Emergency communication system plays an important role in ensuring national defense and dealing with public emergencies，At present, the wireless communication of urban emergency communication system includes Beidou communication, satellite communication, short-wave communication, ultra-short-wave communication and cluster communication，Beidou satellite, satellite communication, short-wave communication for high airspace long-distance communication，It mainly realizes the communication between provinces and cities;The conventional ultrashort wave and cluster communication is near Earth communication，The communication distance is generally 10-30 km，The conventional trunked communication network must rely on the wired network and the construction of more base stations to achieve the signal coverage in a large area，Shortwave communication has a blind area in the range of 20-100 km，Satellite communication has long search time and expensive usage fee, which can not be widely used.In case of disaster，All kinds of fixed base station type conventional communication and network communication are based on wired networks due to interconnection，It is often destroyed after catastrophic disasters such as floods and typhoons, resulting in a lack of command means，I can't connect it, I can't connect it，Disaster situation and emergency plan can not be uploaded and issued in time，Hindering the timely and reliable implementation of emergency rescue。In view of the above situation, the most needed wireless system for urban emergency communication must have mobile portable base stations, long communication coverage distance, smart and portable equipment, long standby time, and multi-system working mode and convenient access to a variety of networks。

Second, the characteristics of Beifeng grid ultra-short wave

Beifeng meshing ultra-short wave non-range visual communication is a new type of digital communication technology. The technical innovation in the field of ultra-short wave communication breaks through the concept of traditional ultra-short wave line-of-sight communication。Networked ultrashort wave realizes long-distance information transmission, solves the bottleneck of difficult communication in the case of long distance and weak signal in various industries and departments, improves the communication distance to more than 3-5 times of the existing traditional communication products, and fills the gap in ultrashort wave ultra-long distance communication。

The mechanism of reflection and superrefraction of wireless signal in troposphere in meshed ultra-short wave digital communication equipment，Adopt hybrid digital coding technology，Adaptive low noise coherent and incoherent demodulation technology, channel frequency domain equalization technology，Innovative RF channel design，Obtain sufficient signal-to-noise ratio gain under very weak signals，Digital speech sensitivity is high。In the ultra-weak field strength signal demodulation, channel error correction coding and other aspects of technical breakthroughs, to achieve over-the-horizon communication, 50W radio communication in flat land areas can achieve 120 kilometers, mobile communication in mountainous areas can achieve more than 40-50 kilometers of long-distance communication。Beifeng meshed ultrashave wave has the typical function of electromagnetic wave refraction over the obstacle of mountains。

Beifeng ultra-short wave non-range visual communication features are as follows:

1, with the same power and the same antenna, the communication distance is 3-5 times that of the existing ultra-short wave radio;Small weather impact, can achieve all-weather high-quality communication;

2, communication can climb mountains to achieve over-the-horizon communication;

3, Beidou short message: when the communication signal is limited or damaged, it can directly rely on satellite communication without the restrictions of the surrounding infrastructure, and communicate anytime and anywhere。

4, the radio comes with GPS/ Beidou positioning, you can use the radio channel to set position return, radio track real-time situation display;

5, the base station can be wireless AD hoc network, can relay, cluster mode;It is easy to cover a wide range with wireless AD hoc networking, which can save a lot of engineering costs such as cable construction;

6、 It can interwork with various IP networks, program-controlled telephone networks, mobile communication networks, satellite communications, DMR/PDT/DMR communication systems and public network intercom systems, and can use radio and mobile phone APP communication, convenient access to a variety of applications;

7, the equipment light weight, military structure, low power consumption, long standby time, the antenna can be folded omnidirectional whip antenna, easy to carry;

Based on the above characteristics, the most prominent applications of ultra-short wave ultra-non-line-of-sight are reflected in:

1) The portable mobile command and dispatch network from each mission site to the mobile command and communication vehicle;

2) Large-scale command dispatching communication coverage of fixed base station networking in complex areas。

3. Typical application of urban emergency communication networking

Field communication in emergency communication