Multiuser Transmit Security Beamforming in Wireless Multiple Access Channels

In this paper, the authors 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. They propose an advantageous semidefinite-programming based beamforming solution for multiple eavesdroppers in multiple-access wire-tap channels. To obtain perfect communication secrecy, it is necessary to have the conditional probability of the cryptogram given a message independent of the actual transmitted message.