الفهرس | Only 14 pages are availabe for public view |
Abstract Nowadays, the need for alternative communication technologies is a result of increased wireless data traffic from the quickly growing wireless mobile devices, which is inspiring compression on the dwindling radio frequency (RF) spectrum. This interest about spectrum led to the formularization of a new technology called visible light communication (VLC). One of the interesting research area regarding VLC is the reduction of the receiver sensitivity requirement while stretching the range of reliable constant rate transmission while satisfying lighting and communication requirements. Two of the main objectives of LED based system are the achievement of dimming and communication support. Although these two objectives are relevant to each other, they are generally treated separately. Dimming and communication support are achieved using different modulation techniques. In this thesis, we explore the bit rate characteristics, receiver sensitivity and power requirements of multicarrier modulation schemes (MCM) for visible light communication (VLC). Before exploring the performance, this study develops the mathematical formulation for merging pulse position modulation (PPM) and overlapping pulse position modulation (OPPM) all with M-ary quadrature amplitude modulation DC-Biased optical orthogonal frequency division multiplexing (MQAM-DCO-OFDM). These schemes are then compared with the conventional merging (i.e MQAM-DCO-OFDM with pulse width modulation (PWM)). To relate with the recent advances in the field, additional comparative study is established with the latest merging platform (i.e M-QAM DCO OFDM with multiple pulse position modulation (MPPM)). Then make the same previous study when replacing PWM and MPPM pulses with variable pulse position modulation (VPPM), color shift keying (CSK) as key schemes of IEEE 802.15. 7 and PPM as key scheme of IrDA protocol Alternatives for the conventional merging scheme are explored. A trade-off issues between the addressed merging schemes are presented. Finally, we design circuits to transmit (using LED) and receive (using photodetector (PD)) the data after merging techniques. The thesis is divided into six chapters, as listed below: • Chapter One: This chapter is an introduction to the thesis that clarifies the history of visible light communication and the aims of this thesis. • Chapter Two: This chapter presents literature review of the topics relevant to the thesis, discussing VLC concept, components, and applications. • Chapter Three: This chapter introduces an elaborated modeling and simulation of the compensating effect of the different pulse position modulation techniques on the conventional M-QAM DCO OFDM PWM modulation dimming techniques. This is done by replacing PWM by MPPM pulses, or PPM or OPPM pulses with the same duty cycle, then assessing the performance of these techniques. The main performance parameter is the bit error rate for energy per bit to noise density ratio. Then for a given bit rate and bit error rate one, the achievable bit rate, receiver sensitivity and required LED power are determined. • Chapter Four: explores the performance of multicarrier VLC modulation schemes results from merging selected schemes from IEEE 802.15. 7 and IrDA with MQAM-DCO-OFDM. • Chapter Five: This chapter discusses the implementation of VLC system. A comparison between the simulated results and measured results is introduced. • Chapter Six: This chapter is devoted to main conclusion and future work for this research point. • Last Part: it includes references for this thesis. |