A Multi-User Schedule Method for Non-Orthogonal Multiple Access in 5G Heterogeneous Network

异构网络下多用户非正交多址接入方法研究

School of Electronics and Information, Northwestern Polytechnical University, Xi’an 710072, China

Received: 11 April 2018

Abstract

Heterogeneous network is supposed to be the dominant network architecture of the fifth generation (5G) cellular network, which means small cells are overlaid on the macrocell. The beamforming (BF) and cell expansion are two important approaches to serve users in small cells. Furthermore, non-orthogonal multiple access (NOMA) is a new type of multiple access multiplexing which improves system performance without taking up extra spectrum resources. Therefore, it becomes one promising technique in 5G. In this paper, NOMA is applied in a 5G heterogeneous network with biased small cells. The BF strategy and the multiuser scheduling method are proposed. The main user in NOMA is scheduled inside the original coverage of the small cell while the side user is chosen from the biased expansion area. The BF strategy that is executed depends on the channel of main user. The multiuser scheduling method is to maximize the rate performance. The proposed method can provide performance benefits. Simulation results show that the proposed methods can be well applied in heterogeneous networks. The achieved performance gain is approximately twice better than traditional OMA and has 10% improvement to the stochastic schedule method. In addition, the average rate of cell edge users is improved.

摘要

第五代移动通信系统（fifth generation，5G）中，异构网络是其基本组网形态，通过在宏小区上部署低功率微小区能够显著提升系统频谱效率和能量效率。波束成形以及扩张覆盖将成为微小区网络服务用户的主要方式。非正交多址接入技术（non-orthogonal multiple access，NOMA）由于能够在单位频谱资源上显著提升网络容量和频谱利用率的优势，已经成为5G的核心备选技术之一。因此，将NOMA技术应用于扩张覆盖的微小区网络，构建波束成形策略及用户调度算法十分必要。NOMA的主用户位于微小区原覆盖区域，从用户位于小区扩张区域，以速率最大化为目标调度用户。基站在相同的空时频资源下，以功率非正交的方式增加服务用户数。仿真结果验证，所提出的方法能有效应用于微小区网络，显著优于传统正交多址方式，在高信噪比条件下能够达到2倍速率提升，并能够保障小区用户性能的同时，提升边缘用户吞吐量。