The Characteristics of Wireless Video Transmission in Urban Traffic Roads
With the further prosperity of the economy, the number of cars is also increasing, which causes great inconvenience to traffic. As a result, the real-time monitoring of urban traffic becomes more and more important. A comprehensive traffic image management system is established. It is the goal of the traffic management department. The traffic intersection video surveillance system establishes a digital network covering major urban arterial roads and intersections, equipped with corresponding image wireless monitoring equipment and software, and can real-time transmit traffic conditions at traffic intersections to dispatch centers to monitor the running status of road vehicles. At the same time, the traffic management department can control the traffic flow of the road according to the actual situation on the site, arrange the vehicles to the unimpeded road sections, reduce the obstruction, ensure the smooth flow of road traffic, and realize the intelligent urban traffic management. This is to solve the problem of urban traffic congestion. very important.
City intersection wireless video surveillance program features
Since the monitoring points of traffic intersections and traffic control centers are generally far apart from each other, and their distribution locations are relatively dispersed, the use of traditional network cabling methods is not only very costly, has a long construction period, but also has poor scalability and flexibility, and needs to be increased or decreased as needed. The monitored points will bring new construction cycles.
The wireless network can connect multiple monitored points with the traffic control center, and can be set up quickly. It can quickly establish wireless network links in the shortest time. The use of wireless bridges can support bridging beyond 50 kilometers.
In order to ensure the stable transmission of video compression files, there must be sufficient network bandwidth. Different video compression files have different requirements for network bandwidth. In order to achieve better video quality, network bandwidth is more important. The network bandwidth defined by the wireless network standard protocol IEEE802.11a is 54 Mbps, the effective data transmission bandwidth is 22 Mbps, and the wireless link can reach a high network bandwidth of 54 Mbps. The high-speed wireless bridge products based on IEEE802.11a support the 54Mbps network bandwidth, and can fully guarantee the stable and reliable transmission of digital video streams using the MPEG-4 format to achieve the purpose of wireless video surveillance.
Wireless video surveillance system has the following advantages and features: easy installation and construction
The use of wireless networks, avoiding or reducing the workload of network cabling, without destroying the original environment facilities, has the characteristics of short construction period and high cost performance.
Fast coverage can be achieved
The greatest advantage of wireless network systems is the ability to achieve rapid coverage. With the point-to-multipoint wireless communication method, generally only one or more wireless central station devices need to be installed, and a broadband wireless access network system covering the entire urban area can be established.
High flexibility
Urban traffic intersections have a wide distribution and geographical dispersion. With the lack of flexibility in the use of wired networks, the need for future development must be considered as much as possible, which necessitates the presupposition of a large number of information points with low utilization. After the wireless network is established, the wireless terminal station can be set up at any position within the coverage area of ​​the wireless signal, and the network access can be realized with high flexibility.
Strong scalability
When there is a need to increase service points, there is no need for a large-scale network transformation. As long as wireless devices at monitored points are increased or decreased, the increase or decrease of monitored points can be completed.
Wireless video surveillance system road composition
The intersection of wireless video surveillance system consists of three parts: video information collection point, wireless transmission system, and traffic control center.
Intersection video image acquisition point
According to the specific conditions of each city, corresponding monitoring cameras (color or black-and-white, fixed or active pan/tilt, fixed focus, or zoom) and software systems are installed at each traffic intersection. One or several surveillance cameras can be installed at each traffic intersection, and each is equipped with a pan/tilt head, a protective cover and a PTZ controller. Each video capture point matches a video codec. Surveillance cameras are used to collect real-time traffic status video signals of all roads in cities, mainly monitoring vehicles within a certain range of traffic intersections. The PTZ can be controlled by the computer in the control center. The user can perform horizontal 360°, vertical 90° and zoom control on the camera.
The video codec is responsible for converting the camera's analog video signal into a digital signal, compressing it at the same time, and also transmitting control signals. The video codec has a built-in 10/100M network card and is connected to a wireless monitoring device via a network cable. The code is compressed after processing. The monitoring information is collected through the wireless network to the traffic monitoring and management center. The monitoring center can see the conditions of the roads and intersections under its jurisdiction. The monitoring personnel can remotely view the video images and the remote control heads through the monitoring center LAN or the Internet.
