Abstract:
Feature control signaling can be transported from a handset to a network-based service platform when the handset is active on an existing call, using three-way calling and Intelligent Network (IN) capabilities to pass feature control information from the user device to a network-based service platform. Although Wireless Intelligent Network (WIN) standards do not support mid-call triggers, handset emulation of three-way-calling (3WC) behavior allows a handset to send a digit string (representing a particular feature-related event) to a network-based service platform (in the context of a pseudo-3WC). Mid-call communications can be accomplished in this manner, allowing a network-based service platform to interpret and take action based on the received digit string, prior to releasing the additional call leg associated with the pseudo-3WC attempt. WIN mechanisms can also be used to send feature control signals from a network-based service platform to a handset. These mechanisms can be used to promote consistent service offerings for users who are served by networks that are comprised of different technologies. These mechanisms can also be used to help operators transition their networks to support emerging network technologies.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims the benefit of U.S. Provisional Patent Application No. 60/781,785, filed Mar. 13, 2006, which is hereby incorporated herein by reference in its entirety. 
     
    
     FIELD OF THE INVENTION 
       [0002]    The present invention relates generally to the field of telecommunications networks and the provisioning and implementation of services in such networks. More particularly, the invention relates to wireless telecommunications networks and IP Multimedia Subsystems (IMS) networks, and the use of Wireless Intelligent Network (WIN) functionality to support an IMS-based centralized service execution model. 
       BACKGROUND OF THE INVENTION 
       [0003]    Wireless standards (Third Generation Partnership Program [3GPP] and 3GPP2 Voice Call Continuity [VCC]) are exploring mechanisms to allow VCC users to move between Circuit-Switched (CS) access (via cellular systems) and other wireless access (e.g., WiFi/Wireless LAN access into an IMS infrastructure). 
         [0004]    It is important that the corresponding “domain transfer” mechanism, applied when an existing call is in progress in one domain, should allow the transfer of the existing bearer path to the alternate domain. The domain transfer mechanism should also support the transfer of a signaling path in the new domain. In addition, the user should ideally experience seamless mobility during and after the domain transfer. 
         [0005]    To address service mobility, the industry has pursued two basic approaches—a distributed service execution model and an (IMS-based) centralized service execution model.  FIG. 1  depicts the basic architecture of these two service models. 
         [0006]    In the CS cellular model  100 , voice services are typically offered via the Mobile Switching Center (MSC)  102 . Such features can be MSC-based features  104 , whereby the service logic resides in the MSC, and the MSC retrieves user profile information  106  from the Home Location Register (HLR)  108  to determine whether a selected feature is subscribed for and is active for a particular user. Alternatively, Intelligent Network (IN) based services  110  can be invoked, using triggers that are armed in the MSC—this mechanism causes the MSC to request instructions from a Service Control Point (SCP)  112 , which executes IN service logic  110  that defines the particular service behavior. 
         [0007]    In the IMS model  120 , similar functionality is provided via a different mechanism. With IMS, the service logic  122  resides in an Application Server  124 . The Home Subscriber Server (HSS)  126  stores user-related profile information  128 , including initial Filter Criteria (iFC) that are used to trigger special service processing. This iFC mechanism is used to arm triggers  130  at a (Serving) Call Session Control Function (CSCF)  132 . When a particular iFC condition is satisfied, the CSCF will communicate with a corresponding Application Server (as designated by the iFC), which will invoke the desired service behavior. 
         [0008]    In general, the distributed service execution model attempts to offer services via the network where the user is currently attached. Thus, the user might access MSC-based or IN-based services when accessing the CS domain—but might access IMS-based services when accessing the IMS domain. 
         [0009]    In contrast, the (IMS-based) centralized service execution model attempts to offer IMS-based services to the user, independent of the network where the user is currently attached (i.e., even when the user is accessing the CS domain). This model promotes consistent execution of IMS-based services, independent of the user&#39;s current access. This model makes more limited use of the CS service infrastructure (as required to enable IMS service execution). 
         [0010]    The centralized service execution model offers a number of advantages over the distributed service execution model. For example, it provides a mechanism to allow the user&#39;s features to operate consistently, independent of the user&#39;s current access. The centralized service execution model also allows the user&#39;s features to be created in a common (IMS-based) manner—thereby avoiding the need to create and deploy multiple versions of the same services (for cellular and IMS domains). The model focuses the feature-interaction problem on a single (IMS) domain, eliminating the need to address interactions between services that might otherwise execute in different domains (e.g., as MSC-based features, IN-based features, or IMS-based features). The centralized service execution model is more forward-looking, consistent with the intended direction of some operators who desire to move toward an IMS-based network infrastructure. The model provides a framework for addressing some difficulties that might otherwise persist with the distributed service execution model. For example, if a user invokes an MSC-based multi-leg call feature, and then moves to the IMS domain, it may be difficult to transfer the current CS connection and call-state information to the IMS domain. 
