Designing and analyzing low-complexity energy-efficient visible light communication systems for IoT and UAV applications

Abstract

IoT interconnect everyday objects via the internet, enabling them to send and receive data by transceivers embedded in it. The number of IoT devices is estimated to reach billions, contributing to half of the global connected devices and connections in the near future. This massive number of connected devices are employed in diverse domains and areas, such as smart cities, smart homes, hospitals, healthcare devices, industries, and transportation systems. Various IoT applications require a vast number of connections per unit area, high aggregate bandwidth, ubiquitous coverage, low power consumption, sustainable energy resources, low latency, low control overhead and a high level of security. With the advent of the emerging IoT paradigm, the already crowded RF spectrum is not expected to serve the projected several billions of IoT devices. A promising communication solution that can address these challenges is light communication.The exponentially increasing demand for wireless data with the onset of wireless devices and internet of things (IoT) everywhere has created scarcity in the radio frequency (RF) spectrum. The existing overcrowded RF spectrum has impelled the hunt for newer technologies. Visible light communication (VLC), having a large amount of unlicensed spectrum, is an emergent alternative technology to supplement the existing short-range wireless systems for faster data transmissions. VLC has numerous unrivalled potentials along with immunity to every day electromagnetic interference, for instance, low energy consumption, data confinement for higher-level security and cheaper installation with existing illumination infrastructure. However, owing to power and hardware limitations of the resource constrained devices (such as IoT and Unmanned Aerial Vehicles (UAVs)), it requires simple, low power, low complex, energy-efficient communication technology. In this dissertation, we have tried to utilize VLC and red, green and blue (RGB) LED in order to support communication with resource constrained devices and their aforementioned requisite. Firstly, we propose a generalized enhancement scheme for different versions of color shift keying (CSK) modulation schemes, we analyze the performance of CSK modulation schemes with probabilistic shaping (PS) of input data. Specifically, we have considered three variants of CSK with respect to receiver structure namely CSK with one photodetector (PD) (CSK-1PD), CSK with three PDs (CSK-3PD) and CSK with one avalanche PD (CSK-1APD). The proposed work comprises of developing algorithms to obtain the optimum probability order for maximizing the received signal-to-noise ratio (SNR) gain. Secondly, in order to support IoT sensor networks with lower cost and higher performance, the low-cost version of standard CSK modulation scheme having single photodetector (PD) at the receiver has been utilized. This work revolves around optimizing the constellation points of CSK-1PD to achieve a more power-efficient modulation scheme. Thirdly, motivated by the diverse requirements of the heterogeneous users i.e. LiFi users and IoT devices, we propose novel green communication schemes that can be used for the coexistence of LiFi users and light communication (LC) enabled IoT devices under a common LiFi access point. The proposed coexistence schemes utilize the amalgamation of wavelength division multiplexing, OFDMA, Hartley transform based DCO-OFDM, null DC element, interleaved subcarrier mapping, modified data sequence to achieve concurrent interference-free, low complex and reliable communication. Additionally, as the multiple access (MA) techniques affect the choice of modulation techniques and overall performance in the system, an analytical delay and throughput framework to corroborate the decision of an appropriate combination of MA and modulation techniques in the coexistence scheme has been included. Lastly, we propose energy and user mobility aware three-dimensional (3-D) deployment of VLC enabled UAV so that maximum coverage of users while ensuring fairness is achieved. Moreover, the VLC enabled UAV’s coverage area to serve ground users has been enhanced with holographic light-shaping diffusers (LSD). A novel RGB LED solution based on light sensitivity to the human eye is proposed to increase the coverage area for the night scenario. The proposed frameworks in this dissertation can be utilized in LiFi standards, especially for resource constrained devices such as IoT and UAVs. It will be helpful for LiFi communi- cation engineers to support an energy-aware green communication at the physical layer and deployment level.