An HF DSP based frequency management system

The requirement to optimise the operation of a high frequency (HF is 2 to 30 MHz) communication link is primarily a function of two main factors; (i) the varying nature of the HF medium causes the need to regularly monitor the operation of high performance links, and (ii) the allocated available spectrum to be utilised with greater efficiency. In response to this challenge, adaptive HF systems have been developed. The definition of an adaptive system provided by Penningtion and Wilkson (1985) is "when path data is in real time or near real time and is used to optimise some parameter of the communications equipment, the overall system can be defined to be adaptive". Path data is usually generated by real time channel evaluation (RTCE) tools. Frequency management routines then assess this information to determine how the system can adapt to counter propagation effects. To ensure that adequately modelled trends are followed, a short term forecast is required in addition to long term prediction. This enhancement is obtained by taking data from long term prediction models and extrapolating the real time data.