Subcarrier-User Assignment in Downlink NOMA for Improving Spectral Efficiency and Fairness

Mohammed Abd-Elnaby,Mohamed Elwekeil,Germien G Sedhom

doi:10.1109/access.2020.3047985

Mohammed Abd-Elnaby, Mohamed Elwekeil + Show 1 more

Open Access

https://doi.org/10.1109/access.2020.3047985

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Journal: IEEE Access	Publication Date: Dec 29, 2020
Citations: 33	License type: CC BY 4.0

Affiliation: Menoufia University, Taif University

Abstract

Non-orthogonal multiple access (NOMA) has been recognized as an essential technology for beyond fifth-generation (beyond-5G) wireless networks to increase connectivity, spectral efficiency, cell-edge throughput, and user fairness. In this paper, we propose two subcarrier-user assignment algorithms (SUAAs) for the downlink NOMA system to enhance the spectral efficiency, the fairness, the data rate of weak users, and the outage probability. The assignment order of the first proposed SUAA is based on the worst subcarrier first (WSF) to avoid selecting a user with the worst channel gain with any subcarrier and called (WSF-SUAA). On the other hand, the second proposed SUAA is based on spectral efficiency maximization (SEM) and called (SEM-SUAA), but requires exhaustive search. The assignment process of both algorithms is based on making the channel gain of the selected paired users per subcarrier as high as possible to increase the data rate of each user. Besides, the assignment process of strong users for all subcarriers is performed before the assignment process of weak users to increase the total system sum-rate. It is exposed throughout the simulation that the two proposed SUAAs can attain significant improvement in the total spectral efficiency, weak user data rate, outage probability, and user fairness compared to the existing algorithms. While the performances of the two proposed SUAAs are convergent, the computational complexity of WSF-SUAA is significantly lower than that of SEM-SUAA and slightly higher than that of the existing algorithms.

Highlights

Due to the enormous demands of various services and fast growth of the mobile Internet and the Internet of Things (IoT) applications, the achievement of the fifth-generation (5G) and beyond-5G wireless system is expected to turn out by 2020s [1], and [2]
SIMULATION RESULTS In this part, we display the simulation results to assess the performance of the two proposed subcarrier-user assignment algorithms (SUAAs) schemes, in comparison with the worst-case user first subcarrier allocation (WCUFSA) algorithm, the ‘‘conventionaluser-pairing’’, ‘‘random pairing’’, and ‘‘orthogonal-multipleaccess system’’ (OMA)
Two new proposed algorithms for the subcarrier-user assignment in the Non-orthogonal multiple access (NOMA) system are investigated in this paper

Summary

Introduction

Due to the enormous demands of various services and fast growth of the mobile Internet and the Internet of Things (IoT) applications, the achievement of the fifth-generation (5G) and beyond-5G wireless system is expected to turn out by 2020s [1], and [2]. Non-orthogonal multiple access (NOMA) is a necessity to empower technology for beyond-5G wireless networks. NOMA related research has been investigated by both academia and industry because of its high spectral efficiency, enhanced cell-edge throughput, very low transmission latency, massive device connectivity, very high achievable data rate, ultra-high reliability, enhanced user fairness, and high energy efficiency [3]–[5]. The NOMA schemes can be categorized into two classes: power-domain NOMA (PD-NOMA) and code-domain NOMA (CD-NOMA).

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