Wireless Network-Coded Three-Way Relaying Using Latin Cubes

TL;DR

This paper introduces a novel approach to physical layer network coding in three-way wireless relaying using Latin cubes, enabling adaptive interference reduction based on channel conditions.

Contribution

It establishes a correspondence between network coding maps satisfying the exclusive law and Latin cubes, extending two-way relaying concepts to three-way scenarios.

Findings

Network coding maps correspond to Latin cubes of second order.

Explicit network code maps are derived for the broadcast phase.

The approach reduces interference during the multiple access stage.

Abstract

The design of modulation schemes for the physical layer network-coded three-way wireless relaying scenario is considered. The protocol employs two phases: Multiple Access (MA) phase and Broadcast (BC) phase with each phase utilizing one channel use. For the two-way relaying scenario, it was observed by Koike-Akino et al. \cite{KPT}, that adaptively changing the network coding map used at the relay according to the channel conditions greatly reduces the impact of multiple access interference which occurs at the relay during the MA phase and all these network coding maps should satisfy a requirement called \textit{exclusive law}. This paper does the equivalent for the three-way relaying scenario. We show that when the three users transmit points from the same 4-PSK constellation, every such network coding map that satisfies the exclusive law can be represented by a Latin Cube of Second Order. The network code map used by the relay for the BC phase is explicitly obtained and is aimed at reducing the effect of interference at the MA stage.