The Research On Turbo Equalization For HF Data Transmission

The serious inter-symbol interference (ISI) caused by multipath will degrade the performance of the HF communication system. Turbo equalization joints equalization and decoding to cancel ISI through an iterative approach.Firstly, some classical equalizers and its equalization algorithms are introduced. Then the principle of Turbo equalization is investigated and some Turbo equalization algorithms are studied to simplify its complexity of calculating the soft information. Considering the performance of these algorithms as well as their complexity, the approximate algorithms based on the minimum mean square error (MMSE) criterion,some modified algorithms of the conventional soft interference canceller (SIC) and the hybrid algorithm of MMSE and SIC are introduced and simulated in a typical ISI channel. The simulation and analytical results show that these algorithms exhibit similar performances as compared to the linear MMSE algorithm while providing the very low linear computational complexity.Finally, Turbo equalization is applied to the HF communication system. Combined with the nonlinear data detection algorithm (NDDE) widely used in HF communication, we obtain a NDDE/SIC algorithm. The results coming from the HF channel simulator show that the algorithm has a good performance.