Channel Distribution Function
35
Channel Distribution Function
This chapter covers RBS functions for Layer 2 communication on A-bis.
The function Channel Distribution switches channels in the transport
network interface to different RBS entities.
The function Scanning of Terrestrial Channels makes it possible to
communicate with RBS on a non-predefined terrestrial channel.
The function Sharing Terrestrial Channel makes it possible to
communicate with both CMRU and a TRX on a common terrestrial
signalling channel.
The function Concentration of LAPD Signals makes it possible to reduce
the number of required physical links between the BSC and the BTS.
The functions Multidrop and Multidrop Bypass makes it possible for
several RBSs to share one PCM line.
35.1
References
Whenever a reference is made to a function described in another chapter,
please refer to the table of contents to find the appropriate chapter.
35.2
Concepts
Channel
A channel is a 16, 32 or 64 kbit/s
connection between two entities connected
to the switch (see Figure 41 on page 218).
A 64 kbit/s connection between a timeslot
in the transport network interface and a
signalling port in a TRX is an example of
a channel.
CF
Central Functions. Functional entity for
handling of RBS common functions.
CMRU
Central Main Replaceable Unit. An RBS
has exactly one Central Main RU. In the
RBS 2000 hardware architecture, the
Distribution Switch is the Central Main
RU.
Local Mode
A unit in Local mode has no
communication with the BSC over the A-
bis interface and is therefore not in
operation.
OML
Operation and Maintenance Link. Layer 2
communication link for operation and
maintenance services on A-bis.
Remote Mode
A unit enters Remote mode when
accepting a layer 2 link establishment on
A-bis. It remains in Remote mode until it
is manually switched to Local mode.
EN/LZT 123 2697
R5A
1998-08-13
217 (306)
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