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High Frequency Wave Forms for Difficult Conditions

Title
High Frequency Wave Forms for Difficult Conditions
Subject
high frequency radio
waveforms
Creator
Arnstein Johansen
David M. E. Ingram
Source
Military Communications and Information Systems Conference and Expo (MilCIS 2020)
Date
2020-11-11
Coverage
Canberra, ACT, Australia
Abstract
High Frequency (HF) Band (2 – 30 MHz range) data communication has been used for many years and is the only medium that is “always there” for long-distance beyond-line-of-sight communications. The disadvantage is that HF communication paths using the ionosphere have some unique challenges. Therefore only low data rates have been achieved, and communication is not always successful. The ionosphere is in constant change, depending on solar activity, time of day and time of year. As a consequence, fading, Doppler spread, multi-path propagation, and interference, are a constant challenge.

This has led to a number of “smart” waveforms being developed to counter these variations. For example, the ADF’s DHFCS system provides many robust waveforms for data communications. Data rates are still slow, typically 75 – 2,400 b/s, and up to 9,600 b/s, but reliability is improved for when messages have to get through.

Recently improved and standardised waveforms being introduced can provide a more useful 9,600 – 64,000 b/s data rates (and beyond) over considerable distances.

Currently in development are newer techniques such as the use of Turbo codes and Gaussian Minimum Shift Keying. These are captured in proposed new standards.

From review of currently published research papers, proposed standards and other currently known research projects as well as discussions with vendors, it is clear that further improvements in performance are possible. Specifically, research can show that further improvements in waveform robustness can improve performance in difficult HF conditions, and over very long distances, using HF as the medium.

Tags

Radio

Citation

Arnstein Johansen and David M. E. Ingram, High Frequency Wave Forms for Difficult Conditions, 2020, accessed January 16, 2025, https://eprints.ingram.id.au/items/show/59

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