A proposed scheme for synchronous MIL-STD/FED-STD ALE

There has been a renewed interest for frequency adaptive HF systems due to the reliable and fully automatic cost-effective voice link and message transfer they can provide. An important requirement for general market acceptance is the existence of a standardised platform, though. This is available in the form of the US MIL-STD-188-141A/FED-STD-1045A standard, popularly referred to as the automatic link establishment (ALE) standard. However, as can be seen from the build-up of other information transfer systems (e.g. the Internet), it is difficult to estimate the sufficient throughput capacity needed to be provided. When store-and-forward type traffic, such as e-mail, became a regular means of communication the overall traffic load broke (and still does) every capacity increase plan made. Therefore it is important to take such (expandability) effects into account when designing automated HF networks. This paper proposes a synchronous scanning scheme which would still enable full compatibility with the current (asynchronously scanning) ALE standard. The proposed scheme makes it possible to use more frequencies which can be dynamically exchanged, thus providing increased resilience to interference and varying propagation conditions. The proposed scheme ought also to be comparably easy to implement since it does not impose any higher performance or implementation requirements than the asynchronous scheme. In fact, a network may consist of both asynchronous stations and synchronous stations.