EP2301223A1

EP2301223A1 - Switching center with presence information detecting unit

Info

Publication number: EP2301223A1
Application number: EP09761526A
Authority: EP
Inventors: Andreas Witzel; Joerg Christian Ewert; Karl-Peter Ranke
Original assignee: Telefonaktiebolaget LM Ericsson AB
Current assignee: Optis Wireless Technology LLC
Priority date: 2008-06-10
Filing date: 2009-01-29
Publication date: 2011-03-30
Also published as: WO2009149963A1

Abstract

The invention relates to enhanced switching center (320) detecting presence information of the user and providing the presence information of the user to a presence server (200). The switching center can take over the role of a presence user agent or of a presence network agent.

Description

Switching center with presence information detecting unit

Technical field

This invention relates to a switching center of a cellular network providing presence information and to a method for providing presence information of a user in a cellular network to a presence service entity.

Background

3GPP TS 23.292 specifies the architectural requirements for delivery of consistent IMS (IP Multimedia Subsystem) services to the user regardless of the attached access type (e.g. circuit switched (CS) domain access, or IP-CAN).

Consideration is given to how to access IMS-based multimedia telephony services while still allowing innovative services.

The solution is applicable for user entities (UE's) with or without ICS functionality, and is applicable for the following deployment scenarios:

- An operator who supports for its subscribers only UEs that have ICS functionality

- An operator who supports for its subscribers only UEs that do not have ICS functionality

- An operator who supports for its subscribers UEs which do and do not have ICS functionality (to different subscribers and the same subscribers) ensuring the coexistence of UEs that have and do not have ICS functionality. In Fig. i an architecture view for IMS centralized services and the related reference points are shown. ICS enables IMS services when using circuit switched access for media transport. A user entity 100 accesses a Mobile Switching Center (MSC) Server no via a 2G/3G access 120. An IM Mediagateway (IM-MGW) 130 is connected to the MSC Server 110. An ICS application server 140 is used providing functions specific to IMS centralized services. A CSCF (Call Session Control Function) unit 160 is a component of the IP Multimedia Subsystem controling the connection of the user entity 100 and establishes multimedia sessions for the user entity 100.

It may now occur the situation that user entity 100 is not ICS-enabled.

3GPPTS 23.141 specifies the presence service which provides the ability for the home network to manage presence information of a user's device, service or service media even whilst roaming. A user's presence information may be obtained through input from the user, information supplied by the network or information supplied by elements external to the home network. Consumers of presence information, i.e. watchers, may be internal or external to the home network.

In Fig. 2 the generic reference architectural model for providing presence service is shown. A presence service entity 200 comprises a presence server 210 contained in a home network of a mobile user entity subscribing to a cellular network which can receive presence information from different resources. Information about the presence of a mobile user entity may be received from a presence network agent 290 receiving information from various network nodes, such as the Mobile Switching Center server (MSC server). When the information is received from the MSC Server the Pc Interface is using a CAMEL (Costumized Application for Mobile Network Enhanced Logic) mechanism for information retrieval. A Pen Interface can be used to forward the information to the presence server 210. Furthermore a presence information may be provided by the user through a presence user agent 280, the presence user agent being the element that collects and sends user related presence information to the presence server 210. Here the capability of the Ut Interface may be reused. The Peu Interface may be used to forward the information to the presence server 210. Furthermore it is possible that presence information is provided to the presence server from outside the network through the presence external agent 270 using the Pex Interface.

A Presentity presence proxy 220, presentity being a combination of the expressions "presence" and "entity", is a functional entity providing the presentity-related functionality such as determining the presence server associated with a presentity. A watcher presence proxy 240 describes the entity that provides watcher related functions such as authentication of watchers, a presence list server 260 being the functional entity storing grouped lists of watched presentities and enabling a watcher application to subscribe to the presence of multiple presentities using a single transaction. Furthermore watcher applications 250 are provided.

Presentity usually refers to a person and describes availability and willingness of this person to communicate via a set of communication services.

Pep and Pen refer to the RFC 3863 for support of transport of presence information under the PIDF (Presence Information Data Format). In addition, Pep provides mechanisms for the presence user agent to obtain information on watcher subscriptions to the presentity's presence information. When a user entity provides presence information to the presence server, the user entity informs the proxy CSCF (P-CSCF), the proxy CSCF informing also the server CSCF (S-CSCF) which evaluates initial filter criteria. The S-CSCF then informs the presence server which publishes the authorisation and acknowledges the received presence information back to the user entity.

