Research On The Key Technologv Of Quasi-Wideband HF Digital Transmission System

Data transmission on high-frequency (HF) channel is to produce severeinter-symbol interference (ISI), so channel equalization technology is needed to reducethe influence. Single-Carrier Frequency Domain Equalization (SC-FDE) has attractedpeople’s attention for its low computational complexity and good performance ineliminating ISI. Low-density parity-check codes (LDPC) are of good property, if theLDPC coding technology is used in the SC-FDE system, the performance of the systemmust be greatly improved.In this thesis, the features of HF channel are introduced; the key technologies ofSC-FDE and the coding and decoding principles of LDPC are analyzed. Based on theprevious principles, Chu sequence is used as unique word, a sliding frequency domainestimation method and an improved frequency domain adaptive algorithm are used forgetting the initial channel information and channel estimation, at the same time,minimum mean square error criterion (MMSE) is used as frequency domainequalization method. A SC-FDE system which includes LDPC and SC-FDE technologyis established, in which serial coding algorithm is used as LDPC coding method andsum-product decoding algorithm is used for LDPC decoding. After that, simulationscheme of the entire system is presented. Moreover, comparison between the systemswhether to include LDPC technology is given for analyzing the gain.At the last, the limitations of the study and some possible improvements are givenbased on simulation results.