On Physical-layer Security Thechniques Based On Polarization Filtering

The issue of security in wireless communication network is significant. In recently years, with the increasing of p opularity of wireless communication tecnology and the growth of wireless network type, security of sercive in wireless network which is applyed by subscribers is facing serious chanllenges. Because of the broadcast characteristics of wireless channel, it i s diffi cult for the transmitted signal to avoid the unintended receivers, T hese adversarial users usually act as eavesdroppers and try to intercept the transmitted signal and extract the information without being detected. It will resulted a inmearable los s when the extracted information is related to fields of commercial or military. For the purpose of solving this kind of problem, research of physical layer security is proposed and getting more and more attention.Based on the thory and bacground of physi cal layer security, this paper foucus on the security performance of wire-tap channel based on relay and cooperative methods. In this type of wire-tap channel, eavesdroppers are usually intersted in the signal transmitted by source and relay nodes. In orde r to enhance the physical layer security performance, users will ask relay nodes for the help of cooperative jamming to damage the receive performance of eavesdroppers, however, the jamming signal will lead to a decrease of ligitimate receiver’s channel ca pacity, as a cosequence, the wireless communication system could not get a satisfying secrecy capacity. To address this problem, this paper deeply researched the method which can bring enhancement of secrecy capacity of a wire-tap channel, besides, research of this paper focus on the nulling of jamming signal at ligitimate receivers, which is the key factors of improvement of physical layer security performance. T hus main reserch content of this paper includes.Firstly, based on the theory and research background, this paper puts forward that the substance of enhancing the secrecy capacity is find a method of improving the capacity of main channel and decreasing the capacity of wire-tap channel, this is because secrecy capacity equals the difference betw een the former and the latter. This paper proposed a phsysical layer security framework, in which half of the relay nodes forward the signal from the source and the others sending the artificial noise to jamming the eavesdroppers.Secondly, after analysis of signal plan and secrcy capacity of the proposed system model, this paper observes the impact of secrecy capacity brought by relay and jammer’s power, and points out the key element suppresses the secrecy capacity is the jamming sigal at the legitima te receiver. Aimming at this problem, this paper proposed bring the polarization sigal processing in wire-tap channel and null the jamming signal at receivers by way of polarized filtering. T hen this paper analyzes the signal plan and proves the feasibilit y of polarizated filtering in nulling the jamming signals.Finally, based on the system model, this paper formulated a optimization problem, in which the secrecy capacity is the objective function and the power allocation is constraints, the optimal solution can be obtained by method of KKT conditions, and this paper examine the security performace of the proposed framework via matlab simulations. After that, this paper compare the secrecy capacity of the proposed system model with the secrecy capacity of the senario in which the jamming signals aren’t nulled at the legitimate reciver.