[Paper Review] Modulation and Multiple Access for 5G Networks

Yunlong Cai, Zhijin Qin+3 more|arXiv (Cornell University)|Feb 21, 2017

Advanced Wireless Communication Technologies72 references4 citations

TL;DR

This paper provides a comprehensive survey of advanced modulation and multiple access (MA) techniques for 5G networks, focusing on spectral efficiency, out-of-band leakage, and bit-error rate in orthogonal MA, and evaluating non-orthogonal MA (NOMA) schemes like power-domain, code-domain, and multi-domain NOMA. It demonstrates that NOMA significantly enhances spectral efficiency and supports massive connectivity by enabling multiplexing of multiple users in the same resource block, despite increased receiver complexity and interference challenges.

ABSTRACT

Fifth generation (5G) wireless networks face various challenges in order to support large-scale heterogeneous traffic and users, therefore new modulation and multiple access (MA) schemes are being developed to meet the changing demands. As this research space is ever increasing, it becomes more important to analyze the various approaches, therefore in this article we present a comprehensive overview of the most promising modulation and MA schemes for 5G networks. We first introduce the different types of modulation that indicate their potential for orthogonal multiple access (OMA) schemes and compare their performance in terms of spectral efficiency, out-of-band leakage, and bit-error rate. We then pay close attention to various types of non-orthogonal multiple access (NOMA) candidates, including power-domain NOMA, code-domain NOMA, and NOMA multiplexing in multiple domains. From this exploration we can identify the opportunities and challenges that will have significant impact on the design of modulation and MA for 5G networks.

Motivation & Objective

• To analyze and compare novel modulation techniques for orthogonal multiple access (OMA) in 5G networks, focusing on spectral efficiency, out-of-band leakage, and bit-error rate.
• To evaluate non-orthogonal multiple access (NOMA) schemes—including power-domain, code-domain, and multi-domain NOMA—as a solution to support massive connectivity and high spectral efficiency in 5G.
• To identify key challenges and opportunities in integrating NOMA with existing modulation schemes like OFDM and filtering techniques.
• To explore the joint design of modulation and NOMA for high-frequency bands (mmWave/THz), where propagation impairments and noise are critical.
• To assess the performance of advanced detection methods such as multi-user detection with successive interference cancellation (SIC) and message passing algorithms (MPA) in NOMA systems.

Proposed method

• Surveying and comparing traditional OFDM and its variants (e.g., filtered OFDM, pulse-shaped OFDM, precoded OFDM) to reduce out-of-band leakage and improve spectral efficiency.
• Analyzing power-domain NOMA, where users are multiplexed in power domain using superposition coding and successive interference cancellation (SIC) at the receiver.
• Evaluating code-domain NOMA schemes such as LDS-CDMA, LDS-OFDM, SCMA, PDMA, BOMA, and LPMA, which use sparse spreading codes and multi-dimensional constellations to enable non-orthogonal user multiplexing.
• Introducing multi-domain NOMA (e.g., PDMA, BOMA) that multiplexes users across power, code, and spatial domains to enhance diversity and system capacity.
• Proposing joint design approaches between modulation (e.g., f-OFDM) and NOMA (e.g., SCMA) to mitigate interference from short cyclic prefixes and improve detection performance.
• Applying message passing algorithm (MPA) with SIC detection in SCMA and PDMA for near-optimal performance, especially in sparse codebook structures.

Experimental results

Research questions

• RQ1 How do advanced modulation techniques (e.g., filtering, pulse shaping, precoding) improve spectral efficiency and reduce out-of-band leakage in OFDM-based OMA for 5G?
• RQ2 What are the performance trade-offs of power-domain NOMA in terms of spectral efficiency, user fairness, and error propagation due to SIC?
• RQ3 How do code-domain NOMA schemes (e.g., SCMA, PDMA) achieve higher spectral efficiency and support more users compared to traditional OMA?
• RQ4 What are the key challenges in designing optimal codebooks and user clustering for code-domain NOMA, and how can joint modulation-NOMA design mitigate interference?
• RQ5 How do mmWave and THz bands affect NOMA performance, and what are the implications of noise, phase noise, and carrier frequency offset in high-frequency NOMA systems?

Key findings

• Power-domain NOMA achieves high spectral efficiency by multiplexing users in the power domain and using SIC at the receiver, but requires user pairing and is sensitive to error propagation.
• Code-domain NOMA schemes such as SCMA and PDMA offer superior spectral efficiency and diversity gains by using sparse spreading codes and multi-dimensional constellations, enabling more users per resource block.
• LDS-OFDM and LDS-CDMA achieve near-optimal MPA detection performance with no need for instantaneous CSI, but require redundancy from coding and careful codebook design.
• SCMA and PDMA benefit from message passing algorithm (MPA) detection with SIC, achieving near-optimal performance, especially when users are clustered based on similar delay profiles.
• Joint design of f-OFDM and SCMA is critical to mitigate inter-symbol interference (ISI) and inter-carrier interference (ICI) caused by short cyclic prefixes in wideband systems.
• High-frequency bands (mmWave/THz) pose significant challenges due to noise, phase noise, and carrier frequency offset, but NOMA remains viable with proper power control and robust receiver design.