Method of provisioning an entry in a subscriber database of an IP Multimedia Subsystem

FIELD OF THE INVENTION

The invention relates to a method of provisioning an account in a subscriber database of an IP Multimedia Subsystem. The invention further relates to a computer readable medium for performing, when executed by a processor, such a method. The invention further relates to a provisioning system, and a telecommunication network system comprising such a provisioning system.

BACKGROUND OF THE INVENTION

An IP Multimedia Subsystem (IMS) as defined in 3GPP Standards of release 5 and higher offers extensive possibilities and opportunities to mobile operators to create new services for subscribers. However, to enable use of these new services, additional measures need to be taken.

Among others, authentication needs to be arranged. For this reason, a central logical database for subscriber data, further referred to as Home Subscriber Server (HSS), needs to be provisioned with additional subscriber-related information. In particular, a so-called IP Multimedia Subsystem Public Identity (IMPI) and an IP Multimedia Subsystem Private User Identity (IMPU) of subscribers are generally added, the IMPU and IMPI being used for addressing and identification in IMS.

Currently, in order to perform IMS, subscriber profiles, i.e. accounts made in the HSS related to a single subscriber, of all subscribers of a mobile operator need to be provisioned in the HSS to enable IMS-services to be provided to any of them. The storage of all these subscriber profiles uses a large amount of space in the HSS. This increases the administrative and licensing costs to be made by an operator, and hence, makes these (IMS-)services less commercially viable.

Limiting the number of subscribers by allowing a particular type of subscribers, e.g. postpaid subscribers, to use IMS-services may well be insufficient to solve aforementioned issue as their number may still be well over the number of subscribers that will actually use the IMS-services when introducing these (IMS-)services.

It is desirable to provision subscriber profiles in the HSS of subscribers who are actually trying and/or willing to use the new IMS-services provided by the mobile operator.

European patent application 1 830 536 describes a method for self-provisioning of subscriber data in an IP multimedia subsystem (IMS). In this method, a subscription entry is created in the subscriber database (HSS) of the IMS based on prior secure identification of the subscriber by an access network that grants access to the IMS. In aforementioned application, the HSS performs additional tasks as compared to functionality defined in 3GPP TR 33.978, a technical report related to security aspects of early- IMS. This technical report serves the purpose to suggest a certain approach to be followed by manufacturers while introducing the related functionality.

Furthermore, for each subscriber who uses user equipment provided with IMS- functionality for the first time, an account is created in the HSS. However, not all users use all services supported by their UE. Thus, in many cases, accounts are created which do not serve any purpose. Hence, still lots of time and money is invested to perform maintenance on accounts in the HSS that are not in use.

It is desirable to provide a method of provisioning an entry in the HSS of an IMS which limits the number of accounts in the HSS related to subscribers not using IMS-services.

Furthermore, it is desirable that such a method does not further complicate the functionality of the HSS as defined in technical report 3GPP TR 33.978.

SUMMARY OF THE INVENTION

Embodiments of the invention relate to a method of provisioning an account in a subscriber database of an IP multimedia subsystem communicatively connected to a provisioning system for managing provisioning requests, the method comprising:

- checking a status regarding earlier use by a subscriber of the IP multimedia subsystem; and if the checking reveals that the subscriber is not a user or potential user of the IP multimedia subsystem:

- adding a subscriber account in the subscriber database, the subscriber account being provided with subscriber information, and

- storing a reference to the subscriber account in the provisioning system; or, if the checking reveals that the subscriber is a user or potential user of the IP multimedia subsystem:

- updating a subscriber account associated with the subscriber in the subscriber database with updated information.

Such a method of provisioning an entry in the HSS of an IMS limits the number of accounts in the HSS related to subscribers not using IMS-services, without further complicating the functionality of the HSS as described in technical report TR 33.978..

The step of checking a status regarding earlier use by the subscriber of the IP multimedia subsystem may comprise checking whether a reference to a subscriber account with respect to the subscriber exists in the provisioning system. Additionally or alternatively, if the checking reveals that the subscriber is not a user or potential user of the IP multimedia subsystem, a subscriber status entry may be added in the provisioning system, the subscriber status entry identifying the subscriber as a temporary subscriber.

In an embodiment, the method further comprises:

- providing a limited services application server, the limited services application server comprising one or more IMS-services available for a first-time user of IMS;

- detecting a request for use of at least one of the one or more IMS-services by the limited service application server;

- notifying the provisioning system that the IP multimedia subsystem has been used by the subscriber for the first time.

