WO2008077669A2

WO2008077669A2 - Access network change

Info

Publication number: WO2008077669A2
Application number: PCT/EP2007/061536
Authority: WO
Inventors: Markku Tuohino; Miikka POIKSELKÄ
Original assignee: Nokia Corporation
Priority date: 2006-12-22
Filing date: 2007-10-26
Publication date: 2008-07-03
Also published as: WO2008077669A3

Abstract

A device is described, which comprises a controller configured to detect an access network change of a transceiver capable of accessing at least two access networks, and to create access network change information indicating the access network change, and a sender configured to transmit the information regarding the access network change.

Description

TITLE OF THE INVENTION: ACCESS NETWORK CHANGE

BACKGROUND OF THE INVENTION

Field of the invention

The invention relates to a method as well as a network element and a mobile node by an access network change of the mobile node can be indicated.

Description of the related art

The invention relates to the multiple access used in the Internet protocol (IP) multimedia subsystem (IMS), although the invention is not limited to IMS.

In particular, in IMS it is possible that the IMS user is moving from one access network to another, e.g. from a wireless local area network (WLAN) to general packet radio service (GPRS) . It is also possible that the IMS user can access from the current location different types of IP-Connectivity Access Networks (IP-CAN) . An example of these IP-CANs is WLAN. A further example of IP-CAN is the GPRS packet core network with GERAN and/or UTRAN radio access networks (GERAN = GSM/EDGE Radio Access

Network, UTRAN = UMTS Terrestrial Radio Access Network) .

In the internet, it is possible to utilise protocols such as Mobile IP that allows to have mobility transparent to applications, but also to various (visited) access networks. Currently in IMS, when the IMS user moves from one IP-CAN to another, the IP address changes and due to the IP address change there is an IMS registration performed. The IMS registration indicates among other things, the contact address (IP address) change. However, when the IP protocols such Mobile IP are utilised in the future also in and between various IP- CANs, there is no need for the IP address change. Therefore, since there is no IP address change in and between various IP-CANs, there is basically no need for the IMS (SIP) registration.

It has been proposed that re-registration will be performed every time when the access network changes.

During the re-registration it is possible to indicate the used access network (IP-CAN), e.g., GERAN, UTRAN, HSPA (High Speed Packet Access), WLAN, etc. However re- registration is considered to generate a lot of traffic to IMS, every re-registration requires a home subscriber server (HSS) query. This is especially the case in 2G-3G and 3G-2G changes/cell reselections . For example, between the 2G-3G accesses, i.e. GERAN - UTRAN radio accesses, the IP address does not change, but the re-registration is still proposed to be performed because it will indicate the used (radio) access network, as mentioned above .

In particular, the use of the REGISTER request is disadvantageous for the following reason: it is the most resource consuming request in the IMS infrastructure. It involves HSS queries and it may trigger a re- authentication procedure which triggers new Security Association between UE-And P-CSCF. Thus, using REGISTER request for this would have negative performance impacts to IMS system.

Fig. 6 illustrates this situation by showing the current functionality for access network change in IMS, namely a IMS Registration (with the P-Access-Network-Info header) . As illustrated, the network elements concerned are a user equipment UE-A, a proxy call session control function (P- CSCF), an interrogating call session control function (I- CSCF) , a home subscriber server (HSS) and a serving call session control function (S-CSCF) .

In step S51, it is assumed that the UE-A performs an access network change. Thus, in step S52, the UE-A sends a REGISTER request to the P-CSCF. The P-CSCF forwards this request to the I-CSCF in step S53. In step S54, the I-CSCF obtains the S-CSCF address from the HSS by performing a corresponding query. Then, the I-CSCF forwards the REGISTER request to the S-CSCF, where the registration is actually performed. In step S56, a profile may be obtained from the HSS, if necessary. This step, however, is optional. In step S57, the S-CSCF acknowledges the registration by sending a 200 OK message to the I-CSCF, which forwards it to the P-CSCF in step S58. Finally, the 200 OK message is forwarded from the P- CSCF to the UE-A in step S59.

