[Paper Review] A Survey on Non-Orthogonal Multiple Access for 5G Networks: Research Challenges and Future Trends

Zhiguo Ding, Xianfu Lei+4 more|arXiv (Cornell University)|Jun 16, 2017

Advanced Wireless Communication TechnologiesEngineering117 references70 citations

TL;DR

This is a comprehensive survey of NOMA for 5G, covering single- and multi-carrier NOMA, MIMO-NOMA, cooperative NOMA, and mmWave integration, with discussion of challenges and future directions.

ABSTRACT

Non-orthogonal multiple access (NOMA) is an essential enabling technology for the fifth generation (5G) wireless networks to meet the heterogeneous demands on low latency, high reliability, massive connectivity, improved fairness, and high throughput. The key idea behind NOMA is to serve multiple users in the same resource block, such as a time slot, subcarrier, or spreading code. The NOMA principle is a general framework, and several recently proposed 5G multiple access schemes can be viewed as special cases. This survey provides an overview of the latest NOMA research and innovations as well as their applications. Thereby, the papers published in this special issue are put into the content of the existing literature. Future research challenges regarding NOMA in 5G and beyond are also discussed.

Motivation & Objective

• Explain the NOMA principle and contrast with orthogonal MA to justify spectral efficiency and fairness benefits.
• Survey existing NOMA variants (power-domain, SCMA, LDS, PDMA) and their applicability to 5G.
• Review single-carrier and multi-carrier NOMA designs, including resource allocation and complexity considerations.
• Discuss MIMO-NOMA design principles, including quasi-degradation and decomposition into SISO-NOMA subchannels.
• Examine cooperative NOMA and mmWave/NOMA integrations, highlighting implementation challenges and future research directions.

Proposed method

• Categorization of NOMA approaches (power-domain, multi-carrier, LDS/SCMA/PDMA, MIMO, cooperative).
• Explanation of key techniques such as superposition coding, SIC, MPA, and joint decoding concepts.
• Discussion of resource allocation, user grouping, and complexity considerations in multi-carrier NOMA.
• Overview of MIMO-NOMA design strategies, including user ordering, decomposition to SISO-NOMA, and GSVD-based approaches.
• Assessment of cooperative NOMA with user relaying and dedicated relays, including relay selection strategies and full-duplex considerations.
• Integration of NOMA with mmWave to enable massive connectivity and spectrum efficiency.

Experimental results

Research questions

• RQ1 What are the spectral efficiency and fairness gains of NOMA over traditional OMA in 5G networks?
• RQ2 How can multi-carrier NOMA be effectively designed and optimized (grouping, subcarrier allocation, power allocation) to support massive connectivity?
• RQ3 What are the challenges and trade-offs in MIMO-NOMA, including user ordering and channel-decomposition approaches?
• RQ4 How can cooperative NOMA (with user relaying or dedicated relays) improve system performance and coverage?
• RQ5 What role does mmWave play in NOMA-enabled 5G, and what implementation challenges arise?

Key findings

• NOMA can improve spectral efficiency and support massive connectivity by serving multiple users on the same resource block.
• CR-NOMA provides QoS guarantees by constraining power allocation to meet target data rates.
• Multi-carrier NOMA variants like SCMA, LDS, and PDMA enable overloading while maintaining manageable complexity through sparse multiplexing and joint decoding.
• MIMO-NOMA design strategies include quasi-degradation, user grouping, random beamforming, spatial-decomposition into SISO-NOMA channels, and GSVD-based approaches.
• Cooperative NOMA with either user relaying or dedicated relays can reduce the number of time slots and improve spectral efficiency, with potential full-duplex benefits.
• MMWave-NOMA supports massive connectivity in high-frequency bands, leveraging NOMA to enhance spectral efficiency in dense networks.