Research On Physical-Layer Secrecy Capacity In Wireless Communications

With the development of wireless communication technology, security issues of wirelesscommunication have become an important factor. Meanwhile, due to the openness and complexityof wireless environment, the research of physical layer security has got a lot of attention in recentyears. The purpose of the physical layer security research is to maximize signal transmission speedas close as to the communication system’s secrecy capacity combing the Shannon informationtheory, probability theory with the advanced wireless communication technologies. In this paper weanalyze the secrecy capacity and security region of the wiretap channel model with the cooperativejammers.The main research work is summarized as follows:(1) From the view of information theory, we analyze that how the location of eavesdropper andcooperative jammers influences the secrecy capacity of communication systems. The numericalsimulations are aslo provided for ergodic secrecy capacity based on geographic variation inRayleigh fading channel with the path loss. Simulation results show that the cooperativejamming can improve system secrecy capacity. Furthermore, the security of communicationsystems can be enhanced by appropriately increasing the number of jammers, flexibly adjustingthe position of jammers and reasonably allocating the power.(2) Combining the cooperative jamming technology and the multiple-input multiple-outputtechnology, this paper proves that when legitimate channel conditions are worse thaneavesdropping channel conditions, the cooperative jamming technology will improve the secureof communication system. Simulation results are described for researching the factors whichaffecting the secrecy capacity of the system.(3) The propagation characteristics of wireless channel are analyzed in this paper with consideringthe path loss, shadow fading and multipath effects. Experimental results show that the wirelesschannel characteristics are closely related to the safety performance of the model, and theimproving of the signal propagation environment plays an important role in ensuring thesecurity of the communication systems.