         [0011]    This problem is illustrated in  FIG. 2 . In  FIG. 2 , if a user handset  200  invokes an MSC-based multi-leg call feature  202 , and subsequently wishes to transfer that connection and call-state information to the IMS domain, this might require the multiple bearer connections to be correlated and established in the IMS domain, in order to re-construct the current call state in the IMS domain. This can require complex processing—and would be further complicated if one of the existing CS call legs  204 ,  206  happened to be on hold at the time of the domain transfer. 
         [0012]    With the centralized service execution model, the MSC  300  would instead maintain a single bearer channel to the IMS domain (e.g., relying on a Media Resource Function (MRF)  302  within the IMS domain to provide any bridging/media-manipulation functionality). This is illustrated in  FIG. 3 . 
         [0013]      FIG. 3  illustrates the need for a mechanism to exchange feature control  304  signaling between the user device  306  and an IMS-based Application Server  308 . This mechanism should support bi-directional operation and should be enabled during an active CS call, allowing the network to send notifications to the user (e.g., notification of incoming call, as used in conjunction with call waiting) and allowing the user to send feature control information to the Application Server (e.g., “hold”, “join”, “request for pre-paid balance”, etc.) 
         [0014]    Whereas existing mechanisms support the ability to exchange feature control messages when the user is served by the IMS domain (i.e., based on use of the Session Initiation Protocol (SIP)), there is a need for a mechanism that can be used to support such feature control signaling when the user is served by the CS domain as illustrated in  FIG. 3 . 
         [0015]    For GSM networks, the use of Unstructured Supplementary Services Data (USSD) capability has been defined for this purpose—allowing a GSM handset to communicate with a network-based service platform. It is noted that this solution is not yet fully defined. Message formats for service requests need to be identified. Some options include the use of SIP templates or feature codes. 
         [0016]    For CDMA network deployments, no USSD-like mechanism is currently available. However, the industry is currently exploring at least two options for this: (i) support for simultaneous packet and circuit service—where the packet capability might be used to enable communications between the user device and a network-based service platform during an active CS call; and, (ii) support for a modified Short Message Service (SMS) capability—allowing the user device to signal via the CS access network, which would then relay such messaging to a network-based service platform. 
         [0017]    Currently, the USSD solution is only defined for GSM networks. Thus, there remains a need for a solution specifically targeted at CDMA networks, where USSD is not available. Other potential solutions for CDMA networks would require network modifications—making them more costly and potentially delaying the deployment of this capability. 
       BRIEF SUMMARY OF THE INVENTION 
       [0018]    The invention enables feature control signaling between the user handset and a network-based service platform (when the user handset is served by CS access) based on the use of Wireless Intelligent Network (WIN) technology. 
         [0019]    In the present invention, WIN mechanisms are used to support the exchange of feature control signals between a handset and a network-based service platform. As used herein, the term “network-based service platform” refers to a network component (which can be composed of a single element or a distributed group of elements) that supports the execution of service logic that is used to offer communications services. The network-based service platform is capable of executing service logic that spans across multiple technology domains, including the ability to communicate via intelligent network (IN) technology. Examples of such a network-based service platform include, but are not limited to, a network component (which can comprise a single element or a distributed group of elements) that supports any of the following: the combined functionality of a Wireless Intelligent Network (WIN) Service Control Point (SCP) and an IMS Application Server (AS); the combined functionality of a Customized Application Mobile Enhanced Logic (CAMEL) Service Control Function (SCF) and an IMS AS; the combined functionality of an Advanced Intelligent Network (AIN) Service Control Point (SCP) and an IMS AS; and the combined functionality of a Core INAP Service Control Function (SCF) and an IMS AS. 
         [0020]    The proposed solution can be broken down into two separable mechanisms. The first mechanism addresses how to allow the user handset to send feature control information to a network-based service platform (e.g., “hold”, “join”, etc.). The present invention makes use of an appropriate originating WIN trigger (e.g., All_Calls) that is armed at the visited MSC when the user handset registers with that MSC. Although WIN standards do not support mid-call triggers, handset emulation of three-way-calling (3WC) behavior allows a digit string (generated by the handset in the context of a pseudo-3WC) to be sent to a network-based service platform. Mid-call communications can be accomplished in this manner, allowing the network-based service platform to interpret and take action based on the received digit string, prior to releasing the additional call leg associated with the pseudo-3WC attempt. 
