Operating in the HF band is an art form. A myriad of factors affect HF propagation such as time-of-day, time-of-year, global location, solar cycle, sunspot activity, and more. These environmental factors produce ionospheric effects which, in turn, produce skywave, skip and bounce conditions. To produce realistic HF communications, these factors must be taken into account in the virtual environment as well. To meet these requirements, ASTi offers its Telstra-based high-frequency (HF) propagation software package.

Based on established communications industry standards and algorithms, ASTi's HF environment serves up appropriate HF band effects (time-of-day, time-of-year, global location, solar cycle, skip and bounce) to produce accurate path loss factors for every transmitter/receiver pair in the simulation exercise. With the increase in wide-area network exercises featuring tens of training devices, hundreds of radios, and thousands of entities, ASTi uses selective optimization, isochronous Linux OS, and a high-performance, P4-based Telestra system to preserve accuracy, and meet ever-increasing network demand.

The HF environment services software is highly flexible with capabilities to support radio and communications models:

• Running locally in the Telestra MBV (Model Builder Visual) environment
• Over the network on other networked Telestra platforms
• Over the network on ASTi's popular DACS platforms

In the military arena, HF usage is still a strong component. While satellite communication is becoming more prominent, satellite equipment vulnerability and infrastructure limitations mean that HF capabilities continue to be a platform requirement for over-the-horizon communications. HF radios have also become more sophisticated with the addition of ALE (Automatic Link Establishment), removing some of the HF operational variables and complexities for the user. ALE provides "Link Quality Assessment", a complex and continuous series of polling and RF tests which determine the optimum transmission frequencies at any given time. In addition, the ability to establish point-to-point links, net and group call capabilities are also provided. Multiple ALE servers may be synchronized permitting automatic updating of Link Quality Assessment information as radio or environmental factors change.

Offering up simulation of these features is no easy task, particularly when they must be accurate and consistent among networked training devices. In true fashion, ASTi has incorporated these features into it's HF propagation services product and radio simulation capabilities. Users can now avail themselves of ALE simulation without having to develop the complicated interplay of messages and radio environment effects across both local and networked architectures. ASTi's new P4-based Telestra system with tuned, isochronous Linux OS provides just the platform to meet the demanding network and high-fidelity simulation needs.