Research On The Construction Of Wireless Access Network Of High Speed Passenger Train Based On The ROF Technology

High speed wireless communication network, effectively improved the communication quality in high-speed mobile environment such as decline of call quality, dropped calls, decreased of data rate and so on. Development of high speed communication and information of high speed railway is promoted. People's demands for wireless communication network in high speed mobile environment is met and a new market is opened by wireless communication into the high speed trains.ROF technology combines wireless communication and optical fiber communication, which has the advantage of optical fiber communication and wireless communication. Optical fiber is used as the transmission link between the base station and the central station in ROF system, which transmits radio frequency signals on optical carrier. Optical fiber only plays the role of transmission. Central station is responsible for switching, controlling and regenerating of signals. The base station only achieves photo electric conversion. The complex and expensive equipment in a central site allow multiple remote base stations to share these devices, which can reduce power consumption and cost of the base station. The difference between highspeed railway communication and traditional communication mainly lies in the object, network structure, geographical environment of base station construction and so on. The free space propagation model is a general model in ideal environment. The model of Okumura Hata is applicable to the network in 150~1000MHz. The model of COST123-Hata is applicable to the network in 1500~2000MHz, and large/small macro cellular environment where base station is higher than the height of surrounding buildings. The model of Keenan-Motley is applicable to the indoor environment.Wireless access networks of high speed train have weak coverage area or blind coverage area due to doppler effect, frequent cell switch, severe penetration loss of the train, difficult to build a base station in the special environment of high speed rail. Through analyzing and researching the influence of these factors, the thesis put forward four key technologies and methods to solve above problems, which is combination of low band frequency and AFC algorithm, “mobile cell”, relay line in train and propagation characteristics of electromagnetic wave.Wireless access networks of high speed train are built in four steps. Firstly, projecting network types, which includes determining goals, projecting frequency and projecting network topological structure between the urban and the suburban. Secondly, designing location of base station, which includes planning horizontal distance among base station and longitudinal distance between base station and rail. Thirdly, projecting single base station, which includes the design of base station types, equipment selection and the design of equipment parameters. Finally, designing radio network in train, which includes the principle of network building and the way of constituting network.The thesis takes feasibility analysis in covering the target, economy and the technology by combining with project of Beijing-Fuzhou high speed railway in Tongling. The thesis projects location of base station of Tongling section based on the flow path of design. The thesis designs base station in two aspects including the selection of equipment and the design of corresponding parameters. The thesis combines design theory and project construction by carrying out construction of machine room of base station and antenna feedback system. The thesis verifies project's results from the coverage, RSRP, SINR and system security.