D2D Assisted Cellular Networks in Licensed and Unlicensed Spectrum: Matching-Iteration-Based Joint User Access and Resource Allocation

Guangyuan Zheng,Chen Xu,Qiuqi Han

doi:10.3390/a14030080

Abstract

Device-to-Device (D2D) communications, which enable direct communication between nearby user devices over the licensed spectrum, have been considered a key technique to improve spectral efficiency and system throughput in cellular networks (CNs). However, the limited spectrum resources cannot be sufficient to support more cellular users (CUs) and D2D users to meet the growth of the traffic data in future wireless networks. Therefore, Long-Term Evolution-Unlicensed (LTE-U) and D2D-Unlicensed (D2D-U) technologies have been proposed to further enhance system capacity by extending the CUs and D2D users on the unlicensed spectrum for communications. In this paper, we consider an LTE network where the CUs and D2D users are allowed to share the unlicensed spectrum with Wi-Fi users. To maximize the sum rate of all users while guaranteeing each user’s quality of service (QoS), we jointly consider user access and resource allocation. To tackle the formulated problem, we propose a matching-iteration-based joint user access and resource allocation algorithm. Simulation results show that the proposed algorithm can significantly improve system throughput compared to the other benchmark algorithms.

Highlights

With the development of communication technologies and the growth of smart devices, mobile traffic data has increased dramatically in the last decade [1]
Many researchers have operated the cellular users (CUs) in the unlicensed spectrum to further improve network capacity and spectral efficiency, which is referred as Long-Term Evolution-unlicensed (LTE-U) [6]
In contrast to the previous works, we propose a hybrid network where D2D users reuse the licensed channels with the existing CUs, and both CUs and D2D users can transmit in the unlicensed spectrum

Summary

Introduction

With the development of communication technologies and the growth of smart devices (such as smart phones, wearable devices and smart unmanned aerial vehicle, etc.), mobile traffic data has increased dramatically in the last decade [1]. Deviceto-Device (D2D) communications have been considered to be a promising technology to improve spectral efficiency and network capacity by allowing two proximal devices sharing the licensed spectrum with cellular users (CUs) to communicate directly bypassing the base station (BS) [2,3,4,5]. The spectrum resource in the licensed spectrum is limited and congested due to the spectrum reusing by many users, especially in hot spots with plenty of data links. To tackle this challenge, the deployment of 5 GHz unlicensed spectrum in CNs may be an excellent solution. As LTE-U technology achieves better network performance, D2D communications in unlicensed spectrum (D2D-U) technology [7] has attracted more and more attention for its great potential capacity in enhancing network capacity

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