Impact of Random Receiver Orientation on Visible Light Communications Channel

Abstract

Visible Light Communications (VLC) has been studied thoroughly in recent years as an alternative or complementary technology to radio frequency communications. The reliability of VLC channels highly depends on the availability and alignment of line of sight links. In this work, we study the effect of random receiver orientation for mobile users over VLC downlink channels, which affects the existence of line of sight links and the receiver field of view. Based on the statistics of vertical receiver orientation and user mobility, we develop a unified analytical framework to characterize the statistical distribution of VLC downlink channels, which is then utilized to obtain the outage probability and the bit error rate. Our analysis is generalized for arbitrary distributions of receiver orientation/location for a single transmitter, and extended to multiple transmitter case for certain scenarios. Extensive Monte Carlo simulations show a perfect match between the analytical and the simulation data in terms of both the statistical channel distribution and the resulting bit error rate. Our results also characterize the channel attenuation due to random receiver orientation/location for various scenarios of interest.Index Terms-Channel statistics, Internet-of-Things (IoT), light-fidelity (Li-Fi), probability density function (pdf), random user orientation, optical wireless communications (OWC), quality of service (QoS). Receiving Axis Transmitting Axis LED Field of View User LOS Link Fig. 1: VLC downlink transmission model with random receiver orientation θ.(BER), respectively. The channel distribution is characterized in a general form so that any random statistics of the orientation and mobility can be employed directly.The analytical findings are verified through extensive simulation data matching in all cases of interest. ii. The nonlinear effect of the receiver FOV is integrated into the analytical framework parametrically, which enables the analysis of channel statistics and error performance for specific FOV chosen from a broad range of values. iii. The proposed framework rigorously handles the single LED and two LEDs cases. In addition, extension of the statistical findings to multiple LED settings are also investigated. The results verify the immediate intuitions that wider FOV and multiple LED deployment can be viable solutions in coping with the adverse effects of random receiver orientation and mobility. The rest of this paper is organized as follows. Section II introduces the system model. Section III presents distribution of the square-channel gain for a single LED case, whereas Section IV investigates channel statistics for a specific scenario with two LEDs. Section V discusses the applicability of the findings for the two LEDs setting to more general multiple LED cases. Finally, Section VI presents the respective numerical results, and Section VII concludes the paper.Notations: N (µ, σ 2 ) denotes the real valued Gaussian distribution with the mean µ and the variance σ 2 , U[a, b] denotes the continuous ...

Adaptive Kalman Tracking for Indoor Visible Light Positioning

“…2. As the user moves around the room, some of the APs might be blocked due to intervening objects, change in the receiver orientation [13], or the limited FOV of the PD. The receiver then localizes itself using the signal that it receives from all the available APs.…”

“…In the simulations, we will find the coefficients using (12), (13), and (14), separately, and compare their performances to investigate the sensitivity of adaptive KF to different coefficients. The coefficients in (13) and (14) are calculated using the data given in Fig. 4.…”

“…The VLC signal highly depends on line-of-sight (LOS) link, and when the LOS links are blocked or misaligned [13], some of the APs may not be available to the user for some time. The varying number of available APs requires the device to use different localization methods with different expected accuracies over the route.…”

Impact of Device Orientation on Error Performance of LiFi Systems

“…Device orientation can affect the users' throughput remarkably and it should be analyzed carefully. Even though a number of studies have considered the impact of random orientation in their analysis [5]- [13]. Device orientation can be measured by the gyroscope and accelerator implemented in every smartphone [14].…”

“…A receiver with four photodetectors (PD) is considered and the optimal angles for each PD are computed. In [13], the impact of the random orientation on the line-of-sight (LOS) channel gain for a randomly located UE is studied. The statistical distribution of the channel gain is presented for a single light-emitting diode (LED) and extended to a scenario with double LEDs.…”