6 Exceptional procedures or unsuccessful outcome

22.0933GPPCompletion of Calls to Busy Subscriber (CCBS)Release 17Service description, Stage 1TS

6.1 Registration

Not applicable.

6.2 Erasure

Not applicable.

6.3 Activation

If the Mobile Station (MS) does not receive information from the network that CCBS is possible, the activation of a CCBS request shall be rejected.

If the network cannot accept subscriber A’s request to activate a CCBS request, the network shall inform subscriber A and give the appropriate reason.

If the request to activate a CCBS request can not be accepted due to special situation regarding CCBS the following indications shall be given to subscriber A:

a) short term denial: The network temporarily cannot accept subscriber A’s request to activate a CCBS request. A later attempt to activate a CCBS request for the same destination B may succeed.

– The maximum number of CCBS requests permitted against destination B has been reached;

– Subscriber A tried to activate a CCBS request against destination B after the CCBS retention timer T1 has expired;

– Subscriber A has reached the maximum number of CCBS requests permitted;

– if there is an interaction with a supplementary service which temporarily prevents the activation of a CCBS request;

b) long term denial: The network cannot accept subscriber A’s request to activate a CCBS request and a later attempt to activate a CCBS request against the same destination B will also be rejected.

– A CCBS request is not allowed against destination B i.e. because the destination B CCBS queue is set to zero;

If subscriber A does not wait for the CCBS recall to a particular destination B, but makes another call to that (busy) destination B and activates another CCBS request then, the following procedures can apply:

– if the two calls are identical, the original CCBS request shall be automatically deactivated and the current CCBS request shall be accepted. The current CCBS request shall be treated as new CCBS request (see subclause 5.5);

NOTE: There will be no restriction how often subscriber A is allowed to activate identical requests like this. If destination B’s CCBS queue is limited to a size of one, i.e. only one CCBS request is allowed to be planted against destination B, then if subscriber A re-activates CCBS request before T3 expires then no other subscriber can activate CCBS against destination B.

– if the two calls are not identical, then the network shall treat this as a new CCBS request. (see subclause 5.5).

In order to decide that the two calls are identical, the originating network shall only compare the basic call information, i.e. the basic service requirements, and called subscriber identity.

The originating network shall check for identical CCBS requests.

6.4 Deactivation

If there are no CCBS requests outstanding which meet the criteria specified in the deactivation request, the network shall inform subscriber A.

6.5 Invocation and operation

If, as a result of processing the entries in the queue, all entries become either suspended or automatically deactivated, no further processing shall take place. If, while destination B is idle, a previously suspended entry is resumed, or a new entry is added to the queue, the network shall process that entry. If destination B becomes idle , the network shall process that entry.

If, while destination B is still idle and no other CCBS call is awaited (CCBS Recall B timer (T9) is not running), a previously suspended entry is resumed or a new entry is added to the destination B CCBS queue, the network shall process that entry as described in subclause 5.7.

6.5.1 Exceptional situation at destination B’s side:

a) Destination B makes an outgoing call during the idle guard timer is running.

If destination B makes an outgoing call while the destination B idle guard timer (T8) is running, then invocation of CCBS shall be deferred until destination B becomes idle again.

b) destination B is NDUB upon arrival of the CCBS call.

If destination B is is NDUB upon arrival of the CCBS call, then two network options exist:

– the corresponding CCBS request shall be automatically deactivated. If subscriber A activates a CCBS request again, this activation shall be considered as a new CCBS request; or

– the original CCBS request shall retain its position in the CCBS queue, and the CCBS service duration timers (T3 and T7) shall not be restarted. If subscriber A attempts to activate a CCBS request again, this shall be treated as an identical request (see subclause 6.3).

NOTE: The option to retain the information of the original CCBS request can only be invoked if both the originating and the destination network support this option. It is the responsibility of networks supporting the option to retain the original CCBS request to provide interworking with those networks that do not.

c) destination B is not reachable.

The network may determine that destination B is not reachable:

– when the network monitors destination B for destination B becoming idle;

– while running the destination B idle guard timer (T8).

In each of the above cases, the CCBS request shall remain in the CCBS queue until. When destination B becomes reachable, the network shall process any CCBS requests in the CCBS queue (see subclause 5.7).

If subscriber A accepts the CCBS recall and destination B is not reachable, then the corresponding CCBS request shall be automatically deactivated.

d) destination B rejects the CCBS call with UDUB.

