[Paper Review] Cognitive Non-Orthogonal Multiple Access with Cooperative Relaying: A New Wireless Frontier for 5G Spectrum Sharing

Lu Lv, Jian Chen+3 more|arXiv (Cornell University)|Jan 12, 2018

Advanced Wireless Communication TechnologiesEngineering14 references21 citations

TL;DR

This paper proposes cognitive non-orthogonal multiple access (NOMA) networks integrating cognitive radio principles with NOMA and cooperative relaying to enhance spectrum efficiency and reliability in 5G. It introduces three architectures—underlay, overlay, and CR-inspired NOMA—and demonstrates that cooperative relaying significantly reduces outage probability across all configurations, improving fairness and reliability in interference-limited environments.

ABSTRACT

Two emerging technologies towards 5G wireless networks, namely non-orthogonal multiple access (NOMA) and cognitive radio (CR), will provide more efficient utilization of wireless spectrum in the future. In this article, we investigate the integration of NOMA with CR into a holistic system, namely cognitive NOMA network, for more intelligent spectrum sharing. Design principles of cognitive NOMA networks are perfectly aligned to functionality requirements of 5G wireless networks, such as high spectrum efficiency, massive connectivity, low latency, and better fairness. Three different cognitive NOMA architectures are presented, including underlay NOMA networks, overlay NOMA networks, and CR-inspired NOMA networks. To address inter- and intra-network interference which largely degrade the performance of cognitive NOMA networks, cooperative relaying strategies are proposed. For each cognitive NOMA architecture, our proposed cooperative relaying strategy shows its potential to significantly lower outage probabilities. Furthermore, we discuss open challenges and future research directions on implementation of cognitive NOMA networks.

Motivation & Objective

• Address the challenge of severe interference in spectrum-sharing 5G networks by integrating NOMA and cognitive radio (CR) technologies.
• Design cognitive NOMA architectures that support high spectral efficiency, massive connectivity, low latency, and improved fairness.
• Mitigate inter-network and intra-network interference in cognitive NOMA using cooperative relaying strategies to enhance reception reliability.
• Identify open challenges and future research directions for practical deployment of cognitive NOMA networks.

Proposed method

• Proposes three cognitive NOMA architectures: underlay NOMA (SUs transmit simultaneously with PUs under power constraints), overlay NOMA (SUs transmit with PUs using power domain multiplexing), and CR-inspired NOMA (SUs opportunistically access spectrum based on sensing and cooperation).
• Introduces cooperative relaying strategies for each architecture to mitigate inter- and intra-network interference, improving signal detection and reducing outage probability.
• Employs successive interference cancellation (SIC) at receivers to decode intended signals while treating others as interference, enabling power-domain multiplexing in both downlink and uplink NOMA.
• Analyzes performance using outage probability as a key metric, evaluating the impact of relay deployment and user pairing on network reliability.
• Considers advanced techniques such as joint transceiver beamforming, relay selection, and physical layer security to enhance performance and robustness.
• Explores integration of full-duplex relaying and MIMO to further improve spectral efficiency and system capacity.

Experimental results

Research questions

• RQ1 How can NOMA and cognitive radio be jointly designed to maximize spectrum efficiency and support massive connectivity in 5G networks?
• RQ2 What are the performance limits of underlay, overlay, and CR-inspired NOMA architectures under interference-limited conditions?
• RQ3 How does cooperative relaying reduce outage probability in cognitive NOMA networks while managing inter- and intra-network interference?
• RQ4 What are the key challenges in user pairing, power allocation, and relay selection in cognitive NOMA with multiple SUs and PUs?
• RQ5 How can physical layer security and full-duplex relaying be integrated into cognitive NOMA to enhance reliability and prevent eavesdropping?

Key findings

• Cooperative relaying strategies significantly reduce outage probability in all three cognitive NOMA architectures—underlay, overlay, and CR-inspired NOMA—thereby improving reception reliability.
• The integration of NOMA and CR enables higher spectral efficiency, supports massive connectivity, and enhances fairness compared to conventional orthogonal multiple access (OMA) schemes.
• Outage performance gains are observed in both downlink and uplink NOMA scenarios when relays are used to mitigate interference from primary and secondary users.
• Joint transceiver beamforming and optimal power allocation in MIMO-NOMA can restrict interference to the primary network while maximizing the sum rate of secondary users.
• Relay selection and user scheduling strategies must jointly optimize reliability for both primary and secondary users, requiring new designs beyond conventional approaches.
• Physical layer security techniques such as cooperative jamming can mitigate risks from untrusted relays and denial-of-service attacks in cognitive NOMA networks.