Passive channel assessment techniques for HF frequency management

Within a HF (high frequency) communication system (3-30 MHz) employing skywave propagation, the use of frequency management (FM) techniques is essential to ensure reliable and accurate data transfer, as and when required. This paper outlines a number of novel techniques to accomplish this task. The techniques considered for communication system FM are based on passive channel assessment alone, using identifiable signals of opportunity and known traffic types. The relative merits and disadvantages of passive assessment are analysed. Channel metrics derived by passive channel assessment can be used in a way similar to actively acquired channel information-for example in ionospheric interpolation and extrapolation. The operation of passive assessment FM making use of both channel selection and channel optimisation procedures is evaluated