Research Of Key Technologies In HF Data Transmission System

Based on the MIL-STD-188-141B protocol of Department of Defense of America which is the 3G shortwave communication network protocol, the paper studies the key technologies of high speed data transmission burst waveform BW2 in physical layer of shortwave telecommunication in HF channel. And with the studied of the key technologies here the sending and receiving projects of BW2 is summarized.On the sending end, the paper focuses on Error Control Coding, Waveform Shaping, Spread Spectrum and 8PSK modulation, etc. On the receiving end, mainly studies the key technologies of Calibration frequency difference, Synchronization and adaptive equalization, of which adaptive equalization has been emphasized the most. Because adaptive equalization technology is the mostly used and effective way to suppress Inter-Symbol Interference (ISI) which is caused by multi-path effect and which acts as the main interference in HF transmission. In this paper the adaptive equalization part adopts the square root Kalman based on U-D decomposition algorithm with proper complexity and function. For the structure, the paper first adopts the Decision Feedback Equalizer (DFE) and then changes it into the Decision Feedback Equalizer with error feedback, that better improve transmission with errors under low SNR. At last, under HF Watterson channel and based on sending and receiving plan, the paper carries out system MATLAB simulation with two different structure of adaptive equalizations and does comparison between them.