Moreover, it is possible that the S-CSCF challenges the UE after receiving the REGISTER request in step S55. This would cause additional REGISTER request from the UE which would consume even more resources than shown in Figure 6.

According to the prior art, this processing is necessary each time an access network change is performed. That is, a considerable amount of signalling has to be exchanged.

Therefore, the REGISTER mechanism is considered as too heavy. SUMMARY

Thus, an object of embodiments of the present invention is to provide a way of indicating an access network change with reduced signaling load.

According to several emeobiments of the present invention, a device is provided which comprises a controller configured to detect an access network change of a transceiver capable of accessing at least two access networks, and to create access network change information indicating the access network change, and a sender configured to transmit the information regarding the access network change.

According to several embodiments of the invention, a device is provided which comprises a controller configured to create a subscribe request regarding an event of an access network change of a terminal, and a sender configured to send the subscribe request to the terminal or an intermediate network element.

According to several embodiments of the invention, a method is provided, which comprises detecting an access network change of a transceiver capable of accessing at least two access networks, creating access network change information indicating the access network change, and transmitting the information regarding the access network change.

According to several embodiments, a method is provided which comprises creating a subscribe request regarding an event of an access network change of a terminal, and send the subscribe request to the terminal or an intermediate network element.

According to several embodiments of the invention, a system is provided which comprises a network device and a network control element. The network device may comprise a controller configured to detect an access network change of a transceiver capable of accessing at least two access networks, and to create access network change information indicating the access network change, and a sender configured to transmit the information regarding the access network change. The network control element may comprise a controller configured to create a subscribe request regarding an event of an access network change of a terminal comprising the transceiver, and a sender configured to send the subscribe request to the network device.

Thus, according to embodiments of the invention, it is possible to easily provide an indication of an access network change to other network elements and/or function modules and the like, without requiring to perform a re- registration or the like.

Further advantageous developments are set out in the dependent claims.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the invention are described by referring to the enclosed drawings, in which:

Fig. 1 shows a network structure according to an embodiment of the invention, Fig. 2 shows a signalling flow according to the embodiment of the invention,

Fig. 3 shows a more detailed signalling flow according to the embodiment,

Fig. 4 shows a use case of the embodiment according to the invention,

Fig. 5A, 5B and 5C show basic structures for network elements involved in the embodiment and an alternative embodiment of the invention, and

Fig. 6 shows a signalling flow of performing a registration after an access network change according to the prior art.

DETAILED DESCRIPTION OF THE EMBODIMENTS

In the following, embodiments of the present invention are described by referring to the attached drawings.

According to several embodiments of the invention, an access network change of a transceiver capable of accessing at least two access networks is detected, and access network change information indicating the access network change is created. Then, this information regarding the access network change is transmitted. For example, this information is transmitted to a serving network control element such as a serving call session control function (S-CSCF) .

The transceiver may be located in a network device such as a terminal, for example a user equipment (UE) . The above-described procedures may be carried out by the terminal, or, alternatively, by an intermediate network element, such as an entry network control element (e.g., a proxy call session control function) .

Moreover, according to several embodiments of the invention, a subscribe request regarding an event of an access network change of a terminal may be created, and the SUBSCRIBE request may be sent to the terminal or an intermediate network element.

The above procedures may be carried out by a serving network control element such as a serving call session control function (S-CSCF) . The intermediate network element may be an entry network control element (e.g., a proxy call session control function) .

In particular, after the subscription, the access network change information may be sent in or in form of an event package, so that the access network change is informed by the event package. Hence, no re-registration of the terminal is necessary.

Fig. 1 shows the basic situation according to an embodiment of the invention. In particular, a user equipment (UE) is connected via an access network ANl to a P-CSCF and an S-CSCF. Moreover, as indicated by the dashed lines, also a second access network AN2 is available, and in the following an access network change between these two access networks is described.

