Communication networks have had a transformative impact on our society as they have revolutionized almost all aspects of human interaction. The explosive growth of data traffic has led to an increased demand on improving the reliability, efficiency and security aspects of the systems. In this paper, we focus on the multiple access channel, a communication model where several transmitters communicate to a common receiver (e.g., a cellular telephone network) in the presence of an external eavesdropper. The goal is to explore the competitive yet cooperative relationship between the transmitters in order to obtain an efficient communication under a certain reliability and security guarantee. Moreover, we take a special look into the inner and outer bounds on the secrecy capacity regions over the 2-transmitter DM-MAC with a degraded eavesdropper (assuming that both transmitters are cooperative). We notice that the inner and outer bounds differentiate themselves in the permissible sets of input distributions and thus not tight in general. This leaves the problem of secrecy capacity regions still open.

communication networks, multiple access channel, secrecy