The reference point presence network agent-MSC server /VLR Pc allows the MSC server/VLR to report the mobility management related events to the network agent, such as attach, detach, location area update, and may allow the MSC server/VLR to report call-related events such as call set-up with the bearer information and call release. This reference point may allow the MSC server/VLR to report mobility states such as detached, idle and connected and call states such as busy with bearer information and idle.

This reference point is implemented using the existing mechanisms of CAMEL phase 4, 3GPP Release 5.

Refering to the architecture for presence, it becomes clear that the network provided information is not affected by the support of ICS. So the CAMEL implementation in the ICS-enhanced MSC server can still be used for providing presence information.

The Pep and Peu Interface are usually direct packet interfaces from the user agent in the terminal to the presence infrastructure. Assuming that even non-ICS terminals support direct packet communication, this interface is in theory fully available for ICS subscribers using non-ICS-enabled terminals.

However, there are a number of practical limitations that make the Pep and the Peu interface unreliable. The availability of the packet switched interface in a terminal depends on the radio technology supported in the network. Parallel circuit switched and packet switched bearers are supported for UTRAN radio access. For GSM radio access this requires either Class A terminals or DTM support in the RAN and the terminal. The latter ones are not supported in any of todays radio networks.

The reliability of the packet switched interface furthermore depends on the radio capabilities of the terminal. For GSM radio access this requires either class A terminals or DTM support in the RAN and the enter terminal. There are no class A terminals available and only very few DTM terminals.

As a consequence in case of GSM radio access the Pep and Peu Interfaces are not available during an ongoing call but only outside a call. Since GSM radio is still the predominant radio technology today, the presence information from the user agent in the terminal is not reliable. This limits the usage and success of presence service.

Another problem is the information limit of the Pc interface. The 3GPP TS 23.141 reuses the CAMEL capability to provide network-based presence information. This means that presence information can only contain information available in CAMEL which also depends on the support level of CAMEL. Since the CAMEL- standardisation has come to an end it is very unlikely to get new information into CAMEL to improve the presence information in level of detail.

Summary

Accordingly a need exists to provide a possibility to reliably provide presence information when no parallel packet and circuit switched data transfer is possible.

This need is met by the features of the independent claims. In the dependant claims preferred embodiments of the invention are described.

According to a first aspect of the invention a switching center of a cellular network is provided comprising a presence information detecting unit detecting a presence information of a user. The switching center furthermore comprises an interface to the presence service entity providing the presence information of the user to said presence service entity. According to this aspect of the invention an ICS-enhanced switching center is used providing presence information. The switching center can provide the presence information the user entity is not able to provide in case of a non-ICS-enabled user entity.

According to one embodiment of the invention the presence information detecting unit detects user-related information, the interface comprising a first interface providing the user related presence information to the presence service entity.

According to this aspect of the invention the ICS-enhanced server is used to complement the user agent provided presence information during an ongoing call for ICS subscribers roaming in GSM radio accesses.

Preferably the switching center comprises a call status determination unit adapted to determine a call status of that user wherein the presence information detecting unit detects the presence information of said user when the call status determination unit has determined an established call for that user. When an established call is detected for a user using a non ICS-enabled terminal or being located in a network where parallel circuit switched and packet switched data transmission is not possible, the switching center takes over the role of the presence user agent providing the presence information to the presence server. The switching center may be a mobile switching center controlling the calls for mobile user entities. However the switching center may be any call control node controlling calls of a mobile user entity.

Furthermore a transmission status determination unit may be provided determining whether, for that user packet switched and circuit switched data transmission is possible in parallel. When the transmission status determination unit determines that no parallel transmission of packet switched and circuit switched data is possible the presence information detecting unit detects the presence information and the first interface provides the presence information to the presence service entity. More specifically when the transmission status determination unit determines that no parallel transmission of packet switched and circuit switched data is possible the presence information detecting unit takes over the role of the presence user agent, and the first interface provides the presence information to a presence proxy of the presence service entity. The call status determination unit and the transmission status determination unit help to determine when the switching center should take over the role of the presence user agent. When an established call is detected and when no parallel transmission of circuit and packet switched data is possible the switching center provides the presence information to the presence user entity.