According to the embodiment, a subscription event package is provided which is flexible utilised during the access network change. With the event package either the terminal or the network element involved with this incident informs a serving network control element such as a serving call session control function (S-CSCF) that the access network has changed. Flexible means that the subscription may be applied to the terminals that are mobile internet protocol (MIP) capable and can access more than one IP-Connectivity access network (IP-CAN). The event package can indicate the current changed access network and in addition all the available access networks that are accessible to the terminal.

This package can be used to optimize 2G-3G transitions by controlling the rate of notifications (e.g. a user equipment (UE) will filter out continuous cell reselections between 2G and 3G) .

The access network change is needed in the serving network control element (such as the S-CSCF) so that either access aware services can be utilised or the incoming voice and or video call can be routed optimally using either the circuit switched (CS) core or the IMS. Thus, the serving network control element may inform other network elements and/or function modules (such as other CSCF or the like) correspondingly.

The event package can include the information that is currently included in the P-Access-Network-Info header in the SIP protocol, for example, or may include newly defined information fields to indicate the desired functionality. The event package can include more than one access network info, e.g. the availability of CS access .

Furthermore, an event package notification can be generated only in order to cover certain critical access network changes, e.g. from non-real-time (non-RT) to real-time (RT) capable access or vice versa. That is, the event package may be sent only when it is necessary. For example, an access network change between networks of the same time (e.g., from one WLAN to another WLAN) may not be indicated.

Moreover, the event package can be tailored to include information about the available accesses to the UE. That is, the UE can indicate all available access networks to the S-CSCF. In this way, the S-CSCF knows in advance all possible access network changes.

Fig. 2 shows a basic message flow according to an embodiment of the invention.

In detail, in step Sl, it is assumed that a normal registration already exists. In step S2 it is assumed that the user equipment (UE) is connected to an access network ANl, and that the UE is assigned an IP address IP addr-1. In step S3, a subscription to the access network info is performed. That is, the serving network control element (in this example, the S-CSCF) subscribes to the event regarding an access network change of the UE.

In step S4, it is assumed that the UE performs an access network change. That is, the UE is then connected to the access network AN2. However, the UE is still assigned the IP address IP addr-1, e.g. because the UE and the related IP-CANs support the MIP or there is no need for the IP address change between the ANl and the AN2. In step S5, the UE sends a NOTIFY message to the S-CSCF, in which the event of the access network change is informed. In particular, the NOTIFY message includes an indication of the new access network AN2. The S-CSCF responds with a 200 OK message in step S6. Moreover, the S-CSCF updates the access network information for access aware services and/or for routing incoming calls properly and the like. Thereafter, the new access network information is known to other network elements/services, so that the call/session can be continued.

Fig. 3 shows the new functionality for access network change in connection with IMS according to the embodiment in more detail. It is noted that the subscription is performed only once, e.g. after registration.

In step SIl, the S-CSCF performs the subscription to the event of the access network change, by sending a corresponding request to the P-CSCF, which forwards the request to the UE-A in step S12. The UE-A acknowledges the request by sending a 200 OK message in step S13 to the P-CSCF, which forwards this to the S-CSCF in step S14.

At this time, it is assumed that the access network is a GPRS network (e.g. the above-mentioned access network ANl may be a GERAN radio access network attached to the GPRS packet core network) . Hence, this is informed to the S-

CSCF by sending a NOTIFY message including GPRS (GERAN) to the P-CSCF in step S15, which forwards it to the S-CSCF in step S16. The S-CSCF acknowledges the NOTIFY message by sending a 200 OK message in steps S17 and S18.

In step S19, an access network change is performed. For example, the access network is now a UTRAN radio access network attached to the GPRS packet core network (e.g., the above-mentioned access network AN2 may be a GPRS (UTRAN) network) . This event is informed in a NOTIFY request, which is sent in steps S20 and S21 to the S- CSCF. The S-CSCF acknowledges this NOTIFY message in steps S22 and S23.

In step S24, a further access network change is performed. In this case, it is assumed that the new access networks is GPRS(UTRAN) and/or WLAN. This event is informed in a NOTIFY request, which is sent in steps S25 and S26 to the S-CSCF. The S-CSCF acknowledges this NOTIFY message in steps S27 and S28.