The addition of these actions further assures that no additional accounts will be provisioned with respect to the same subscriber in the subscriber database.

In a further embodiment, if a subscriber uses the IP multimedia subsystem for the first time, the method further comprises:

- amending the subscriber status entry in the provisioning system such that it identifies the subscriber as a permanent subscriber.

The addition of this action further assures that the subscriber will be able to use IMS-services directly without further need for provisioning all subscribers in the subscriber database beforehand.

In a further embodiment, wherein the IP multimedia subsystem is further communicatively connected to an application server system comprising an application server communicatively connected to an application database, the method further comprises provisioning the application server system with information associated with the subscriber as a permanent user.

An application database comprises information regarding available IMS-services. The availability of these services may be stored per subscriber. Provisioning the application server system in a way as described above, avoids that accounts are created in the application

database which do not serve any purpose. Hence, less time and money is needed to perform maintenance on accounts in the AS that are not in use.

In embodiments of the invention, if the subscriber has a status of temporary subscriber for a time exceeding a predetermined threshold value, the method further comprises:

- deleting the subscriber account in the subscriber database;

- removing the reference to the subscriber account in the provisioning system, and

- removing the subscriber status entry.

The addition of these action ensures that the number of subscriber accounts in the subscriber database are limited as much as possible. In embodiments thereof, the method may further comprise periodic checking of the subscriber status entries related to temporary subscribers. In comparison to raising a flag for each temporary user when its status exceeds the predetermined threshold value, periodic checking is less complex.

Aforementioned updated information may comprise the current IP-address of the subscriber.

In embodiments of the invention, the method further comprises

- forwarding information regarding available services to the subscriber database; and

- coupling the information regarding available services to the subscriber information in the subscriber account in the subscriber database.

This allows efficient registration of the IMS-services a subscriber is allowed to use.

Embodiments of the invention further relate to a computer readable medium for performing, when executed by a processor, embodiments of the method of provisioning an entry in a subscriber database of an IP multimedia subsystem as described above. An embodiment of the invention further relates to a provisioning system comprising:

- an auto-provisioning unit for checking a status of a subscriber regarding earlier use of an IP multimedia subsystem, and for sending a status information signal after the checking; and

- an auto-provisioning database, communicatively connected to the auto-provisioning unit, for storing a subscriber status entry, the subscriber status entry comprising one or more elements of subscriber information including the status of the subscriber, and for allowing the checking by the auto-provisioning unit.

In a further embodiment thereof, the auto-provisioning unit is arranged to, upon receipt of updated information regarding the subscriber, update the subscriber status entry in the auto-provisioning database with the updated information.

The provisioning database may comprise:

- a first database portion for storing subscriber status entries related to a temporary subscriber; and

- a second database portion for storing subscriber status entries related to a permanent subscriber.

Embodiments of the invention further relate to a telecommunication network system comprising:

- an access network;

- an application server communicatively connected to an application database; and

- an IP Multimedia Subsystem comprising a subscriber database, the subscriber database being communicatively connected to both the access network and the application server; characterized in that the telecommunication network system further comprises an embodiment of a provisioning system as described above.

In an embodiment, the telecommunication network system further comprises an operator database that is communicatively connected to the auto-provisioning unit, the operator database comprising information regarding subscribers that can be used by the provisioning system to decide, for each subscriber, whether or not services of the IP multimedia subsystem are available for that subscriber.

In aforementioned embodiment, the telecommunication network system further comprises an additional application server that is communicatively connected to the IP Multimedia Subsystem.

Further aspects of the invention and embodiments as defined in the claims will be clarified with reference to the attached drawings and corresponding description. It will be understood that the invention is not in anyway restricted to the embodiments disclosed in these drawings.

BRIEF DESCRIPTION OF THE DRAWINGS In the drawings:

FIG. 1 depicts a communication diagram of a method of authenticating an entry in a subscriber database of an IMS with early IMS security according to technical report 3GPP TR 33.978;

FIG. 2 schematically depicts a telecommunications network system according to an embodiment of the invention;

FIG. 3 depicts a communication diagram of an aspect of method of provisioning an entry in a subscriber database of an IMS according to an embodiment of the invention;

FIG. 4 depicts a communication diagram of a further aspect of a method of provisioning an entry in a subscriber database of an IMS according to an embodiment of the invention;

FIG. 5 depicts a communication diagram of another further aspect of a method of provisioning an entry in a subscriber database of an IMS according to an embodiment of the invention.

