Research On Multipath Fading Of High-speed Train’s Signal Based On ROF

The21st century is full of information that is passed everywhere, people are increasingly demanding communications, receive calls while hoping to get better call quality. Facing with off the network, not normally call and cut, dropping calls multipath fading of signals and other phenomena. Radio over fiber (ROF) communication technology provide a solution to communication on the high-speed train. We can use it to solve dropped calls, switching frequently and other problems. Therefore, the railway can form seamless network coverage with the antenna distributing along railway, it can improve the utilization of coverage and simplifying signal switching problem. Facing with signal transmission in multipath fading, OFDM modulation technique can effectively reduce the multipath effect caused by multipath fading.This paper research the ROF system in the high-speed railway, multipath fading and OFDM modulation technology which can overcome multipath effects. And then build and simulate modules, compare simulation results and conclusion. Specific work is as follows:First, studying the basic theory of ROF technology in this paper, including the composition of ROF system, the features of ROF technology, its key technologies and applications in various fields.Second, researching the application of high-speed railway in ROF, analyzing its development and the principles of GSM-R standard of railway communication; Because the high-speed railway communication is very important to people, so the author analyzing several methods high-speed railway broadband access. And the author focus on this methods——ROF scheme.Third, studying the basic theory of the multipath propagation, multipath fading and multipath fading caused by multipath effects,Including concepts, features, and its effect; Then analyzing the multipath fading channel type, parameters, and model; Finally, using MATLAB and Simulink software to build system and simulate for multipath fading in high-speed railway. In this part, the author analyzing high-speed rail signal multipath fading based on60GHz millimeter-wave of ROF system, the infulence of multipath fading at different speeds. And then verifying that the greater the impact of multipath fading when the train faster. Furthermore, in contrast to multipath fading of the GSM-R standard, the author obtaining a conclusion that the impact of multipath fading became bigger when the carrier frequency is bigger. Fourth, researching the basic theory of OFDM, including concepts, principles, and cyclic prefix guard interval, the advantages and disadvantages.Then, using Optisystem to simulate OFDM modulation based on ROF60GHz millimeter-wave. And obtaining spectrum after modulated signal transmission, analyzing spread spectrum; In addition, compared to spectrum obtained from other modulation methods, the author deriving a conclusion that OFDM modulation to overcome multipath effects have a good effect.