Multiuser Rate-Diverse Network-Coded Multiple Access

TL;DR

This paper introduces a rate-diverse NCMA system allowing users with different channel conditions to adopt suitable modulations, significantly improving throughput over traditional homogeneous NCMA systems.

Contribution

It presents the first design of channel-coded rate-diverse PNC with symbol-splitting, enabling effective multi-user decoding over varied modulations in NCMA.

Findings

Rate-diverse NCMA outperforms homogeneous NCMA by 80% in throughput.

Symbol-splitting coding enables reliable decoding across different modulations.

Experimental validation on software-defined radios demonstrates practical benefits.

Abstract

This paper presents the first Network-Coded Multiple Access (NCMA) system with multiple users adopting different signal modulations, referred to as rate-diverse NCMA. A distinguishing feature of NCMA is the joint use of physical-layer network coding (PNC) and multiuser decoding (MUD) to boost throughput of multipacket reception systems. In previous NCMA systems, users adopt the same modulation regardless of their individual channel conditions. This leads to suboptimal throughput for many practical scenarios, especially when different users have widely varying channel conditions. A rate-diverse NCMA system allows different users to use modulations that are commensurate with their channel conditions. A key challenge is the design of the PNC mapping and decoding mechanisms in NCMA when different users adopt different modulations. While there have been past work on non-channel-coded rate-diverse PNC, this paper is the first attempt to design channel-coded rate-diverse PNC to ensure the reliability of the overall NCMA system. Specifically, we put forth a symbol-splitting channel coding and modulation design so that PNC/NCMA can work over different modulations. We implemented our rate-diverse NCMA system on software-defined radios. Experimental results show that the throughput of rate-diverse NCMA can outperform the state-of-the-art rate-homogeneous NCMA by 80%. Overall, the introduction of rate diversity significantly boosts the NCMA system throughput in practical scenarios.