The generalized cutoff rate of time- and frequency-selective fading channels is evaluated for M-ary frequency-shift keying (MFSK) and M-ary differential phase-shift keying (MDPSK) modulation with soft decoding. The optimal signaling rate and code rate for dispersive channels are evaluated. The guard time effect, is used in multipath spread channels, is evaluated for frequency-selective channels, and the optimal combination of signaling rate, code rate, and guard time is presented. Special attention is given to CCIR (International Radio Consultative Committee) HF channel models.>

An efficient real-time realization for the estimation of the HF channel parameters is presented and the estimation errors are evaluated. The parameters that were chosen are the Doppler spread, multipath spread, Doppler shift and signal-to-noise ratio, which are the dominant ionospheric propagation parameters. The estimation procedures were real-time implemented on a digital signal processor and tested on a real-time HF channel simulator based on the so-called Watterson model. The estimated parameters can be used in numerous ways in adaptive HF communication setups, including real-time channel quality evaluation for link or equipment adaptation.