User Manual

Architecture
Nortel Networks Confidential
3–56
PE/DCL/DD/0063
411–9001–063
Standard 12.07/EN September 2000
GSM/BSS V12
AMNU Unit
Start–up, downloading, initialization
The AMNU unit is started by a hardware reset or a re–initialization message sent
by the BTS. It configures the LAPD and establishes an OML link with the BSC.
Depending the BTS request, the BTS systematically initiates a downloading phase
of the catalogue files and software units.
Follow by a re–flashing of the units for which the software versions are different.
Configuration
The transmission is configured by the BSC via the BTS.
The configuration provides:
a general configuration. It contains the configuration of the TDMA frame and
provides the logic unit parameters shared by the whole cell, such as:
• cell to identity (BSIC)
• BCCH frequency
• indication of frequency hop implementation
• the frequency of the TDMA frame if there is no frequency hopping
a configuration of the radio TS. It specifies the logic channel type to use for TS.
a configuration of the frequency hop. It specifies, for TS, the list of frequencies
to use, as well as sequencing. This configuration is optional and only appears if
the frequency hop was requested in the TDMA frame configuration.
Supervision
The BTS regularly sends status requests to detect any problems.
LAPD break
A timer monitors the LAPD with the OML and RSL links. If level two loss is
detected, the BSC and the AMNU try to reconnect. If connection is not
re–established before the end of the time–out, the AMNU is reinitialized.
Event reports
The AMNU:
collects all events detected (internal or external alarms)
provides the filtration and reports errors (transmission/reception) to the BSC
provides the filtration to prevent repetition of non–transient events, which means
it can send to the BSC a single indication