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Re: [MT63] What is MT63 good for?

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  • Tomi Manninen
    ... Yes, Hamish has got it right. :) ... This isn t exactly true either. It is possible to implement interleaving so that it does not decrease throughput. And
    Message 1 of 9 , Jan 1, 2008
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      dalite01@... wrote:

      > Your description is most likely much more technically correct.

      Yes, Hamish has got it right. :)

      > The end result is latency or decreased throughput.

      This isn't exactly true either. It is possible to implement
      interleaving so that it does not decrease throughput. And with
      packetized data, it is possible to do it so that there is no
      (extra) hit on latency either.

      That said, the way interleaving is done in MT63 does increase
      latency and, with the short messages passed in typical QSOs,
      it has a significant impact on throughput as well.

      > FWIW, my seat of the pants relating FEC to redundancy would probably not
      > pass muster in the technical arena either :) . I have always equated FEC
      > with sending multiple instances of the same information, which the
      receiving
      > station must reassemble multiple instances of verification before
      printing
      > the data to the screen. In the case of MT-63, (If I remember
      correctly) the
      > authors say that up to a 25% loss of redundancy will not affect accurate
      > copy. I am sure that there is a more factual way to present the process,
      > but the concept of redundancy and verification through redundancy
      seems to
      > be easier to comprehend to those using and not writing the software.

      FEC is always done by adding redundancy to the sent data. Sending
      multiple copies of the same message is one way of adding redundancy
      but it so happens that it is very inefficient way of doing it. Using
      clever math, it is possible to add redundancy in much better ways,
      giving greater "coding gain".

      --
      Tomi Manninen / OH2BNS / KP20JF60TP
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