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.