Research on Wireless Monitoring Video Transmission Technology for Rail Transit Vehicles

With the rapid development of China's rail transit construction, the wireless transmission system for rail transit has become increasingly demanding for mobility. This article briefly introduces the current state of the technology development in this part.

Rail transit has features such as large capacity, high speed, safety, punctuality, environmental protection, energy conservation and land use. At present, countries have generally recognized that the fundamental solution to the traffic problem lies in giving priority to the development of mass transit-based public transportation systems.

Urban rail transit and railway belong to the category of rail transit. Urban rapid rail transit includes subways, light rails, trams, and maglev trains. Because trams and maglev trains have little market share, they generally refer to subways and light rails. The basis for dividing the two is the size of one-way maximum peak hour passenger flow: using a medium-capacity passenger compartment, a light rail that can adapt to a one-way maximum peak hour hour passenger flow of 1.5 to 30 million passengers; a large-capacity passenger compartment The passenger trains that can adapt to the long-term one-way maximum peak hours are 3.0 to 60,000 passengers. The railways referred to in the "PRC Railway Law" include the national railways, local railways, special railways and special railway lines. Internationally divided according to the maximum allowable operating speed of railway lines: railways include ordinary railways (100-160km/h), express railways (160-200km/h) and high-speed railways (reconstruction of existing lines> 200km/h; newly-built lines> 250km /h). At present, the highest speed of Chinese high-speed rail is close to 400 kilometers. With the rapid development of rail transit, the wireless transmission system for rail transit has become increasingly demanding for mobility.

Wireless transmission technology The rail transit wireless transmission technology, namely wireless communication technology, is divided into civil wireless communication, special wireless communication and train control wireless communication. The civil wireless communication system mainly implements the coverage of public mobile signals such as paging, GSM, CDMA, 3G (including 3G-UMTS, 3G-UWB, and 3G-LTE), and is used for civilian communication of rail transit; the dedicated wireless communication system mainly implements TETRA. Coverage of dedicated signals such as GOTA, GT-800, iDen, WLAN, DVB-T, WIMAX, etc. is used for the operation and production of rail transit, and provides links between vehicle dispatching command and other related departments, including train dispatching and environmental control. Wireless communications such as dispatching, public security dispatching, depots and yards, maintenance departments, etc., are used for rail transit special communications, public security communications, PIS/CCTV wireless transmission, and mobile TV; train control wireless communication is the most important part of the rail transit signal system. One of them is used to control the interval between trains.

At present, the wireless communication technologies used in the domestic rail transit industry mainly include WLAN, GSM-R, TETRA, GSM, CDMA, 3G, WiMAX, and DVB-T.

Analysis of vehicle-to-ground wireless transmission requirements Wireless transmission needs of urban rail transit industry Wireless and communication technologies are increasingly used in the communication between trains and the ground of urban rail transit. In addition to civil communications, there are currently three service subsystems that require wireless. Communication: Downstream bandwidth requirement in passenger information system (PIS) is about 8Mbps (1 roadmap clear), bandwidth of on-board video surveillance system is about 6~8Mbps (1 channel up, 1 channel down), bandwidth requirement of CBTC signal system For hundreds of Kbps.

Passenger Advisory System (PIS)

The system is equipped with a liquid crystal display (with a maximum of eight cars in a car) distributed in the train compartment. Passengers can get real-time information about train operation status and arrival information. They can also watch live TV programs and advertisements.