Tag: Mobile Wireless Video Surveillance
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I. Overview of the railway video industry demand
At present, the wireless system subsystem of the domestic railway car is based on the open industry standard: the wired communication part adopts the IEEE802.3 Ethernet standard, and the wireless part mainly has two series of standards of AP and PMP point-to-multipoint bridge. In combination with the actual demand and line characteristics of rail transit, we recommend the appropriate solution, namely the wireless communication solution for PMP vehicles. The mobile broadband video transmission network of the vehicle and the ground should have the capability of real-time two-way broadband video data transmission between the train and the ground under the condition of high train speed. The effective bandwidth of the mobile broadband transmission should be no less than 15Mb/s, which can guarantee the vehicle. Real-time playback does not interrupt video images and data, has the same transmission content of the breakpoint resume transmission function, and ensures that the transmitted image should be smooth and clear, can not appear picture interruption or jump broadcast and mosaic phenomenon.
It satisfies the video signal of MPEG-2 format transmitted by each train and guarantees the image quality of D1 (720*576); uploads video surveillance information of no less than 2 channels to the broadcast center (MPEG-4 or H.264) Format), each video image occupies a bandwidth of 1M (PAL is 1-25 frames/S adjustable). It also has broadcast, multicast or unicast and addressing capabilities.
The trackside wireless unit installed in the depot and parking lot should also be used to meet the requirements of uploading and downloading monitoring signals for pre-recorded programs in the train-in-vehicle PIS system.
Second, the application characteristics and advantages of railway mobile wireless video surveillance
The coverage is large and the maintenance cost is low. The base station is used to cover the running line in the train wireless system. The setting location of the base station is completely set according to the actual situation of the line, and one AP every 300 or 400 meters. This method can achieve the best wireless coverage level according to the actual situation of the line, and achieves a good use effect in the tunnel.
Instantaneous seamless switching, always online, base station switching is done autonomously by the fast roaming client, and the switching mode is soft switching mode.
The network structure is simple, easy to manage, and the network structure is simple, and the existing data transmission network can be easily accessed.
Support remote maintenance/configuration, management and maintenance interface is intuitive, and support remote maintenance. In the control center, the operation status of each base station and its parameters can be visually seen through the computer, and various parameters (such as transmission power, modulation mode, working frequency, burst rate, etc.) of any base station can be performed at the center according to maintenance requirements. )to modify.
Easy to upgrade in the future, depending on the actual situation and business development needs, in the future, you can add base stations at any location or increase the equipment on the train (such as providing passengers to the Internet in the future). In this case, you only need to add the corresponding equipment in the overall IP configuration. The IP address is OK, and there is no need to modify the entire network structure.
The upstream and downstream bandwidths are adaptively adjusted. The wireless technology used in this system is developed and produced on the basis of the PMP standard. The OFDM modulation mode is adopted, and the bandwidth can be adjusted according to the actual service, that is, the train monitoring image transmission and the digital video information transmission bandwidth.
Third, the overall solution architecture diagram
System networking design
The system can be divided into: the vehicle part, the ground base station part,
The distributed system architecture: the vehicle monitoring center--the vehicle-ground communication part---the fiber part---ground monitoring center.
The vehicle monitoring center can be divided into: car monitoring points, vehicle monitoring centers.
Car wireless communication part: fast roaming client, ground base station part.
Fiber section: The ground trunk link is fiber.
Ground monitoring center: fiber optic transceiver, firewall, server, PC.
Train mobile wireless video surveillance mainly monitors the sudden situation on the train, so that the command center can keep abreast of the train's various compartments.
Ground station coverage diagram:
Each base station will deploy two MOBISYSMB2412-Es to cover both directions at the same time. In each direction, two frequencies will be supported at the same time, and one base station will be deployed every 0.5 km, so that the cellular scheme can be switched between the vehicle and the base station.
Vehicle system design part:
Implementation of the vehicle ground wireless system;
The vehicle-to-ground wireless communication is a wireless communication established between the in-vehicle roaming client and the wireless bridge, which can provide:
A fixed IP address per train, ensuring that each device can be managed in the network center
No matter how the vehicle moves, an uninterrupted communication link is always provided through an in-vehicle roaming client
Based on the IEEE802.11 standard wireless network technology, the essence of the system is to establish an IP channel between the communication control unit located in the vehicle (the monitoring center located in the network center. The function of the wireless vehicle network system is through the train and the center. The established data channel bidirectionally transmits various IP-based data, thereby providing high reliability data transmission, Internet access, CCTV, video program broadcasting and the like.
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