In order to fully guarantee the bandwidth of each monitoring point, the MPEG4 encoding standard is adopted, the bandwidth is occupied lower, and the image can be transmitted and stored with high quality, and the transmission distance is relatively long, which is suitable for monitoring in a wide area of ​​the city.
Wireless video transmission system
Through the wireless broadband access equipment, a wireless broadband network covering an urban intersection is established in a point-to-multipoint manner. A wireless bridge Sunet 5800 (central station) is installed at the center point, and a Sunet 5800-RU (remote station) is installed at the remote monitoring point. The central station chooses to be installed at the commanding heights of the city, such as high-rise buildings, steel tower tops, and high mountain tops, in order to ensure that it can receive the signals transmitted from each branch point.
A central point and several distributed access points are connected, and each distributed access point shares the total channel bandwidth provided by the central point in a shared manner, and the shared mode may allocate the total bandwidth according to the real-time needs of the access users. The system adopts the 802.11a protocol standard. The total system bandwidth is 54Mbps, and the effective bandwidth is 22Mbps. Each central station is connected to 3-5 wireless remote monitoring points. The effective access bandwidth of each distributed access point is generally 4Mbps. Both the Sunet5800 remote station and the central station equipment provide 10/100BaseT Ethernet interfaces. The switches, video decoders, and cameras in the monitoring center can be directly connected to the 10/100BaseT Ethernet interface of the Sunet5800 device in twisted pair.
Traffic Control Center
The monitoring center is mainly composed of a video codec, a matrix video wall, a monitoring server, a hard disk recorder, etc. It can complete the reception and display of live image at the intersection, storage, retrieval, playback, backup, and recovery of the video.
The video codec encodes and decodes the video signal collected by the front-end surveillance point camera transmitted via the wireless network, passes it to the video surveillance server of the surveillance management center LAN, and then is transmitted via the switch to the customers of various related departments or personnel through the internal local area network. end.
The user can view the images of multiple monitoring sites on the site through the multi-channel video wall in the center. The matrix video wall display mode can display 9/16 camera images at the same time.
The control commands issued by the wireless monitoring center for pan-tilt, lens, etc. are transmitted to the monitoring point through the wireless device. The user can control the pan/tilt, lens aperture, focal length, and zoom of any point on the spot through the PTZ control device located at the monitoring center; PTZ's up, down, left, right, automatic or auxiliary control of the remote power supply, camera switch Wait.
The video images transmitted from the scene are converted into digital signals and stored on the hard disk video recorder. The data can be stored, updated, searched and backed up conveniently and quickly, providing a basis for traffic law enforcement and other law enforcement work.
Since a large number of 2.4GHz spread spectrum communication products have been deployed in urban areas and the interference in the 2.4GHz frequency band is severe, the wireless network products operating in the 5.8GHz frequency band can obtain better signal noise than the 2.4GHz wireless network products. In contrast, a stable network link can be established. Therefore, products with 5.8GHz band should be used as far as possible in product selection. At the same time, 5.8GHz products can also provide higher bandwidth (54Mbps). After testing, it can meet both bandwidth requirements and link stability. In the end, we decided to use the Sunet 5800 series 54M high-speed wireless bridge from the company as our preferred access device.
Sunet5800 series devices can use 5 independent frequency points to work, such as found in the field test too much interference, video signal interruption phenomenon, can be flexibly adjusted by the use of frequency points can be timely to remove the frequency of interference to ensure the device The normal work. If you encounter building blockage and signal attenuation is too great, add a 5.8GHz signal amplifier to increase the wireless signal strength. If the monitoring site and the monitoring center are blocked by the building as a non-visible condition, in order to ensure the monitoring center image receiving effect, it is also possible to find out the third point that the monitoring site and the center can see, and install the wireless relay equipment transmission.
Equipment needed to build the system: The center station uses Sunet5800-AU high-speed wireless bridge, adopts OFDM technology, the rate is 54Mbps, supports point-to-multipoint wireless communication; the remote station adopts Sunet5800-RU, adopts OFDM technology, and the speed is 54M, supporting point-to-point wireless Communication. The central station uses a plate sector antenna with 18 dBi gain, and the remote station uses a parabolic directional antenna with 24 dBi gain. Other accessories include arresters, feeders, and patch cords.
The video uses MPEG4 ACE compression algorithm, the amount of data is much smaller than the MEPG1 and MPEG2 algorithms, saves disk space, is suitable for network transmission, can provide users with high-speed video images, each video stream speed can reach 30 frames per second, can be for users Provides smooth image effects.
