The HF skywave channel: measured scattering functions for midlatitude and auroral channels and estimates for short-term wideband HF Rake modem performance

Scattering functions for a variety of HF skywave channels, varying from benign or nondisturbed to highly disturbed, have been observed and are presented to illustrate the range of conditions that the communications system designer must contend with. Corresponding short-term performance predictions are presented for a decision-directed wideband Rake modem/codec corresponding to transmission of a 1-MHz direct-sequence spread-spectrum signal. It is found that the channel scattering function is an excellent descriptor of the performance potential of the HF skywave channel. As a minimum, it is possible to establish whether the channel is nondistributed or disturbed, and important quasi-stationary parameters such as short-term signal power, Doppler shift, delay spread, and Doppler spread can be determined