Date

2017

Document Type

Thesis

Degree

Master of Science

Department

Electrical Engineering

First Adviser

Li, Jing

Abstract

With the increasing demand for accurate indoor localization and widespread deployment of light-emitting diodes (LEDs) for lighting, there has been a dramatic rise in research activities in many areas of indoor localization based on visible light communication (VLC), including modeling of VLC channels, localization methods, localization algorithms, and localization systems. In VLC based indoor localization systems, the reflection, interference and noise in the VLC channels cause the loss, fading and distortion of the transmitted signals. The bandwidth and the signal-to-noise ratio (SNR) of the channel directly affect the channel capacity, the design of modulation scheme, the transmitted power and the data rate. Therefore, it is imperative to capture the characteristics of different VLC channels and properly model them for dual purpose of illumination and localization. We start by a systematic investigation of the VLC channel models. We first investigate three possible configurations of indoor VLC links, and evaluate two widely used VLC channel models – the directed light-of-sight (LOS) optical channel and the nondirected LOS optical channel model. We next investigate the electrical SNR for VLC channels with intersymbol interference (ISI) and without ISI, and provide closed-form derivations to clarify some confusion on the electrical SNR in the literature.To help design and especially evaluate VLC localization schemes, we investigate, analyze and compare four possible localization methods applied to indoor VLC localization – time of arrival (TOA) methods, time difference of arrival (TDOA) methods, received signal strength (RSS) methods and angle of arrival (AOA) methods. For practicality, we consider intensity modulation and direct detection (IM/DD) and explore the dilution of precision (DOP) analysis, a metric that has been successfully deployed in GPS localization and AOA-based localization. For RSS-based indoor VLC localization, we establish a closed-form relation between positional DOP (PDOP) and the accuracy of RSS-based indoor VLC localization, use PDOP to analyze two localization scenarios with different LED grid patterns, and quantize the effect of LED grid patterns on the position errors. Simulation results confirm the effectiveness of the proposed approach.

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