A Study Of Physical Layer Security Based On Decode And Forward Strategy

Communication security has always been a focus of public attention, while the characteristics of wireless communication make it a greater challenge to its security problem. Cooperative communication strategies used in the physical layer security provide a good solution to the wireless communication security. Based on the multi-relay wiretap channel model, this paper studies the performance and property of decode and forward(DF) strategy, the main content of which includes the following aspects.First, the security capacity of the DF strategy is studied, and the expression of the relays weights is obtained to get the maximum value. Based on this, the strategies are simulated respectively under multiple scenarios. Simulation result, which is consistent with the theoretical analysis, shows that the security capacity of the DF strategy is related to the position and distance between each node, transmit power of the source and relays and other factors.Second, group-sparse penalty is added to the expression of DF security capacity, and to solve the problem of the optimal value, proximal gradient algorithm(PGA) is adopted. Simulation under different scenarios shows that the solution based on new algorithm can take both security capacity and relay efficiency into account. Compared with the reference method, it lowers the number and the power of the relays, improving the security capacity of unit relay power as well. In addition, the penalty factor also makes a difference to the performance of the new algorithm.Third, we continue using PGA to study the DJF strategy, which is the combination of DF and cooperative jamming(CJ) strategy. Then DAF strategy is studied in the same way, which is the combination of DF and amplify and forward(AF) strategy. Further simulation shows that the introduction of CJ policy does not improve security capacity of the DF strategy. Therefore, DJF policy shows no advantage in contrast to DF policy. However, in some scenarios DF strategy in conjunction with AF can well enhance the security capacity and efficiency of the relays, indicating that a rational allocation of the number of DF and AF relays may make DAF strategy get good results.