[Paper Review] Non-Orthogonal Multiple Access (NOMA): How It Meets 5G and Beyond

S. M. Riazul Islam, Ming Zeng+2 more|arXiv (Cornell University)|Jul 23, 2019

Advanced Wireless Communication Technologies79 references17 citations

TL;DR

This paper presents a comprehensive overview of Non-Orthogonal Multiple Access (NOMA) as a key radio access technique for 5G and beyond networks, emphasizing its superiority in spectral efficiency over traditional Orthogonal Multiple Access (OMA). It details power-domain and code-domain NOMA in single- and multi-antenna systems, resource allocation strategies like user pairing and power allocation, cooperative NOMA variants, and integration challenges with mmWave and heterogeneous networks.

ABSTRACT

Due to massive connectivity and increasing demands of various services and data-hungry applications, a full-scale implementation of the fifth generation (5G) wireless systems requires more effective radio access techniques. In this regard, non-orthogonal multiple access (NOMA) has recently gained ever-growing attention from both academia and industry. Compared to orthogonal multiple access (OMA) techniques, NOMA is superior in terms of spectral efficiency and is thus appropriate for 5G and Beyond. In this article, we provide an overview of NOMA principles and applications. Specifically, the article discusses the fundamentals of power-domain NOMA with single and multiple antennas in both uplink and downlink settings. In addition, the basic principles of code-domain NOMA are elaborated. Further, the article explains various resource allocation techniques such as user pairing and power allocation for NOMA systems; discusses the basic form of cooperative NOMA and its variants; and addresses several opportunities and challenges associated with the compatibility of NOMA with other advanced communication paradigms such as heterogeneous networks and millimeter wave communications.

Motivation & Objective

• Address the growing demand for spectral efficiency and massive connectivity in 5G and future wireless networks.
• Overcome the limitations of Orthogonal Multiple Access (OMA) in supporting massive device connectivity and high data rates.
• Provide a unified technical overview of NOMA principles, including power-domain and code-domain implementations.
• Investigate resource allocation techniques such as user pairing and power allocation to optimize NOMA performance.
• Examine the integration of NOMA with emerging paradigms like millimeter wave communications and heterogeneous networks.

Proposed method

• Analyzes power-domain NOMA in both uplink and downlink scenarios using single and multiple antennas.
• Explains code-domain NOMA based on sparse code multiple access (SCMA) and low-density signature (LDS) techniques.
• Proposes user pairing strategies to maximize spectral efficiency and fairness in NOMA systems.
• Introduces power allocation algorithms to balance throughput and user fairness in NOMA networks.
• Reviews cooperative NOMA schemes, including decode-and-forward and amplify-and-forward relaying protocols.
• Discusses system-level challenges in integrating NOMA with mmWave and heterogeneous networks, including beamforming and interference management.

Experimental results

Research questions

• RQ1 How does NOMA improve spectral efficiency compared to conventional OMA in 5G and beyond systems?
• RQ2 What are the optimal user pairing and power allocation strategies for maximizing NOMA system performance?
• RQ3 How can code-domain NOMA techniques like SCMA be effectively deployed in multi-antenna and multi-user scenarios?
• RQ4 What are the key challenges and solutions for integrating NOMA with millimeter wave and heterogeneous networks?
• RQ5 How does cooperative NOMA enhance coverage and reliability in high-mobility or low-SNR environments?

Key findings

• NOMA achieves higher spectral efficiency than OMA by allowing multiple users to share the same time-frequency resource block through power-domain multiplexing.
• User pairing based on channel gain differences significantly improves sum rate and fairness in NOMA systems.
• Power allocation in NOMA can be optimized to balance throughput and user fairness, especially in multi-antenna and multi-user scenarios.
• Code-domain NOMA, particularly SCMA, enables massive connectivity by supporting more users per resource block than power-domain NOMA.
• Cooperative NOMA improves coverage and reliability, especially in cell-edge and high-mobility scenarios, through relaying techniques.
• Integration of NOMA with mmWave and heterogeneous networks is feasible but requires advanced beamforming and interference coordination techniques.