A Method of Achieving Fully Automatic Frequency Management for HF Systems

This paper describes the automatic frequency management system (AFMS) approach which is currently being developed and tested by Rockwell to satisfy new and evolving requirements to make HF communications systems more self-adaptive to the channel requirements and less operator-intensive. Most modern HF systems currently utilize digital data modulation in conjunction with digitized or analog voice modulation to transfer information across secure or non-secured links. The established trend is toward all digital networks in which record traffic, facsimile, and synthesized or real time (digital) voice modes are accommodated by digital signal processing (DSP) techniques to transfer data in a significantly more robust fashion than was possible prior to the advent of DSP technology. The AFMS system described here will ultimately exploit this trend toward digitized data by extracting from normal communications the link quality information needed to measure the channel. The measurement data currently being tested is extracted from advanced link quality analyzer (ALQA) test transmissions and is reduced to a single MOF value for each measured link by a MOF determination algorithm. This algorithm allows n measured links to provide the MOF data necessary to adequately forecast the MUF on m unmeasured links, where n is much less than m. The forecasting technique is based on providing near-real time updates (pseudo SSN) to the well known MINIMUF 3.5 model. The measurement and forecasting process is carried out continuously and automatically allowing the updates to the in-place frequency plan.