Iterative Equalization Technology Research Of Shortwave Communication

HF communication have advantages of non-relay telecommunications, invulnerability and strong, flexible and fast network reconfiguration and so on, and it is widely used in military, marine and outdoor long distance communication. In recent years, with the development of new technologies and the new system, shortwave communication has come back into public sight. Equalization is a significant part of shortwave communications receiver, and it is an important means to suppress the ISI. Especially, equalization with high data transfer rates, higher order modulation mode, is currently a serious problem need to solve.In this paper, we study and implement under9600bps data rate,64QAM modulation high rate HF modem receiver equalization algorithm simulation based on the US military standard MIL-STD-188-110C Appendix C data format.Firstly, we discuss about single-carrier shortwave communication systems waveform formed program described in Appendix C of the US military standard MIL-STD-188-110C.Appendix C described in detail about the sender coding, interleaving, data framing and modulation. The sender is designed in accordance with the program when emulating. Next, we study the Watterson channel model in detail based on the transmission characteristics of the HF channel, and Verify the feasibility of Watterson channel model simulation shortwave communication channels by modeling and simulation.Because the presence of multipath fading, Doppler shift and other effects in the channel of HF communication will cause distortion, receiver need to performs equalization processing of received signal to eliminate inter-symbol interference caused by channel.This paper describes the linear equalizer and decision feedback equalizers of the time-domain equalization, and shows the analysis and comparison of the two classical channel estimation method which include LMS and RMS. Then we mainly study linear and judgment feedback equalizer structure and algorithm based on MMSE criterion, MAP decoding algorithm and Simplified Max-Log-MAP decoding algorithm.Finally, we simulate the entire system by using Matlab-based software platform,then obtain iterative equalization in the performance curve of the system, at the same time, they meet the performance requirements in Appendix C of US standard in the conditions of the Gaussian white noise channel and ITU-R channel. In addition, we get the influence of algorithm performance by analyzing the number of iterations, the filter length, frame length of the interleaving and other parameters in connection with simulation results and analysis and comparison of MMSE-LE and MMSE-DFE two algorithms. At last, we recommend parameter settings of the algorithm for the further research.