Coverage and Rate Analysis for Co-Existing RF/VLC Downlink Cellular Networks

Abstract

Integrating visible light communication (VLC) with conventional radio frequency (RF)-enabled wireless networks has been shown to improve the achievable data rates of mobile users. This paper provides a stochastic geometry framework to perform the coverage and rate analysis of a typical user in co-existing VLC and RF networks covering a large indoor area. The developed framework can be customized to capture the performance of a typical user in various network configurations such as (i) RF-only, in which only small base-stations (SBSs) are available to provide the coverage to a user, (ii) VLC-only, in which only optical BSs (OBSs) are available to provide the coverage to a user, (iii) opportunistic RF/VLC, where a user selects the network with maximum received signal power, and (iv) hybrid RF/VLC, where a user can simultaneously utilize the available resources from both RF and VLC networks. The developed model for VLC network precisely captures the impact of the field-of-view (FOV) of the photo-detector (PD) receiver on the number of interferers, distribution of the aggregate interference, association probability, and the coverage of a typical user. Closed-form approximations are presented for special cases of practical interest and for asymptotic scenarios such as when the intensity of SBSs becomes very low. The derived expressions enable us to obtain closed-form solutions for various network design parameters (such as intensity of OBSs and SBSs, transmit power, and/or FOV) such that the number of active users can be distributed optimally among RF and VLC networks. Also, we optimize the network parameters in order to prioritize the association of users to VLC network. Finally, simulations are carried out to verify the derived analytical solutions. It is shown that the performance of VLC network depends significantly on the receiver's FOV/intensity of SBSs/OBSs and careful selection of such parameters is crucial to harness the benefits of VLC networks. Important trade-offs between height and intensity of OBSs are highlighted to optimize the performance of a user in VLC networks. Multi-cell downlink visible light communication (VLC) networks, rate coverage probability, fieldof-view, traffic load distribution, Poisson Point Process (PPP). optical signals do not interfere with the RF electronic systems and can be used in sensitive areas such as hospitals [8] and aircrafts henceforth. Contrary to RF, VLC is susceptible to indoor blockages (walls, human, material objects, etc.) thus naturally confined to a small area. The received power at PD depends heavily on the line of sight (LoS) signals that may get blocked due to limited field-of-view (FOV) of the PD receivers, and/or radiance angle of the optical LEDs. As such, the dense deployment of LEDs may not guarantee a reliable coverage. VLC is thus considered as a complimentary rather than substituting technology to RF [9]-[11]. A. Background Work Recently, few research proposals have investigated the performance of hybrid RF/VLC systems [12]-[15]. In [12], energy effici...

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

“…Specifically, authors quantified the minimum required RF resources (bandwidth and power) for the VLC networks to achieve a predefined (per user) rate outage performance. In [104], Tabassum and Hossain used the stochastic geometry to analyze the coverage and the rate of a typical user and compared the results in four types of networks: RF-only, VLC-only, opportunistic RF/VLC (either the user connected to RF or VLC), and the hybrid RF/VLC (the user can gain the resources from both the RF and VLC APs) networks. Based on several parameters including the FoV receiver, number of interfering LEDs, distribution of the interference, association and coverage probability, and the average rate of the typical users, they found closed-form solutions to distribute the users among the VLC and RF APs.…”

Optimal LED placement in indoor VLC networks

“…The need to guarantee communication coverage in hybrid network scenarios is still a challenge [10][11][12]. Tabassum and Hossain [13] presented a stochastic geometry framework to perform the coverage and rate analysis in co-existing VLC and RF networks. However, when considering only VLC technology, the optimal LEDs placement is still an open issue.…”

Interference Characterization in Downlink Li-Fi Optical Attocell Networks

“…But, the characterization for both one and two dimension attocell networks and for any separation distance between the LEDs has not been shown. In [15], for the calculation of outage probability and SINR in a random deployment of LEDs, the interference is characterized by extracting its moments from its complementary function and approximation similar to the one in [16]. But an explicit simple closed form expression for interference in a deterministic LED arrangement has not been provided.…”