Thus, access network changes can easily be informed by the NOTIFY messages, so that no re-registration or the like is necessary. Moreover, the subscription is carried out only once, so that the signalling load on the network is low. The I-CSCF and the HSS shown in Fig. 3 are not involved.

Fig. 4 shows a use example of the embodiment described above. Here, it is assumed that the IMS user has two UEs (UE-A, UE-B) simultaneously registered with the same public user identity. In this example, it is assumed that a voice over internet protocol (VoIP) session is to be targeted to the IMS user with the public user identity registered to both UEs, UE-A and UE-B. The subscription of the S-CSCF to the access network change events of UE-A and UE-B is carried out similar as shown in Fig. 3.

In the beginning, it is assumed that the access network of UE-A is GPRS(GERAN), whereas the access network of UE- B is WLAN. In step S31, an INVITE request for a VoIP session is received by the I-CSCF. In step S32, the I- CSCF obtains the address of the S-CSCF and forwards the INVITE request to the S-CSCF in step S33. The S-CSCF knows (due to the subscription) that the access network of UE-A is GPRS (GERAN) , and that the access network of UE-B is WLAN. Hence, since the real time bearer capability (e.g. WLAN) is required for the terminating session, so in this case the INVITE request is forwarded to UE-B in steps S34 and S35, via the P-CSCF.

In step S36, an access network change of UE-A is carried out, so that the new access network is a GPRS (GERAN) and/or GPRS(UTRAN) network. In step S37, the UE-A notifies this to the S-CSCF in a similar way as described above in Fig. 3.

In step S38, a new invitation for a VoIP session is received at the I-CSCF. After obtaining the S-CSCF address from the HSS in step S39, the I-CSCF forwards the INVITE request to the S-CSCF. Since the S-CSCF now knows the current access networks of UE-A and UE-B, it forwards now the INVITE request to UE-A in steps S41 and S42. It may be assumed that UTRAN has larger coverage than WLAN, so therefore the UTRAN is preferred. Another option in this case is that the terminating request is forked to both terminals, if it is considered that the both accesses (WLAN, UTRAN) are equal.

Hence, in case a user has multiple UEs simultaneously registered, the S-CSCF can easily forward a call/session to that UE which is appropriate for the particular call/session, since the S-CSCF is notified about possible access network changes.

It is noted that according to the embodiment described above, the UE is involved in the subscription. That is, the UE informs the S-CSCF about the access network change. However, the invention is not limited to this. For example, according to an alternative embodiment, also an intermediate network control element (e.g., the P-CSCF described above) may perform this functionality. In this case, the S-CSCF subscribes with the P-CSCF, an in case the P-CSCF detects an access network change of the UE, the P-CSCF notifies this to the S-CSCF.

There are several possiblities how the P-CSCF actually knows that the access network of the UE has changed. For example, the terminal may not be able to provide the access network info for some reason or there is no reliable information available for the UE. The latter is the case, for example, when there is a local/residential WLAN connection to, for example, an xDSL access. The terminal sees only the local WLAN access. In this case the P-CSCF may have a connection via so called e2 interface to the CLF functional entity: - e2 interface is between the P-CSCF and the Connectivity Session Location and Repository Function (CLF) in ETSI TISPAN NGN architecture. The Interface e2 is defined in ETSI ES 283035 "Network Attachment Sub-System (NASS) ; e2 interface based on the DIAMETER protocol") . The P-CSCF acts now as a notifier towards the S-CSCF to indicate or update the access network info.

The basic structures of the network elements involved are shown in Figs. 5A to 5C. Fig. 5A shows a user equipment (UE, UE-A or UE-B) according to the present embodiments. The UE comprises a controller Ul and a transceiver U2. The controller may create the NOTIFY messages and the like, and the transceiver sends the messages to the P- CSCF.

Fig. 5B shows a P-CSCF according to the alternative embodiment described above, namely for the case that the P-CSCF informs the access network change of the UE to the S-CSCF. The P-CSCF comprises a controller Pl and a transceiver P2, which are similar to those described above for the UE.

