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Watson-TDM-Manual-W.doc

Version 2.0-01

Watson TDM

Operating Manual

Revision: 2008-02-07 3-3

When a Watson TDM modem is operating in configured for 3- or 4-pair mode

against a Watson 5 modem then the following restrictions apply:

Max data rate of E1 user interface 32 x 64kbit/s

Max data rate of nx64 user interface 96 x 64kbit/s

3-pair operation

Max user data rate per pair 32 x 64kbit/s

Max data rate of E1 user interface 32 x 64kbit/s

Max data rate of nx64 user interface 72 x 64kbit/s

4-pair operation

Max user data rate per pair 18 x 64 kbit/s

Table 3-2: 3p and 4p restrictions with Watson 5 modems

Note:

These restrictions are only applicable in mixed links with Watson 5 and Watson

TDM. Links terminated with Watson TDM modems at both ends have no restric-

tions they support the full payload rate of 3 x 89 = 267 x 64 kbit/s in 3-pair mode

and 4 x 89 = 356 x 64 kbit/s in 4-pair mode.

3.1.4 DSL Clocking options

Watson TDM has a crystal controlled DSL clock that does not depend on the

clocking of the user interface signals. Data rate adaptation between the user in-

terface signal clock and the DSL clock is achieved by stuffing/deleting bits in the

DSL frames (plesiochronous operation).

Watson TDM supports clock modes 1 and 2, see [10]:

Clock-

mode

Mode STU-C Symbol

Clock Reference

STU-R Symbol

Clock Reference

Example Applica-

tion

1 Plesiochronous Local oscillator Received symbol

clock

"Classic" SHDSL.

2 Plesiochronous

with timing refer-

ence

Network refer-

ence clock

Received symbol

clock

SHDSL with em-

bedded timing

reference.

Table 3-3: DSL Clock Modes

If the E1 signals use the same Network reference clock as the DSL then no addi-

tional Wander is generated in Clock mode 2 by the DSL transmission. This is es-

pecially useful for low linerates.

An external 2 Mbps Clock input is available on the Watson subrack and minirack

mechanics.

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