Design And Implementation Of Equalization Algorithm About Shortwave High-speed Data Transmission Based On 3KHz Bandwidth

HF communication is an important way in the middle and long distance wireless communication, which has been widely used in practice. However, because of the channel characteristics such as multipath propagation, fading and Doppler frequency shift, serious inter-symbol interference（ISI） and signal distortion, the system performance is greatly reduced. The multipath propagation of the channel can be overcome by equalization.Firstly, three channel estimation algorithms on known transmitted data are discussed in this thesis, which are the autocorrelation channel estimation algorithm, the minimum mean square error algorithm and recursive least squares algorithm. Based on the data frame structure about the American military standard MIL_STD₁88₁10C, a channel interpolation estimation algorithm is given. Secondly, frequency-domain Turbo equalization based on the minimum mean square error（MMSE） criterion changes the calculation of convolution in time domain to the point multiplication calculations in frequency domain, reducing the amount of computation and implementation complexity. And with the use of iterative soft interference cancellation（SIC）, the transmission performance can is improved in this thesis. Then, if the length of unknown data in the transmission frame is too big, high-order interpolation channel estimation can be used to improve the accuracy of the estimated channel, thereby improving performance of the frequency domain equalization. Finally, the algorithms given in this thesis are simulated and tested. The results show: the performance of the frequency domain is improved by 3 d B compared with MIL_STD₁88₁10C.The fractional tap equalizer has also been described in this thesis and its sampling rate is not lower than the Nyquist rate to reduce the sensitive to the timing information for the equalizer. And a simplified algorithm is introduced in this thesis. The simulation shows: the performance of the fractional tap equalizer is corresponding to MIL_STD₁88₁10C.