Non-Orthogonal Multiple Access (NOMA) in 5G and Beyond

Breanna Ivy^*
*Correspondence: Breanna Ivy, Department of Electronics, Military University of Technology, 00-908 Warsaw, Poland, Email:

Introduction

The rapid growth of wireless communications, fueled by the surge in mobile internet usage, smart devices and emerging applications such as Augmented Reality (AR), Virtual Reality (VR) and Internet of Things (IoT), has imposed unprecedented demands on network capacity and connectivity. The Fifth Generation (5G) wireless networks aim to address these challenges by enhancing spectral efficiency, supporting massive device connectivity and providing diverse Quality of Service (QoS) requirements. A critical enabler for achieving these objectives is the adoption of innovative multiple access techniques that move beyond the traditional orthogonal access methods. Non-Orthogonal Multiple Access (NOMA) is one such promising technology that has attracted significant attention from academia and industry for its ability to improve spectrum utilization and network throughput by allowing multiple users to share the same time-frequency resources simultaneously. Unlike conventional Orthogonal Multiple Access (OMA) schemes, which assign orthogonal channels in time, frequency, or code domains to avoid interference, NOMA exploits the power domain to multiplex users, thereby increasing connectivity and fairness. This article provides an in-depth analysis of NOMAâ??s principles, advantages, implementation challenges, recent advances and its role in 5G and beyond wireless networks [1].

Description

Non-Orthogonal Multiple Access fundamentally transforms how users share the wireless medium by allowing multiple users to occupy the same time and frequency resources but differentiated by distinct power levels. This is achieved through superposition coding at the transmitter, where signals intended for different users are combined with different power weights. Typically, users with weaker channel conditions are allocated higher transmission power to ensure sufficient signal quality, while users with stronger channels are allocated less power. At the receiver side, Successive Interference Cancellation (SIC) is employed to decode the signals in order of decreasing power levels. The user with the strongest received signal is decoded first, subtracted from the composite received signal and then the receiver moves on to decode the next user. This process continues iteratively until all user signals are decoded. By allowing resource sharing in this manner, NOMA can serve multiple users simultaneously within the same resource block, significantly enhancing spectral efficiency [2].

The benefits of NOMA extend beyond mere capacity improvements. It inherently provides better user fairness by dynamically allocating power based on channel conditions, ensuring that users at the cell edge or with poor reception still achieve acceptable service levels. This aspect is particularly important in 5G scenarios where heterogeneous user requirements exist ranging from high-speed data transmission for enhanced Mobile Broadband (eMBB) users to Ultra-Reliable Low-Latency Communication (URLLC) for mission-critical applications. Furthermore, NOMA is capable of supporting massive connectivity required by IoT devices by enabling a large number of low-power devices to access the network simultaneously without requiring orthogonal resource allocation. Moreover, NOMAâ??s flexibility allows it to be combined with other 5G key technologies such as Massive MIMO and millimeter-wave communications. When integrated with Massive MIMO, NOMA can exploit both spatial and power domains to increase user multiplexing gains, further improving capacity and energy efficiency. For millimeter-wave communications, which often suffer from high path loss and require beamforming, NOMAâ??s power domain multiplexing adds another dimension to accommodate more users within narrow beams, thus enhancing overall system throughput.

Conclusion

Non-Orthogonal Multiple Access represents a paradigm shift in multiple access technology, crucial for addressing the demanding requirements of 5G and beyond wireless networks. By enabling multiple users to simultaneously share the same time-frequency resources differentiated by power levels, NOMA dramatically improves spectral efficiency, user fairness and massive connectivity. Its compatibility with other key 5G technologies like Massive MIMO and millimeter-wave communications makes it a versatile and powerful technique. However, challenges related to interference cancellation complexity, power allocation optimization, hardware limitations and inter-cell interference must be tackled to realize its full potential. Ongoing research and development efforts, including advanced algorithms, low-complexity receivers and hybrid access schemes, are paving the way for practical and scalable NOMA deployments. As wireless communication continues its rapid evolution toward 6G, NOMA is poised to play an essential role in shaping future networks that are more efficient, inclusive and capable of supporting diverse applications and massive user populations.

Acknowledgment

None.

Conflict of Interest

None.

References

1. Besinovic, Nikola, Raphael Ferrari Nassar and Christopher Szymula. "Resilience assessment of railway networks: Combining infrastructure restoration and transport management." Reliab Eng Syst Saf 224 (2022): 108538.

Google Scholar  Cross Ref  Indexed at

2. Cardoni, A., G. P. Cimellaro, M. Domaneschi, S. Sordo and A. Mazza. "Modeling the interdependency between buildings and the electrical distribution system for seismic resilience assessment." Int J Disaster Risk 42 (2020): 101315.

Google Scholar  Cross Ref  Indexed at