Research Of OFDM Channel Estimation And Turbo Equalization Techniques On The HF Channel

The High-Frequency communication plays an important role in remote communication. With the development of communication technology, seeking a convenient and reliable means of high-speed HF communication is our goal. In HF communication, the domain obstacle to further increase the data rate of transmission is the channel distortion caused by multipath delay spread and Doppler shift. Because of the efficient spectrum utilization and the effective anti-multipath capability, the usage of OFDM in HF communication has received extensive attention.Because of the selective fading caused by multipath and various other factors, OFDM need channel estimation and equalization to compensate the channel characteristic so that the performance loss of demodulation could be minimized. This thesis is focus on these two key techniques for OFDM system used in HF communication, and carries out a detailed study. This thesis is organized as follows:Chapter one gives an overview of HF communication and OFDM technology, and introduces the researches of the OFDM-based HF communication systems.Chapter two gives the HF channel model and HF OFDM system model. Through the analyzing of the channel effect in OFDM system, leads to several key technologies need to be solved, which are channel estimation and channel equalization technologies.In Chapter three, we focus on the channel estimation techniques in the HF OFDM system. Several basic channel estimation algorithms are described in detail. Then from the HF channel characteristics, we design a channel estimation technique which is suitable for HF channel, and discuss the improvement scheme based on this technique.Chapter four discusses the channel equalization techniques in the HF OFDM system. We design an iterative equalization algorithm for the OFDM systems with short CP. The length of the CP and the channel estimation results on the performance of the proposed algorithm are analyzed by simulation.Chapter five proposes the iterative equalization techniques with theoretical derivation in the multi-antenna HF OFDM systems, and gives the performance simulation results.