Crocus SHDSL G703.pdf - FTP Directory Listing

92 Crocus SHDSL G703 Chapter 5
User manual
Step-by-step configuration
5.6.3 Purpose of the minimum line pair speed
Easily upgrading the user speed
You could determine in advance what the maximum speed is that can be achieved on the line (e.g. 1024
kbps) and set the minimum line pair speed to this value (e.g. minLinePairSpeed = 1024kbps). Suppose the
customer initially wants 256 kbps. So you set the user speed to 256 kbps (speed(2P) = 256kbps). Now when
the customer decides he wants a higher user speed (e.g. 640kbps), then you can easily change the user
speed to this higher speed (e.g. speed(2P) = 640kbps) without first having to determine again whether the
line can handle this speed. What is more, the line does not have to retrain after you changed the user
speed. So you can perform user speed upgrades in an easy, cost-efficient way.
Low speed operation - compatibility with other SHDSL devices
If you want to use only 1 or 2 time slots (or 2 or 4 time slots in case of a 2 pair version), then you have
to set the minimum line pair speed to 192 kbps (minLinePairSpeed = 192kbps). This to insure correct time slot
synchronisation on both sides.
Low speed operation - 2 time slots and 2 applications
If you want to use only 2 time slots (or 4 time slots in case of a 2 pair version) and each time slot carries
the data of a different application, then you also have to set the minimum line pair speed to 192 kbps
(minLinePairSpeed = 192kbps). This to insure that on the remote side the data is separated correctly.
The reason is the following:
• In case you select only 2 time slots (or 4 time slots in case of a 2 pair version) but you do not configure
the minimum line pair speed (minLinePairSpeed = ), then the SHDSL line operates in Nx64 mode
(refer to crocusShdslTtRpG703/line/framerType on page 166 for more information on this mode).
Since in this case the user data has become a continuous bit stream on the SHDSL line, it is almost
impossible to correctly separate the data from the two different applications at the remote end.
• In case you select only 2 time slots (or 4 time slots in case of a 2 pair version) but you configure the
minimum line pair speed to be 192 kbps (minLinePairSpeed = 192kbps), then the SHDSL line operates in
slotted E1 mode (refer to crocusShdslTtRpG703/line/framerType on page 166 for more information
on this mode). Since in this case the user data is also put in time slots on the SHDSL line, it is perfectly
possible to separate the data from the two different applications at the remote end.