According to another aspect of the invention the presence service detecting unit detects network related information of the user, the interface comprising a second interface providing said network related presence information of the user to the presence server of the presence service entity. According to this aspect of the invention the ICS-enhanced switching center complements the network agent provided presence information for all ICS subscribers beyond what is available today by CAMEL. Instead of using CAMEL, the CAMEL provided presence information can also be directly provided by the ICS- enhanced switching center to the presence server. This simplifies the handling and minimizes network resource usage. According to this aspect of the invention the Pen Interface is extended such that it can directly be served by the switching center.

By way of example, the presence information detecting unit may take over the role of the presence network agent, the second interface directly providing the network related presence information to the presence server.

According to another aspect of the invention, a method for providing presence information of the user to the presence service entity is provided, in which the switching center detects the presence information of the user and provides the detected presence information to the presence service entity.

According to one embodiment of the invention user related presence information may be detected by the switching center and may be transmitted to the presence service entity via a first interface. Additionally a call status of the user can be determined and when an established call for said user has been determined the presence information is detected and provided to the presence service entity by the switching center. Furthermore it is possible that the call status of that user is determined and when an established call of said user has been determined the presence information is detected and provided to the presence service entity by the switching center.

Additionally it may be determined whether packet switched and circuit switched data transmission is possible in parallel, wherein if this is not the case, the presence information is detected and provided to the presence service entity by the switching center, meaning that the switching center takes over the role of the presence user agent providing the user related information to the presence proxy of the presence service entity. When an established call of a user is finished the switching center terminates to provide presence information. Further the switching center may determine a busy or idle condition of the user and may provide this information about the busy or idle condition to the presence service entity. When a network related presence information is detected, the network related presence information can be transmitted to the presence service entity via the second interface. By way of example for network related presence information the switching center may determine a location information of the user and may transmit the location information to the presence service entity,

Brief description of the drawings

The invention, as well as a preferred mode of use, further objectives and advantages thereof, will be understood by reference to the following detailed description of illustrative embodiments when read in conjunction with the accompanying drawings, wherein

Fig. i shows the known ICS architecture,

Fig. 2 shows the known presence information related architecture,

Fig. 3 shows the architecture of a switching center enhanced with an ICS feature according to the invention,

Fig. 4 shows a schematically view of the enhanced switching center of Fig. 3,

Fig. 5 shows a flow chart containing the steps how the switching center works for determining whether it should provide presence information or not,

Fig. 6 shows a flow chart in case of an originating call request the switching center taking over the role of the presence user agent,

Fig. 7 shows a flow chart comprising the steps in case of a terminating call request, Fig. 8 shows a flow chart comprising the steps when the switching center publishes the idle condition of the subscriber,

Fig. 9 shows a flow chart comprising the steps when one subscriber decides to take over the costs of the entire session,

Fig. io shows a schematic view of an ICS-enhanced mobile switching center server extending the Pen Interface,

Fig. ii shows a flow chart comprising the steps of an presence attribute indicating that the user is at home or not,

Fig. 12 shows a flow chart comprising the steps where the watchers are informed of the presence of the user at home.

Detailed description of preferred embodiments

In Fig. 3 a schematic view of the architecture is shown with which a presence information can be updated even when the mobile user entity, here the legacy user entity 340, cannot transmit circuit switched and packet switched data in parallel. An enhanced mobile switching center server 320 provides presence information and is called eMSC-S. In the embodiment shown it supports a radio interface to the user entity 340 which is assumed not to be updated with ICS functions. For session control the eMSC server 320 uses the session and bearer control interface towards an IMS 310 (IP Mulitmedia Subsystem). In the user plan the user entity 340 is connected via a media gateway 330 to the IMS 310. The user entity further has a packet switched radio access via the packet switched Pep interface to a presence service entity 200. The presence service entity 200 and an ICS (IMS centralized service) application server 350 interface the IMS core via an ISC interface. According to the invention an ICS Pep Interface between the eMSC server 320 and the presence service entity 200 is provided supplying information to the presence service entity when a call is established for the user entity 340. The eMSC server 320 is shown in Fig. 4 in more detail. The eMSC server 320 comprises a call controller 321 controlling the call of the user entity 340. A call status determination unit 322 is provided which is adapted to determine a call status of the user. A presence information detecting unit 323 detects a present information of the user of the user entity 340 and a transmission status determination unit 324 determines whether, for that user, packet switched and circuit switched data transmission is possible in parallel. Two interfaces 325 and 326 represent the interface towards the present service entity 200. As will be explained in more detail further below, the first interface may be used to provide user related presence information to the presence service entity whereas second interface 326 is used to provide network related presence information to the presence service entity. In the embodiment shown the two interfaces 325 and 326 are designed as two seperate units. However, it should be understood that these two units may also be incorporated to one physical unit together with one of the other units provided in the switching center, the different functions being obtained by an appropriate processing unit and by providing instructions to the processing unit by software.

