Joint User Clustering and Beamforming in Non-Orthogonal Multiple Access Networks

Ha-Ryung Kim,Jongwon Yoon,Jiasi Chen

doi:10.1109/access.2020.3002774

Abstract

The demand for higher data rate in wireless networks continues to grow, however the wireless spectrum cannot meet ever-increasing demands. Non-orthogonal Multiple Access (NOMA) technology is attracting attentions to overcome the lack of resource spectrum and increase spatial reuse. Traditionally, data is delivered in an orthogonal fashion in the frequency or time domain, whereas NOMA leverages power domain to improve spectral reuse. User clustering is one of the key features that significantly affects NOMA's throughput performance and fairness among the users in the network. In addition to NOMA, beamforming increases spectral efficiency by improving SNR for specific users (and groups) and reducing interference across the clusters. However, combining beamforming with NOMA is a challenging and complex problem because beamforming for improving the reuse of spectral resources is tightly coupled with user clustering in NOMA. In this paper, we introduce a joint user clustering and beamforming scheme that maximizes the network throughput in NOMA with beamforming. Toward this goal, we carefully analyze several features that significantly affect the system throughput and design a heuristic algorithm based on the inferences. Our algorithm increase the signal power in NOMA and effectively reduce both beamforming and NOMA interference. Evaluation results reveal that our solution provide higher utility (sum rate) than other existing schemes and significantly improve fairness among users regardless of the channel conditions.

Highlights

The rapid growth of hand-held devices and the emergence of various IoT devices generate large amounts of wireless traffic
Unlike the conventional user clustering in Non-Orthogonal Multiple Access (NOMA), we show that clustering users in vicinity is not harmful, and can improve performance when jointly using beamforming
Sayed-Ahmed et al [18] solved the sum rate maximization problem with successive interference cancellation (SIC) constraint while assuming two-user clustering. They found the optimal beamforming vector, two-user clustering cannot maximize the benefits of clustering. They solved the problem while focusing on beamforming rather than efficient clustering Our contribution differs from [17], [18] because we proposed a clustering algorithm for multiple users, and identified several factors that effectively perform user clustering

Summary

Introduction

The rapid growth of hand-held devices and the emergence of various IoT devices generate large amounts of wireless traffic. Despite the thirst for high data rate, wireless resources are limited and must be shared by multiple users. Orthogonal Multiple Access (OMA) which orthogonally divides frequency resources into multiple channels and allocates them to each user, is actively used. The higher the transmit power toward intended direction, the better the SNR (Signal-to-Noise Ratio) for the desired user. It allows reuse of spectral resources, eventually increases spatial reuse. In addition to NOMA that reuses the same resources for multiple user, beamforming with smart algorithm can further improve the reuse gain

Objectives

Results

Conclusion