A QoS-based joint user association and resource allocation scheme in ultra-dense networks

Zhiwei Si,Gang Chuai,Xiangyu Chen,Jinxi Zhang,Weidong Gao,Kaisa Zhang

doi:10.1186/s13638-020-01882-3

Abstract

Ultra-dense networks (UDNs) have become an important architecture for the fifth generation (5G) networks. A large number of small base stations (SBSs) are deployed to provide high-speed and seamless connections for users in the network. However, the advantage of increasing the system capacity brought by the dense distribution of SBSs comes at the cost of severe inter-cell interference. Although the user-centric virtual cell method has been proposed to solve the interference problem, some challenges have been encountered in practical applications. For example, inter-cell interference still exists to a certain extent, and the cell load may be imbalance. Hence, under the virtual cell architecture, we propose a quality of service (QoS)-based joint user association and resource allocation scheme in UDNs. In order to mitigate the interference, balance cell load and improve the system throughput, a non-convex NP-hard problem is formulated. To effectively solve this problem, we decouple the formulated problem into three sub-problems: user association, physical resource block (PRB) allocation and power allocation. First, we consider the QoS requirements of user equipment (UE) and perform user association based on the PRB estimation method. Then, based on the overlapped virtual cells constructed, we propose a graph-based PRB allocation scheme for reducing virtual inter-cell interference. Moreover, we solve power allocation sub-problem by using the difference of concave (DC) programing method. The simulation results show that our proposed scheme is superior to other schemes in terms of user rates, cell load and system throughput.

Highlights

The regular heterogeneous networks consisting of macro base stations and several small base stations (SBSs) are incapable of meeting of imminent tele-traffic demands.As one of the key technologies of The fifth generation (5G) networks, Ultra-dense networks (UDNs) can greatly increase user communication rates [1,2,3,4]
The graph is constructed as G = (V, E), where V is the set of vertices {C1, C2, ..., CK } corresponding to the virtual cell clusters {C1, C2, ..., CK }, and E is the edge connecting any two vertices. d(Ck ) represents the degree of the vertex Ck, which is equal to the number of all edges associated with the vertex Ck
It is clearly observed that the small cell (SC) load is balanced by Algorithm1, and SBSs are reselected as cooperative SBSs cluster for user equipment (UE) that cannot associate to the overload SBSs

Summary

Introduction

The regular heterogeneous networks consisting of macro base stations and several small base stations (SBSs) are incapable of meeting of imminent tele-traffic demands. The joint user association and resource allocation scheme under the virtual cell architecture, considering the use of multiple PRBs for each user to reduce interference, cell load balance, guarantee QoS requirements and improve system throughput, has not been studied in previous work. Under the virtual cell architecture, a QoS-based joint user association and resource allocation scheme is proposed to mitigate the interference, balance cell load and improve the system throughput. A novel framework is proposed for jointly designing QoS-based user association and resource allocation under the virtual cell architecture This is the first attempt to consider the use of multiple PRBs for each user to reduce interference, balance cell load, guarantee QoS requirements of UE and improve system throughput.

Graph construction

Graph coloring

Simulation results and discussion

Conclusion