The Cognitive Interference Channel With a Causal Relay in Very Strong Interference

We study the cognitive interference channel where an additional node (a relay) is present. In our model the relay´s operation is causal rather than strictly causal, i.e., the relay´s transmit symbol depends not only on its past but also on its current received symbol. We derive outer bounds for the discrete and Gaussian cases in very strong interference. A scheme for achievability based on instantaneous amplify-and-forward relaying is proposed for this model. The inner and outer bounds coincide for a special case of very strong interference.