Reference Manual

Transmission Interface Handling G.703 2048 kbit/s
01_0306A
RBS 2
PCM-A
PCM-B
PCM-A
PCM-B
Downstream Downstream
Mobile
Station
Downstream
Upstream
Upstream
RBS 1
BSC
Upstream
Upstream
Figure 142 Upstream and Downstream
For further information, see ITU-T G.704 White Book.
53.3 Functions
53.3.1 Layer 1 Termination 2048 kbit/s
The function is initiated during restart of DXU.
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 or 120 ohm selectable 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 subsection
Section 53.3.2 on page 414.
• Detection of fault conditions, alarm states, and consequent actions.
This includes detection of:
− LOS (Loss Of Signal)
− LOF (Loss Of Frame alignment)
− ERATE (Error RATE)
− AIS (Alarm Indication Signal)
− RAI (Remote Alarm Indication)
The consequent actions are transmission of:
EN/LZT 720 0008 P2A
2001-11-28
413 (485)
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