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Re: Fade remover



Hi,

On Saturday 03 February 2001 04:47, you wrote:
> I have NO problem with "repeat three times".  That is a very simple example 
> of coding and interleaving.  Should be very effective.

Actually repetative coding is a very inefficient type of ECC. It is equivalent
to just reducing the symbol rate. I.e. repeating every block 3 times would be
equivalent to reducing the bitrate to 400/3=133.3 bps and thus increasing the
symbol length to 7.5 ms. It does not produce any major gain since the
constraint length of this code is 1, i.e. we do not implement a state machine
at all.
The only "effectiveness" lies in the fact that deep fades can be compensated
for due to the form of interleaving introduced by repeating blockwise.

A real ECC on the other hand could decrease the _average_ power required
to receive the telemetry data at a decent bit error rate (10E-5 is usually
taken as reference) - as Phil proved mathematically on this list some weeks
ago - by about 10dB with a R=1/2 convolutional code. Note that this is no
black magic at all - just 30 year old information theory as Franklin pointed
out before.

  -- Jens

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