Adaptive control and channel encoding in an automatic HF communication system

The HF region of the radio spectrum is normally regarded as being unsuitable for reliable 24-hour communications due to time and spatial variability which can affect the availability and reliability of channels. The main parameters of concern are the variation in maximum and lowest usable frequencies, maximum data rate achievable, and the fading/interference structure at any time. Traditional approaches to overcoming the above variability in the channel can be grouped into three main categories, each having its own problems.<>