In the emergency communication network, the network nodes in the on-site wireless network need to be composed of several mobile vehicles and several independent personnel. The vehicles and personnel are equipped with wireless network nodes, and real-time interconnection is required between vehicles, personnel and groups. .
This article takes the actual needs as an example to illustrate the way of transmitting information and the type of service.
Table 1-1 Field network and communication system transmission information
(1) Establish a normal communication link on site without interference;
(2) Establishing a normal communication link in the field in the case of interference in the frequency band below 3 GHz;
(3) Under the premise of ensuring smooth wireless communication and transmitting data security, complete the transmission of the required image and voice.
System technical indicators
(1) After the position of each car mesh module and portable mesh module is basically determined, the time from the powering up of the device to the network node in the system is less than 4 minutes.
(2) The real-time transmission bandwidth between each person and vehicle, vehicle and vehicle is not less than 6M
(3) In the case where the line of sight is visible, the coverage of the vehicle mesh module is not less than 1000 meters, and the coverage of the portable mesh module is not less than 300 meters.
(4) After 10 hops of the portable mesh module, the transmission bandwidth is not less than 6M.
(5) After 10 hops of the portable mesh module, the network delay does not exceed 200ms.
(6) Portable mesh module with independent power supply equipment (battery), mesh module and battery should be a unified, closed structure as a whole
(7) For different application modes of the system, each mesh module can be flexibly adapted without manual analysis and configuration.
Network TopologyNetwork return method
The emergency communication network utilizes mesh mesh technology to form a mobile, self-organizing emergency communication network between vehicles and between vehicles and personnel. Then, the information of the mesh emergency network is transmitted back to the command center through any vehicle.
How to make the video, voice and data information of the team in real time is the main challenge of emergency communication. There are currently three main types of methods:
(1). optical fiber
Wired network is used to connect any vehicle to the nearest fiber network, so that the mesh emergency network information is transmitted back to the command center.
(2). satellite
Installation of satellite transmitting and receiving equipment in one of the vehicles
(3). Wireless backhaul
This method makes full use of the characteristics of the wireless mesh network, and provides fixed wireless base stations to the vehicles in the urban area every 2-5 kilometers in the main high-rise buildings in the urban area. The fixed base stations communicate by wireless mesh protocol and finally return to the control center.
As shown in the following figure: After the vehicle enters the scene, the vehicle responsible for the wireless return and the nearest fixed base station will be interconnected with the nearest fixed base station, thereby realizing the information backhaul of the entire team.
Figure 3-1 Flat network deployment diagram
Among them, the site range of the site is within the radius of 500 meters, and the relative position between each vehicle and personnel is relatively random, and any situation may occur. Therefore, the wireless network system is required to be flexible and has no edge points. A mesh topology is formed between the vehicle and the personnel, and wireless communication is not affected by mutual position changes.
Stereo network
In the field monitoring and signal acquisition, people often need to move in a three-dimensional manner, such as the depth of the subway or high-rise buildings. As shown in the figure, the people in the subway wirelessly transmit the live image to the vehicle on the ground through the mesh network multi-bounce mode.
Figure 3-2 Stereoscopic network deployment diagram
Mobile network
In the field environment, vehicles can move to each other in order to be able to perform effective arming. In this case, it is still necessary to maintain the necessary communication between the vehicles. Using the mobility of the on-site mesh network to solve this problem, in the case of an omnidirectional antenna in a flat terrain, the network can reach a data transmission rate of 6 Mbps in a high-speed mobile state with a speed of 120 km/h in an effective communication range. . As shown, the vehicle transmits the live image to the rear through the mesh network while moving.
Figure 3-3 Mobile network deployment diagram
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