A Survey of Positioning Systems Using Visible LED Lights

© 2018 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertising or promotional purposes, creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other works.As Global Positioning System (GPS) cannot provide satisfying performance in indoor environments, indoor positioning technology, which utilizes indoor wireless signals instead of GPS signals, has grown rapidly in recent years. Meanwhile, visible light communication (VLC) using light devices such as light emitting diodes (LEDs) has been deemed to be a promising candidate in the heterogeneous wireless networks that may collaborate with radio frequencies (RF) wireless networks. In particular, light-fidelity has a great potential for deployment in future indoor environments because of its high throughput and security advantages. This paper provides a comprehensive study of a novel positioning technology based on visible white LED lights, which has attracted much attention from both academia and industry. The essential characteristics and principles of this system are deeply discussed, and relevant positioning algorithms and designs are classified and elaborated. This paper undertakes a thorough investigation into current LED-based indoor positioning systems and compares their performance through many aspects, such as test environment, accuracy, and cost. It presents indoor hybrid positioning systems among VLC and other systems (e.g., inertial sensors and RF systems). We also review and classify outdoor VLC positioning applications for the first time. Finally, this paper surveys major advances as well as open issues, challenges, and future research directions in VLC positioning systems.Peer reviewe

Smart receiver for visible light communications: Design and Analysis

This paper presents the concept, design and analysis for a visible light communications receiver to guard against blocking and enhance mobility. Different geometrical shapes have been investigated, with two being chosen and analyzed in MATLAB for the received power and the root–mean–square(RMS) delay spread. The results show that the receiver is fully mobile within the test area and can handle data rates far greater than that offered by commercially available LEDs

Accuracy of the point-source model of a multi-LED array in high-speed visible light communication channel characterization

During the procedure of indoor visible light communication (VLC) channel modeling, the transmitter constituted by an array of LEDs is frequently modeled as single point-source for convenience. But how accurate this simplified treatment is remains unanswered. This paper compares the channel characteristics of both the simplified point-source model and six practical cases having various numbers of LEDs. Our numerical results show that the deviations in terms of the channel’s optical path loss (OPL) as well as its bandwidth and the channel’s delay spread are increased steadily upon increasing the number of LEDs of each transmitter, until LEDs spread almost over the entire ceiling. Even in the worst case, the deviation of the OPL remains below 0.41 dBo, while that of the 3-dB transmission bandwidth is below 1.67 MHz. However, the deviation in terms of the root mean square (RMS) delay spread can reach 1.88 ns. Moreover, in terms of spatial distribution of the RMS delay spread, there is a non-negligible difference between the simplified point-source model and different transmitter configurations

Mobile Multi-Gigabit Visible Light Communication System in Realistic Indoor Environment

The main challenges facing high data rate visible light communication (VLC) are the low-modulation bandwidth of the current transmitters (i.e., light emitting diodes), the intersymbol interference (ISI) caused by the multipath propagation and cochannel interference (CCI) due to multiple transmitters. In this paper, for the first time, to the best of our knowledge, we propose, design, and evaluate the use of laser diodes (LDs) for communication as well as illumination. In addition, we propose an imaging receiver for a mobile VLC system to mitigate ISI. A novel delay adaptation technique is proposed to mitigate CCI, maximize the signal to noise ratio, and reduce the impact of multipath dispersion under user mobility.The proposed imaging system is able to provide data rates of 5 Gb/s in the worst-case scenario.The combination of a delay adaptation approach with an imaging receiver (DAT imaging LD-VLC system) adds a degree of freedom to the link design, which results in a VLC system that has the ability to provide higher data rates (i.e., 10 Gb/s) in the considered harsh indoor environment.The proposed technique (delay adaptation) achieves significant improvements in the VLC channel bandwidth (more than 16 GHz) over an imaging system in the worst-case scenario.The VLC channel characteristics and links were evaluated under diverse situations including an empty room and a room with very strong shadowing effects resulting from minicubicle offices