4 Flexible Alerting (FA)

24.2393GPPFlexible Alerting (FA) using IP Multimedia (IM) Core Network (CN) subsystemProtocol specificationRelease 17TS

Tools: ARFCN - Frequency Conversion for 5G NR/LTE/UMTS/GSM

4.1 Introduction

Flexible Alerting (FA) causes a call to a Pilot Identity to branch the call into several legs to alert several termination addresses (group members) simultaneously. Additional calls may be delivered to the FA Pilot Identity at any time. The first leg to be answered is connected to the calling party. The other call legs are abandoned.

The members of an FA group are described by a list of termination addresses.

4.2 Description

4.2.1 General description

FA may be used for either a single user or multiple users. The difference between the two is in determining when the FA group is busy. In the single user case, the group is considered to be busy when one of the members is considered to be busy. In the multiple user case, the group is considered to be busy when all of the accessible members are considered to be busy. A member is considered to be busy when it cannot accept the presentation of another call.

The FA pilot identity may have features to manage incoming calls (e.g., Incoming Communications Barring). These features should take precedence over the corresponding features of individual members as described in clause 4.6.

If an FA pilot identity is an FA member Identity, the FA member loses his or her individual incoming call features. In this case, the FA member’s incoming call features are superseded by the incoming call features of the FA pilot identity.

If an FA pilot identity is not an FA member Identity, the features of the FA pilot identity may be changed only through user or service provider configuration.

FA does not affect the ability of an FA member to originate calls. FA may affect the ability of an FA member to receive calls.

If an FA member has only a single identity that is the same as the FA pilot identity, the FA member may not receive calls except through the FA pilot identity.

If an FA member has an identity different than the FA pilot identity, the FA member may receive calls as an individual as well as calls through the FA pilot identity. Such an FA member may use revertive calling (i.e., a call to itself) for other purposes, such as retrieval of voice mail.

4.3 Operational requirements

4.3.1 Provision/withdrawal

The FA service may be provided after prior arrangement with the service provider. The establishment of the initial constituency (membership) of the FA group, along with additions to or subtractions from the set of group members, is performed by the service provider.

The FA service may be withdrawn at the subscriber’s request or for administrative reasons. Withdrawal of the FA service means dissolution of the FA group and results in calls to the Pilot Identity being treated as calls to a vacant identity. Withdrawal of the FA service is performed by the service provider.

As determined by service provider provisioning, the FA group may have the following subscription options, as summarized in table 4.3.1-1.

Table 4.3.1-1: FA group subscription options

Subscription option values

Values

Type

‑ Single User. The FA group is considered to be busy when any member of the group is considered to be busy.

‑ Multiple Users. The FA group is considered to be busy when all accessible members of the group are considered to be busy.

As determined by service provider provisioning, the FA member may have the following subscription options, as summarized in table 4.3.1-2.

Table 4.3.1-2: FA member subscription options

Subscription option values

Values

Membership

‑ Demand. An FA member is authorized to activate or deactivate his or her membership in the FA group(s).

‑ Permanent. An FA member is always a member of his or her registered FA group(s).

If an FA group is of type ‘demand activation’, any configured FA member is able to, by means of user configuration, change their status in the FA group from ‘active’ to ‘inactive’ or from ‘inactive’ to ‘active’. The FA member status options are summarized in table 4.3.1-3.

Table 4.3.1-3: FA member status options

Subscription option values

Values

Status

‑ Active. An FA member is eligible to be alerted when a call is placed to the Pilot Identity.

‑ Inactive. An FA member is not eligible to be alerted when a call is placed to the Pilot Identity..

Available user configuration actions for FA are described in clause 4.5.2.

For user configuration of FA, the SIP-based user configuration capability as described in 3GPP TS 24.238 [4] or the Ut interface as described in 3GPP TS 24.623 [6] could be used. More detail is described in clause 4.8.

Other possibilities for provisioning could be used too, like web based provisioning or pre-provisioning by the operator.

4.3.2 Requirements on the originating network side

There are no requirements on the originating network side for FA. FA is a terminating network side service.

4.3.3 Requirements on the terminating network side

The public user identity that represents the pilot identity of the FA group has an always-registered presence on the IM CN subsystem. The pilot identity is associated with a typical IM CN subsystem user service profile.

4.4 Syntax requirements

There are no special SIP syntax requirements for the FA service. The FA service is invoked when an IM CN subsystem session is terminated to the pilot identity of an FA group.

4.5 Signalling procedures

4.5.1 General

For user configuration of the FA service by a member of the FA group, either the Ut interface or the SIP-based user configuration capability (as specified by 3GPP TS 24.238 [4]) should be used.

The enhancements to the XML schema for use over the Ut interface are described in clause 4.8.

NOTE: Other possibilities for user configuration, such as web-based provisioning, are outside the scope of the present document.

4.5.2 Activation/deactivation

4.5.2.1 General

The FA service is activated at provisioning and deactivated at withdrawal.

For an FA group that is of type ‘demand activation’, activation or deactivation of membership is accomplished by means of user configuration and may be achieved by using either:

– the Ut interface using XCAP as enabling protocol as described in 3GPP TS 24.623 [6]; or

– SIP based user configuration as described in 3GPP TS 24.238 [3];

NOTE: Other possibilities for user configuration, such as web-based provisioning or pre-provisioning by the operator are outside the scope of the present document, but are not precluded.

The enhancements to the XML schema for use over the Ut interface are described in clause 4.9.

4.5.2.2 Demand member activation of a subscriber’s default FA group(s)

For an FA group that is of type ‘demand activation’, an FA member may activate his or her membership in the subscriber’s default FA group(s) by specifying the FA membership activation feature code:

An example of the code is: *FC

If the activation is accepted, the system shall indicate success with feature confirmation treatment.

