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ALE HF Data Communications
Source : http://www.wikipedia.org
The new US government standards for Automatic Link Establishment (ALE) in High Frequency (HF) radio systems specifies the use of an extended (24,12) Golay block code for forward error correction (FEC).
• The Extended (24,12) Golay Code specified is a (24,12) block code.
• This code encodes 12 data bits to produce 24-bit code words.
• It is furthermore a systematic code, meaning that the 12 data bits are present in unchanged form in the code word.
• The generator polynomial for this code is
g(x) = x11 + x9 + x7 + x6 + x5 + x + 1 (a variation of CRC-12?)
The minimum Hamming distance between any two code words (the number of bits by which any pair of code words differs) is 8, giving this code the power to detect up to 7 errors in each code word (and correct none), correct up to 3 while detecting 4, or any intermediate combination.
• These modes may be listed as (0,7), (1,6), (2,5), and (3,4), where the first number indicates the number of errors which may be corrected, and the second the number of errors which will be detected by each mode.
HF ALE system Solution
Source : http://www.rockwellcollins.com
An important part of the total HF ALE system Solution from Rockwell Collins, inventors of ALE
HF Automatic Link Establishment (ALE) radio systems make life easier for those who use HF radios to communicate over long distances or short non-line-of-sight paths by automating the channel selection and linking processes. With ALE, HF radio users no longer need to understand and deal with the complexities of ionospheric skywave propagation or continually monitor a list of alternate frequencies for possible incoming calls.
The automation provided by ALE has dramatically reduced the operator workload and improved communications quality and reliability. HF ALE is undoubtedly the best thing that has happened to HF communications since the implementation of single sideband.
Although HF ALE systems make life easier for those who actually operate the radios, a higher degree of expertise is required on the part of a few people who work behind the scenes to design, implement, and support a successful HF ALE communications network. These behind-the-scenes experts need specialized tools and training to be successful. The HF-CPS™ software program from Rockwell Collins, is a tool that can be used at all levels of the supporting organization from the inception and design of an HF ALE network through the preparation and loading of datafill information into each radio in the network.
Just like ALE makes life easier for the HF radio operator, the HF-CPS™ program makes life easier for the behind-the-scenes experts who manage the HF ALE network and maintain the radio systems. The HF-CPS™ software program truly is an important part of the total HF ALE system solution.
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