Hi Gullik,
On 26-10-12 17:15, Gullik Webjörn wrote:
> Hello Jim,
>
> Awsome test, a very important tool for designing correction. To me it
> indicates
> that we don't have to be too afraid of error rates in the % range, 1/48
> works
> for most bits with 100% intelligibility, while some few bits create an
> awful listening
> experience and need to be correctable.
>
> Considering that error rate will probably vary over time ( aka.
> fluttering ) single
> corrupted frames (with low error rates) interleaved with good frames
> will have
> a good chance of propagating acceptable / enjoyable audio.
I think you make a very valid point; transmission errors might vary
quite a lot during a QSO.
One of the advantages of golay is that they provide some feedback on the
number of errors ("BER": bit error rate) of the decoded bittrain. Based
on this, we can design the decoding process that -if it notices that the
BER goes to high- it is perhaps better to simply drop the bad
audio-frame and -either- repeat the preceding frame or mute the audio.
This is also important if we decide to do next.
After we have released the first 2400 bps modem (based on fixed 40 ms
timeslots and golay) there are multiple options. One of them is to look
at more complex FEC systems using blocks on data spanning multiple frames.
However, the ability to provide BER information is -I think- an
important element that should be concidered when chosing what FEC system
to use next.
> 73 de SM6FBD
Kristoff - ON1ARF
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