User Manual

Software descrIption
Nortel Networks Confidential
4–6
PE/DCL/DD/0063
411–9001–063
Standard 12.07/EN September 2000
GSM/BSS V12
4.2 BTS software functions
BTS software is distributed among three major units (see Figure 4–1 and
Figure 4–2):
The DRX (or e–DRX) unit is designed to transmit and receive (modulate and
demodulate) and manage TDMA frames on the radio channel.
The CBCF and BCF manage their slave units:
• CBCF: CPCMI, RECAL, DRX (or e–DRX), CC8
• BCF: ALCO, DSC, DRX Interface, PCMI, Tx, and SYNC
The TIL unit is used for in–factory testing of the BTS, and to configure, control,
and supervise the BTS on site.
The following terms are used in this chapter:
BIST: Basic hardware self–test programs of a BTS subsystem subassembly.
These tests validate a subassembly intrinsically, without disturbing the other
subassemblies. An example is the AMNU BIST, which tests the components
(such as memory) of the AMNU unit on the DRX logical board.
Self–tests: Global, functional test programs, which use several subassemblies in
order to validate an assembly (such as the DRX or e–DRX). These tests can be
broken down into tests of more or less elementary functions. This may require
external equipment (so the term may be misleading).
Downloading: A process which consists of installing, in the DRX or e–DRX
(logical part), software from an external entity (terminal, Ethernet network,
BSC, etc.).
Loading: A process used to load, into the subassemblies of the DRX or e–DRX
(logical part), the software it requires for its nominal operation.
4.2.1 DRX or e–DRX software functions
It is downloaded by the BSC, configured and supervised by the BSC and the CSWM
(BCF) or CMCF (CBCF) through a LAPD link and a serial link. It serves as a
gateway between the radio channel and the BSC. It handles both signaling and voice
for all the logical channels carried by a given TDMA frame.
The module has four functions:
The AMNU (LAPDm, L3 RSL, L3 O&M) is the DRX’s management unit.
The SPU is a gateway between the radio network and the BSC.
TX and RX manage radio transmission and transmission.
The BDT manages the GSM TIME.