Analysis Of The Secrecy Performance Of Poisson Channel With An Eavesdropper

The application of the wireless communication greatly improve people's communication, make the communication and exchange for people can finish anytime and anywhere. However, not all information or resources are shared. In the pattern of wireless communication, any users will receive the signals from the sender. This makes some private information to suffer eavesdropping and intercepting. Wireless optical communication, is inherently more secure than RF communicati- on due to the intrinsic aspects of the signal propagation in the optical and near-optical frequency range. Especially for laser communication, its monochromatic, orientation, coherence and high brightness characteristics make it become the ideal light source of optical communication. But due small scale fading it is difficult to predict which of the main or wire tapper channel has a better quality. The purpose of this paper is to study the security capacity of a direct detection optical communication system, provide the basis for optical communication security.This paper mainly researches the capacity region of Poisson channel with eavesdropper. The problem of capacity regions of BSC/BEC broadcast channel has always been a basic problem. At first, this paper deeply analyses the achievable rate region of BSC/BEC broadcast channel in different probability values and proves its achievability. Then this paper presents the assumption that one of receivers is eavesdropper channel, which obtains the containing relationship chart among the more capable channel, degraded channel and less noise channel.With the optical communications security theory, a study in this paper is the security capacity of Poisson wiretap channel. For the same input distribution, its capacity will have different performance under different dark current and peak power constraints. This paper summarizes the capacity results of Poisson channel under different constraints and analyses the encoding and decoding methods. In addition, for the Poisson wiretap channel with private message set, the maximum likelihood decoding method is given under the optimal situation. Finally, the achievability of the capacity region in the degraded Poisson wiretap channel is proved and this paper also proposes another kind of representation of degradation conditions in Poisson wiretap channel.