Modeling and performance evaluation of free space optical link for ground-to-train communications

• Main Author: Bakhit Mabrouk, Wafi Adam
• Format: Thesis
• Language: English; English; English
• Published: 2019
• Subjects: TK5101-6720 Telecommunication. Including telegraphy, telephone, radio, radar, television
• Online Access: http://eprints.uthm.edu.my/134/1/WAFI%20ADAM%20BAKHIT%20MABROUK%20COPYRIGHT%20DECLARATION.pdf; http://eprints.uthm.edu.my/134/2/24p%20WAFI%20ADAM%20BAKHIT%20MABROUK.pdf; http://eprints.uthm.edu.my/134/3/WAFI%20ADAM%20BAKHIT%20MABROUK%20WATERMARK.pdf; http://eprints.uthm.edu.my/134/

There is an increased demand for high-speed train (HSR) services. Consequently, onboard high-speed internet access needs increased as passengers travel to and from work. This sudden surge in demand introduced new challenges in delivering a seamless internet connection on-board fast-moving trains. Free Space Optical (FSO) Communications technology promises a bright future for various applications, due to its cost-effectiveness, ease of deployment, and huge unregulated bandwidth, which gives it an edge over contemporary technologies. However, there is a lack of significant research on FSO links for railway communications. In this thesis, straight, curved, and new double curved tracks mathematical models for FSO Ground-to-train (G2T-FSO) links have been proposed to overcome this issue and satisfy increased demand. G2T-FSO links feature base stations located beside the track to provide a LOS link for traveling trains. Moreover, FSO links comprise of intensity modulated transmitters with Direct detection receiver, that utilize RZ and NRZ OOK modulation formats at 2.5 Gbps. In addition, multiple transmitters concept has been implemented to enhance the link performance, in which single, dual, triple, and quad transmitters have been developed. Furthermore, geometrical parameters have been optimized to achieve optimal link performance. Measured meteorological data have been incorporated to simulate rain and fog weather attenuations. Performance evaluation has been conducted in terms of Received power, Q factor, SNR, BER, and Eye diagram patterns using MATLAB® and Optisystem®. Simulation results show significant effects of geometrical and atmospheric losses on single and dual transmitters link performances. However, Quad and triple transmitters have obtained a feasible error-free G2T-FSO link with BER of 10-9 for NRZ and RZ formats. Significantly enhanced ranges of up to 680m for straight track and 618m for curved track under clear weather condition have been achieved. G2T-FSO links promise an unmatched performance over contemporary HSR communications technology.