Bit errors, is this really an issue ?

[Jordi Nelissen - Alcatel Bell Research <[e-mail]>]

Dear tcpsat,

I have a question with respect to the effect of BER on TCP performance
on satellite links. From draft-ietf-tcpsat-stand-mech-06.txt, I read :

'Typical bit error rates (BER) for a satellite link today are on the
order of 1 error per 10 million bits (1 x 10^-7) or less frequent. 
Advanced error control coding (e.g., Reed Solomon) can be added to
existing satellite services and is currently being used by many
services.  Satellite error performance approaching fiber will become
more common as advanced error control coding is used in new systems.'

As I understand this, in optimal operation, a modern satellite link can
approach fiber BER, provided adequate FEC is used. Further on I also
read :

'FEC should not be expected to fix all problems associated with noisy
satellite links.  There are some situations where FEC cannot be expected
to solve the noise problem (such as military jamming, deep space
missions, noise caused by rain fade, etc.).'

Let us take the most common situation, i.e. rain fade. Can someone
explain to me its quantitative impact on BER. Is the satellite link
completely out of order when it rains or can we still find rescue in
methods like ARQ or some TCP which is able to distinguish corruption
from congestion ? Is there information available on the noise
characteristics on modern satellite links ? (BER, distribution of bit
errors, ...)

thanks, Jordi
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Jordi Nelissen - [e-mail]

Alcatel Research - Network Architecture - Traffic Technology
Francis Wellesplein 1, 2018 Antwerp, Belgium
Phone: external: [phone], alcanet: +6057192
Fax:   external: [phone], alcanet: +6059932

Visit our webpage : 
http://www.rc.bel.alcatel.be/projects/networkarchitecture/traffic
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