Abstract:
The invention refers to providing call control within a mobile network with respect to a subscriber associated to one or a plurality of user equipments ( 10 ), the mobile network comprising an application server—SCC-AS—( 18 ) responsible for an access domain selection, the application server performing the receiving an indication to provide a best effort—BE—access domain with respect to the user equipment ( 10 ), and selecting an access domain in dependency of the received indication for routing a call with respect to the one or the plurality of user equipments. The invention further refers to an application server ( 18 ), a computer program loadable into the application server and a user equipment ( 10 ).

Description:
TECHNICAL FIELD 
       [0001]    The invention refers to call routing and especially refers best effort preference with respect to radio access selection. 
       BACKGROUND 
       [0002]    Mobile communications networks are currently evolving from circuit switched (CS) networks towards packet switched (PS) networks, and by that integrate into Internet Protocol (IP) based infrastructures that are e.g. used by the Internet and the World Wide Web respectively. 
         [0003]    More recently, an architecture called IP Multimedia Subsystem (IMS) has been defined by the Third Generation Partnership Project (3GPP) for delivering multimedia services over mobile communication networks. IMS is able to provide new and rich person-to-person communication services or network-to-person communication services by means of text, audio, video, and/or messaging or any combination thereof, employing IP for transport and Session Initiation Protocol (SIP) for service signaling. Hereto, calls from and to subscribers of the multimedia services using a Circuit Switched based access (e.g. WCDMA/GERAN), in the following also being referred to as CS access, are routed through the IMS network in order to reach an IMS service engine. This concept is called IMS Centralized Services (ICS), and is described in the standardization documents TS 23.237 (this application referring to release 11.3.0), TS 23.292 (this application referring to release 11.1.0), and 3GPP TS 23.228 (this application referring to release 11.3.0) established by the 3rd Generation Partnership Project—3GPP—. 
         [0004]    Terminating Access Domain Selection T-ADS according to TS 23.292, section 5.3.1 provides:
       Directs an incoming session to an ICS User;   For one or more UEs of an ICS User:
           Influences the selection of one or more contacts amongst the registered contacts and;   Influences the selection of an access network for delivery of the incoming session to the selected contact, or;   Performs breakout to the CS Domain by fetching the CSRN.   
               
 
         [0010]    T-ADS shall take into account the access network&#39;s capabilities, UE capabilities, IMS registration status, CS status, existing active sessions, user preferences, operator policies such as access network specific voice domain preferences and the media component types. In addition, T-ADS may take into account the access network information provided directly by the UE. 
         [0011]    The current procedures for T-ADS as described in current 3GPP documents might not provide for allowing a best effort packet switched access at choice of the user. The user might prefer a certain packet switched access even in cases where other packet or circuit switched access is available at presumably better quality. Such possibility of choice might be especially preferable e.g. in case that the subscriber has, besides the first line telephony service, also a second-line voice (or voice and video call) service that he or she prefers to use in certain areas or situations, e.g. when roaming, or in a hotel. 
       SUMMARY 
       [0012]    It is an objective of the present invention to provide a possibility for performing best effort (packet switched) access even in cases of an available alternative access. This objective is achieved by the independent claims. Advantageous embodiments are described in the dependent claims. 
         [0013]    According to embodiments, a service is provided with respect to a user equipment—UE—that allows conveying a best effort—BE—indication to an access application server, e.g. a so-called service centralization and continuity application server—SCC AS—as specified by 3GPP, being responsible for an access (domain) selection for the UE. The SCC AS initiates or controls an access selection in dependency of the BE information. 
         [0014]    According to embodiments, during call control, the SCC AS identifies that a BE indication is present associated to the UE and performs an access selection with respect to the UE in accordance to the BE information. In an embodiment, the access selection, e.g. packet switched—PS—access selection, is performed regardless of a quality level (QoS) or capability supported (or guaranteed) for the radio access. 
         [0015]    In an embodiment, the SCC AS initiates routing a call to PS access regardless if that is supporting IMS voice over PS access. In other words, even in case that 
         [0016]    IMS voice over PS access is not supported, the call is routed to PS access instead of routing the call over CS access. Thus, it allows the application server for terminating on PS access even if that is not supporting IMS Voice over PS access. Such termination might be provided either for voice and video call or for video call only. 
         [0017]    Above described embodiments allow to control that terminated calls are not routed to CS access or other contacts. 
         [0018]    In an embodiment, the CSS AS (e.g. by interacting with the HSS) retrieves currently used access information and/or IMS voice over PS support indication (as described in 3GPP specifications). In case that BE information is present and currently used access information indicates LTE or HSPA, the call is routed over PS access; otherwise, if the current access information indicates GERAN, the call is not routed to PS access. 
         [0019]    In an embodiment, the BE indication is conveyed by means of a BE support information inserted in a SIP REGISTER message to be exchanged between a UE and the SCC-AS during SIP registration, wherein the such extended SIP REGISTER message might be sent via a P-CSCF, I-CSCF and S-CSCF. This indicator indicates that best effort access is supported and can be used. 
         [0020]    Alternatively or additionally, the BE indication is inserted in a SIP INVITE transmitted from the UE to the SCC AS when originating a new call in order to inform that the call may be treated as a best effort call. In an embodiment, the SCC AS will not initiate any reservation of certain resources for the terminal but instead allows the media to be sent over a corresponding best effort bearer. 
         [0021]    According to embodiments of the invention, depending on an indication provided to the SCC AS, the SCC AS forwards all terminating calls directed to a first terminal or contact to a second terminal or contact associated to BE PS access, e.g. to MSISDN1 if a call is ongoing on MSISDN2 (wherein MSISDN1 may be different from MSISDN2). 
         [0022]    The present invention also concerns computer programs comprising portions of software codes in order to implement the method as described above when operated by a respective processing unit of a network node (SCC AS, S-CSCF) or user device. The computer program can be stored on a computer readable medium associated to the UE, the SCC AS, S-CSCF or any other node involved in the service provision as described above. The computer-readable medium can be a permanent or rewritable memory. The respective computer program can be also transferred to the user device for example via a cable or a wireless link as a sequence of signals. 
         [0023]    In the following, detailed embodiments of the present invention shall be described in order to give the skilled person a full and complete understanding. However, these embodiments are illustrative and not intended to be limiting. 
     
