A New Capacity Result for the Z-Gaussian Cognitive Interference Channel

TL;DR

This paper introduces a new outer bound for the Gaussian cognitive interference channel, demonstrating its tightness and achievability in the Z-channel case with strong interference, and suggests potential generalization.

Contribution

It proposes a novel outer bound based on multi-antenna broadcast channel capacity and proves its achievability for the Z-channel with strong interference.

Findings

The outer bound is the tightest among known bounds for the Z-channel.

The outer bound is achievable for sufficiently strong interference.

Numerical evaluations suggest the results may extend beyond the Z-channel.

Abstract

This work proposes a novel outer bound for the Gaussian cognitive interference channel in strong interference at the primary receiver based on the capacity of a multi-antenna broadcast channel with degraded message set. It then shows that for the Z-channel, i.e., when the secondary receiver experiences no interference and the primary receiver experiences strong interference, the proposed outer bound not only is the tightest among known bounds but is actually achievable for sufficiently strong interference. The latter is a novel capacity result that from numerical evaluations appears to be generalizable to a larger (i.e., non-Z) class of Gaussian channels.