Achievable Rates for the Gaussian Relay Interferer Channel with a Cognitive Source

A relay interferer channel consists of the classic relay channel with an additional source of interference. A three- terminal full-duplex Gaussian relay interferer channel with a cognitive source is analyzed. Each of the relay node and the destination node experiences on its link an additive Gaussian outside interference, in addition to additive noise. Only the source node, referred to as being the cognitive encoder, knows the interferences, in a non-causal manner. We first focus on the case in which the links to the relay and to the destination are corrupted by the same interference; and then we focus on the case of independent interferences. For each of these two models, we establish a lower bound on the channel capacity. The coding schemes for the lower bounds use techniques of dirty paper coding or carbon copying onto dirty paper, interference reduction at the source and decode-and-forward relaying. The results reveal that, by opposition to carbon copying onto dirty paper and its root Costa´s initial dirty paper coding (DPC), it may be beneficial in our setup that the informed source uses a part of its power to partially cancel the effect of the interference so that the uninformed relay benefits from this cancellation, and so the source benefits in turn.