Design And Implementation Of Data Transmission Protocal For The HF Frequency Selection And Link Establishment System

HF communication possesses the incomparable capability of anti-destruction, which makes it establishes an irreplaceable position in military and emergency communication. In recent years, with the promotion of new technologies, HF communication develops rapidly. On the basis of the second generation HF communication system, the laboratory developed the third generation HF frequency and link establishment system, so as to improve the speed of link establishment and efficiency of data transmission. The data transmission module of the system is studied in this paper, and the main work are as follows:1.The overall scheme of the system is analysed and the data transmission protocols of link layer are presented. The protocols mainly include TM protocol and HDL protocol. The frame format and the contents of protocol unit are designed, and the meaning and function of each protocol unit are given.2.On the basis of realizing the transmission of small files, we deeply studied the process of using the network port and serial port to send and receive data, the timer timeout mechanism,buffer cycle operation, error control technology, sliding window mechanism and adaptive variable speed mechanism, and finally the transmission of large files is completed. At the same time, the function of breakpoint retransmission is also completed. When the transmission is interrupted, the link is established again, the program can locate interruption position accurately and complete the transmission of the entire file.3.The function test and performance test of the data transmission module are done, and the test data are analyzed. First simulation test is done, namely two ARM plates are connected directly. The channel simulation program is inserted to the sender and we can set different BER and capture rate to simulate different channel conditions, so as to complete the test of data transmission module. Then indoor joint debugging is carried out,namely all hardware devices are connected to do debugging and testing, and large number of tests of different files are done. Through the analysis of test data, it can be concluded that the data transmission module can transfer various files correctly and the test results are consistent with the expected results of the design.