Requirements for future models and simulators of the HF transmission channel

This paper deals with methods for the modelling and simulation of the ionospheric transmission channel in the HF band. Most existing HF channel simulators are based either on the replay of time sequences of data (measured by link analysers) or on parametric models of the channel. In the latter case, part of the required channel parameters can be deduced from standard propagation models. However, existing propagation models generally fail to predict correctly those parameters that are related to the short-term dynamics of the medium. In addition, HF channel models and simulators have so far been related to transmission systems using only one antenna at each terminal (Tx and Rx) of the radio link. In addition, transmission systems are now under study, which take advantage of multiple antennas at one or both terminals. As a consequence, it is of interest to extend the channel model characteristics to incorporate these new features. The concept of an array simulator is thus introduced and related possible developments in channel modelling are outlined.