Research Of Channel Estimation And Synchronization Technology In HF Communication

HF communication is an important means of communication for remote data transmission. It is mainly used in military communications with operating band3MHz-30MHz.In the thesis, research on the key technologies of high-speed high-frequency single-carrier serial modem, according to MIL-STD-188-110C Appendix C. Transmitter adopts64QAM modulation for data rate of9600bps and carrier frequency is1800Hz. The Watterson HF channel model shall be implemented using a tap-delay line, which consists of two independent but equal average power Rayleigh fading paths, with a fixed2ms delay between paths,3kHz bandwidth, and maximum75Hz Doppler frequency offset, and with a fading bandwidth of1Hz. The main work of this thesis is to research synchronization and channel estimation algorithms for HF serial modem. Based on the theoretical analysis, design synchronization system and HF channel estimation solutions.The thesis mainly includes the following three aspects:Firstly, reference to the US military shortwave communication standard MIL-STD-188-110C Appendix E, deduce the time-frequency characteristics of narrowband HF channel model, and build Watterson HF channel model to verify its fading characteristics.Secondly, research on synchronization technology for single-carrier serial modem. According to the data frame structure, calculate and simulate the autocorrelation properties of pseudo-random sequence, Barker code sequences, and Frank-Heimiller sequence. Research various synchronization algorithms. Design improved Schmidl&Cox synchronization algorithm based on repeated training sequence. Design Synchronization system scheme; respectively verify its reliability for each synchronization module and the system performance of synchronization solutions.Finally, research on HF channel estimation algorithms. According to HF communication system, deduce the algorithm principle of LMS, RLS, LS and MMSE; regard mean square error as an evaluation index to simulate its performance; decide to adopt improved RLS channel estimation algorithm. Simulate the performance of interpolation algorithm, including linear interpolation, parabolic interpolation, cubic spline interpolation and Lagrange interpolation. Design soft iterative HF channel estimation solutions. Under different SNR, simulate and receive the BER curve to verify the effectiveness of HF iterative channel estimation.