Tektronix CTS 850, User Manual

Page: 83 / 178

Functional Overview
CTS850 SDH/PDH Test Set User Manual
2–33
45 Mbit/s Map/Demap Implementation
If your CTS 850 test set supports the 45 Mb/s map/demap option
(Option 55), the following is an overview of what the 45 Mb/s option
offers.
To determine if Option 55 is present in the CTS 850 test set, press
the Utility button on the front panel, then press the Instrument
Configuration (INST CONFIG) softkey. In the menu that is displayed
after pressing this button and softkey, there is a line that says
Options. In this line, should be the number 55, for Option 55. Also,
in the line that says PDH Options, should be the number 45, for 45
Mb/s.
45 Mbit/s is transmitted or received as a B3ZS or HDB3 encoded
line rate, and mapped or demapped into a VC–3 structure into an
STM–1. Mapping and demapping has the same configuration,
options and nomenclature as the current TU–3 mapping/demapping
selections available for 34 Mbit/s signals.
An external 45 Mbit/s payload is added when the signal is being
mapped into an SDH output. The user can insert the same defects
and anomalies as are supported in a 34 Mbit/s externally–added
signal.
Demapped payloads are dropped out through the front panel as a 45
Mbit/s line rate.
The payload for 45 Mbit/s is PRBS, a fixed 8, 16, or 24–bit pattern,
or externally–added data only. The payload can not be muxed or
demuxed from or into DS1 or any PDH rates. The same PRBS
patterns as for 34 Mbit/s are supported. Overhead bytes are the same
as for TU–3 mapping and demapping. The default C2 value is the
same for 34 Mbit/s (0x04).
There is no support for 45 Mbit/s bit slip measurements.
G.821, G.826 and M.2100 analysis is performed on the received 45
Mbit/s signal, subject to the same restrictions as other PDH signals.
Because of architectural limitations, the PDH rates (2 Mbit/s, 8
Mbit/s, 34 Mbit/s, and 140 Mbit/s) are not supported at the same
time as 45 Mbit/s. The RX and TX sides of the tributary card are
“linked” at 45 Mbit/s. The tributary board will run RX and TX at 45