In connection with Figs. 5 to 9 embodiments are described in which the MSC server 320 takes over the role of the presence user agent providing presence information of the user. In Fig. 5 the provision of user related presence information by the MSC server is shown in more detail. In the flow chart the method shown starts in step 50 and in step 51 it is detected that a terminating call or originating call has to be established for the user entity 340. When the eMSC server 320 has to establish the call it checks the capabilities of the terminal and the radio technology used to communicate with the terminal by checking whether a packet switched connection is possible in parallel to the circuit switched connection (step 52). By way of example this may also be derived from operator preferences (by static O and M setting). If a packet switched connection is possible in parallel no further action is taken and the method ends in step 53. If, however, no parallel packet switched connection is possible the eMSC server 320 takes over the role of the presence user agent for the duration of the call (step 54). When the established call is terminated in step 55 the eMSC server 320 terminates the presence information supply via the Pep Interface 56, the method ending in step 57. In the following examples shown in Figs. 6 to 9 more detailed examples of the above logic for different traffic cases are discussed. Please note that the flows are simplified in order to focus on the main aspects of the invention. In Fig. 6 an originating call request is discussed in more detail, originating from a non-ICS user entity. In steps 1 to 10 of Fig. 6 the originating session is established towards a B-Party meaning that in a first step a setup message is sent from the user entity to the eMSC server. The eMSC server transmits an SIP invite messge to the CSCF where an IMS service control is initiated as shown in step 3 of Fig. 6. A SIP invite message is then transmitted to the B-Party which sends the OK message back to the user entity. In steps 5 to 7 the user entity is sending an connection acknowledgement message to the eMSC server in step 8. After that the eMSC server determines that it has to take over the role of the presence user agent (step 9). As a consequence the eMSC server transmits the information that the user entity is busy to the CSCF in step 10 from where the information is transmitted to the presence server in step 11. On the presence server the presence information is updated (step 12) and the watchers are informed in step 13, an OK message being sent back from the presence server via the CSCF to the eMSC server in steps 14 and 15 of Fig. 6. As can be seen from Fig. 6, when a connection between the two parties has been established, the eMSC server detects this information and starts to provide presence information to the presence server.

In Fig. 6 the call request was initiated by the user entity whereas in the embodiment shown in Fig. 7 the B-Party initiates the call request resulting in a terminating call request in view of the user entity 340. In steps 1 to 12 of Fig. 7 a terminating session is established from the B-Party to the non ICS-enhanced user entity. Steps 1 to 12 are known to those of ordinary skill in the art and are therefore not discussed in detail. When the OK message has been sent from the eMSC server 320 to the Party B in steps 10 to 12 the eMSC determines that it has to take over the presence user agent role (step 13). The eMSC server then informs the S-CSCF that the user entity is busy (step 14), the latter transmitting the updated information to the presence server in step 15. In step 16 the presence server can update its presence information and can inform the watchers in step 17 before OK messages are sent to the S-CSCF and from the latter to the eMSC server in step 19. The next example shown in Fig. 8 shows the situation at the end of an ongoing session. In case a user entity terminates a call the disconnection message is sent from the user entity to the B-Party in steps i to 3. In step 4 the CSCF takes over the IMS service control. In steps 5 to 7 the OK message is sent back to the user entity wherein the eMSC server releases the user entity in step 7, the user entity informing the eMSC of the release complete in step 8. After the release the packet switch connection is restored. As a consequence the eMSC can suspend to handle the PUA role since the packet switched connection is about to be restored. The eMSC then publishes the idle condition of the subscriber (steps 10,11) the presence server updating the presence information about the idle condition and informing the watchers in step 13 of the idle condition. In steps 14 and 15 an OK message is sent back to the eMSC server.