    
     
       BRIEF DESCRIPTION OF THE FIGURES 
         [0024]      FIG. 1  shows a first sequence diagram showing an extended SIP registration at the network to comprising an indicator that that BE access is supported and can be used, 
           [0025]      FIG. 2  shows a second sequence diagram showing to forwarding the indicator during an originating call to inform the network that the call may be treated as an best effort call, 
           [0026]      FIG. 3  shows a third sequence diagram showing both SCC AS terminal selection and access domain selection with respect to an incoming call, 
           [0027]      FIG. 4  shows a fourth sequence diagram for BE controlling that terminating calls are not routed to CS access, 
           [0028]      FIG. 5 ,  6  show a fifth and a sixth sequence diagram controlling forwarding all terminating calls to MSISDN1 if a call is ongoing on MSISDN2, and 
           [0029]      FIG. 7  shows a block diagram of an exemplary communication network for performing sequences described under  FIG. 1-FIG .  6 . 
       
    
    
     DETAILED DESCRIPTION 
       [0030]    The  FIGS. 1-7  involve amongst other nodes a user equipment UE  10 , a P-CSCF  12 , an I-CSCF  13 , an S-CSCF  14 , an HSS  16 , and an application server  18  also being referred to as SCC AS  18  or as SCC AS/TAS  18 , by way of example combining the SCC AS with a so-called Telephony Application Server—TAS—that carries out functions not directly related to the routing of messages through the network. Further information about these nodes and the further involved nodes can be retrieved from 3GPP specifications as cited above. 
         [0031]    The HSS  16  is a database that supports the PS network entities in handling calls. It comprises subscription related information (e.g. being stored as subscriber profiles), performs authentication and authorization of the user, and might further provide information about the subscriber&#39;s location and address information (e.g. IP address). According to embodiments of the invention, the HSS interacts with the SCC AS to inform the SCC AS e.g. about the currently used access and IMS Voice over PS support indication. 
         [0032]    The Call State Control Function—CSCF—nodes P-SCSF  12 , I-CSCF  13  and S-CSCF  14  provide session control for user terminals by processing SIP signalling packets in the IMS. 
         [0033]    The P-CSCF  12  (Proxy CSCF) is a SIP proxy that is the first point of contact for the terminal. Amongst other functions, this node supports a subscriber authentication and ensures that the IMS terminals do not behave correctly (by inspecting the signaling). 
         [0034]    The S-CSCF  13  (Serving CSCF) is the central node of the signaling plane. It communicates with the HSS e.g. to get subscriber profiles This node further handles SIP registrations, which allows it to bind the user location (e.g. the IP address of the terminal) and the SIP address 
         [0035]    The I-CSCF  14  (Interrogating CSCF) is a SIP function e.g. located at the edge of an administrative domain. Its IP address is published in the Domain Name System (DNS) to be found by remote servers. Amongst other functions this node queries the HSS to retrieve the address of the S-CSCF and assign it to a user performing a SIP registration, and also forwards SIP request or response to the S-CSCF. 
         [0036]    The service centralization and continuity application server—SCC AS- 18  is a home network based IMS Application that provides functionality required to enable IMS Centralized Services. The SCC AS- 18  may be regarded as a call control server (communicating by means of the SIP protocol) controlling a communication between the mobile terminal UE and a remote side (e.g. a further UE). Amongst other functions according to above-cited 3GPP standard TS 23.292 (e.g. section 5.3.1), the SCC AS 18 comprises so-called Terminating Access Domain Selection (T-ADS) capabilities comprising means to direct an incoming session to an ICS User. For one or more UEs of an ICS user, this function influences the selection of one or more contacts amongst the registered contacts and influences the selection of an access network for delivery of the incoming session to the selected contact, T-ADS shall take into account the access network&#39;s capabilities, UE capabilities, IMS registration status, CS status, existing active sessions, user preferences, operator policies such as access network specific voice domain preferences and the media component types. In addition, T-ADS may take into account the access network information provided directly by the UE  10 . 
