For the last decade or so, major developments in the fields of large scale integration (LSI) and digital signal processing (DSP) technologies have brought forward promising techniques to increase the transmitted data rate over the HF sky-wave channel. The lack of processing power restricting HF systems to low transmission rates has long been overcome and the potential of spread spectrum (SS) technologies for resolving multipath returns may now be better exploited. A wideband HF sky-wave channel model, based on the Ionospheric Parameters Model (IPM) has been implemented in software and is used to demonstrate the potential of direct sequence (DS) spread spectrum over wideband HF channels. New performance results of a RAKE receiver-based system are presented and conclusions regarding its most promising configuration with Reed-Solomon and convolutional codes are advanced in terms of improved channel reliability and transmission rate.
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