Secure Transmission with Artificial Noise in Distributed Antenna Systems and Achievable Secrecy-Rate Power Optimization

In this paper, the physical layer security is analyzed in distributed antenna systems (DAS). Firstly, we add artificial noise (AN) to the information bearing signal in order to disturb the passive eavesdropper without degrading the intended receiver's channel. Then, a power allocation (PA) problem maximizing achievable secrecy rate (SR) is formulated and transformed as a convex problem by use of Taylor expansion and am-gm inequality. At last, numerical results verify the effectiveness of the proposed algorithms, and provide a new insight that optimal power allocation from each AP to each user can improve SR by an order of magnitude compared with equal PA proportion to AN.