DETAILED DESCRIPTION OF THE DRAWINGS

The following is a description of certain embodiments of the invention, given by way of example only.

FIG. 1 depicts a communication diagram of a method of authenticating an entry in a subscriber database of an IMS with early IMS security according to technical report 3GPP TR 33.978 based on prior secure identification of the subscriber by an access network.

First, in action 101, a packet data protocol (PDP) context activation request is sent to the access network (AN). That is, user equipment (UE), e.g. a mobile phone, tries to set up a packet switched connection with an access network (AN) using a Packet Data Protocol (PDP). Instead of UE also the expression user agent (UA) may be used.

In technical report 3GPP TR 33.978, the AN is a Gateway GPRS Support Node (GGSN), where GPRS stands for General Packet Radio Service. Upon reception of the PDP- context activation request, in action 102, the GGSN sends an authentication request to an authentication server, in this case a Remote Authentication Dial In User Service (RADIUS)- server. The authentication request comprises an International Mobile Subscriber Identity (IMSI), i.e. a unique subscriber identity stored in the Subscriber Identity Module (SIM) in the UE .

The RADIUS-server checks the IMSI received in the authentication request, and if authentication turns out to be correct, assigns an IP-address to the UE which is sent, in action 103 to the GGSN.

Subsequently, in action 104, an accounting request start message is sent to a RADIUS-server. Note that in 3GPP TR 33.978, a RADIUS-server is located in the HSS. However, in general, also a separate RADIUS-server may be used. The accounting request

start message subscriber information is forwarded from the RADIUS-client in the GGSN to the HSS. The subscriber information comprises the IMSI and the Mobile Station ISDN Number (MSISDN) of the UE, the MSISDN being the number to be dialed to connect a call to the UE. Furthermore, the accounting request start message sends the IP-address assigned to the UE to the HSS.

The HSS contains subscriber accounts. The subscriber account generally includes the IMSI, and MSISDN of the subscriber as well as his IMPI and IMPU. Furthermore, the subscriber account for early IMS security includes the most recent IP-address assigned to the subscriber.

Via RADIUS, the GGSN informs the HSS when the PDP-context is deactivated and/or modified so that the IP-address can be updated in the HSS. Hence, in the HSS, the recent IP-address is stored against the IMPI and/or the IMPU of the subscriber allowing authentication of the UE and enabling IMS-services to be used. Further details may be found in technical report 3GPP TR 33.978.

After successfully storing the recent IP-address in the HSS, the HSS will send, in action 105, an accounting request start confirmation message to the GGSN.

In action 106, the GGSN sends a PDP-context activation acceptance message to the UE that IMS registration is now possible. Further details with respect to aforementioned actions 105 and 106 may be found in technical report 3GPP TR 33.978. Note that in FIG. 1 and technical report 3GPP TR 33.978, a sending of a PDP-context activation acceptance message appears to be sent to the UE after reception of the accounting request start confirmation message. However, in practice, it is also possible that action 106 is performed before action 105 as will be known to a person skilled in the art.

The UE will then register, while following Session Initiation Protocol (SIP), with the GGSN, the Proxy Call Session Control Function (P-CSCF) of the IMS, and the Interrogating Call Session Control Function (I-CSCF) of the IMS, in actions 107, 108, and 109 respectively. Note that, in case the UE transmits an IP packet with a source IP-address different to the one assigned by the GGSN during PDP context activation transmission of this IP packet will be impossible, because the GGSN is arranged to detect this so-called IP address spoofing.

Subsequently, the I-CSCF may check with the HSS whether a subscriber account with the IMPI and IMPU mentioned in the registration message exists or not. The HSS may respond in the affirmative or negative, and may also provide information to the I-CSCF regarding the location of the S-CSCF for that subscriber. The interaction between I-CSCF and HSS is schematically denoted as action 110.

If the location of the S-CSCF for the subscriber is known, in action 111, a SIP- registration request will be send to a Serving Call Session Control Function (S-CSCF) of the IMS.

As schematically denoted by action 112, the S-CSCF may query the HSS with respect to several aspects of the SIP-registration request, e.g. check whether the IMPU and IP- address are correct.

Finally, in action 113, if everything has been performed correctly, an OK response is sent to the UE. Note that such an OK response may be sent to the UE via I-CSCF, P-CSCF, and GGSN, as will be known to a person skilled in the art.