         [0021]    The second mechanism addresses how to allow the network to send notifications to the user handset (e.g., notification of an incoming call, as used in conjunction with call waiting). 
         [0022]    By combining the two mechanisms that are illustrated in  FIGS. 4 and 5 , standard WIN-based capabilities can be applied to enable feature control signaling between the user handset and a network-based service platform (when the user is served via CS access). 
         [0023]    The result of combining the mechanisms is a system that does not require any new capabilities in existing cellular Radio Access Networks or in existing MSCs (or in existing HLRs, as with the USSD approach). It relies solely on existing (i.e., already standardized) WIN capabilities from the current cellular networks, thereby avoiding the need for additional network enhancements. 
         [0024]    The following detailed description focuses on the use of WIN to support the desired capabilities. CDMA networks are viewed as a principal application for this capability. However, it is noted that analogous solutions are possible for other IN-based network technologies, other than WIN (e.g., corresponding Customized Application Mobile Enhanced Logic (CAMEL)-based procedures might be pursued if USSD capabilities are not available, or if a more common approach is desired across GSM and CDMA solutions). A similar approach might also be pursued for wireline networks, potentially helping to facilitate the migration path for existing wireline network operators as they evolve their networks towards an IMS-based approach. 
         [0025]    The present invention will be more clearly understood when the following detailed description is read in conjunction with the accompanying drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0026]      FIG. 1  shows the architecture of the CS cellular and IMS service execution models. 
           [0027]      FIG. 2  shows multi-leg treatment of a session within a distributed service execution model. 
           [0028]      FIG. 3  shows multi-leg treatment of a session within a centralized service execution model. 
           [0029]      FIG. 4  shows the mechanism to support feature control signaling from a user to a network-based service platform (with feedback in the reverse direction). 
           [0030]      FIG. 5  shows the mechanism for using standard WIN Call Control Directive (CCDIR) messages to request the MSC to take particular feature-related actions during an existing call. 
           [0031]      FIG. 6  shows a signal flow associated with a Call Waiting application. 
           [0032]      FIG. 7  shows a signal flow associated with a Three Way Calling application. 
       
    
    
     DETAILED DESCRIPTION 
       [0033]    The proposed approach to enable feature control signaling between a user handset and a network-based service platform (when the user handset is served by CS access) is based on the use of Wireless Intelligent Network (WIN) technology. Current WIN standards do not include support for any mid-call triggers. Thus, a ‘conventional’ IN approach for supporting the delivery of mid-call feature-related signaling from the handset to a network-based service platform is not available. Also, the continued expansion of WIN capabilities on existing MSCs is not generally favored, given the current emphasis on more forward-looking IMS technologies for deployment of advanced services, so the addition of mid-call triggers in future WIN standards is unlikely to be pursued. The present invention provides a mechanism for supporting such mid-call feature-related signaling. 
         [0034]    The solution is broken down into two separable mechanisms. The first mechanism addresses how to allow the user to send feature control information to a network-based service platform (e.g., “hold”, “join”, etc.). This proposed mechanism is illustrated in  FIG. 4 . The proposed approach makes use of existing WIN call origination triggers. Any one from a number of existing originating WIN triggers can be used, such as the All_Calls, Double_Introducing_Star, Single_Introducing_Star, Double_Introducing_Pound, Single_Introducing_Pound, K_Digit, or Origination_Attempt_Authorized triggers. The specific trigger type to be chosen may depend on the specific format of the feature code digits to be delivered, as well as whether particular triggers are to be applied by the network operator for other purposes—yet this decision does not impact the general mechanism proposed here. The present invention uses an appropriate originating WIN trigger (e.g., All_Calls) that is armed at the visited MSC (using standard cellular procedures, when the user handset registers with that MSC). In addition, the present invention requires that (the CallingFeaturesIndicator item within) the user profile (normally obtained from the HLR during registration) should indicate that the user is subscribed to the three-way calling (3WC) feature. This differs from the normal rule for the IMS centralized service execution model, which would suggest that MSC-based features should be disabled, in favor of execution of corresponding IMS-based services. 
