EFFICIENT ESTIMATORS FOR AN HF RADIO LINK

A promising technique for the estimation of the sampled impulse response of an HF radio link was developed a few years ago, and was shown by computer-simulation tests to have a substantial potential advantage in performance over more conventional systems. The technique uses a knowledge of the number of different paths (separate sky waves) in the HF radio link. A number of further developments have now been made to the system, leading to some interesting new channel estimators. In some of these, a Kalman filter is incorporated into the system in such a way that the filter operates on only a few variable quantities, and is therefore considerably less complex than a conventional Kalman filter. Three different Kalman niters are studied, two of these being designed for a channel varying linearly (at a constant rate) with time, and the third being a conventional Kalman filter that is designed for a time-invariant or very slowly time-varying channel. All of these employ an exponential window, and therefore operate with a fading memory. The paper describes the various estimators and presents the results of a series of computer-simulation tests, comparing the accuracies of the channel estimates given by the different systems. © 1990 IEEE