Capacity region of the dirty two-way relay channel to within constant bits

Abstract

In this paper, we consider a dirty Gaussian two-way relay channel, where the two user nodes exchange messages with the help of a relay node. The three nodes experience two independent additive interferences which are assumed to be known at some nodes. We consider two cases: (1) the two user nodes know each of the two interferences respectively; (2) the relay node knows both the interferences. With nested lattice coding and compute-and-forward relaying, we derive achievable rate regions for the above two cases. The achievable rate regions are shown to be within constant bits from the cut-set outer bound for all channel parameters regardless of the interferences. Comparing the two achievable rate regions of the above two cases, it is shown that more information about the interferences the relay node knows more interferences will be canceled, larger achievable rate region can be achieved.