D2D-U: Device-to-Device Communications in Unlicensed Bands for 5G and Beyond

TL;DR

This paper introduces D2D-U, a scheme enabling device-to-device communication in unlicensed bands for 5G, enhancing network capacity by optimizing subchannel allocation and coexistence with Wi-Fi.

Contribution

It proposes a sensing-based protocol for unlicensed channel access and formulates a subchannel allocation as a many-to-many matching problem with an iterative swap algorithm.

Findings

Significant increase in system sum-rate with D2D-U scheme

Effective coexistence with Wi-Fi systems demonstrated

Improved spectrum efficiency in 5G networks

Abstract

Device-to-Device (D2D) communication, which enables direct communication between nearby mobile devices, is an attractive add-on component to improve spectrum efficiency and user experience by reusing licensed cellular spectrum in 5G system. In this paper, we propose to enable D2D communication in unlicensed spectrum (D2D-U) as an underlay of the uplink LTE network for further booming the network capacity. A sensing-based protocol is designed to support the unlicensed channel access for both LTE and D2D users. We further investigate the subchannel allocation problem to maximize the sum rate of LTE and D2D users while taking into account their interference to the existing Wi-Fi systems. Specifically, we formulate the subchannel allocation as a many-to-many matching problem with externalities, and develop an iterative user-subchannel swap algorithm. Analytical and simulation results show that the proposed D2D-U scheme can significantly improve the system sum-rate.