FIG. 2 schematically depicts a telecommunications network system 201 according to an embodiment of the invention. The telecommunications network system 201 comprises an access network (GGSN) 203, an IP Multimedia Subsystem (IMS) 205 and an application server (AS) 207. The IMS 205 is communicatively connected to both the GGSN 203 and AS 207.

The GGSN 203 is arranged to communicate with a UE 204. Furthermore, the GGSN 203 is arranged to communicate with a RADIUS 229.

The IMS 205 comprises a subscriber database (HSS) 209, a P-CSCF 211, an I-CSCF 213 and a S-CSCF 215.

The AS 207 is communicatively connected to an application database 219 comprising information regarding available IMS-services. The availability of these services may be stored per subscriber in an account. In this specification, the combination AS 207 and application database 219 may be referred to as an application server system.

GGSN 203, RADIUS 229, P-CSCF 211, I-CSCF 213, S-CSCF 215 and HSS 209 may be arranged to communicate in accordance with technical report 3GPP 33.978, as schematically described with reference to FIG. 1.

The telecommunications network 201 further comprises an auto-provisioning unit (APU) 221 and an additional application server, further referred to as limited services application server (LAS) 223. The APU 221 is communicatively connected to a auto- provisioning database 227. The auto-provisioning database 227 may comprise separate database portions 227A, 227B. A first database portion 227A may be arranged to store data for a predetermined period of time, i.e. store information with respect to subscribers identified as temporary subscriber. A second database portion 227B may be arranged to store data "permanently", i.e. store information with respect to subscribers identified as permanent

subscribers. The combination of the APU 221 and auto-provisioning database 227 may be referred to as a provisioning system.

Additionally, the APU 221 is communicatively connected to the RADIUS 229 and HSS 209, and may further be communicatively connected to an operator database 217, further referred to as Operational Data Store (ODS) 217. In an embodiment, the APU 221 comprises the RADIUS-server.

In the embodiment shown, the APU 221 is further communicatively connected to the LAS 223 and the application database 219. The LAS 223 is further communicatively connected to the S-CSCF 215 in the IMS 205.

Communication between the components shown in FIG. 2 may be performed via interface protocols well known to persons skilled in the art.

Operation of the telecommunications network system 201 as well as specific functions of elements thereof will be discussed with reference to FIGS. 3 — 5.

It must be understood that embodiments of the invention are not limited to the telecommunications network system 201 depicted in FIG. 2. Embodiments of the invention may omit some elements shown in FIG. 2 as will become apparent from the description with reference to FIGS. 3 - 5.

FIGS. 3 - 5 depict communication diagrams of different aspects of a method of provisioning an entry in a subscriber database of an IMS according to an embodiment of the invention.

Actions 301, 302 and 303 are similar to actions 101, 102 and 103 described with reference to FIG. 1.

However, in action 304, the accounting request start message is not sent to a server in the HSS, but is directed to the APU instead.

In the APU, in action 305, a subscriber status is checked to see if the subscriber is a user of the IMS. For example, the APU may review whether the subscriber is registered as an IMS-user, herein also referred to as permanent subscriber, and, if this is not the case, whether the subscriber activated a PDP-context within a predetermined time interval prior to the time of checking. Alternatively, the APU may check whether the provisioning system comprises a reference to a subscriber account in the HSS with respect to the subscriber. A case in which a PDP-context has been activated within the predetermined time interval is further referred to as being recent, while a case in which the PDP-context has been activated outside the predetermined period of time is further referred to as being non-recent.

The status of the subscriber may be stored in a subscriber status entry in the auto- provisioning database. Furthermore, the APU may check a subscriber status in the ODS for filtering purposes. That is, the actions described hereinafter may be performed for a specific group of subscribers, e.g. postpaid subscribers, while another group of subscribers may be excluded, e.g. prepaid subscribers or subscribers of a Mobile Virtual Network Operator (MVNO). The APU can then decide, upon analysis of the information available in the ODS whether or not services of the IP multimedia subsystem are available for a subscriber or not.

After checking the subscriber status, the subscriber status may be updated, e.g. by updating the respective subscriber status entry in the auto-provisioning database shown in FIG. 2. If the subscriber is registered as an IMS-user, updating may comprise changing the IP-address in the entry of the subscriber. If the subscriber is not registered as an IMS-user, but has activated a PDP-context recently, and therefore may be considered as a potential user, updating may further comprise initiating a new time interval by updating corresponding information in the subscriber entry, e.g. a date time stamp.