         [0037]    For 3GPP PS access networks and for incoming sessions with bi-directional speech media destined to a selected contact, the SCC AS  18  retrieves (via the HSS) the most recent access network capabilities (“IMS voice over PS Session Supported Indication”, current radio access technology—RAT—type). If the most recently used PS access network indicates that IMS voice over PS is supported, then bi-directional speech media can be delivered on this access. Otherwise, bi-directional speech media will not be delivered on this access unless no BE registration is stored in the SCC AS  18 . 
         [0038]    According to embodiments, a new indication referred to as BE support info is included in SIP REGISTER (e.g., as a new ICSI, new sub classed ICSI, new IARI, new other feature tag). The BE support info is indicative of a preference of PS access over CS access thus influencing an access domain selection with respect to the UE  10 . The SCC AS  18  stores this information and will terminate future calls routed to PS access even if that is not supporting IMS voice over PS access. The SCC AS  18  may still interact with the HSS  12  to retrieve the currently used access (and IMS Voice over PS support indication as e.g. specified in TS 23.237, TS 23.401 and TS 23.060), but may only use the currently used access information to determine whether to route to PS access (e.g. OK, if LTE (Long Term Evolution) or HSPA (High Speed Packet Access) is currently used, and not OK if GERAN (GSM EDGE Radio Access Network) is currently used). 
         [0039]    In the following exemplary sequence diagrams are shown with respect to different embodiments: 
         [0040]      FIG. 1  shows an exemplary registration procedure being extended to include an additional indicator that indicates to the network that BE access is supported and can be used. 
         [0041]    Thereto, the UE  10  may transmit a first SIP register message M 1  over P-CSCF  12 , I-CSCF  13  to S-SCSF  14 . The first SIP register message comprises above described information indicative of BE support. The S-CSCF  14  may store this information and further send this information as SIP third party register information M 2  to the SCC AS/TAS  18 . The registration process may be terminated by a SIP OK sequence including UE authentication. 
         [0042]      FIG. 2  shows an exemplary sequence wherein the terminating UE sends a request for best effort PS access while originating a new call. When the UE  10  originates the new call, it may include the BE indicator to inform the network that the call may be treated as a best effort call. This may then result in that the network does not try to reserve special dedicated resources for the terminal, but instead only allows the media to be sent over a best effort bearer. 
         [0043]    Thereto, the UE  10  may send a third SIP invite message M 3  over an Evolved Packet Core—EPC—network  11 , P-CSCF  12 , S-CSCF  14  to SCC AS  18 . The SIP invite message M 3  comprises information indicative of a request for best effort PS access. In response to receiving the message M 3  in the P-CSCF  14 , the P-CSCF  14  will initiate a best effort bearer setup in the EPC  11 . Call completion will then be performed taking into account the request. 
         [0044]      FIG. 3  shows an exemplary sequence for an incoming call handling. The network (SCC AS/TAS) may do both contact/terminal selection and access domain selection. As part of these procedures, the SCC AS  18  may decide to which contact or terminal to route the call to (if more than one terminal or contact is present). This selection may include difference preferences. For example:
       the SCC AS  18  first may try to terminate the call towards any of the contact(s)/terminal(s) that are/is not using best effort, but either CS access or a VoIP access according to T-ADS in TS 23.293 and TS 23.237; if this terminating fails, then the call may be routed over the indicated BE access (being stored in the SCC AS  18 ); or   the SCC AS  18  may always try the BE access first, if an T-ADS information (e.g. from the HSS) suggests that the UE is still on UTRAN or E-UTRAN; if the UE is on GERAN (that may be considered as having too low throughput), the call is sent towards a contact or terminal (UEs/accesses) with VoIP support or CS access.       
 
