GSM 09.02 - Version 5.3.0 - Digital cellular telecommunications - ETSI

21.3 The page and search macros
21.3.1 Macro PAGE_MSC
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GSM 09.02 Version 5.3.0: August 1996
This macro (see figure 21.3/1) is called if a mobile terminating call set-up, an unstructured SS notification,
a network-initiated unstructured SS request or a mobile terminating short message is to be delivered to the
MS and the current location area identity of the MS is known in the VLR.
When the MSC receives a MAP_PAGE indication, parameter checks are performed first (macro
Check_Indication, see subclause 21.2). If parameter errors are detected, the MSC returns a MAP_PAGE
response containing the appropriate error cause and the macro terminates with unsuccessful outcome.
Thereafter, several checks on the indication content are performed. The macro terminates by returning the
MAP_PAGE response with error:
Unknown Location Area if the LAI is not known in the MSC;
System Failure if the call has been released by the calling subscriber or the SMS or SS transaction
for this subscriber has been released by the originating entity in the meantime.
Next, the MSC checks if an MM-connection over the radio link already exists for the given IMSI. If so,
- in the case of mobile terminating call set-up the MSC determines whether the busy condition can be
established (see TS GSM 02.01 for a definition of busy states). If the MSC determines that the MS
is busy, it returns a MAP_PAGE response with error Busy Subscriber, qualified by either More Calls
Allowed or No More Calls Allowed. The macro then terminates with unsuccessful outcome.
- if the service requested is short message service or an unstructured SS notification or
network-initiated unstructured SS request, or if the service is mobile terminating call set-up, but the
existing connection is for signalling purposes only (i.e. a service different from call set-up), the
access connection status is set according to the characteristics of the existing connection (i.e.
RR-connection established, ciphering mode on/off, MM-connection existing and authenticated or
not), and the macro terminates with successful outcome.
If no MM-connection for the given IMSI exists, paging is initiated at the radio interface within all cells of the
location area indicated by the VLR. If the VLR provided the TMSI, the MSC uses it to identify the MS at
the radio interface; otherwise the MSC uses the IMSI. The IMSI will also be used to determine the page
group (see TS GSM 04.08). There are several possible outcomes of paging:
- the MS responds to paging, causing the access connection status to be set accordingly (i.e. no
RR-connection, in which case other values are not significant), and the macro terminates with
successful outcome;
- the MS responds with a channel request containing an establishment cause which is not "answer to
paging". The MSC sends a MAP_PAGE response primitive with user error Busy Subscriber before
the macro terminates with unsuccessful outcome. This will give priority to the mobile originating
request. Alternatively, as an implementation option, the MSC may treat this as a response to
paging, which will give priority to the mobile terminating request.
- there is no response from the MS. The MSC sends a MAP_PAGE response primitive with user error
Absent Subscriber before the macro terminates with unsuccessful outcome;
- the call handling connection or MAP transaction on which the call, SMS or unstructured SS
transaction is waiting for delivery, is released before a response is received from the MS (indicated
in the SDL by the input signal I-REL). The MAP transaction with the VLR will be released in this
case by a MAP_U_ABORT request, and the unsuccessful macro termination will indicate transaction
termination.