With the further prosperity of the economy, the number of cars is also increasing, which causes great inconvenience to traffic. As a result, the real-time monitoring of urban traffic becomes more and more important. A comprehensive traffic image management system is established. It is the goal of the traffic management department. The traffic intersection video surveillance system establishes a digital network covering major urban arterial roads and intersections, equipped with corresponding image wireless monitoring equipment and software, and can real-time transmit traffic conditions at traffic intersections to dispatch centers to monitor the running status of road vehicles. At the same time, the traffic management department can control the traffic flow of the road according to the actual situation on the site, arrange the vehicles to the unimpeded road sections, reduce the obstruction, ensure the smooth flow of road traffic, and realize the intelligent urban traffic management. This is to solve the problem of urban traffic congestion. very important.
City intersection wireless video surveillance program features
Since the monitoring points of traffic intersections and traffic control centers are generally far apart from each other, and their distribution locations are relatively dispersed, the use of traditional network cabling methods is not only very costly, has a long construction period, but also has poor scalability and flexibility, and needs to be increased or decreased as needed. The monitored points will bring new construction cycles.
The wireless network can connect multiple monitored points with the traffic control center, and can be set up quickly. It can quickly establish wireless network links in the shortest time. The use of wireless bridges can support bridging beyond 50 kilometers.
In order to ensure the stable transmission of video compression files, there must be sufficient network bandwidth. Different video compression files have different requirements for network bandwidth. In order to achieve better video quality, network bandwidth is more important. The network bandwidth defined by the wireless network standard protocol IEEE802.11a is 54 Mbps, the effective data transmission bandwidth is 22 Mbps, and the wireless link can reach a high network bandwidth of 54 Mbps. The high-speed wireless bridge products based on IEEE802.11a support the 54Mbps network bandwidth, and can fully guarantee the stable and reliable transmission of digital video streams using the MPEG-4 format to achieve the purpose of wireless video surveillance.
Wireless video surveillance system has the following advantages and features: easy installation and construction
The use of wireless networks, avoiding or reducing the workload of network cabling, without destroying the original environment facilities, has the characteristics of short construction period and high cost performance.
Fast coverage can be achieved
The greatest advantage of wireless network systems is the ability to achieve rapid coverage. With the point-to-multipoint wireless communication method, generally only one or more wireless central station devices need to be installed, and a broadband wireless access network system covering the entire urban area can be established.
High flexibility
Urban traffic intersections have a wide distribution and geographical dispersion. With the lack of flexibility in the use of wired networks, the need for future development must be considered as much as possible, which necessitates the presupposition of a large number of information points with low utilization. After the wireless network is established, the wireless terminal station can be set up at any position within the coverage area of ​​the wireless signal, and the network access can be realized with high flexibility.
Strong scalability
When there is a need to increase service points, there is no need for a large-scale network transformation. As long as wireless devices at monitored points are increased or decreased, the increase or decrease of monitored points can be completed.
Wireless video surveillance system road composition
The intersection of wireless video surveillance system consists of three parts: video information collection point, wireless transmission system, and traffic control center.
Intersection video image acquisition point
According to the specific conditions of each city, corresponding monitoring cameras (color or black-and-white, fixed or active pan/tilt, fixed focus, or zoom) and software systems are installed at each traffic intersection. One or several surveillance cameras can be installed at each traffic intersection, and each is equipped with a pan/tilt head, a protective cover and a PTZ controller. Each video capture point matches a video codec. Surveillance cameras are used to collect real-time traffic status video signals of all roads in cities, mainly monitoring vehicles within a certain range of traffic intersections. The PTZ can be controlled by the computer in the control center. The user can perform horizontal 360°, vertical 90° and zoom control on the camera.
The video codec is responsible for converting the camera's analog video signal into a digital signal, compressing it at the same time, and also transmitting control signals. The video codec has a built-in 10/100M network card and is connected to a wireless monitoring device via a network cable. The code is compressed after processing. The monitoring information is collected through the wireless network to the traffic monitoring and management center. The monitoring center can see the conditions of the roads and intersections under its jurisdiction. The monitoring personnel can remotely view the video images and the remote control heads through the monitoring center LAN or the Internet.
In order to fully guarantee the bandwidth of each monitoring point, the MPEG4 encoding standard is adopted, the bandwidth is occupied lower, and the image can be transmitted and stored with high quality, and the transmission distance is relatively long, which is suitable for monitoring in a wide area of ​​the city.
