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Re: ULE and FEC





Benoit Oger wrote:

Hello,

as new subjects are raised, like encryption, I was thinking it could be
interessant for ULE to propose a FEC system (Forward Error Correction). ULE
is aimed for a wide range of physical media, more or less exposed to noise
and error; therefore an error correction ability could be useful. Actually,
we could be inspired by the DVB-H draft that provide MPE with such a system,
called MPE-FEC. DVB-H derive from DVB-T standard, it deals with optimisation
for wireless communication like the reduction of the average power
consumption for mobile or a better resistance to noise.

MPE-FEC simply combine datagrams interleaving and a Reed-Solomon code. It is
designed in such a way that it will be transparent for a receiver not
supporting MPE-FEC. Datagrams are encapsulated and sent as usual.
Reed-Solomon parity bytes are transmitted on the same Pid but with a
different section type , for ULE it migth be a different type.

I don't have precise opinion about the usefullness of such FEC. But
indeed, if it was needed, the FEC itself could be inserted in an
"extension header", associated to the SNDU itself, as I proposed some
time ago (http://www.erg.abdn.ac.uk/ip-dvb/archive/msg00527.html)
Such an extension would then be of type : optional extension, if not known, just skip and process next.

Regards.
Alain.
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Alain RITOUX
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