Physical Network Coding in Two-Way Wireless Relay Channels

TL;DR

This paper analyzes physical network coding schemes in two-way wireless relay channels, comparing their efficiency and identifying conditions under which different schemes achieve optimal two-way communication rates.

Contribution

It classifies existing physical network coding schemes into two categories and compares their maximum achievable rates, revealing scenarios where simpler schemes match the best possible performance.

Findings

DNF scheme can offer the highest two-way rate under certain conditions.

JDF scheme can achieve the same rate as DNF for some SNR configurations.

The paper provides conditions for maximizing the two-way rate for each scheme.

Abstract

It has recently been recognized that the wireless networks represent a fertile ground for devising communication modes based on network coding. A particularly suitable application of the network coding arises for the two--way relay channels, where two nodes communicate with each other assisted by using a third, relay node. Such a scenario enables application of \emph{physical network coding}, where the network coding is either done (a) jointly with the channel coding or (b) through physical combining of the communication flows over the multiple access channel. In this paper we first group the existing schemes for physical network coding into two generic schemes, termed 3--step and 2--step scheme, respectively. We investigate the conditions for maximization of the two--way rate for each individual scheme: (1) the Decode--and--Forward (DF) 3--step schemes (2) three different schemes with two steps: Amplify--and--Forward (AF), JDF and Denoise--and--Forward (DNF). While the DNF scheme has a potential to offer the best two--way rate, the most interesting result of the paper is that, for some SNR configurations of the source--relay links, JDF yields identical maximal two--way rate as the upper bound on the rate for DNF.