Fig. 5C shows a S-CSCF according to the embodiment described above, which comprises a controller Sl and a transceiver S2.

The controllers described above may include a CPU and different kinds of memory means such as RAM, ROM, a harddisk, a CD ROM reader or the like. A computer program may be stored in memory means (not shown) and may comprise software code portions for carrying out the method according to the embodiment. This computer program may be stored on a recording medium such as a CD ROM, for example, and may be directly loadable into the work memory of the controller. Alternatively, the computer program may be loaded via the network into the memory of the controller.

It is noted that the tranceivers, senders and receivers mentioned above may comprise suitable interfaces which are configured for possible different access technologies of the network concerned.

According to the embodiments described above, the following advantages may be achieved:

- According to the embodiments, a new SIP registration is not needed since the access network change can be informed with a lighter method using the subscription event package.

- An event package notification can be generated only to cover certain critical access network changes, e.g. from non-real-time (non-RT) to real-time (RT) capable access or vice versa.

- The event package can be tailored to include information about the available accesses to the UE.

- The event package can be used to those terminals that have the required capabilities, e.g. they are mobile IP capable, and are multiradio (or multi access) capable, i.e. can have access to various access networks, e.g. GPRS (GERAN, UTRAN, HSPA) , WLAN, xdsl, packet cable etc.

The procedures according to the embodiments described above are in particular advantageous when mobile IP is used. Namely, when the access network changes, there is no IP address changed and therefore no contact address change needs to be indicated.

The invention is not limited to the embodiments described above.

In particular, the terminal is not limited to a mobile node. For example, also a fixed network terminal may change its access network (e.g., may connect to different networks) . Moreover, a change between access networks can also be performed between a cable connection and a radio connection (e.g., a laptop computer having a WLAN functionality which also may be connected via a cable to an access router) .

Moreover, the subscription can be provided with a timer, which can be very long, so that re-subscriptions are needed only very rarely. Also, the subscription may be made only after an initial registration. Both measures may serve to further reduce the load on the UE and also on the network.

Claims

1 . A device , compri s ing a controller configured to detect an access network change of a transceiver capable of accessing at least two access networks, and to create access network change information indicating the access network change, and a sender configured to transmit the information regarding the access network change.

2. The device according to claim 1, wherein the sender is configured to transmit the access network change information to a serving network control element .

3. The device according to claim 1 or 2, wherein the access network change information includes information regarding the new access network.

4. The device according to one of the claims 1 to 3, wherein the controller is configured to create the access network change information only in case of predetermined access network change types.

5. The device according to claim 4, wherein the predetermined access network change types comprise a change between a real-time access network and a non-realtime access network.

6. The device according to one of the claims 1 to 5, further comprising a receiver configured to receive a subscribe request, in which a serving network control element subscribes to the event of an access network change .

7. The device according to claim 6, wherein the access network change information is included in a subscription event package sent due to the subscription of the serving network control element.

8. The device according to one of the claims 1 to 7, wherein the network information includes information regarding available access networks.

9. The device according to one of the claims 1 to 8, wherein the transceiver is located in a terminal.

10. The device according to claim 9, wherein the device is the terminal.

11. The device according to claim 9, wherein the device is an intermediate network element.

12. The device according to claim 11, wherein the intermediate network element is a network entry element for the terminal .

13. The device according to one of the claims 1 to 12, wherein the controller is configured to control the rate of notifications based on the access network change information .

14. The device according to one of the claims 1 to 13, wherein the device comprises at least two user entities, the transceiver is configured to access at least two networks at the same time, and the controller is configured to create the access network change information for each user entity.

15. A device, comprising a controller configured to create a subscribe request regarding an event of an access network change of a terminal, and a sender configured to send the subscribe request to the terminal or an intermediate network element.

16. The device according to claim 15, further comprising a receiver configured to receive a subscription event package including access network change information of the terminal.

17. The device according to claim 16, wherein the access network change information includes information regarding the new access network of the terminal.

18. The device according to claim 16 or 17, wherein the network information includes information regarding available access networks of the terminal.