Wireless video transmission system
Through the wireless broadband access equipment, a wireless broadband network covering an urban intersection is established in a point-to-multipoint manner. A wireless bridge Sunet 5800 (central station) is installed at the center point, and a Sunet 5800-RU (remote station) is installed at the remote monitoring point. The central station chooses to be installed at the commanding heights of the city, such as high-rise buildings, steel tower tops, and high mountain tops, in order to ensure that it can receive the signals transmitted from each branch point.
A central point and several distributed access points are connected, and each distributed access point shares the total channel bandwidth provided by the central point in a shared manner, and the shared mode may allocate the total bandwidth according to the real-time needs of the access users. The system adopts the 802.11a protocol standard. The total system bandwidth is 54Mbps, and the effective bandwidth is 22Mbps. Each central station is connected to 3-5 wireless remote monitoring points. The effective access bandwidth of each distributed access point is generally 4Mbps. Both the Sunet5800 remote station and the central station equipment provide 10/100BaseT Ethernet interfaces. The switches, video decoders, and cameras in the monitoring center can be directly connected to the 10/100BaseT Ethernet interface of the Sunet5800 device in twisted pair.
Traffic Control Center
The monitoring center is mainly composed of a video codec, a matrix video wall, a monitoring server, a hard disk recorder, etc. It can complete the reception and display of live image at the intersection, storage, retrieval, playback, backup, and recovery of the video.
The video codec encodes and decodes the video signal collected by the front-end surveillance point camera transmitted via the wireless network, passes it to the video surveillance server of the surveillance management center LAN, and then is transmitted via the switch to the customers of various related departments or personnel through the internal local area network. end.
The user can view the images of multiple monitoring sites on the site through the multi-channel video wall in the center. The matrix video wall display mode can display 9/16 camera images at the same time.
The control commands issued by the wireless monitoring center for pan-tilt, lens, etc. are transmitted to the monitoring point through the wireless device. The user can control the pan/tilt, lens aperture, focal length, and zoom of any point on the spot through the PTZ control device located at the monitoring center; PTZ's up, down, left, right, automatic or auxiliary control of the remote power supply, camera switch Wait.
The video images transmitted from the scene are converted into digital signals and stored on the hard disk video recorder. The data can be stored, updated, searched and backed up conveniently and quickly, providing a basis for traffic law enforcement and other law enforcement work.
Since a large number of 2.4GHz spread spectrum communication products have been deployed in urban areas and the interference in the 2.4GHz frequency band is severe, the wireless network products operating in the 5.8GHz frequency band can obtain better signal noise than the 2.4GHz wireless network products. In contrast, a stable network link can be established. Therefore, products with 5.8GHz band should be used as far as possible in product selection. At the same time, 5.8GHz products can also provide higher bandwidth (54Mbps). After testing, it can meet both bandwidth requirements and link stability. In the end, we decided to use the Sunet 5800 series 54M high-speed wireless bridge from the company as our preferred access device.
Sunet5800 series devices can use 5 independent frequency points to work, such as found in the field test too much interference, video signal interruption phenomenon, can be flexibly adjusted by the use of frequency points can be timely to remove the frequency of interference to ensure the device The normal work. If you encounter building blockage and signal attenuation is too great, add a 5.8GHz signal amplifier to increase the wireless signal strength. If the monitoring site and the monitoring center are blocked by the building as a non-visible condition, in order to ensure the monitoring center image receiving effect, it is also possible to find out the third point that the monitoring site and the center can see, and install the wireless relay equipment transmission.
Equipment needed to build the system: The center station uses Sunet5800-AU high-speed wireless bridge, adopts OFDM technology, the rate is 54Mbps, supports point-to-multipoint wireless communication; the remote station adopts Sunet5800-RU, adopts OFDM technology, and the speed is 54M, supporting point-to-point wireless Communication. The central station uses a plate sector antenna with 18 dBi gain, and the remote station uses a parabolic directional antenna with 24 dBi gain. Other accessories include arresters, feeders, and patch cords.
The video uses MPEG4 ACE compression algorithm, the amount of data is much smaller than the MEPG1 and MPEG2 algorithms, saves disk space, is suitable for network transmission, can provide users with high-speed video images, each video stream speed can reach 30 frames per second, can be for users Provides smooth image effects.
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