Artificial noise aided path selection for secure TR communications

Time reversal (TR) transmission is a promising technique for wireless communications. Recently, the security problem in TR communication has drawn growing attention. In this paper, we firstly propose a path selection based physical layer security method, where a subset of paths with larger channel gains are selected for transmitting information signals. We then propose to add artificial noise (AN) on remaining paths to mask the information signals. The corresponding average secrecy rates are approximately derived in closed form. Analytical and simulation results show that the secrecy performance can be considerably improved with the help of path selection, and further improved with the AN aided approach. The optimal values of the selected path number and the power allocation between information signals and AN are also investigated. Simulation results show that costing a small amount of power on AN and transmitting AN on a few paths, we can achieve good secrecy performance.