Flexible Alerting

3GPP defines Flexible Alerting in TS 24.239 and the flexible alerting subscriber data schema is defined in TS 24.239 and TS 29.364. The service allows the creation of a group of member identities bound to a single number, called the Pilot Number. When a call to the Pilot Number is identified, VoLTE will alert all the members of the group and the caller is bound to the first member of the group that answers the call.

The group of identities that may be contacted by the Flexible Alerting feature is called the FA Group.

There can be two types of FA Group:

These groups have different rules for dealing with SIP responses.

For single-user

For multiple-users

There are two alerting modes for FA. These are:

In the sequential alerting mode the group members are alerted in order, with each member sending a final response or timing out before the next is alerted. In the parallel alerting mode all group members are alerted at once.

Flexible Alerting allows the call to continue after final responses on one or more group members.

OpenCloud’s Flexible Alerting supports both Parallel or Sequential alerting mode by a configuration under MMTelDetermineFAConfigProfileTable. The configuration table can be accessed through REM and is specified using the MMTelDetermineFAConfigProfileTable profile table name. The feature profile is scoped by the sentinel key and the pilot number, meaning that each Pilot Number requires a profile, otherwise VoLTE will fallback to a default profile not scoped by the Pilot Number.