Because of the exponentially increasing demand of wireless data, the Radio Frequency (RF) spectrum crunch is rising rapidly. The amount of available RF spectrum is being shrunk at a very heavy rate, and spectral management is becoming more difficult. Visible Light Communication (VLC) is a recent promising technology complementary to RF spectrum which operates at the visible light spectrum band (400 THz to 780 THz) and it has 10,000 times bigger bandwidth than radio waves (3 kHz to 300 GHz). Due to this tremendous potential, VLC has captured a lot of interest recently as there is already an extensive deployment of energy efficient Light Emitting Diodes (LEDs). The advancements in LED technology with fast nanosecond switching times is also very encouraging. One of the biggest advantages of VLC over other communication systems is that it can provide illumination and data communication simultaneously without needing any extra deployment. Although it is essential to provide data rate at a blazing speed to all the users nowadays, maintaining a satisfactory level in the distribution of lighting is also important. In this work, we present a multi-element multi-datastream (MEMD) VLC architecture capable of simultaneously providing lighting uniformity and communication coverage in an indoor setting. The architecture consists of a multi-element hemispherical bulb design, where it is possible to transmit multiple data streams from the bulb using multiple LED modules. We present the detailed components of the architecture and formulate joint optimization problems considering requirements for several scenarios. We formulate an optimization problem that jointly addresses the LED-user associations as well as the LEDs' transmit powers to maximize the Signal-to-Interference plus Noise Ratio (SINR) while taking an acceptable illumination uniformity constraint into consideration. We propose a near-optimal solution using Geometric Programming (GP) to solve the optimization problem and compare the performance of this GP solution to low complexity heuristics. To further improve the performance, we propose a mirror employment approach to redirect the reflected LED beams on the wall to darker spots in the room floor. We compare the performance of our heuristic approaches to solve the proposed two-stage optimization problem and show that about threefold increase in average illumination and fourfold increase in average throughput can be achieved when the mirror placement is applied which is a significant performance improvement. Also, we explore the use case of our architecture to provide scalable communications to Internet-of-Things (IoT) devices, where we minimize the total consumed energy emitted by each LED. Because of the non-convexity of the problem, we propose a two-stage heuristic solution and illustrate the performance of our method via simulations.
Doctor of Philosophy (Ph.D.)
College of Engineering and Computer Science
Electrical and Computer Engineering
Length of Campus-only Access
Doctoral Dissertation (Campus-only Access)
Ibne Mushfique, Sifat, "Multi-Element Multi-Datastream Visible Light Communication Networks" (2020). Electronic Theses and Dissertations, 2020-. 367.