Reference Manual

Call Control
Precondition and Initiation
Channel combination supported is defined in section Channel Activation
above /GSM 04.06:5.4.4/.
The Link Establish Indication function is applicable for:
•
SAPI-0 on SDCCH and FACCH
•
SAPI-3 on SDCCH and FACCH/T
There are two cases of establishment as described in /GSM 04.06:5.4.1/:
• Normal establishment
•
Contention resolution establishment
The function is initiated when the RBS receives an SABM from MS.
Description
The following procedure is used by RBS to indicate to BSC that a link
layer on the air interface has been established by an initiative from the
MS. After reception of a first SABM an indication (ESTablish
INDication) is sent to the BSC that a link layer on the radio path has
been established in multiframe mode.
It is the MS that takes initiative of the establishment. This is done when
the mobile, for example, wants to send a measurement report to the
network.
P003016A
RBS
BSC
EST IND
MS
first SABM
UA
Figure 126 Link establish indication
The Normal Establishment is utilized for SAPI-0 links (in conjunction
with a normal assign or handover) as well as for SAPI-3 links (at SMS
point-to-point).
The Contention Resolution Establishment is utilized for SAPI-0 links
only (in conjunction with an immediate assign).
An attempt to establish an SAPI-3 link is rejected (Disconnect Mode
response to MS if the SAPI-0 link is not established).
Messages queued for transmission are lost if the link is re-established.
• Collision cases are treated as specified in Technical Specification /
GSM 04.06/
• Fault handling related to the link establish procedure is in
accordance with /GSM 04.06:5.4.4/
EN/LZT 720 0008 P2A
2001-11-28
261 (485)
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