6 Exceptional procedures or unsuccessful outcome

22.0873GPPService descriptionStage 1TSUser-to-User Signalling (UUS)

6.1 Provision and Withdrawal

No exceptional procedures.

6.2 Registration and Erasure

not applicable.

6.3 Handling of UUS services

6.3.1 Activation

If the network cannot accept an implicit request for the activation of UUS service 1, no notification shall be given to the subscriber.

In all other cases, if the network cannot accept a request for the activation of a UUS service, the network shall reject the activation. In addition, the network shall indicate which of service 1, service 2 and/or service 3 have been rejected. For the rejection of the activation request the following reasons may be possible:

– service not subscribed to;

– necessary signalling connectivity does not exist between sending and receiving subscribers;

– conflicting situation with other supplementary service (e.g. CUG, incoming call barring);

– service is already active;

– network congestion.

6.3.2 Invocation

The subscriber may not be able to interpret incoming UUI. In such situations, the user can discard this information without disrupting normal call handling. No specific signalling is provided by the network to accommodate this situation.

Under circumstances of network congestion or failure, the network may discard services 2 and 3 UUI.