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Technical Manual
Airbridge BTS3612A CDMA Base Station
7.3 Abis Signaling Message Flow
The Abis signaling messages are carried by the Access Channel (ACH) and the Paging
Channel (PCH). These messages are refer to as outband signals (compared to the
inband signals in the Abis traffic).
The Abis signaling message flow is represented by the green continuous line in Figure
7-1. The following introduces the flow in the forward and the reverse directions
respectively.
I. Forward
1)
The ATM cells from the BSC are carried by the E1/T1 link to the BCIM. The BCIM
processes the ATM cells through IMA, and then under the control of the MC of the
BCKM sends the signal to BCPM through the Cell Bus.
2)
The BCPM completes channel processing. The baseband signals carrying the
Abis signaling messages (received over the PCH) from the BCIM are coded,
interleaved, spread, modulated and multiplexed by the BCPM before being sent to
the BRDM over the electrical Gbit Ethernet interface.
3)
The BRDM allocates channel resources, and sends the baseband signals over the
optical Gbit Ethernet interface to the BTRM.
4)
The BTRM performs demultiplexing, up-conversion and wave filtering on the
received baseband signals, and sends them to the BHPA.
5)
The BHPA amplifies the signals and forwards them to the DDU, from where the
signals are transmitted by the antenna.
II. Reverse
In the reverse direction the signals are handled in the reverse order.
1)
Through the main and diversity antennae, the DDU receives two CDMA signals
transmitted from the MS. After being divided and amplified by the RLDU, the
signals are sent to the BTRM.
2)
The BTRM performs wave filtering, down-conversion and multiplexing on the main
and diversity signals, and sends them to BRDM over the optical Gbit Ethernet.
3)
The BRDM allocates channel resources, and sends the baseband signals over the
electrical Gbit Ethernet interface to the BCPM.
4)
The BCPM completes channel processing. The baseband signals carrying the
Abis traffic (received over the ACH) from the BRDM are demultiplexed,
demodulated, de-interleaved and decoded by the BCPM. Then under the control
of BCKM, the obtained signals are sent to the BCIM over the Cell Bus in form of
ATM cell.
5)
The ATM cells are processed by the BCIM through IMA, and then sent to the BSC
over the E1/T1 link.
7-4
System Principle
Chapter 7 BTS Signal Flows
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