On cooperative encoding with partially known non-causal interference

Abstract

We consider a three-terminal Gaussian relay channel corrupted by a Gaussian interference. We assume that the interference is non-causally known to only some, i.e, not to all, the terminals. We examine two different scenarios: 1) both the source and the relay, but not the destination, know the interference and collaborate to cancel out its effect and 2) only the source knows the interference. The first scenario exhibits some symmetry and we refer to it as “informed source and relay”. The second scenario exhibits some asymmetry and we refer to it as “informed source only”. For the Gaussian relay channel with informed source and relay, we derive a lower bound on channel capacity, based on the source and the relay both employing standard dirty paper coding (DPC) and the relay using the decode-and-forward scheme. We also show that this lower bound meets with the cut-set bound, and thus gives capacity, if the channel is degraded. For the Gaussian relay channel with informed source only, we derive a lower bound on channel capacity. This lower bound is based on a generalized DPC that consists in a combination of partial cancellation of the known interference and standard DPC. In the asymmetric scenario, the performance characterizations reveal that, by opposition to Costa's initial DPC, it may be beneficial that the informed source uses a part of its power to (partially) cancel the effect of this interference so that the uninformed relay benefits from this cancellation.