In addition to the traffic cases discussed above also mid-call services and activities of the subscriber which affects the presence attributes are reported to the presence server as will be discussed in connection with Fig. 9. As an example to illustrate the mechanism of mid-call handling a charging related service is discussed in more detail. The idea of this charging-service is to give the subscriber the possibility to take over the costs of a session. As shown on Fig. 9 a session is going on and Party A decides to pay for the entire session or conference call. Party A can decide either to take over the costs for the entire sessions or from a certain point in time onwards until the end of the session. This can also be used for conference sessions so the presence information may be updated to indicate that the served subscriber is running a conference and that admittance to this conferences is free. At a certain point in time the subscriber decides to take over the costs of the entire session or conference (step 1). This can be indicated to the eMSC server by using USSD mechanisms, and forwarded to the IMS domaine using SIP options or any equivalent method (step 2). In step 3 the CSCF takes over the IMS service control and transfers the session costs to subscriber A. CSCF sends an acknowledgement back to subscriber A in steps 4 and 5. As discussed above the eMSC server has presently the role of the presence user agent as an established call has been detected for said user. Accordingly it has to update the presence server accordingly. In step 6 and 7 the new payment situation is transmitted from the eMSC server to the presence server, in step 8 the presence server updating the information who is paying for the ongoing session. In step 9 the watchers are informed accordingly, and last but not least in steps io and ii an OK message is sent back to the eMSC server.

The mechanism that the MSC server acts as presence user agent in the case the user entity is busy can also be used for other services. One additional example is to provide location information to network-based applications.

So if the user entity is idle, it provides location information related presence information directly via the packet switched connection. This location information can be based on the cell in which the user entity is currently located since the information on the current cell is available in the user entity, and the user entity based presence user agent can use this information to keep the presence information and the presence server up to date.

However, if the user entity is busy in GSM circuit switched network without DTM, then the MSC server provides the cell information as presence user agent because for ongoing calls the MSC server holds the mobility info on cell level. The MSC server is informed by BSSMAP handover performed message about cell change within BSC (Based Station Controller) or about external handover with handover required message. Accordingly the invention can be used to keep the presence information on a consistent accuracy level also during ongoing calls.

In Fig. io an embodiment is shown with which the eMSC can provide network related information to the presence service entity. The architecture of this embodiment is very similar to the one shown in Fig. 3 so that a detailed discussion of entities already discussed in connection with Fig. 3 is omitted. In the embodiment shown in Fig. 10 the eMSC server 320 is used to extend the Pen Interface such that it can directly be served by the eMSC. As shown in Fig. 10 a Pen Interface exists between the eMSC server 320 and the service entity 200. This Pen Interface complements the Pep Interface which is directly served by the user entity. In connection with Figs. 11 and 12 an example of presence attribute is shown in more detail. In the embodiment shown in presence attribute is called "I am home" and "I'm at work".

The user of this presence attribute has the possibility to mark a certain location with the attribute " I am at home" and another location with the attribute "I am at work". This can be done by using, for example, a pre-defined USSD string which the subscriber sends of a particular location which shall be marked. The eMSC server 320 then stores the current location area, the LAI or SAI, (location area indicator or surface area indicator) when the USSD string is received. As shown in Fig. 11 in case the user is located at a particular location he wants to mark as home location the USSD string is sent to the eMSC server in step 1 the eMSC server determining the current location (step 2). The eMSC server then monitors the roaming of the subscriber and each time the subscriber enters one of the stored location areas the eMSC server updates the present information towards the server to indicate "I am home" (step 3). In step 4 an USSD string (acknowledgement) is sent back to the user entity.

When the roaming of a subscriber is monitored as shown in Fig. 12 the MSC server checks each time whether the user entity has entered a marked area (steps 2 and 3). If this is the case, a location update acceptance message is sent to the user entity in step 4 and the information that the subscriber is at home is sent to the presence server in step 5, the latter updating the presence information and informing the watchers in step 6 and 7. In step 8 the OK message is sent back to the eMSC server.

