Approximate sum-capacity of full- and half-duplex asymmetric interference channels with unilateral source cooperation

This paper focuses on the causal cognitive radio channel. This model consists of a two-user Gaussian interference channel where a cooperative secondary/cognitive source can causally learn the message of a primary source through a noisy link. The generalized Degrees-of-Freedom (gDoF) and the sum-capacity to within a constant gap are characterized for channels where one destination does not experience interference, referred to as interference-asymmetric channels. Both cases where the cognitive source operates in full- and half-duplex mode are considered. The different models are compared among themselves and with the case of interference-symmetric channels with either bilateral or unilateral source cooperation. In particular, the parameter regimes where causal cognition, or unilateral cooperation, attains the same gDoF of classical channel models, such as the noncooperative interference channel and the non-causal cognitive channel, are identified in order to determine when causal cognitive radio offers benefits in practical systems.