User Manual

Architecture
Nortel Networks Confidential
3–14
PE/DCL/DD/0063
411–9001–063
Standard 12.07/EN September 2000
GSM/BSS V12
3.2.1.8 DSC–oriented defense actions
The CSWM undertakes defense action when the DSC sends an event report on the
O&M bus or when the scanner no longer detects DSC activity.
The following faults can occur:
hardware fault
The DSC is faulty if any of its connections fail. Then the DSC is reset, and
external tests are run.
unexpected frames or queue overflow
The CSWM sends an event report to the BSC which takes the appropriate action.
loss on the O&M bus
The CSWM triggers defense action, the DSC is reset, and external tests are run.
A DSC is initialized by a reset command on the O&M bus. Start–up tests are run.
If the external test results are fault–free the DSC can be returned to the list of useable
units. If not, the unit must be replaced.
CSWM defense actions are determined in terms of equipment redundancy:
If there is no redundant DSC:
• if the DSC that is down supported O&M communication with the BSC. The
CSWM must isolate the faulty DSC by breaking off connections on the
switching matrix. The switching matrix restores communication with the
BSC on the same PCM as before. When communication is restored, the
CSWM informs the BSC that all communication previously established via
that DSC is lost and cannot be recovered. The BSC then takes the appropriate
action ;
• if the lost DSC did not support O&M communication with the BSC, the
CSWM must inform the BSC that all communications passing through this
DSC were lost and cannot be recovered. The next actions are determined by
the BSC.
If a redundant DSC is available, the CSWM breaks off faulty DSC connections
on the switching matrix and reconnects the redundant DSC to match the faulty
one. All the communication previously established via that DSC is restored and
an event report is sent to the BSC.
3.2.1.9 PCMI–oriented defense actions
In the event of a PCMI hardware fault, the CSWM activates self–tests by sending
the appropriate commands via the O&M bus. If the results of the self tests are
fault–free, the PCMI returns to operational status and the BSC is informed.
If the quality of transmission is the cause, the PCMI feeds back the information to
the BSC, whether it has been able to restore communication or not.