Research Of Communication System For Emergency Based On Troposcatter Communication

In recent years, a variety of emergencies have occurred because of the grim domestic and foreign situation. The rapid response capability has been improved by the Emergency command system when the functional department face with public safety, emergency management, large-scale gatherings, earthquake relief,combat terrorism and safeguard stability, and multiple unexpected events.In China, more and more attention is being paid on the development and deployment of the National Emergency System. Over the years, satellite communication was relied on in emergency system as the trunk transmission mode, supplemented by radio, wireless image transmission and other wireless communication means. With the surge in data traffic, it has been unable to fully meet the requirements.Through investigation and research, there are some problems as follows in the process of using satellite communication mode.1. The need of multimedia communication transmission can't be met because of the narrow satellite bandwidth.2. Expensive satellite channel renting.3. The satellite communication has been interfered by criminals usually when national major events.4. Normal activities is affected by the limited satellite resources even when the spectrum resources can't be apply in the coastal areas.Troposcatter communication is a military trunk transmission means which is widely used at home and abroad. It is a new concept to introduce the troposcatter communication to the field of emergency communication, and it has been break the traditional pattern, provided a strong guarantee for the emergency communication.This thesis designs the troposcatter communication system which communication distance can reach 120km(@8Mbps), constructs the mobile command headquarters and the fixed command center, integrates with multiple communication methods and multiple information collection and processing system. The whole system can realize the service of voice, video and data transmission with high qualities. It guarantees the fixed command center on the event live to understand and dispatch when the emergency events happens.In terms of mobile command post, the following works have been mainly completed.1. Study a variety of communication method. Troposcatter communication is used as the main transmission link and according to different scenarios at the same time, also a variety of communication ways are increased in the system such as the beidou, HF radio, VHF radio, multi-band radio, air radio and so on.2. Study command and scheduling functions. Images, voice, data and other information should be provided to the command center. In the aspect of image, some cameras have been installed in the communication vehicle, so the monition of inside, outside, on the top of vehicle image, and also the video conference with the command center can be realized. In the aspect of voice, through the professional mixer, voice information collected form microphone, outdoor and all kinds of indoor equipment, can be played in the local and transmitted to fixed command center. In the aspect of data, the function of remote data access and remote office can be realized in the mobile command post.3. Study the antenna automatic alignment and antenna fix method. Electronic compass is used to direction finding, which has low accuracy, and is easy to be affected by the environment, and need to calibrate data in the future. To prove the accuracy of antenna automatic alignment and reduce the maintenance in the future, the azimuth reference standard based on beidou directional system has been proposed. The accuracy of the beidou directional system can reach to 0.1 degrees, and can well meet the requirements. In the fix method of antenna, the electromagnet fix method is used instead of hook fix method. In the antenna automatic control program, the logic control of the electromagnet has been increased to ensure the antenna normal open and collection.In this thesis, the pulling-away and network combination test data is given and it obtained the desired results and recognition of the whole system by the user.