The Cognitive Multiple Access Wire-Tap Channel

A cognitive Multiple Access Channel with a Wire-tapper (cMAC-WT) is studied, where one of the two encoders is cognitive, in the sense that it knows a priori the message of the other encoder. Both the discrete and Gaussian models are considered. General achievable rates and outer bounds to the secrecy capacity region are derived, and the secrecy capacity region is identified for the special cases of less noisy discrete cMAC-WT, degraded Gaussian cMAC-WT and degraded Gaussian cMAC-WT with orthogonal components. Numerical results are provided to illustrate the main findings.