Transmission Interface Handling G.703 2048 kbit/s
01_0428A
RBS 2
PCM-A
PCM-B
PCM-A
PCM-B
RBS 1
BSC
DXB
DXB
Transport network
Figure 39 Upstream and Downstream
CMRU Central Main Replaceable Unit. An RBS
has exactly one CMRU. In the RBS 2000
hardware architecture the Distribution
Switch is the CMRU.
For further information, see ITU-T G.704 White Book.
32.3 Functions
32.3.1 Layer 1 Termination 2048 kbit/s, 75 Ohm
The function is initiated during restart of CMRU.
Layer 1 termination of the transport network interface is handled
according to /GSM:08.54:4.0.0/. This includes :
• Physical and electrical characteristics according to ITU-T rec.
G.703 (interface at 2048 kbit/s, 75 ohm and over-voltage
protection according to Annex B)
• Frame structure according to ITU-T rec. G.704 section 2.3
(includes handling of the E-bit in timeslot 0)
• Frame alignment and CRC-4 procedures according to ITU-T rec.
G.706 section 4
• Synchronization of layer 1 handling is described in Section 32.3.3
on page 190.
• Detection of fault conditions, alarm states, and consequent actions.
This includes detection of:
− LOS (Loss Of Signal)
− LOF (Loss Of Frame alignment)
EN/LZT 123 2697 R5A
1998-08-13
189 (306)
© Ericsson Radio Systems AB
— All Rights Reserved —
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