19. The device according to one of the claims 15 to 18, wherein the controller is configured to create information regarding the access network change of the terminal, and the sender is configured to send this information to network elements and/or function modules concerned.

20. The device according to claim 19, wherein the controller is configured to create the information only in case of predetermined access network change types.

21. The device according to one of the claims 15 to 19, wherein the access network change information comprise predetermined access network change types.

22. The device according to claim 20 or 21, wherein the predetermined access network change types comprise a change between a real-time access network and a non-realtime access network.

23. The device according to one of the claims 15 to 22, wherein the controller is configured to control the rate of notifications based on the access network change information .

24. The device according to one of the claims 15 to 23, wherein the terminal comprises at least two user entities, and the access network change information are created for each user entity.

25. A method, comprising detecting an access network change of a transceiver capable of accessing at least two access networks, creating access network change information indicating the access network change, and transmitting the information regarding the access network change.

26. The method according to claim 25, wherein the access network change information is transmitted to a serving network control element.

27. The method according to claim 25 or 26, wherein the access network change information includes information regarding the new access network.

28. The method according to one of the claims 25 to 27, wherein the controller is configured to create the access network change information only in case of predetermined access network change types.

29. The method according to claim 28, wherein the predetermined access network change types comprise a change between a real-time access network and a non-realtime access network.

30. The method according to one of the claims 25 to 29, further comprising receiving a subscribe request, in which a serving network control element subscribes to the event of an access network change.

31. The method according to claim 30, wherein the access network change information is included in a subscription event package sent due to the subscription of the serving network control element.

32. The method according to one of the claims 25 to 31, wherein the network information includes information regarding available access networks.

33. The method according to one of the claims 25 to 32, wherein the transceiver is located in a terminal.

34. The method according to claim 33, wherein the method is carried out in the terminal.

35. The method according to claim 33, wherein the method is carried out in an intermediate network element.

36. The method according to claim 35, wherein the intermediate network element is a network entry element for the terminal .

37. The method according to one of the claims 25 to 36, further comprising controlling the rate of notifications based on the access network change information.

38. The method according to one of the claims 25 to 38, wherein a terminal comprising the transceiver comprises at least two user entities, and the transceiver is configured to access at least two networks at the same time, the method further comprising creating the access network change information for each user entity.

39. A method, comprising creating a subscribe request regarding an event of an access network change of a terminal, and send the subscribe request to the terminal or an intermediate network element.

40. The method according to claim 39, further comprising receiving a subscription event package including access network change information of the terminal.

41. The method according to claim 40, wherein the access network change information includes information regarding the new access network of the terminal.

42. The method according to claim 40 or 41, wherein the network information includes information regarding available access networks of the terminal.

43. The method according to one of the claims 39 to 42, further comprising creating information regarding the access network change of the terminal, and sending this information to network elements and/or function modules concerned.

44. The method according to claim 43, wherein the information is created only in case of predetermined access network change types.

45. The method according to one of the claims 39 to 43, wherein the access network change information comprise predetermined access network change types.

46. The method according to claim 44 or 45, wherein the predetermined access network change types comprise a change between a real-time access network and a non-realtime access network.

47. The method according to one of the claims 39 to 46, further comprising controlling the rate of notifications based on the access network change information.

48. The method according to one of the claims 39 to 47, wherein the terminal comprises at least two user entities, the method further comprising creating the access network change information for each user entity.

49. A computer program product for a computer, comprising software code portions for performing the steps of any one of the claims 25 to 48 when the program is run on the computer .

50. The computer program product according to claim 49, wherein the computer program product comprises a computer-readable medium on which the software code portions are stored.

51. A system comprising a device according to one of the claims 1 to 14 and a device according to one of the claims 15 to 24.

52. A system, comprising a network device and a network control element, the network device comprising a controller configured to detect an access network change of a transceiver capable of accessing at least two access networks, and to create access network change information indicating the access network change, and a sender configured to transmit the information regarding the access network change, and the network control element comprising a controller configured to create a subscribe request regarding an event of an access network change of a terminal comprising the transceiver, and a sender configured to send the subscribe request to the network device.