If the subscriber is not registered as an IMS-user, or no PDP-context activation is known with respect to this subscriber, i.e. the subscriber is not considered as a potential user, a new subscriber status entry is added in the auto-provisioning database of the provisioning system.

Information stored in the subscriber status entry may include whether the subscriber is registered as an IMS-user, the most recent IP-address assigned to the subscriber, the last time a PDP-context was activated if applicable, and further subscriber information, e.g. the IMSI of the subscriber, the MSISDN of the subscriber, etc.

After checking the subscriber status, in action 306, the APU sends subscriber information to the HSS. The HSS, in action 307, then uses the subscriber information to provision a subscriber account in the following way. Besides the information already discussed above, the subscriber information may further comprise initial filtering criteria (IFC). The IFC provide information regarding the IMS-services available to the subscriber as well as location information as to where to find the IMS-services, e.g. LAS or AS in FIG. 2.

If the checking of the subscriber status in action 305 has revealed that the subscriber has used the IMS before or that he has initiated an earlier provisioning request within the predetermined period of time, i.e. the subscriber is a user or a potential user of the IP multimedia subsystem respectively, the subscriber information sent in action 306 may be limited to sufficient information to identify the subscriber, e.g. the IMSI or the MSISDN of the subscriber, and the current IP-address assigned by the GGSN. In action 307, the HSS then

updates a subscriber account in the HSS by insertion of the current IP-address, e.g. by replacement.

On the other hand, if the checking of the subscriber status in action 305 has revealed that the subscriber has not used the IMS before or has initiated an earlier provisioning request outside a predetermined time interval before the checking, i.e. that the subscriber is not identified as a user of a potential user of the IP multimedia subsystem respectively, the subscriber information sent in action 306 may further comprise information needed to enable IMS-services to be performed, e.g. the IMPI and/or IMPU of the subscriber. In action 307, the HSS then adds an account in the HSS, in which the account is provided with the subscriber information, i.e. the current IP-address of the subscriber, at least one of the IMSI and MSISDN of the subscriber, and at least one of the IMPI and IMPU of the subscriber. The account added in the HSS is a temporary account. The status of the account may be stored in the provisioning system, e.g. by storing the status of the subscriber as temporary subscriber in the auto-provisioning database of the provisioning system.

Subsequently, actions 308 and 309 will be performed, actions which are similar to actions 105 and 106 described with reference to FIG. 1.

FIG. 4 depicts a communication diagram of a further aspect of a method of provisioning an entry in a subscriber database of an IMS according to an embodiment of the invention. The actions schematically depicted in the communication diagram relate to actions that may follow up on actions performed in accordance to the method described with reference to FIG. 3. Hence, the method described with reference to FIG. 4 departs from the situation in which the UE has received a PDP-context message that IMS-registration is possible.

Actions 311, 312 and 313 relate to the UE registering following the Session Initiation Protocol (SIP) with the GGSN, the Proxy Call Session Control Function (P-CSCF) of the IMS, and the Interrogating Call Session Control Function (I-CSCF) of the IMS, respectively. Note that, in case the UE transmits an IP packet with a source IP-address different to the one assigned by the GGSN during PDP context activation transmission of this IP packet will be impossible, because the GGSN is arranged to detect this so-called IP address spoofing.

Subsequently, the I-CSCF may check with the HSS whether a subscriber account with the IMPI and IMPU mentioned in the registration message exists or not. The HSS may respond in the affirmative or negative, and may also provide information to the I-CSCF regarding the location of the S-CSCF for that subscriber. Furthermore, IFC stored in the HSS

associated with the respective subscriber may be forwarded to the I-CSCF as well. The interaction between I-CSCF and HSS is schematically denoted as action 314.

If the location of the S-CSCF for the subscriber is known, in action 315, a SIP- registration request will be send to a Serving Call Session Control Function (S-CSCF) of the IMS. Furthermore, subscriber information including IFC may be forwarded for storage in the S-CSCF.

In action 316, the S-CSCF informs the UE that registration has succeeded.

Subsequently, in action 317, a registration request is forwarded to the LAS because the LAS is mentioned in the IFC as destination.

In action 318, the LAS informs the APU that a service request for an IMS-service has taken place. The APU now knows that the subscriber is an IMS-user.

