A Survey on Resource Allocation for 5G Heterogeneous Networks: Current
Research, Future Trends and Challenges
Abstract
In the fifth-generation (5G) wireless communications system, various
service requirements under different communication environments are
expected to be satisfied. As a new evolution network structure,
heterogeneous networks (HetNet) have been fully studied in recent years.
In contrast to conventional homogeneous networks, the key feature of
HetNet is to increase the opportunity of spatial resource reuse and
improve the quality of service of users by allowing small cells to
cooperate in macrocell networks. However, since the mutual interference
among different users and the limited resource are existing in HetNets,
efficient resource allocation (RA) schemes are very important to reduce
the interference and achieve spectrum sharing. In this paper, we provide
a comprehensive survey on RA in HetNets for 5G communications.
Specifically, we first introduce the definition and different network
scenarios of HetNet. Second, RA models are discussed. Then, we present
classification to analyze current RA schemes in the existing references.
Finally, some challenging open issues and future research trends are
addressed in this field. We also provide two effective approaches for
the sixth-generation (6G) communications to solve the RA problems of
future HetNets, namely, a learning-based approach and a control
theory-based approach. This paper provides important information on
HetNets, which can be used to guide the development of more efficient RA
schemes in this area.