [12].…”

“…However, http://jwcn.eurasipjournals.com/content/2012/1/326 LED LED only a few works have been done for the channel estimation for diffused WOC systems [11][12][13]. In [11], TS-based channel estimation for WOC systems has been investigated, and the optimal TSs for a better channel estimation performance have been found by computer search in [12]. Based on the "two-sided" channel estimation, Wang et al [13] focuses on the complementary sets of sequences for estimating a channel impulse response in WOC systems.…”

“…Motivated by the research [7][8][9][10][11][12][13][14][15], this article focuses on the TS-based channel estimation methods in FD for WOC systems. Considering the propagation property of light and the characteristics of optical modulation, this article establishes the mathematical channel model for indoor WOC systems.…”

Average bit error rate analysis for free-space optical communications over weak turbulence with pointing errors

“…Free-space optical (FSO) communications, as a complementary technology to the radio frequency (RF) technology, [7][8][9] has attracted significant attention recently. However, wireless mobile communications suffers from severe multipath fading and path loss.…”