Capacity of the Gaussian Two-way Relay Channel to within 1/2 Bit

TL;DR

This paper demonstrates that a specific coding scheme for the Gaussian two-way relay channel can achieve rates within 1/2 bit of the theoretical maximum, approaching optimality at high SNRs.

Contribution

The paper introduces a nested lattice coding scheme that closely approaches the capacity of the Gaussian two-way relay channel within a constant gap.

Findings

Achieves within 1/2 bit of the cut-set bound for all channel parameters.

Scheme becomes asymptotically optimal at high SNRs.

Uses structured coding techniques for both uplink and downlink.

Abstract

In this paper, a Gaussian two-way relay channel, where two source nodes exchange messages with each other through a relay, is considered. We assume that all nodes operate in full-duplex mode and there is no direct channel between the source nodes. We propose an achievable scheme composed of nested lattice codes for the uplink and structured binning for the downlink. We show that the scheme achieves within 1/2 bit from the cut-set bound for all channel parameters and becomes asymptotically optimal as the signal to noise ratios increase.