Blind Equalization Using Higher-Order Statistics For Atmosphere Laser Communication Channel

Atmosphere Laser Communication (ALC) refers to the technology of transmitting voice, data and graphics using laser bean. Because of its advantage of narrow transmission bean, small antenna size, broad information capability and high performance to price, it impressed many people in communication area. So it has good application foreground in resolve of "The Last Kilometer Problem" and emergence communication.Although the Atmosphere Laser Communication has the two characteristics of board-band and wireless, this point to-point communication based atmosphere channel and medium of laser have inevitable defect itself. The transmission of laser in atmosphere was affected by kinds of factors in atmosphere channel. It brought signal attenuation and inter-symbol interferences. It leaded the addition of bit error rate. Approach the technique of being against the effect of atmosphere channel transmission factor to ladder transmission for ensure the normal of laser communication link have a very important meaning.This paper solved the problem about signal attenuation and ISI in the ALC system through blind equalization technique. Firstly, the dissertation introduced the Atmosphere Laser Communication system and its characteristic simply, and then the scheme about research of blind equalization in atmosphere laser communication system was advanced. The dissertation focuses on the performance of blind equalization using higher-order statistics implicitly and explicitly in accordance according the characteristic of Atmosphere Laser Communication channel. The research consists of several aspects as follows:1.The mathematics' model of Bussgang BE and its relevant algorithm including Sato alg--orithm, Godard algorithm and DD(Decision-Directed) algorithm is discussed in our research, and the adaptive CDLMS filter base third-order cumulant algorithm, combining the conventional blind equalization algorithm with the decision direction, is presented. Furthermore, the result from the simulation about that algorithm which is presented in this paper is that the smaller steady-state error results from these algorithms than the DD (Decision-Directed) algorithm.2.The explicitly cumulant algorithms and the even-order normalized cumulant algorithm's is studied. The result of simulation about performance of these algorithm is that the rapidity of convergence of the explicitly cumulant algorithms is faster than the even-order normalized cumulant algorithms; the stability of the even-order normalized cumulant algorithms is very good.3.According to the problem of the different effect on the signal transmission by different the weather regime, The ALC channel is analog, using the data measuring from the ALC system. We demonstrate the efficiency of several blind equalization algorithms based the analogic ALC channel, including comparison study and evaluation of their performance.