         [0047]    The SCC AS  18  may use the BE support info indicator to influence the S-CSCF  16  to select the UE  10  fo which the BE support has been stored (and a corresponding access domain, e.g. PS access domain). 
         [0048]    Thereto, a remote side (another UE)  20  may send a SIP invite message M 4  to the S-CSCF  14 , that forwards this message to the SCC AS  18 . The SCC AS  18  detects a storage of a BE support info associated to the terminating user  10 , performs contact/terminal selection (in case of a plurality of contacts/terminals)/access domain selection and sends an adapted SIP invite message M 5  comprising the BE support info to influence/advice the S-CSCF  16  as discussed above. 
         [0049]      FIG. 4  shows an exemplary sequence allowing to control that terminating calls are not routed to CS access. According to the example, if a new indication BE preference (which may be realized by using the same tag as BE support info) is included in SIP REGISTER, all terminating calls are routed to this contact and not to CS access. 
         [0050]    Thereto, a similar sequence as discussed under  FIG. 1  may be performed with the difference that an variant SIP register message M 1 ′ is transmitted comprising a BE preference information to request a routing of terminating calls to this contact and not to any contact associated to CS access. 
         [0051]      FIG. 5  shows an exemplary sequence allowing forwarding all terminating calls to MSISDN1 or number A (a Mobile Subscriber Integrated Services Digital Network Number—MSISDN—uniquely identifies a subscription in a GSM or a UMTS mobile network) if a call is ongoing on MSISDN2 or number B (MSISDN1 may be different from MSISDN2). According to the example, if an indication “Reroute” is included in the SIP INVITE for originating calls or responses in case of terminating call, the SCC AS  18  routes all terminating calls intended for a contact associated to the number/contact A to the contact for number B as long as this call with that reroute indication is ongoing (using BE PS access). The indication may be accompanied by B and may only be included on user request (i.e. based on a setting in the UE). 
         [0052]    When the UE ( 10 ) establishes a call, it indicates in the call setup that it wishes to have any additional incoming calls redirected to the contact/number B (instead of its own contact/number A). 
         [0053]    Thereto, the UE  10  may send a fourth SIP invite message M 6  over P-CSCF  12 , S-CSCF  14  to SCC AS  18 . This SIP invite message M 6  comprises information indicative of a preference to re-route to a further contact/terminal B as described above) In response to receiving this message in the SCC AS  18 , a further call directed to the contact/terminal A is routed to the contact/terminal B using BE PS access domain. 
         [0054]      FIG. 6  shows an exemplary sequence corresponding to  FIG. 5 , wherein when retrieving the incoming call, the SCC AS  18  detects that an ongoing call is in progress, and that any new incoming call should be rerouted to the number/contact B. 
         [0055]    Thereto the remote side  20  may send a SIP invite message directed to the number/contact A. over the S-CSCF  14  to the SCC AS  10 . The SCC AS  18  decides to select a contact associated to the number/contact B using BE access and sends a correspondingly modified invite message towards the S-CSCF, that further forwards this message over the P-CSCF  12  to the terminating UE  10 . 
         [0056]      FIG. 7  shows a block diagram of an exemplary communication network comprising the UE  10 , the evolved packet core  11 , a PCRF comprising the P-CSCF  12 , the I-CSCF  13 , and the S-CSCF  14 , the HSS  16 , and the application server  18  comprising the SCC AS and the TAS as discussed above. Further PS access network  11   a,  a CS access network  21   a  and a CS core network  21  are shown. A fPS connection line is shown from the UE  10 , over the PS access network  11   a,  the EPS  11 , the CSCF nodes  12 ,  13 , and  14  and the application server  18 . A CS connection line is shown from the UE  10 , over the CS access network  12   a,  the CS core network  11 , and S-CSCF  14  to the application server  18 . The UE  10  may have a plurality of terminals or contacts having different capabilities. The user may register a BE preference indication associated to a certain contact/terminal by means of sending the SIP register message M 1  over the PS connection to the S-CSCF, that in turn sends this information as SIP 3 rd  party information M 2  to the application server as shown in  FIG. 1 . The application server  18  will perform terminal/contact selection taking into account the BE preference indication as discussed above. 
         [0057]    Above described embodiments allow to choose a best effort access service within the frame of IMS. Amongst others, they allow to terminate on PS access even if that is not supporting IMS Voice over PS access, (e.g. either for voice and Videocall or for Videocall only). They further allow performing terminating call control in that CS access may not be used.