Preferably, in action 319, the APU provisions the application server system with information associated with the subscriber as a permanent user. That is, the APU informs the AS that the subscriber has become an IMS-user. As a result, the AS may provision the application database communicatively connected thereto, to be ready for IFC-amendments. Action 319 may result in a limitation of the number of accounts in the application database..

In action 320, the APU sends a provisioning request to the HSS with respect to the subscriber. The provisioning request comprises subscriber information. The subscriber information may include new IFC, as more services may become available because the subscriber has become an IMS-user.

The HSS, in action 321, upon receipt of the request for provisioning the subscriber, updates the account in the HSS. The status of the account now is a permanent account. The status is then stored in the provisioning system, e.g. by storing the status of the subscriber as permanent subscriber in the auto-provisioning database of the provisioning system.

Then, in action 322, the HSS sends a confirmation of receipt of the provisioning request to the APU.

The APU, in action 323, upon receipt of the confirmation of receipt of the provisioning request, updates its subscriber entry with respect to the subscriber such that in case of future authentication requests, described as action 304 with reference to Figure 3, the APU will identify the subscriber as an IMS-user. Furthermore, the APU may provision updated information related to applications that may be performed by certain subscribers to the application database of the AS, e.g. application database 219 shown in FIG. 2.

Finally, in action 324, the HSS may forward updated IFC to the S-CSCF, such that a subscriber as IMS-user may now be able to use IMS-services available through the AS in a conventional way.

FIG. 5 depicts a communication diagram of another aspect of a method of provisioning an account in a subscriber database of an IMS according to an embodiment of the invention. The actions depicted in the communication diagram of FIG. 5 relate to the situation in which a subscriber has a status as temporary subscriber for a time exceeding a predetermined threshold value. The time associated with the predetermined threshold value is generally shorter than the predetermined period for periodically removing unused accounts .

In action 501, the APU determines whether subscriber status entries related to temporary users are in existence for a period exceeding the predetermined threshold value or not. This determining may be performed periodically or may be performed on the basis of a timer initiated upon creation of the respective subscriber status entry.

If this determining reveals that the time lapsed from initiating the subscriber status entry related to a temporary account in the HSS exceeds aforementioned predetermined threshold value, and no registration to an IMS-service has taken place, the APU sends, in action 502, a request for removal of the account with respect to the respective subscriber to the HSS.

Upon receipt of the request for removal of the account, the HSS, in action 503, executes the request. That is, the account with respect to this subscriber is removed from the HSS.

Subsequently, in action 504, the HSS sends a message to the APU that the account of the subscriber has been removed in accordance with the request sent in action 502.

Finally, upon receipt of confirmation of removal from the HSS, the APU, in action 505, removes the subscriber status entry from the auto-provisioning database. Hence, checking of the status in case the APU receives an accounting request start message regarding the subscriber in the future will reveal that the subscriber is not known as an IMS user and no account with respect to the subscriber is present in the HSS.

The invention has been described by reference to certain embodiments discussed above. It will be recognized that these embodiments are susceptible to various modifications and alternative forms well known to those of skill in the art.

In the application, reference is made to a RADIUS. As will be understood by a person skilled in the art, instead of a RADIUS, alternative systems with similar functionality may be used as well. Such systems include systems in which an authentication request is forwarded to the APU in a modified way.

Embodiments of the method as described in this application may be stored in a suitable way on a computer readable medium. As will be understood by a person skilled in the art, such a computer readable medium, when executed by a processor, is able to perform embodiments of the method of provisioning an entry in a subscriber database of an IP multimedia subsystem.

Abbreviations

3GPP 3 ^rd Generation Partnership Project

APU Auto-Provisioning Unit

AS Application Server

GGSN Gateway GPRS Support Node

GPRS General Packet Radio Service

HSS Home Subscriber Server

I-CSCF Interrogating Call Session Control Function

IFC Initial Filter Criteria

IMPI IP Multimedia Private Identity

IMPU IP Multimedia Public Identity

IMS IP -based Multimedia Subsystem

IMSI International Mobile Subscriber Identity

IP Internet Protocol

LAS Limited services Application Server

LDAP Lightweight Directory Access Protocol

MS-ISDN Mobile Station ISDN Number

MVNO Mobile Virtual Network Operator

ODS Operational Data Store

P-CSCF Proxy Call Session Control Function

PDP Packet Data Protocol

RADIUS Remote Authentication Dial In User Service

S-CSCF Serving Call Session Control Function

SIM Subscriber Identity Module

SIP Session Initiation Protocol

UA User Agent

UE User Equipment