Multiple-Source Transmit Beamforming for Physical Layer Security in Wireless Multiple Access Channels

In this paper, we investigate beamforming approaches for multiple access secrecy channels. This paper investigates the equivalency between beamforming weight solutions under a fixed sum transmit power constraint and those under a fixed secrecy rate when multiple eavesdroppers are available. We propose a class of beamforming solutions for one and multiple eavesdroppers in multiple-access wire-tap channels. This paper proves the optimality of proposed beamforming solutions under both given sum and individual power constraints for the case of a single eavesdropper.