Shortwave Channel Tcm Decoding, Adaptive Equalization Joint

For years, shortwave communication has been one of the most important method of long distance communication. And the high speed data transmission by shortwave has also been a great topic for research in the field of Digital Communications. A bulk of research has been devoted into the combination of the TCM (Trellis Coded Modulation) decoding with adaptive equalization in serial data high frequency modem.Due to the property of severe noise, time variety and multi-path transmission, HF channels are poor. TCM has been introduced to improve it's tolerance of noise, and adaptive equalization has been adopted to eliminate the Inter-Symbol Interferences(ISI) . aroused by multi-path transmission.And a brand new structure of Decision Feedback Equalization(DEF), i.e.Iterative DFE(ItDFE), is proposed for the performance of the joint of TCM decoding and adaptive equalization based on existing strategy of TCM equalization. In the scheme of ItDFE, the decoding and equalization are performed iteratively.Without training process, ItDFE is regarded as a type of blind equalization. The hard decision of the input signals are used as the initial input into the feedback filter, and during the performance of iteration, the more reliable soft decisions from the Viterbi decoder are fed back to the feedback filter as maximum likelihood sequence estimation, thereby reducing the Bit Error Rate(BER). And at the same time, TCM decoding is completed. Simulation results in typical HF channels, particularly the BER, are provided, which proves a higher noise tolerance of ItDFE than DFE and a more simple practice compared with other methods of blind equalization.