4.5.2.3 Demand member activation of a specified FA group

For an FA group that is of type ‘demand activation’, an FA member may activate his or her membership in a particular FA group by specifying the FA membership activation feature code and a specific FA pilot identity:

An example of the code is: *FC + FA pilot identity

If the activation is accepted, the system shall indicate success with feature confirmation treatment.

4.5.2.4 Demand member deactivation of a subscriber’s default FA group(s)

For an FA group that is of type ‘demand activation’, an FA member may deactivate his or her membership in the subscriber’s default FA group(s) by specifying the FA membership deactivation feature code:

An example of the code is: *FC0

If the deactivation is accepted, the system shall indicate success with feature confirmation treatment.

4.5.2.5 Demand member deactivation of a specified FA group

For an FA group that is of type ‘demand activation’, an FA member may deactivate his or her membership in a particular FA group by specifying the FA membership deactivation feature code and a specific FA pilot identity:

An example of the code is: *FC0 + FA pilot identity

If the deactivation is accepted, the system shall indicate success with feature confirmation treatment.

4.5.3 Registration/erasure

Individual members of the FA group may be added or deleted at any time by the service provider.

4.5.4 Interrogation

4.5.4.1 General

For interrogation, the mechanisms described in clause 4.5.1 should be used.

4.5.4.2 Interrogation using Ut interface

The enhancements to the XML schema for use over the Ut interface are described in clause 4.9.

4.5.4.3 Interrogation using the SIP-based user configuration

For an FA group that is of type ‘demand activation’, an FA member may interrogate his or her membership status in the subscriber’s default FA group(s) by specifying the FA membership interrogation feature code:

An example of the code is: *FC1

For an FA group that is of type ‘demand activation’, an FA member may interrogate his or her membership status in a particular FA group by specifying the FA membership interrogation feature code and a specific FA pilot identity:

An example of the code is: *FC1 + FA pilot identity

NOTE 1: The response to such interrogation is not specified for the FA service. AS interactions with the MRF over the CR reference point or a solution based on IVR can be used as a possible interrogation response.

4.5.5 Invocation and operation

4.5.5.1 Actions at the AS serving the originating UE

There are no procedures at the originating AS relevant to the FA service.

4.5.5.2 Actions at the AS serving the pilot identity

Procedures specified in 3GPP TS 24.229 [5] for an AS acting as a routing B2BUA shall apply, with the additions described in this clause.

The AS shall support procedures of notification about registration status defined in clause 5.7.1.1 of 3GPP TS 24.229 [5].

Upon receiving an incoming SIP INVITE request destined to the pilot identity, based on operator policy the AS shall either:

1) Alert the UEs of FA member identities in parallel by sending the SIP INVITE request to all the member identities within the FA group; or

2) alert the UEs of the FA member identities sequentially by sending the SIP INVITE request to the Public User Identities of the FA group or to their specifc registered UEs in sequence, either progressing through the group based on failure to respond from the UE (the nature of the failures used is based on nature of the implementation) or on a fixed and locally configured timer.

NOTE 1: The order in which members of the FA group and their registered UEs are alerted depends on application-specific criteria (including static preferences, last used device, last registered device).

NOTE 2: Two mechanisms for the AS to select a specific registered UE for a registered Public User Identity are, 1) the AS can set the Request-URI of the INVITE request to the public GRUU of the selected UE, if available, 2) insert in the INVITE request the Accept-Contact header field containing a sip.instance media feature tag equal to the instance-id associated to the selected UE and the "require" and the "explicit" tags.

Upon receiving a SIP 200 (OK) response to the SIP INVITE request from a member UE, the AS shall:

– send SIP CANCEL request to cancel any outstanding SIP INVITE request other member UEs that have not sent a final response; and

– send the SIP 200 (OK) response for the SIP INVITE request to the originating UE.

For a single-user FA group, if the AS receives SIP 486 (Busy Here) response from any of the member UEs before receiving SIP 2xx responses, the AS shall:

– send SIP CANCEL request to cancel any outstanding SIP INVITE request other member UEs that have not sent a final response; and

– send the SIP 486 (Busy Here) response to the originating UE.

For a multiple-user FA group, if the AS receives SIP 486 (Busy Here) responses from each (all) of the member UEs, the AS shall send a SIP 486 (Busy Here) response to the originating UE.

4.6 Interaction with other services

4.6.1 Communication session Hold (HOLD)

No impact, i.e. neither service shall affect the operation of the other service.

4.6.2 Terminating Identification Presentation (TIP)

If the FA pilot identity did not apply TIR, the termination identification is the FA pilot identity.

4.6.3 Terminating Identification Restriction (TIR)

If the FA pilot identity has TIR activated, the termination identification is not presented.

4.6.4 Originating Identification Presentation (OIP)

If the FA pilot identity has OIP activated, incoming calls to the FA pilot identity apply OIP to the members of the FA group.

4.6.5 Originating Identification Restriction (OIR)

No impact, i.e. neither service shall affect the operation of the other service.

4.6.6 Conference (CONF)

No impact, i.e. neither service shall affect the operation of the other service.

4.6.7 Communication DIVersion services (CDIV)

4.6.7.1 Communication Forwarding Unconditional (CFU)

CFU is applicable to FA. If CFU is active for the Pilot Identity, the FA AS shall perform the procedures related to CFU prior to executing the FA service.

CFU of the FA Pilot Identity takes precedence over CFU of the individual FA members. That is, if both the FA Pilot Identity and an FA member have CFU active, CFU treatment is determined by the Pilot Identity’s service profile.