D.3 Mobile Terminated Call Set-up

22.0013GPPPrinciples of circuit telecommunication services supported by a Public Land Mobile Network (PLMN)Release 17TS

Using the procedures described in 3GPP TS 22.011, the network knows the location area where the UE is positioned. If the UE is not already in two way radio communication with the network, the network pages the MS. Upon receiving its page message, the UE establishes communication with the selected cell. The network then allocates a channel which is used for signalling and sends call set-up information to the UE.

A traffic channel may be allocated at any instant until just after the call is answered by the UE.

The network indicates to the UE that it wishes to offer the UE a call. This notification includes the proposed bearer capability information, where available (see subclause D.2.5).

D.3.1 Bearer Type

If the calling party specifies the required bearer capability this shall be used for the call set-up attempt. If the calling party does not specify the required bearer capability (e.g. because the call originated in the PSTN), the network shall attempt to determine the bearer capability to be used as described below.

The network may use a multi-numbering scheme to define the bearer capability by the MSISDN. In a multi-numbering scheme several MSISDNs are associated with one IMSI. Each MSISDN is used for a different bearer capability. If the network uses a multi-numbering scheme and the calling party has not specified the required bearer capability then the network shall use the bearer capability associated with the called party MSISDN.

The network may use a single-numbering scheme, in which one MSISDN is associated with each IMSI. If the network uses a single-numbering scheme and the calling party has not specified the required service then the network shall omit the bearer capability information.

D.3.2 Response of the UE

On receipt of the call set-up request from the network, the UE shall check that it is able to support the type of call requested and that it is not User Determined User Busy (see annex C). The UE then alerts the user.

If the UE is unable to support the type of call requested, or the information is incomplete, the UE shall, if possible and not restricted by requirements in other ETSs, reply to the network proposing an alternative set of parameters, indicating those that are different from those proposed by the network. The network then either accepts this new proposal or terminates the call attempt.

D.3.3 Description of Call Re-establishment

Call re-establishment allows the user equipment to attempt to reconnect a call following the loss of radio coverage between the UE and the network while a call is in progress. Call re-establishment may be initiated by the UE when it detects this situation, if supported in the network.

Call re-establishment is mandatory in the ME and optional in the network.

Annex E (normative):
Automatic calling repeat call attempt restrictions

Call set up attempts referred to in this annex are assumed to be initiated from peripheral equipment or automatically from the MT itself.

A repeat call attempt may be made when a call attempt is unsuccessful for the reasons listed below (as defined in 3GPP TS 24.008 [13]).

These reasons are classified in three major categories:

1) "Busy destination":

– cause number 17 User busy.

2) "Unobtainable destination – temporary":

– cause number 18 No user responding;

19 User alerting, no answer;

27 Destination out of order;

34 No circuit/channel available;

41 Temporary failure;

42 Switching Equipment congestion;

44 Requested circuit/channel not available;

47 Resources unavailable, unspecified.

3) "Unobtainable destination – permanent/long term":

– cause number 1 Unassigned (unallocated) number;

3 No route to destination;

22 Number changed;

28 Invalid number format (uncompleted number);

38 Network out of order.

NOTE 1: Optionally, it is allowed to implement cause number 27 in Category 3, instead of Category 2, as this is desirable already in Phase 1.

The table below describes a repeat call restriction pattern to any B number. This pattern defines a maximum number (n) of call repeat attempts; when this number n is reached, the associated B number shall be blacklisted by the MT until a manual re-set at the MT is performed in respect of that B number. When a repeat attempt to anyone B number fails, or is blacklisted, this does not prevent calls being made to other B numbers.

For the categories 1 and 2 above, n shall be 10; for category 3, n shall be 1.

call attempts	Minimum duration between Call attempt
Initial call attempt	–
1st repeat attempt	5 sec
2nd repeat attempt	1 min
3rd repeat attempt	1 min
4th repeat attempt	1 min
5th repeat attempt	3 min
nth repeat attempt	3 min

The number of B numbers that can be held in the blacklist is at the manufacturers discretion but there shall be at least 8. However, when the blacklist is full the MT shall prohibit further automatic call attempts to any one number until the blacklist is manually cleared at the MT in respect of one or more B numbers.

When automatic calling apparatus is connected to an MT1 or MT2, or where an MTO is capable of auto-calling, then the MT shall process the call requests in accordance with the sequence of repeat attempts defined above, i.e. requests for repeat attempts with less than the minimum allowed duration between them shall be rejected by the MT.

A successful call attempt to a number which has been subject to the call restrictions shown above (i.e. an unsuccessful call set up attempt has previously occurred) shall reset the "counter" for that number.

The "counter" for an unsuccessfully attempted B number shall be maintained in 24 hours or until the MT is switched off.

The automatic calling repeat call attempt restrictions apply to speech and data services.

NOTE 2: The restrictions only apply to unsuccessful Call Control activity, not to Radio Resource Management or to Mobility Management, so multiple attempts at radio channel access are not limited by this mechanism.

Annex F(informative):
Procedures for call progress indications