If destination B rejects the CCBS call using UDUB, the CCBS request shall be automatically deactivated. The network shall not offer subscriber A the opportunity to activate a CCBS request for this call again.

e) supplementary service interaction on destination B’s side:

If a supplementary service is active and operative on destination B side which prohibits the invocation of the CCBS supplementary service (for details see also Clause 7), then the processing of the B CCBS queue shall be stopped. The outstanding CCBS requests shall remain in destination B CCBS request CCBS queue. If the supplementary service interaction ends the outstanding CCBS requests shall be processed (see subclause 5.7).

f) CCBS request becomes suspended while awaiting the CCBS call:

If a CCBS request becomes suspended while being processed, the network shall stop the CCBS recall timer (T9) and process the next non-suspended CCBS request.

g) CCBS service duration timer (T7) expires:

If the CCBS service duration timer (T7) expires and the subscriber A has not been informed that destination B is idle for that CCBS request, i.e. the CCBS recall timer (T9) is not running, then the network shall automatically deactivate the CCBS request.

If the CCBS service duration timer (T7) expires after the subscriber A has been informed that destination B is idle for that CCBS request, i.e. the CCBS recall B timer (T9) is running, then the CCBS request shall not be automatically deactivated until the processing of the CCBS request is completed.

h) CCBS recall B timer (T9) expires:

If the CCBS recall B timer (T9) expires then the network shall automatically deactivate the CCBS request.

6.5.2 Exceptional situation at subscriber A’s side:

a) non-acceptance or rejection of CCBS recall when subscriber A is found to be idle.

If subscriber A rejects the CCBS recall or the CCBS recall timer (T4) expires, then the CCBS request shall be automatically deactivated.

If subscriber A tries to suspend the CCBS recall then the CCBS request shall be automatically deactivated.

b) subscriber A is found to be not idle.

When the destination B’s idle guard timer (T8) expires and subscriber A is found to be not idle, the network shall notify subscriber A and start the CCBS notification timer (T10). While the CCBS notification timer (T10) is running, subscriber A may:

– Accept the CCBS recall: The subscriber A has to free up the required resources to set-up the CCBS call, e.g. by releasing the existing calls or put the existing call on hold. The CCBS recall shall then be handled in the same way as when subscriber A is idle (subclause 5.7).

– Reject the CCBS notification. The network shall automatically deactivate the CCBS request.

– Ignore the CCBS notification. When the CCBS notification timer (T10) expires, the network shall suspend the CCBS request if T3 is still running. If T10 expires while T3 has already expired, then the CCBS request shall be automatically deactivated.

– Suspend the CCBS request . The request may later be resumed according to subclause 6.5.2.e.

c) subscriber A is found to be CCBS busy.

If subscriber A is CCBS busy when destination B’s idle guard timer (T8) expires, the network shall suspend the CCBS request without notifying subscriber A.

d) Subscriber A is not reachable.

If it is identified that subscriber A is not reachable when the destination B idle guard timer expires, then the CCBS request shall be suspended until subscriber A becomes reachable again.

e) If subscriber A becomes idle after being not idle or CCBS busy, or subscriber A becomes reachable again and there are one or more suspended CCBS requests in subscriber A’s CCBS queue, this queue shall be processed in the following way:

The first suspended CCBS request shall be resumed. The CCBS resume timer (T11) is started, provided that subscriber A’s CCBS queue holds more than one CCBS request;

– If no CCBS recall results from the resume procedure before the CCBS resume timer (T11) expires, processing of subscriber A’s CCBS queue shall be continued as described above until no more suspended CCBS requests are left in that queue;

– If a CCBS recall results from the resume procedure, the CCBS resume timer (T11) is stopped, and the CCBS recall is treated in the normal way as described in subclause 5.7.

f) CCBS service duration timer (T3) expires:

– If the CCBS service duration timer (T3) expires and the subscriber A has not been informed that destination B is idle for that CCBS request, i.e. the CCBS recall timer (T4) or the CCBS notification timer (T10) are not running then the network shall automatically deactivate the CCBS request.

– If the CCBS service duration timer (T3) expires and the subscriber A has been informed that destination B is idle, i.e. the CCBS recall timer (T4) or the CCBS notification timer (T10) are running, then the CCBS request shall not be automatically deactivated until the processing of the CCBS request is completed.

g) CCBS recall timer (T4) expires:

If the CCBS recall timer (T4) expires then the network shall automatically deactivate the CCBS request.

6.5.3 Exceptional situations in the network

If the CCBS call fails for any other reason than described in subclauses 6.5.1 and 6.5.2, then subscriber A shall be informed as for the basic call procedures, and the CCBS request shall be automatically deactivated.