Channel Estimation For Indoor Visible Light Communication Systems

Indoor visible light communication (VLC) is a new broadband wireless access technology. In theresearch on future mobile communication systems, indoor VLC systems may play an important role inwireless communications. Based on the training sequence, this thesis studies the channel estimation inindoor wireless VLCs using LEDs. The research results can significantly improve the performance forchannel estimation in VLC systems and provided a better basis of the future commercialization.The main contents can be summarized as follows:Firstly, as the introduction section, Chapter1introduces the history of indoor VLC and thetechnology status. Then, the research topics of this thesis are discussed.Then, Chapter2studies the mathematical channel model for indoor VLC systems. Consideringthe propagation property of light and the characteristics of communication links, this thesis establishesthe mathematical channel model for indoor VLC systems.Based on the established link model, three time domain (TD) channel estimation methods, suchas the correlation (TD-CORR) method, the least square (TD-LS) method and the minimum meansquare error (TD-MMSE) method, are proposed in Chapter3. Moreover, this thesis evaluates theperformance of the proposed three methods by computer simulation. Then, the optimal trainingsequences (TSs) in TD are found by computer search.Based on the channel estimation methods discussed in Chapter2, we propose the complementarysequence (CS)-based channel estimation method. Further, Based on the basic idea of “two-sided”channel estimation method, CS-based channel estimation can not only offer a solution to the problemof time consuming, but also achieve the minimum estimation variance. It can significantly improvethe performance for channel estimation in VLC systems. Then, optimum odd-periodic complementarysequences (OPCSs) are obtained by computer search.Additional, Chapter5proposes three frequency domain (FD) channel estimation methods, suchas the FD-LS method, the FD-MMSE method and the FD-ORL-MMSE method. The computationalcomplexity analysis gives time complexities of the three channel estimation methods in FD. ThisChapter also evaluates the performance of the proposed three methods by computer simulation,measuring in terms of MSE and BER, respectively. Further more, optimal TSs are found andtabulated for different channel responses and TS lengths.Finally, Chapter6concludes the thesis.