On the Capacity Region of the Two-user Interference Channel with a Cognitive Relay

TL;DR

This paper investigates the capacity region of a two-user interference channel enhanced by a cognitive relay, deriving bounds and characterizing the capacity in certain regimes for both deterministic and Gaussian models.

Contribution

It provides the first complete characterization of the symmetric linear deterministic approximation and an approximate capacity region for the symmetric Gaussian interference channel with a cognitive relay.

Findings

Sum-rate upper bounds derived for the ICCR.

Capacity region characterized for the symmetric LDA except for certain regimes.

Approximate capacity region for the symmetric GICCR within a constant gap.

Abstract

This paper considers a variation of the classical two-user interference channel where the communication of two interfering source-destination pairs is aided by an additional node that has a priori knowledge of the messages to be transmitted, which is referred to as the it cognitive relay. For this Interference Channel with a Cognitive Relay (ICCR) In particular, for the class of injective semi-deterministic ICCRs, a sum-rate upper bound is derived for the general memoryless ICCR and further tightened for the Linear Deterministic Approximation (LDA) of the Gaussian noise channel at high SNR, which disregards the noise and focuses on the interaction among the users' signals. The capacity region of the symmetric LDA is completely characterized except for the regime of moderately weak interference and weak links from the CR to the destinations. The insights gained from the analysis of the LDA are then translated back to the symmetric Gaussian noise channel (GICCR). For the symmetric GICCR, an approximate characterization (to within a constant gap) of the capacity region is provided for a parameter regime where capacity was previously unknown. The approximately optimal scheme suggests that message cognition at a relay is beneficial for interference management as it enables simultaneous over the air neutralization of the interference at both destinations.