Patent Description:
The SBI capable HSS offers the following services via the Nhss_ims interface:.

Nhss_imsUEContextManagement Service:
For the Nhss_imsUEContextManagement service the following service operations are defined:.

IMS restoration procedures are specified in 3GPP TS <NUM>.

The Nhss_imsUEContextManagement Service is used by Consumer NFs (I-CSCF/S-CSCF) to:.

For the Nhss_imsSubscriberDataManagement service the following service operations are defined:.

The Nhss_imsSubscriberDataManagement Service is used by Consumer NFs (S-CSCF, IMS-AS) to subscribe to notifications relevant to the consumer NF. In particular, it may be used to subscribe individually (per UE) to notifications relevant to the consumer NF for serving the UE, such as notifications due to changes to a user profile (e.g. IMS profile) of the UE.

Each subscription is characterized by subscription data. The subscription data comprise typically:.

The Nhss_imsSubscriberDataManagement Service may be further used by I-CSCF to retrieve S-CSCF capabilities or the assigned S-CSCF, from the SBI capable HSS by means of the Get service operation.

If the consumer NF supports the feature "sharedData", the retrieved individual subscription data for the UE may contain shared data identifier identifying additional parts of subscription data shared by several UEs. If so, the Nhss_imsSubscriberDataManagement Service is also used by Consumer NFs to retrieve shared subscription data from the HSS by means of the Get service operation.

A UE registers at S-CSCF by two registration steps. A first registration step (shown in <FIG>, taken from 3GPP TS <NUM>) to authenticate the UE, and a second registration step to register at the S-CSCF.

The SBI between S-CSCF and HSS is based on HTTP requests (PUT, POST, GET, PATCH, etc.). HTTP responses numbered as 2XX (i.e. <NUM>. <NUM>) mean that the HTTP request was successful.

Further cited prior art documents are <CIT> showing a method for reassignment of S-CSCF services to registered IMS users of a home subscriber servers HSS and <CIT> showing a transmitting authentication information.

It is an object of the present invention to improve the prior art.

According to a first aspect of the invention, there is provided an apparatus according to claim <NUM>.

According to a second aspect of the invention, there is provided a method according to the respective claim.

The method of the second aspect may be a method of restoring.

According to a third aspect of the invention, there is provided a computer program product comprising a set of instructions which, when executed on an apparatus, is configured to cause the apparatus to carry out the method according to the second aspect. The computer program product may be embodied as a computer-readable medium or directly loadable into a computer.

According to some embodiments of the invention, at least one of the following advantages may be achieved:.

Further details, features, objects, and advantages are apparent from the following detailed description of embodiments of the present invention which is to be taken in conjunction with the appended drawings, wherein:.

Herein below, certain embodiments of the present invention are described in detail with reference to the accompanying drawings, wherein the features of the embodiments can be freely combined with each other unless otherwise described. However, it is to be expressly understood that the description of certain embodiments is given by way of example only, and that it is by no way intended to be understood as limiting the invention to the disclosed details.

HSS and UDM may be considered as synonyms in the present application, unless otherwise indicated. They are examples of a user data repository.

In Service Based Interface reference model, S-CSCF Registration, S-CSCF Restoration and S-CSCF Subscription towards Nhss are done separately in the following sequence:.

Assume the following scenario: After a successful registration of a UE at S-CSCF, S-CSCF processes have to restart, or the registration info is lost somehow. The S-CSCF gets any request for that subscriber (say SUBSCRIBE or INVITE). This request leads to restoration of registration Info from UDM. Restoration info is information required for the S-CSCF to handle traffic for a registered user. S-CSCF instructs UDM to store the restoration information.

As per 3GPP TS <NUM> V16. <NUM>, the restoration procedure defines only restoration of registration related information for a subscriber but the restoration information does not comprise any subscription data (in particular: ImsSdmSubscription data), such as subscriptions upon registration. In Section <NUM>. <NUM>, Restorationlnfo does not have any fields for restoring the ImsSdmSubscription data.

As Subscription to notifications on changes of data in the HSS (e.g. IMS SDM Data) is not restored at S-CSCF, it does not know about the active subscriptions it has done during or after the registration time, but UDM will have the subscriptions in active state.