Theoretically this service could also be realised by the user updating his own presence profile each time he comes home or enters work. But as this usually happens quite often it is very cumbersome to do so and is very likely forgotten. This would render the presence information unreliable. This service could also be realised using CAMEL mobility notifications. However, this consumes more network resources since CAMEL mobility triggers only support the reporting of every relocation update but not a location update into a specific area. Thus a seperate service mode would have to receive all notifications related to location update events and then filter out the ones into the home location area in order to achieve the same service behaviour. This would produce clearly much more load and is much more difficult to implement and run in a real network.

Summarizing, accurate presence information is obtained also when no packet switched connection is available. Furthermore the invention provides support for general, ICS access specific presence information.

Simpler service implementation is obtained since the presence information can be provided via the Pep Interface from the eMSC server instead of using complicated CAMEL network, and network resources. Furthermore it is possible to provide additional presence information which would not be available via CAMEL interfaces due to limitations on the interface.

Claims

CLAIM S

l. A switching center (320) of a cellular network comprising:

- a presence information detecting unit (323) detecting a presence information of a user,

- an interface (325, 326) to a presence service entity (200) providing the presence information of said user to said presence service entity (200).

2. The switching center according to claim 1, wherein the presence information detecting unit (323) detects user related presence information, the interface comprising a first interface (325) providing the user related information via a first interface to the presence service entity (200).

3. The switching center according to claim 1 or 2, further comprising a call status determination unit (321) adapted to determine a call status of said user, wherein the presence information detecting unit (323) detects the presence information of said user when the call status determination unit has determined an established call for said user.

4. The switching center according to any of the preceding claims, further comprising a transmission status determination unit (324) determining whether, for said user, packet switched and circuit switched data transmission is possible in parallel, wherein, when the transmission status determination unit determines that no parallel transmission of packet switched data and circuit switched data is possible, the presence information detecting unit (323) detects the presence information, the first interface (325) providing the presence information to said presence service entity (200).

5. The switching center according to claim 4, wherein, when the transmission status determination unit (324) determines that no parallel transmission of packet switched data and circuit switched data is possible, the presence information detecting unit (323) takes over a role of a presence user agent, the first interface (325) providing the presence information to a presence proxy (220) of the presence service entity (200).

6. The switching center according to any of the preceding claims, wherein the presence service detecting unit (323) detects network related information of said user, the interface comprising a second interface (326) providing said network related presence information of said user to a presence server (210) of the presence service entity (200).

7. The switching center according to claim 6, wherein the presence information detecting unit (323) takes over a role of a presence network agent, the second interface (326) directly providing the network related presence information to the presence server.

8. A method for providing presence information of a user in a cellular network to a presence service entity (200), comprising the steps of:

- detecting by a switching center (320) of the cellular network, a presence information of said user, and

- providing, by the switching center (320), the detected presence information to said presence service entity (200).

9. The method according to claim 8, wherein a user related presence information is detected by said switching center (320), said user related presence information being transmitted to the presence service entity via a first interface (325).

10. The method according to claim 8 or 9, further comprising the step of determining a call status of said user, wherein, when an established call of said user has been determined, the presence information is detected and provided to the presence service entity (200) by the switching center (320).

11. The method according to any of claims 8 to 10, further comprising the step of determing whether packet switched and circuit switched data transmission is possible for said user in parallel, wherein, when no parallel transmission of packet switched data and circuit switched data is possible, the presence information is detected and provided to the presence service entity (200) by the switching center (320).

12. The method according to claim 11, wherein when it is determined that no parallel transmission of packet switched data and circuit switched data is possible and when an established call has been detected for said user, the switching center (320) takes over the role of a presence user agent providing user related presence information to a presence proxy (230) of said presence service entity (200).

13. The method according to any of claims 8 to 12, wherein the switching center (320) terminates to provide presence information when the established call is terminated.

14. The method according to any of claims 8 to 13, wherein the switching center (320) determines a busy or an idle condition of said user and provides the information about said busy or idle condition to the presence service entity (200).

15. The method according to any of claims 8 to 14, wherein a network related presence information is detected by said switching center (320), said network related presence information being transmitted to the presence service entity (200) via a second interface (326).

16. The method according to claim 15, wherein the switching center (320) determines a location information of said user and transmits said location information to the location service entity.