An Efficient Code-Domain NOMA Transceiver for mm-Wave Hybrid Massive MIMO Architectures

TL;DR

This paper introduces a novel code-domain NOMA transceiver architecture for mm-wave massive MIMO systems, demonstrating improved performance and lower complexity in uplink scenarios with limited RF chains.

Contribution

It proposes a hybrid beamforming framework integrating code-domain NOMA, and introduces a new receiver architecture for MUSA, enhancing uplink performance and reducing complexity.

Findings

Code-domain NOMA outperforms conventional methods with few RF chains.

The new MUSA receiver reduces complexity compared to classical designs.

Performance analysis shows benefits in bit-error rate and information rate.

Abstract

Massive MIMO and non-orthogonal multiple access (NOMA) are crucial methods for future wireless systems as they provide many advantages over conventional systems. Power-domain NOMA methods are investigated in massive MIMO systems, whereas there is little work on integration of code-domain NOMA and massive MIMO which is the subject of this study. We propose a general framework employing user-grouping based hybrid beamforming architecture for mm-wave massive MIMO systems where NOMA is considered as an intra-group process. It is shown that classical receivers of sparse code multiple access (SCMA) and multi-user shared access (MUSA) can be directly adapted. Additionally, a novel receiver architecture which is an improvement over classical one is proposed for uplink MUSA. This receiver makes MUSA preferable over SCMA for uplink transmission with lower complexity. We provide a lower bound on achievable information rate (AIR) as a performance measure. We show that code-domain NOMA schemes outperform conventional methods with very limited number of radio frequency (RF) chains where users are spatially close to each other. Furthermore, we provide an analysis in terms of bit-error rate and AIR under different code length and overloading scenarios for uplink transmission where flexible structure of MUSA is exploited.