City traffic police at major junctions installed DVR, able to take pictures of vehicles illegally stored down. These stored images are currently stored in the field of computers because the equipment is not networked, it can not capture images through the network management center is returned, the staff can only be copied back to the scene to a day treatment center, not only waste a lot of human and material resources, but can not guarantee that data transmission in real time.
The use of equipment based on user characteristics and the status of a city communications network, we recommend the use of wireless private network approach. Currently the city is the best way to fast network wireless, wireless networking, there are two: wireless public networks or wireless private network, the biggest advantage of the public network base station equipment has been building, without the user management, network coverage area However, there are many problems: the wireless public network such as the current transmission speed is low, the fastest upload speed CDMA network is merely a 30kbps, and data transmission by the network conditions and the impact of other applications; the event of an emergency, wireless data services is difficult to ensure, once the base station problems, only solutions such as telecom operators, they can not in time; for the public security system in some of the confidential contents can not be in the public network transmission, while large amount of data transmission makes the cost of public network become very expensive or even unacceptable. Wireless Network is just the opposite: you need to build their own base stations, their management, problems can be solved in time; transmission speed, easy expansion, the base station set up simple; in cases of emergency when the public will not be affected by heavy use; use their own network, an internal network, without any contact with the public network, confidentiality, one-time investment in networking equipment, do not use the latter part of the basic fee.
Now widely known as spread spectrum microwave Although high-bandwidth, but limited to high-frequency points, can be visual communication, it is difficult to achieve in the city, especially in medium and large cities, as skyscrapers, can not provide the center of the wireless remote device visual environment, wireless link is very difficult, and general narrow-band products, although with low frequency, the diffraction ability, the characteristics of transmission distance, but the rate is lower difficult to meet the requirements of image transmission.
According to the city's wireless environment, urban built environment and user requirements for network transmission capacity, we chose to build the system iNET300 radio link, iNET300 advanced frequency hopping spread spectrum radio technology, equipment, very strong anti-interference ability; with special encryption, strong safety performance; simple wireless networking support multipoint, can be easily set up multiple base stations of cellular networks. Work on 340MHz radio frequency band, low frequency, with a strong diffraction ability and penetration, so long transmission distance, and when the radio base station and remote obstruction between the time to ensure that wireless communications can work, and because the station uses digital signal processing technology with the FEC forward Error Correction technology, it has a high signal reception sensitivity and can guarantee a reliable signal transmission to make it more difficult to adapt to urban wireless environment is the case of the application. The device itself as the standard industrial equipment, product quality and stable performance in harsh work environments. Base stations and remote radio equipment using the same hardware platform, only can be achieved through the exchange of software settings, radio cheap, easy to set up, when the wireless network needs to expand coverage or increase network bandwidth when you can easily add number of base stations, base station location and when the time need to change only the antenna needs to be re-erected in the new location can be only one person in a very short period of time to complete. Radio provides an Ethernet interface, through standard TCP / IP protocol for transmission, so users do not need special hardware or software associated with. Radio air transmission rate of up to 512/256kbps, to meet the general image of the requirements over the same time providing a device Ethernet port, two serial ports, with video servers and other devices that can provide images, voice and data solutions.
We have done some in the city of mobile video test, the master set up upstairs in the Public Security Council, one end of the moving vehicle, the coverage of the main station in about 3-4 km. Council for Public Security building height is not very high, and the vehicle moving low end of the antenna height, antenna gain antenna used car is not high, while crossing the traffic police the application of image transmission systems and mobile video is different: due to a base station can not cover the whole of a city, need to select more than one location set up base stations, base station antennas can choose to place as high as possible, point the remote point can be used because it is fixed high-gain directional antenna and the antenna can be mounted on light poles, have a greater height increase, so the coverage of each base station should be greatly improved. At the same time, we believe that if the mobile vehicle image transmission system to an existing system, the entire traffic police monitoring function of the system has greatly improved, and iNET300 radio base stations to support roaming between multiple switches, allowing the entire system can be a vehicle City can use.
The city Public Security Bureau uses a GPS positioning system 4710 radio stations, including the suburbs of the city's nine base stations set up all the coverage, we can reuse the infrastructure base station can also be set up iNET300 stations cover the entire city. For some parts of the large amount of data transmission equipment, base station capacity is not enough, we can add one or even in the same location a few base stations to improve the system transmission capacity. For some dead ends, can also be achieved in the vicinity of base stations to increase coverage. User data rates requires that each point can not be less than 20Kbps, our equipment can provide the highest effective bandwidth can be more than 400Kbps, to ensure that each point in the case of concurrent bandwidth of 20Kbps, while a base station can link 20 remote points, but actual use, multi-point while uploading the data is not necessarily a lot, so the base can be increased under a number of remote points, each base station according to 50 remote stations, and the whole city to 24 base stations, these base station can be installed in each branch or appropriate police station, between base stations and base stations by the public security of the wired network connected together to form a large wireless network.
System structure:
