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**Table 1-1 Field network and communication system transmission information**
1. Establish a normal communication link on site without interference.
2. Establish a normal communication link in the field even when there is interference in the frequency band below 3 GHz.
3. Ensure smooth wireless communication and data security while transmitting required images and voice.
**System technical indicators**
1. After the positions of each car mesh module and portable mesh module are basically determined, the time from device power-up to network node establishment in the system is less than 4 minutes.
2. The real-time transmission bandwidth between individuals, vehicles, and among vehicles is not less than 6 Mbps.
3. In line-of-sight conditions, the coverage of the vehicle mesh module is at least 1,000 meters, and the portable mesh module covers at least 300 meters.
4. After 10 hops, the transmission bandwidth of the portable mesh module remains above 6 Mbps.
5. After 10 hops, the network delay does not exceed 200 ms.
6. The portable mesh module is equipped with an independent power supply (battery), and the mesh module and battery must be integrated into a single, sealed unit.
7. The system should allow each mesh module to adapt flexibly to different application modes without manual configuration or analysis.
**Network Topology**
**Network Return Method**
The emergency communication network uses mesh technology to create a mobile, self-organizing network between vehicles and between vehicles and personnel. Information from the mesh network is then transmitted back to the command center through any connected vehicle.
One of the main challenges in emergency communication is ensuring real-time transmission of video, voice, and data from the team. There are currently three primary methods used:
1. **Fiber Optic** – A wired network connects each vehicle to the nearest fiber network, allowing the mesh emergency network information to be sent back to the command center.
2. **Satellite** – Satellite transmitting and receiving equipment is installed in one of the vehicles to enable long-range communication.
3. **Wireless Backhaul** – This method utilizes the characteristics of the wireless mesh network by placing fixed wireless base stations every 2–5 kilometers in urban areas. These base stations communicate via a wireless mesh protocol and ultimately return data to the control center.
As shown in the figure, once a vehicle enters the scene, it connects to the nearest fixed base station, enabling the entire team’s information to be backhauled effectively.
**Figure 3-1 Flat network deployment diagram**
The site area is typically within a 500-meter radius, and the relative positions of vehicles and personnel are random. Therefore, the wireless network system must be flexible and have no edge points. A mesh topology is formed between vehicles and personnel, ensuring that wireless communication remains unaffected by changes in their positions.
**Stereo Network**
In field monitoring and signal acquisition, personnel often need to move in three dimensions, such as in subways or high-rise buildings. As shown in the figure, individuals in a subway use a multi-hop mesh network to wirelessly transmit live images to a vehicle on the ground.
**Figure 3-2 Stereoscopic network deployment diagram**
**Mobile Network**
In the field environment, vehicles can move freely to perform effective operations. Even in such scenarios, maintaining communication between vehicles is essential. By leveraging the mobility of the on-site mesh network, communication can be maintained. For example, in flat terrain with omnidirectional antennas, the network can achieve a data transmission rate of 6 Mbps at speeds up to 120 km/h within the effective communication range.
As shown, a moving vehicle transmits live video to the rear through the mesh network.
**Figure 3-3 Mobile network deployment diagram**
Case analysis of emergency communication field in wireless Mesh technology
In the emergency communication network, on-site wireless nodes are composed of multiple mobile vehicles and independent personnel. Each vehicle and individual is equipped with a wireless network node, enabling real-time connectivity between vehicles, personnel, and groups. This setup ensures seamless communication in dynamic and challenging environments.
This article illustrates the methods of information transmission and the types of services provided, based on actual field requirements. The following figure shows how information is transferred within the field network and communication system.