Research On HF Air-Ground Communication Technique And Software Implementation

HF communication can achieve the purpose of remote communication, compared with other methods of communication, it has unparalleled advantages of strong subsistence and good flexibilities in military and emergency communication fields. As HF communication is most vulnerable to ionospheric effects, it must adjust the operting frequency dynamicly in order to assure reliability according to real-time link quality. Aiming at some disadvantages of air-ground HF network, such as poor connectivity, narrow channel bandwidth, lack of remote communication means, etc., techniques of HF communication networking and frequency management are emphatically studied. A scheme of HF networking with high link rate is proposed and a frequency management system with strong adaptability is designed to enhance the link rate of air-ground communication. The main work of this paper is as follows:1. A scheme of HF networking is proposed and it improves link rate by combining frequency diversity with geographical diversity. Combined with analyzing simulation results, it has validated that the link rate can achieve 95 percent.2. According to the actual demand of HF air-ground network, a scheme of spectrum sharing based frequency management without transmitting navigation sounds is adapted after comparing two basic HF networks with and without transmitting navigation sounds. In addition, a frequency planning scheme is proposed to support 200 ground users and 200 airborne users.Under the condition of loss probability is less than 5%, the whole network’s frequency resource is planned, including downlink DCH, downlink HF signaling channels and uplink HF radio broadcasting. Moreover, the system call flow based on SIP is designed to meet the project requirements.3. The design of relevant modules of frequency management software are completed, including user registration, network guidance, link maintenance, link probe and frequency setting. The implementation of relevant modules of the software based on MFC frame is completed. In addition, the protocol conversion module converting SLIP to TCP or TCP to SLIP is designed and the implementation of software is conducted.4. The testing on relevant modules of frequency management software is conducted by designing the management and control software of HF radio. The system debugging is also completed in a local environment using virtual serial port and socket technology by designing test cases. Simulated results verify the correctness and feasibility of related modules, such as user registration, network guidance, link maintenance, link probe and frequency setting.