Mobility management for D2D communication combining radio frequency and visible light communications bands
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Mobility management for D2D communication combining radio frequency and visible light communications bands Zdenek Becvar1
•
Ray-Guang Cheng2 • Martin Charvat1 • Pavel Mach1
Springer Science+Business Media, LLC, part of Springer Nature 2020
Abstract Combination of radio frequency (RF) and visible light communication (VLC) bands for device-to-device (D2D) communication is seen as a promising way to both increase the system capacity and cope with an overcrowded RF bands. The main concern, however, is a proper mobility management and selection of the band that is beneficial at the moment. While the VLC usually provides a much higher throughput than RF, it is also very sensitive to a signal blockage and shadowing. Therefore, throughput as well as potential sudden drops in VLC channel quality should be considered in a design of handover between VLC and RF to avoid redundant handovers. In this paper, we propose an algorithm, tailored for D2D communication, deciding whether or not it is beneficial for a user equipment to switch from VLC to RF or vice versa. If handover to RF is not beneficial at the moment despite a drop in VLC channel quality, a dwell timer waits for a specific time if VLC channel recovers. We propose an optimization of the dwell timer according to estimated throughput in RF and VLC and delay due to handover. Simulations show that the proposed algorithm increases an average throughput when compared to existing state-of-the-art algorithms while number of handovers and average interruption are still very low. Keywords Device-to-device Visible light communication Radio frequency Handover Mobility management
1 Introduction The demands for mobile data consumption of a user increase continuously. While in 2016, the data traffic was 7 exabytes per month, the estimated data traffic for 2021 is supposed to climb to 49 exabytes [1]. To handle such amount of data, new and more efficient approaches for data delivery must be developed. One possible course of action is to improve a spectral efficiency in currently exploited radio frequency (RF) bands. However, even this is not enough to cope with a phenomenon known as a spectrum crunch [2]. A possible solution to complement RF and, thus, to avoid the spectrum crunch is to exploit Visible Light Communication (VLC) [3, 4]. The VLC provides a
& Zdenek Becvar [email protected] 1
Department of Telecommunication Engineering, Czech Technical University in Prague, Prague, Czech Republic
2
National Taiwan University of Science and Technologies, Taipei, Taiwan
wide unlicensed spectrum bands that offers a high-speed data transmission [5, 6]. While the introduction of VLC as a complementary technology to RF brings many benefits, it also introduces new challenges that have to be addressed. Probably the most crucial one is developing an efficient Vertical Handover (VHO) scheme between RF and VLC bands. Without a proper decision on which band should be used, the user experience might not be improved and can be ev
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