Network-Coded Multiple Access

TL;DR

This paper introduces Network-Coded Multiple Access (NCMA), a novel WLAN scheme combining physical-layer network coding and multiuser decoding to significantly increase throughput in non-relay settings.

Contribution

It is the first practical implementation demonstrating PNC's usefulness in a non-relay multiple access scenario with real-time decoding.

Findings

NCMA can double throughput at medium-high SNR levels.

The system is feasible with real-time processing on USRP hardware.

Further improvements possible with more than two simultaneous transmitters.

Abstract

This paper proposes and experimentally demonstrates a first wireless local area network (WLAN) system that jointly exploits physical-layer network coding (PNC) and multiuser decoding (MUD) to boost system throughput. We refer to this multiple access mode as Network-Coded Multiple Access (NCMA). Prior studies on PNC mostly focused on relay networks. NCMA is the first realized multiple access scheme that establishes the usefulness of PNC in a non-relay setting. NCMA allows multiple nodes to transmit simultaneously to the access point (AP) to boost throughput. In the non-relay setting, when two nodes A and B transmit to the AP simultaneously, the AP aims to obtain both packet A and packet B rather than their network-coded packet. An interesting question is whether network coding, specifically PNC which extracts packet (A XOR B), can still be useful in such a setting. We provide an affirmative answer to this question with a novel two-layer decoding approach amenable to real-time implementation. Our USRP prototype indicates that NCMA can boost throughput by 100% in the medium-high SNR regime (>=10dB). We believe further throughput enhancement is possible by allowing more than two users to transmit together.