Investigation On Electromagnetic Environment Of Radio-over-Fiber Based Broadband Wireless Access System Inside High-speed Vehicle

With the development of high-speed vehicles including civil aviation and high-speed train, the demand on wireless access in those high-speed vehicles is increasingly growing. However, the electromagnetic interference(EMI) caused by the wireless access system to the on-board sensitive devices is still a big issue. Due to low transmission loss, distributed scheme, low EMI and high energy efficiency, the radio-over-fiber(ROF) which incorporates the optical communication and the wireless communication technologies is considered to be an enabling technique for broadband wireless access scheme in these scenarios. Therefore, an ROF-based distributed access scheme is proposed to provide broadband wireless access service for passengers in high-speed vehicles, and the corresponding electromagnetic environment is investigated.For civil aviation, a model for analyzing the electromagnetic environment inside aircraft cabin is developed by using simulation software. In order to make the simulation match the real situation as much as possible, there are not only the business class and economy class area, but also the passenger seat, rack, port and other details inside the cabin model. In the mean time, to highlight the advantage of reducing electromagnetic interference of ROF, the distributed scheme is compared with a centralized scheme. By using an in-cabin path loss model, the transmission power of each access point both in the ROF distributed scheme and in the centralized scheme is obtained, then the electromagnetic distributions in aircraft cabin of these two schemes are calculated at frequencies of 800MHz,1900MHz and 2400MHz, respectively. The simulation results indicate that the ROF distributed scheme has a 4-8dB decline in in-cabin coupling electric field strength and a lower radio frequency transmission power, compared with the centralized scheme at the three frequencies. After that, the ROF distributed scheme is applied for broadband wireless access system in high-speed rail as well A China high-speed rail, CRH1 compartment, is modeled to evaluate the EMI of the scheme, and the electromagnetic environments are analyzed in different frequencies. The simulation outcomes show that ROF distributed scheme is characterized by low EMI and high energy efficiency.To verify the electromagnetic distribution of the wireless access in the high-speed vehicles, a wireless coverage testing platform is built in lab. The wireless signal coverage intensity based on the centralized scheme and the distributed scheme is tested. According to the experiment results, the receiving power distribution agrees well with the previous simulation results, no matter the centralized system or the distributed scheme.The work in this dissertation might be valuable for implementing broadband wireless access inside high-speed vehicles, such as the design, the development, the analysis and the evaluation of underlying threat induced by EMI.