Ericsson RBS 2106 Reference Manual page 443

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RBS searches all terrestrial signalling channels, plus a number of
unoccupied terrestrial channels, for data link establishment attempts
directed towards CF.
Searching for the establishment attempt is performed by the CF in
intervals of one second. The searching can be performed in two ways.
Initially, when no valid CDF configuration exists, one set of unoccupied
terrestrial channels is searched in each interval. If no establishment
attempt is found during an interval, the search is continued on the next
set of unoccupied terrestrial channels. The search is repeated until an
establishment attempt is found.
If the scanning function is initiated when a valid CDF configuration
exists, the search in each interval is performed on all the configured
terrestrial signalling channels plus one set of unoccupied terrestrial
channels. Thus all unoccupied terrestrial channels are searched in a
cyclic way and all configured terrestrial signalling channels are searched
continuously.
After a search-time of 5 minutes, the entire configuration of the channel
distribution function except TN O&M channel is erased (all set up
connections are lost and have to be reconfigured). The search continues
but now all terrestrial channels are defined as unoccupied.
Timeslot for TN O&M is considered as occupied and is not scanned in
CF scanning procedure.
The function is terminated when the layer 2 link to CF is established or
when CMRU enters Local mode.
56.3.3 Sharing Terrestrial Signalling Channel
The function is initiated when the channel distribution function becomes
configured in such a way that the same terrestrial signalling channel is
used for signalling to both MO CF and to one or more TRXs. This is
the normal condition that occurs at configuration of the first TRX.
It is also initiated when RBS has, during scanning of terrestrial
channels, found a link establishment to CF on a terrestrial signalling
channel already used for signalling to one or more TRXs.
The function shares signalling to/from MO CF and signalling to/from
one or more TRXs on a shared terrestrial signalling channel.
EN/LZT 720 0008 P2A
2001-11-28
When the CMRU is in Local mode and the Remote button is
pressed
When the CMRU is in Remote mode and (re-)started
When CF has lost its layer 2 connection to BSC
When the CF link is disconnected (reception of DISC command
frame)
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Channel Distribution Function
441 (485)