Cognitive cooperative communications on the Multiple Access Channel

In this paper, we investigate a three-user cognitive communication network where a primary two-user Multiple Access Channel (MAC) suffers interference from a secondary point-to-point (P2P) channel, sharing the same medium. While the P2P channel transmitter — transmitter 3 — causes an interference at the primary MAC receiver, we assume that the primary channel transmitters — transmitters 1 and 2 — do not cause any interference at the P2P receiver. It is assumed that one of the MAC transmitters has cognitive capabilities and cribs causally from the other MAC transmitter. Furthermore, we assume that the cognitive transmitter knows the message of transmitter 3 in a noncausal manner, thus introducing the three-user Multiple Access Cognitive Z-Interference Channel (MA-CZIC). We obtain inner and outer bounds on the capacity region of the three-user MA-CZIC for both strictly and nonstrictly causal cribbing cognitive encoders.