User Manual

WipLL System Description
2-12 of 2-12 Issue 03
4Mbit - Draft 05
1QDF10134AAP-SYD-FCC
PSTN has traditionally been a low delay network and has not bothered with echo
cancellation, at least in smaller countries, if the round trip delay is below 50ms.
Echo cancellers are used in international calls between different PSTNs.
The key principle is that the network that causes the echo should cancel it. Applying
this principle to the introduction of IP based WLL systems means that echo should
be handled in the access system. To this end, in Marconi Communications’ WipLL
system echo cancellation has been implemented in both the SDA (up to 8ms) and the
head-end gateways (up to 64ms).