As one option to maintain the same subscriptions even after the subscription data are lost at S-CSCF, S-CSCF may re-trigger the subscription (i.e. subscribe again to the same notification). However, this will be an extra subscription in UDM and the earlier subscription would be stale and it has to be cleared up after expiry.

The subscription considered here may be individual for a UE, for a group of UEs, or general (independent from any UE). As an example for a subscription individual for a UE, a subscription to notifications triggered by changes of IMS SDM Subscriber level data may be considered.

The problem is shown in the message flow of <FIG> is a pictorial representation of the problem described above. For simplicity sake, the message flows of <FIG> start after successful "Authenticated REGISTER" (shown in <FIG>).

However, the restoration info does not comprise any ImsSdmsubscription data. Potentially, S-CSCF may subscribe to the same notifications again. However, in this case, the previous subscriptions are still active on the HSS until they expire, without any use.

Some example embodiments of the invention provide a solution to solve the lack of subscription data at S-CSCF after they are lost (e.g. due to a process restart) in spite of the existing restoration procedure. The subscription data may be for a subscriber, but they may be for a group of subscribers or independent from a subscriber, too.

In UE IMS registration flow, typically after successful update of scscf-registration & scscf-restoration-info (through PUT request) in UDM, for that subscriber, S-CSCF performs one or more subscriptions for the UE. Once this is successful, S-CSCF has both registration info and subscription data for the subscriber.

According to some example embodiments of the invention, Restoration Info comprises an extra attribute(e.g. named imsSdmSubscriptions), so that S-CSCF is able to restore both registration info and subscription data during restoration. As an example, the extra attribute might be added as in the Table <NUM>:.

The extra attribute (named e.g. imsSDMSubscription) comprises a map of <NUM> to N entries with the subscriptionld as a key, and the values comprises at least one of.

Subscription ID is the URI of the created resource for the subscription in Nhss/UDM. Typically, each entry in the map comprises all the values which characterize the subscription. However, in some cases, S-CSCF may replace one or more of the values by a default value. In such cases, the respective value need not be present in the Restoration Info.

The addition of the new attribute might be reflected in a modification in the API as defined in the 3GPP standard, as shown in Table <NUM>:
<IMG>.

Whenever S-CSCF gets restarted or lost registration info and the S-CSCF receives a request for the subscriber (e.g. SIP INVITE), it triggers restoration procedure from UDM. As the restoration information stored in UDM has both registration info and subscription data for that UE (identified e.g. by IMPU) both will be restored by S-CSCF.

Once restoration is complete, S-CSCF may modify the subscription using PATCH Operation with one or more of the following parameters:.

Typically, the PATCH operation comprises at least the first three of these parameters.

In this way, subscriptions including individual subscriber's (user's) IMS SDM subscription will be maintained in UDM and still be used after the subscription information was lost in S-CSCF. In this process, subscription data for groups of UEs or independent from any UE may be restored, too. As an alternative or in addition, S-CSCF may run an additional process (e.g. periodically or triggered by a process restart) to restore subscriptions not being related to an individual user.

The following description of some solutions according to some example embodiments of the invention is related to subscriptions to notifications triggered by changes of IMS SDM Subscriber Level data. They are typically specific to a UE. However, the invention is not limited to IMS SDM Subscriber Level data. It may be applied to any data stored in the user data repository, independent of whether they are related to one user, a group of users, or not at all user related.

In UE IMS registration flow, after successful scscf-registration & scscf-restoration-info (through PUT request) in UDM (or an update thereof), for that subscriber, S-CSCF performs subscription for UE and/or shared data (i.e. subscribes to notifications caused by changes of UE data and/or shared data). Once this is successful, S-CSCF has both registration info and subscription data for that subscriber.

Solution <NUM> is shown in <FIG>. The message flow starts after successful "Authenticated REGISTER" (shown in <FIG>). Messages <NUM> to <NUM> are the same as those described with respect to <FIG>. Messages <NUM> and <NUM> correspond to messages <NUM> and <NUM> of <FIG>.

