A Survey on Resource Allocation for 5G Heterogeneous Networks: Current Research, Future Trends, and Challenges

Yongjun Xu,Fumiyuki Adachi,Haris Gacanin,Guan Gui

doi:10.1109/comst.2021.3059896

Abstract

In the fifth-generation (5G) mobile communication system, various service requirements of different communication environments are expected to be satisfied. As a new evolution network structure, heterogeneous network (HetNet) has been studied in recent years. Compared with homogeneous networks, HetNets can increase the opportunity in the spatial resource reuse and improve users’ quality of service by developing small cells into the coverage of macrocells. Since there is mutual interference among different users and the limited spectrum resource in HetNets, however, efficient resource allocation (RA) algorithms are vitally important to reduce the mutual interference and achieve spectrum sharing. In this article, we provide a comprehensive survey on RA in HetNets for 5G communications. Specifically, we first introduce the definition and different network scenarios of HetNets. Second, RA models are discussed. Then, we present a classification to analyze current RA algorithms for the existing works. Finally, some challenging issues and future research trends are discussed. Accordingly, we provide two potential structures for 6G communications to solve the RA problems of the next-generation HetNets, such as a learning-based RA structure and a control-based RA structure. The goal of this article is to provide important information on HetNets, which could be used to guide the development of more efficient techniques in this research area.

Highlights

With the exponential growth of mobile smart terminals, the fifth generation (5G) networks are designed to improve the capacity 1000 times compared from the fourth generation (4G) [1]–[6]
This paper presents a comprehensive survey on resource allocation (RA) in heterogeneous networks (HetNet)
A detailed survey on RA issues has been done for HetNets

Summary

Introduction

With the exponential growth of mobile smart terminals, the fifth generation (5G) networks are designed to improve the capacity 1000 times compared from the fourth generation (4G) [1]–[6]. Spectrum efficiency (SE) improves 5 ∼ 15 times compared to the 4G mobile networks [7]. HetNet allows many types of smallcells to coexist while overlapping macrocell networks at the same location or the same spectrum band, which greatly improves SE and decreases the coverage holes. Cell types and communication scenarios of HetNets. II-A Cell types in HetNets II-A-1 Macrocell network II-A-2 Microcell network II-A-3 Picrocell network II-A-4 Femtocell network. Resource allocation taxonomy in HetNets IV-A RA in traditional HetNet IV-B RA in OFDMA-based HetNet IV-C RA in NOMA-based HetNet IV-D RA in relay-based HetNet IV-E RA in H-CRAN IV-F RA in multi-antenna HetNet IV-G Other RAs in HetNet. IV-G-A Full-duplex HetNet IV-G-B NOMA H-CRAN IV-G-C MEC-based HetNet IV-G-D Energy harvesting-based HetNet IV-G-E Other scenarios of HetNet V.

Methods

Discussion

Conclusion