Device-to-Device Communications in Unlicensed Spectrum: Problem Identification and Performance Maximization

Abstract

Device-to-device (D2D) communication is such a paradigm that anticipated to play a cabalistic role for the next-generation cellular networks especially for the 5G cellular network as it promises to extend the network coverage and offload some traffics from the cellular transceiver's side to the user devices' side and it may operate in both licensed and unlicensed spectra simultaneously. D2D communication in the unlicensed spectrum may facilitate the purpose of D2D communication as the licensed spectrum almost possessed. Interference is the main drawback of the unlicensed spectrum. In this paper, we propose the request-to-send/clear-to-send (RTS/CTS) mechanism with the free-to-receive (FTR)-MNAV technique to improve the performance of the D2D communication in the unlicensed spectrum. Deployment of the carrier sense multiple access with collision avoidance (CSMA/CA) protocol can alleviate interference, but collisions occur due to the hidden node problem. The integration of the RTS/CTS mechanism with the CSMA/CA protocol can minimize the hidden node problem, but the blocking and false blocking problems are introduced. The proposed scheme can reduce the blocking and false blocking problems, which improves the performance of the D2D communication in the unlicensed spectrum where neighbor nodes maintain Multiple Network Allocation Vector (MNAV) to resolve the blocking problem and broadcast the FTR control packet to the respective neighbor nodes if the transmission is completed prior to the expiration of the timer or actual communication does not take place due to any reason, thus solving the false blocking problem and improving the performance of the D2D communication in the unlicensed spectrum. INDEX TERMS D2D, spectrum allocation, collision, blocking and false blocking problems. I. INTRODUCTION

Coexistence Analysis of D2D‐Unlicensed and Wi‐Fi Communications

“…The network model provides a higher D2D system throughput and a better network management between different kinds of networks and spectra, but it is difficult to maintain network quality of service (QoS). In [30], a new RTS/CTS mechanism based on free-to-receive multiple network allocation vector (MNAV) is proposed for D2D-U networks to improve spectrum efficiency and network capacity. This mechanism can reduce blocking time by using MNAV, resulting in a more efficient use of an unlicensed spectrum.…”

Statistical Qos Guarantees for Licensed-Unlicensed Spectrum Interoperable D2D Communication

“…[27] investigate the spectrum access problem for cellular and D2D users by maximizing the total throughput of the network which is an entirely different problem as compared to ours. [28] proposed a new scheme for the medium access control protocol for D2D communication in an unlicensed spectrum. They have proposed the request-to-send/clear-to-send mechanism with the free-to-receive technique to improve the performance of the D2D communication in the unlicensed spectrum.…”

“…Now by substituting (31) in 28, we can find the down-link channel capacity. Now to find the overall capacity of the link D T → AP → D R , substitute (26) and (28) in (25),…”