Solution <NUM> is shown in <FIG>. The message flow starts after successful "Authenticated REGISTER" (shown in <FIG>). Messages <NUM>, <NUM>, <NUM>, and <NUM> are the same as those described with respect to <FIG>. Message <NUM> correspond to messages <NUM> of <FIG>. While according to solution <NUM>, S-CSCF stores the restoration info twice in HSS (messages <NUM> and <NUM> of <FIG>), according to solution <NUM>-CSCF stores the restoration info only once in HSS (message <NUM> of <FIG>).

<FIG> shows an apparatus according to an example. The apparatus may be a call session control function such as a S-CSCF, or an element thereof. <FIG> shows a method according to an example. The apparatus according to <FIG> may perform the method of <FIG> but is not limited to this method. The method of <FIG> may be performed by the apparatus of <FIG> but is not limited to being performed by this apparatus.

The apparatus comprises means for instructing <NUM>, means for monitoring <NUM>, means for getting <NUM>, and means for restoring <NUM>. The means for instructing <NUM>, means for monitoring <NUM>, means for getting <NUM>, and means for restoring <NUM> may be an instructing means, monitoring means, getting means, and restoring means, respectively. The means for instructing <NUM>, means for monitoring <NUM>, means for getting <NUM>, and means for restoring <NUM> may be an instructor, monitor, getter, and restorer, respectively. The means for instructing <NUM>, means for monitoring <NUM>, means for getting <NUM>, and means for restoring <NUM> may be an instructing processor, monitoring processor, getting processor, and restoring processor, respectively.

The means for instructing <NUM> instructs a user data repository to store subscription data (S10). The subscription data comprise information on a notification from the user data repository to which a call session control function (e.g. S-CSCF) subscribed by a subscription. For example, the subscription data may comprise information used to create a notification from the user data (user profiles). However, in general, the subscription data may comprise information used to create a notification from any data stored in the user data repository. Typically, the call session control function instructs the user data repository to store subscription data. However, in an alternative option, the user data repository stores the subscription data for restoring of the S-CSCF once it created the subscription.

The means for monitoring <NUM> monitors whether the call session control function has an indication that the call session control function might have lost the subscription data (S20). For example, if the call session control function lost the registration info for a user, it is an indication that the call session control function might have lost the subscription data. As another option, the means for monitoring may monitor if certain processes have to restart. Such a restart may be considered as the indication that the call session control function might have lost the subscription data. As still another option, the operator may input such an indication. As yet another option, the means for monitoring may assume periodically that the call session control function might have lost the subscription data.

It is not necessary that the call session control function actually has lost the subscription data. For example, even if the call session control function lost the registration info, it might not have lost the subscription data. Also, the call session control function might not have subscribed to any notifications. Thus, it cannot have lost any subscription data.

If the call session control function has the indication that the call session control function might have lost the subscription data (S20 = yes), the means for getting <NUM> gets the subscription data from the user data repository for the call session control function (S30). Then, the means for restoring <NUM> restores the subscription data at the call session control function according to the subscription data got from the user data repository (S40). , the call session control function may use the subscription data as if they were never lost.

<FIG> shows an apparatus according to an example. The apparatus comprises at least one processor <NUM>, at least one memory <NUM> including computer program code, and the at least one processor <NUM>, with the at least one memory <NUM> and the computer program code, being arranged to cause the apparatus to at least perform at least the method according to <FIG> and related description.

Claim 1:
Apparatus comprising:
one or more processors (<NUM>), and
memory (<NUM>) storing instructions that, when executed by the one or more processors, cause the apparatus to:
instruct (S10) a user data repository to store IMS SDM subscription data, wherein the IMS SDM subscription data comprise information on a notification from the user data repository to which a call session control function subscribed by a subscription and a subscription identifier of the subscription and at least one of:
• an instance identification of the call session control function;
• a callback reference for the notification;
• an identification of a resource of the user data repository for which a change triggers the notification; and
• an expiry time of the subscription;
get (S30) the IMS SDM subscription data from the user data repository for the call session control function if the call session control function has an indication that the call session control function might have lost the IMS SDM subscription data;
restore (S40) the IMS SDM subscription data at the call session control function according to the IMS SDM subscription data got from the user data repository.