Limited Feedback-Based User Clustering for Non-Orthogonal Multiple Access in mmWave Systems

Thanh Ngoc Nguyen ,Taehyun Jeon

doi:10.1109/access.2021.3067995

Thanh Ngoc Nguyen , Taehyun Jeon

Open Access

https://doi.org/10.1109/access.2021.3067995

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Abstract

Non-orthogonal multiple access (NOMA) and mmWave are considered to be promising techniques for 5G and beyond cellular network communication systems. While the mmWave band provides a very wide under-utilized bandwidth, NOMA enhances the spectral efficiency compared to orthogonal multiple access (OMA). The combination of these two techniques could be considered as the key solution to the high required data rates in next-generation communication systems. The implementation of NOMA is studied and verified under an ideal condition with perfect knowledge of the channel state information (CSI) at the base station (BS). However, under the practical conditions, the fluctuation of the wireless channel makes perfect CSI unachievable at the BS. Hence, we proposed to use the angle of departure (AoD) as feedback information from UEs to the BS. We assume that, mobile users (UEs) perfectly estimate the channel by detecting the pilot signals. Then, UEs quantize the AoD and feed back to the BS. Finally, the BS uses the AoD to perform user clustering, power allocation and beamforming. To reduce the feedback overhead further, we proposed a user clustering algorithm which uses one-bit feedback to determine the change of the AoD. Numerical results demonstrate that the proposed NOMA system outperforms the conventional orthogonal multiple-access (OMA) system with the same amount of feedback information.

Highlights

The steady increase of high rate wireless communications means that fifth generation (5G) and beyond 5G networks must guarantee much higher spectrum efficiency and energy efficiency compared to the current 4G
To deal with practical conditions, in which the perfect channel state information (CSI) is not available at the base station (BS), we propose to use angle of departure (AoD) and one-bit determining the change of AoD as the partial feedback in millimeter wave (mmWave) MIMO Non-orthogonal multiple access (NOMA) system as modeled in early work [17], [28]
The proposed NOMA scheme in which the AoD is utilized as feedback information to form the NOMA cluster and perform beamforming is referred to as the AoD-based NOMA

Summary

INTRODUCTION

The steady increase of high rate wireless communications means that fifth generation (5G) and beyond 5G networks must guarantee much higher spectrum efficiency and energy efficiency compared to the current 4G. In NOMA, the BS transmits signals of multiple UEs at the same time, frequency and code but at different power levels. The propagation of mmWave differs from that on the conventional sub-6 GHz band, it features low scattering and high directionality, which allows for spectrum reuse by limiting the amount of inter-cell interference [6]. The enhanced propagation loss on mmWave band significantly reduces the interference experienced by UEs in a NOMA-based network. This is the main motivation behind the combination of mmWave and NOMA in this paper. Jeon: Limited Feedback-Based User Clustering for NOMA in mmWave Systems

CURRENT RELATED WORK

CRITERIAS

USER CLUSTERING ALGORITHMS

12: Include k-th UE into each cluster

6: UEs detect the pilot signal and estimate the channel parameters:

CONCLUSION