“The video surveillance system of urban rail transit trains is mainly composed of two parts: in-vehicle monitoring and transmission, and control center monitoring. The first part realizes the centralized monitoring of real-time video of each car by the driver’s cab, so that the driver can quickly respond to the emergencies in the car; the second part is composed of the urban rail transit control center and adjacent stations, and is transmitted through wireless video. The technology realizes real-time monitoring of the running train compartment, so that the control center can understand the scene situation in the first time, and quickly make overall instructions and solutions.
Rail transit is an important part of urban public transportation system, and the main types include subway, light rail, tram, maglev train, etc.
Because rail transit has obvious advantages in guiding urban layout adjustment, saving land resources, protecting the environment, saving energy, solving residents’ travel, and promoting industrial and economic development, it has always been valued by countries around the world.
In the second half of 2008, affected by the international financial crisis, China adjusted its macroeconomic policies in a timely manner, and proposed policies to expand domestic demand and maintain economic growth. A large number of cities have begun to prepare for the construction of rail transit. According to the first batch of urban rail transit project plans approved by the State Council, by 2015, the planned line length is 2,400 kilometers, and the investment scale is nearly 700 billion yuan.
These data all show that China’s rail transit construction is ushering in a historic opportunity for large-scale development under the influence of various factors. As an important part of rail transit security, security video surveillance in the rail transit industry has also gained unprecedented market development opportunities.
The urban rail transit system is a public place with high mobility and high concentration of people. Unsafe factors such as crowding give criminals an opportunity. Crimes such as theft and robbery occur from time to time, so the urban rail transit system especially needs to use video surveillance to achieve full and all-round security prevention. Urban rail transit video surveillance generally includes two parts: monitoring in the station and monitoring in the train. At present, video surveillance systems have been installed in urban rail transit stations in major cities in China, and cameras are usually installed in the platforms and station halls to realize in-station monitoring; however, the in-car monitoring of urban rail transit has just started in China. In order to prevent the occurrence of urban rail transit emergencies, implement the scientific development concept and the concept of people-oriented, ensure the safety of the people, and actively develop the train video monitoring system of urban rail transit, it is a very urgent and important task at present.
Discussion on System Development Technology
The video surveillance system of urban rail transit trains is mainly composed of two parts: in-vehicle monitoring and transmission, and control center monitoring. The first part realizes the centralized monitoring of real-time video of each car by the driver’s cab, so that the driver can quickly respond to the emergencies in the car; the second part is composed of the urban rail transit control center and adjacent stations, and is transmitted through wireless video. The technology realizes real-time monitoring of the running train compartment, so that the control center can understand the scene situation in the first time, and quickly make overall instructions and solutions.
Since the train is connected by several carriages, the video signal transmission between the carriages can be realized through jumper cable connectors (generally using aviation plugs). The system first transmits the video data obtained by the front-end equipment (cameras) of each car to the train driver’s cab in real time, displays it through the monitor and stores it in the storage medium, and realizes the real-time video centralized monitoring of each car by the driver’s cab. In order to realize the real-time monitoring of the running train compartment by the urban rail transit control center, and to transmit the video surveillance images in the running train compartment to the control center in real time, the wireless transmission method must be used to realize the construction of a wireless video transmission system. In order to realize the transmission of monitoring images.
There are many wireless video transmission technologies that can now be implemented, such as 3G mobile communication, wireless local area network (Wi-Fi), broadband wireless network (WiMAX) and so on. Through comprehensive comparison, it is a relatively mature solution to choose the combination of 3G mobile communication and wireless local area network (Wi-Fi). The video signal transmission of the signal saves the cost of base station infrastructure construction; on the other hand, in places where the 3G signal is poor or cannot be covered, the construction of wireless local area network (Wi-Fi) base stations is carried out to realize the entire wireless network inside the station and in the subway tunnel. Signal coverage to achieve continuous transmission of wireless video signals.
For the development and application of video surveillance system for urban rail transit trains, the main research and development directions are the application of video compression technology and wireless transmission technology, the development and application of information security technology, and the application of dedicated short-range communication technology.
