Research On Time-domain Equalization Of HF Data Transmission

Shortwave communication occupies an important place in the communications fields. Channel distortion and multipath will create inter-symbol interference (ISI), then the validity and reliability of data transmission is greatly reduced, affecting the quality of data transmission, usually through equalization to compensate for ISI. The time-domain equalizer, including Turbo equalization and non-linear-block data detection (NDDE) is mainly studied in this thesis.Equalization usually requires channel information, so channel estimation can play an important role on the performance of Equalization algorithm. Therefore, good performance of the channel estimation algorithm is needed to update the parameter of the equalization for real-time tracking for the change of channel. A channel estimation algorithm based on interpolation is given in connection with the frame structure be of long unknown data, and the iterative channel estimation method is used in iterative equalization. Turbo equalization joints equalization and decoding to cancel ISI through an iterative approach. In this thesis, two kinds of Turbo equalization algorithms, the linear MMSE (LE-MMSE) and soft interference canceller (SIC), have been improved. A performance improvement of0.5dB and0.7dB is obtained respectively in high signal to noise ratio(SNR). In the non-iterative equalization algorithm, since the original NDDE algorithm does not compute soft information, modified soft-output NDDE algorithm based on NDDE is discussed and simulated, with1.2dB performance improvement in high SNR.Through this work, the improved algorithm based on NDDE, the iterative channel estimation method and the SIC are successfully combined and realized in the HF communications platform based on DSP. The HF communications platform based on DSP. Therefore the performance of short-wave communication system is improved.