Link Selection in Hybrid RF/VLC Systems Under Statistical Queueing Constraints

Abstract

The co-deployment of radio frequency (RF) and visible light communications (VLC) technologies has been investigated in indoor environments to enhance network performances and to address specific quality-of-service (QoS) constraints. In this paper, we explore the benefits of employing both technologies when the QoS requirements are imposed as limits on the buffer overflow and delay violation probabilities, which are important metrics in designing low latency wireless networks. Particularly, we consider a multi-mechanism scenario that utilizes RF and VLC links for data transmission in an indoor environment, and then propose a link selection process through which the transmitter sends data over the link that sustains the desired QoS guarantees the most. Considering an ON-OFF data source, we employ the maximum average data arrival rate at the transmitter buffer and the non-asymptotic bounds on data buffering delay as the main performance measures. We formulate the performance measures under the assumption that both links are subject to average and peak power constraints. Furthermore, we investigate the performance levels when either one of the two links is used for data transmission, or when both are used simultaneously. Finally, we show the impacts of different physical layer parameters on the system performance through numerical analysis. Index TermsVisible light communications, quality-of-service constraints, buffering delay bound, link selection, multi-mechanisms. M. Hammouda, S. Akın, and J. Peissig are with the Institute of Communications Technology, Leibniz Universität Hannover, 30167 Hanover, Germany. E-mails: {marwan.hammouda, sami.akin, and peissig}@ikt.uni-hannover.de. A. M. Vegni is with COMLAB laboratory, Such networks are practically feasible as RF and VLC systems can coexist without causing interference on each other and operate in the same environment, such as offices and rooms. Comparing hybrid RF/VLC systems with systems that employ either RF or VLC only, the authors in [1], [3], [4], [7], [14] demonstrated a remarkable increase in data transmission throughput, energy efficiency and delay performance in hybrid RF/VLC systems. Moreover, the authors in [5], [6] projected a hybrid system in which they use VLC links for down-link communication and RF links for up-link communication. In such a system, the authors in [8]-[10] and the ones in [12], [13], [15] investigated handover and load balancing mechanisms, respectively. Alternatively, considering an outdoor environment, the authors in [16] studied a point-to-point transmission scenario in which the system can switch between RF links and VLC links after comparing the signal-to-noise ratio levels in each link. Regarding the same system setting, the authors in [17] assumed that both RF and VLC links have the same transmission rates, and then proposed a diversity-based transmission scheme such that the transmitter sends data by employing both links simultaneously.The aforementioned studies analyzed the hybrid RF/VLC systems mostly from the physical layer ...

VLC Systems with Fixed-Rate Transmissions under Statistical Queueing Constraints

“…We set γ s = 0.3 and β s = 0.7 and we consider different transmission power values. For each value of the transmission power, we find the value of θ that minimizes the channel-related buffer overflow probability, following (13). We then compute the average transmission rate that corresponds to the optimal channel log-moment generating function at that θ level, i.e., p o,c ρ .…”

On Optimizing VLC Networks for Downlink Multi-User Transmission: A Survey

“…By imposing the QoS constraints based on the data link metrics, i.e. the limits on the buffer overflow and buffering delay probabilities, Hammouda et al [105] showed that the VLC links offered queuing delays lower than RF links when the data arrival rates at the transmitter buffer were low; however, the RF links supported the higher data arrival rates.…”

Client-Centric Access Device Selection for Heterogeneous QoS Requirements in Beyond 5G IoT Networks

“…With the availability of multiple RATs in B5G networks, suitable access device selection to improve provided QoS is possible. Although network-based approaches [15]- [21] provide a more optimal access device allocation, using such approaches would result in a huge amount of signaling information being transmitted between network elements and IoT nodes. Besides, scalability issues of network-core would arise because of the expected massive number of IoT devices.…”

“…The paper discusses using indoor networks and transportation systems' while considering a Femto AP and a LiFi AP. A hybrid WiFi and LiFi system for QoS provisioning using link selection is proposed with buffer overflow constraints and delay in [21]. Because of the smaller coverage regions of LiFi APs, a concept of handover skipping is proposed in [39] to enable handover between nonadjacent APs for hybrid WiFi and LiFi networks.…”