This rail transit vehicle-mounted video surveillance system is a complete, high-efficiency and cost-effective network multimedia video surveillance system. It integrates wireless data communication function and digital video coding function, and adopts embedded integrated design, with high integration and convenient installation and maintenance.
The image collected by the high-definition camera is compressed by the video compression and coding module, and then the intelligent wireless communication terminal transmits the real-time video signal to the Internet through the combination of 3G and Wi-Fi wireless network to realize the video data. Interaction, send/receive, encryption and decryption, encryption and decoding and other functions. The monitoring center can obtain real-time image information from the system terminal through the Internet. The system integrates the advantages of wireless networks and the Internet, and achieves breakthrough expansion in space and distance.
The system is mainly composed of front-end equipment, transmission network, monitoring center and monitoring terminal
Figure 1: System structure based on Wi-Fi/3G network
Front-end equipment: high-definition cameras capture front-end video; the encoding and encryption module of the vehicle-mounted computer performs encoding, compression and encryption of video data; and then transmits and transmits video compressed data through the signal transmission module;
・Transmission network: Through the combination of 3G and Wi-Fi wireless networks, video compression and encryption signals are transmitted to the public network to realize remote video transmission;
・Monitoring center: the central server connected to the Internet network, it needs to have an independent, fixed IP address or domain name, so that both front-end wireless transmission equipment and monitoring terminals can access it on the Internet network;
・Monitoring terminal: Office computers, notebooks, and PDAs access the server through the Internet, and use real-time and diversified monitoring methods to retrieve monitoring images
Figure 2: Diversified access methods for office computers, notebooks, and PDA phones
System software composition
Based on IP broadband wireless network, the system platform can realize distributed video surveillance solutions of image remote monitoring, mass storage, remote transmission, hierarchical management and many value-added services. It has the characteristics of open architecture, stable system performance, rich service experience, carrier-class operation and maintenance. It can provide an intuitive, interactive, operable, manageable and secondary development video surveillance management tool for the management of various industries.
Figure 3 Software composition diagram of video surveillance system for urban rail transit trains
1. Central server software
ServerKit service control software:
Set the basic parameters of service operation and control the start and stop of various services.
VideoService video service:
・Data exchange service – realize the two-way exchange of data between front-end equipment, back-end server, and monitoring terminal;
・Real-time video broadcasting service – live video broadcast to clients upon request;
・Background recording and storage of video data – record and archive all received video data in the background;
・Monitoring terminal connection management – client software connection support.
TransServer File Transfer Service:
Provide the client with the retrieval and download service of the background video, and the file download supports the resuming of the breakpoint.
2. ManagementService remote management service
Remote management middle layer – access to remote management client software to translate and execute system management instructions.
3. VideoSurveillant video surveillance client software
・Front-end video access – selectively access front-end videos according to permissions;
・Front-end coding parameter settings – flexibly adjust coding parameter settings according to monitoring requirements and actual front-end network conditions.
・Make full use of existing wireless base stations and network resources as much as possible, the system is easy to install, quick to open, simple to wiring, saves implementation costs, and has a short construction period;
・Front-end equipment can be arbitrarily deployed in places with 3G and WI-FI network signals, not limited by distance, wide monitoring range, and strong expansion capability;
・Long transmission distance, low latency (critical for video applications), cost-effective system software and front-end equipment, can provide efficient and economical video transmission solutions;
・The selected wireless network is stable and reliable, with high transmission rate and strong real-time performance, which can ensure uninterrupted video surveillance;
・Low operating cost of the system, suitable for large-scale deployment;
・With matching wired broadband video surveillance equipment, wired equipment and wireless equipment can be connected to the same monitoring platform;
・Information security: Make full use of network tunnel, 128-bit encryption algorithm, firewall/VPN, encryption lock, rights management, security authentication, real-time clock and other technologies to ensure that the monitoring system and video data are not used and destroyed without authorization;
・Powerful management platform: distributed hierarchical management, users can conduct real-time monitoring, real-time management, real-time viewing, and real-time command of monitoring and management targets without being limited by time and space.
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