Theory Research Of Optical Orthogonal Codes For Indoor Wireless Commumications With Diffuse Channel

In recent years, the production of optics technology has become more mature. And the wireless optical communication has a lot of advantages, such as no license requirement, etc. So it has become the focus of research a new generation of communications technology. As Internet users increase exponentially every year, multiple access has become one of the problems to be overcome in wireless optical communications. Many multiple access techniques, such as time-division multiple access (TDMA), frequency-division multiple access (FDMA), Wavelength divided multiple access (WDMA), etc., has been widely applied. However, compared with the code division multiple access technique (CDMA), the deployment of these multiple access techniques is relatively complex. Therefore, CDMA become a hot research topic of the multiple access technology. And it was important to select the best codes for the system. Mashhadi and Salehi have shown that OOCs are the best possible class of positive codes.The indoor wireless optical communication has been researched for more than 10 years and indoor optical wireless communication channel has been studied very well. However, most researchers generally have not considered the problem of multipath interference when they studied the indoor optical wireless communication. Few people studied the diffuse reflection model. Even though some people did some research, but they did not consider the problem of multipath interference. Compared to the los channel, the system using the diffuse channel is more stable. Because the system communication may breakdown if there is an obstacle blocking the los path in the los channel. But for the diffuse channel, there are other reflection paths.In this thesis, the channel model of indoor wireless optical communications have been simulated and analyzed in detail. The optical orthogonal code (OOC) has been introduced. The property of the OOC has been analyzed and the upper bound of OOC codes has been derived. The thesis has improved the greedy algorithm and accelerated greedy algorithm. And the two algorithms have been checked by matlab simulation. The advantages and disadvantages of the two algorithms are pointed out. The thesis has analyzed and simulated diffuses channel. It also has introduced each part of the system. Multi-user access interference and multipath interference have been analyzed and bit error rate of the system has been derived. And multipath interference on the system has been analyzed. The theoretical BER has been verified by matlab simulation. The error rate of the system has been strictly deduced. The performance of strict optical orthogonal code and generalized optical orthogonal code has been compared, which has certain instructiveness for actual system to select optimal optical orthogonal codes.