         [0035]    By arming the above WIN trigger and enabling the MSC-based 3WC feature, it is noted that virtually all originating call requests (excluding emergency calls, but including requests to establish an additional call leg for a three-way call) will result in the corresponding WIN trigger condition being satisfied at the MSC. Thus, whenever the handset is active on a CS call and subsequently initiates an additional call (as in step  1  of  FIG. 4 ), the MSC will send a WIN OriginationRequest (ORREQ) message that is directed to a network-based service platform (i.e., SCP, as specified for the corresponding trigger). The ORREQ message (step  2 ) will include the digits that were received from the user handset, along with other information such as the Mobile Station Identifier (MSID) and the specific type of trigger that was detected. At this point, the SCP will interpret the digits received in the ORREQ message to determine the intended service request and (behaving as an Application Server in the IMS domain) will invoke the necessary processing for the desired service. The SCP then responds back to the MSC (step  3 ) to instruct the MSC to abort further processing associated with this “3WC” (feature) request—and may also optionally request that an indication be provided to the user (e.g., via the inclusion of the DisplayText and/or AnnouncementList parameters). To instruct the MSC to drop this new call leg (associated with the 3WC attempt) and still retain the existing call, the SCP can populate the appropriate AccessDeniedReason parameter (e.g., with a value of “Service denied”) or ActionCode parameter (e.g., with a value of “Disconnect Call Leg”). Depending upon MSC support for such treatment, the SCP can alternately return a special Digits(dialed) or TerminationList value, to cause the MSC to route the additional call leg into the IMS network (from where appropriate IMS feature/leg-release processing could be provided). 
         [0036]    The second mechanism addresses how to allow the network to send notifications to the user (e.g., notification of incoming call, as used in conjunction with call waiting). This mechanism is illustrated in  FIG. 5 .  FIG. 5  illustrates how the standard WIN Call Control Directive (CCDIR) message can be used to request the MSC to take particular feature-related actions during an existing call. Note that this mid-call mechanism already exists in the WIN standards (e.g., used to support Pre-Paid Charging)—yet is not considered a mid-call trigger, since trigger conditions are detected and acted upon by the MSC, whereas this message originates from the SCP. 
         [0037]    To support the delivery of feature-related information from the network to the handset, the SCP will send a WIN CCDIR message (step  1 ) that is directed to the MSC. The DisplayText parameter enables the delivery of a textual message to the user (e.g., a notification of an additional incoming call, to allow the user to invoke call waiting—via the mechanism outlined previously in  FIG. 4 ). The BillingID parameter identifies the specific existing call (to which this message is associated), and the ActionCode and/or AnnouncementList parameters are used to designate any desired feature-related actions (e.g., call tear-down, or playing of an announcement/tone). The MSC performs the requested actions (e.g., delivering text to be displayed via the handset, as depicted in step  2 ) and responds back to the SCP (as illustrated in step  3 ). 
         [0038]    By combining the mechanisms that are illustrated in  FIGS. 4 and 5 , the result is a novel approach for how standard WIN-based capabilities can be applied to enable feature control signaling between the user handset and a network-based service platform (when the user handset is served via CS access). The present invention has the following properties. First, the invention requires new logic that must be incorporated into the applicable dual-mode handsets. Such handsets must be able to interpret user inputs (via appropriate function keys or other handset-specific user interface technologies) in order to determine associated digit strings for each feature control event. These digit strings may be sent as ‘feature codes’ in the context of “pseudo-3WC” invocations. 
         [0039]    Second, the invention does not require any new capabilities in existing cellular Radio Access Networks or in existing MSCs (or in existing HLRs, as with the USSD approach). It relies solely on existing (i.e., already standardized) WIN capabilities from the current cellular networks, thereby avoiding the need for additional network enhancements. 
         [0040]    This present invention focuses on the use of WIN to support the desired capabilities. CDMA networks are viewed as the principal market for this capability (given the lack of other suitable solutions for addressing this market need). However, it is noted that analogous solutions might be pursued for other IN-based network technologies, other than WIN (e.g., corresponding CAMEL-based procedures might be pursued if USSD capabilities are not available, or if a more common approach is desired across GSM and CDMA solutions). A similar approach might also be pursued for wireline networks, potentially helping to facilitate the migration path for existing wireline network operators as they evolve their networks towards an IMS-based approach. Thus, this concept can be applied to the following areas: (i) use of WIN to support an IMS centralized service control model (as described herein); (ii) use of Customized Application Mobile Enhanced Logic (CAMEL) to support an IMS centralized service control model; (iii) use of wireline IN-based technologies such as Advanced Intelligent Networks (AIN) to support an IMS centralized service control model; and, (iv) use of wireline IN-based technologies such as Core INAP to support an IMS centralized service control model. 
       Usage of Invention for Several Illustrative Services 
       [0041]    Having described the invention in general terms, the following description illustrates how this invention could be applied to several specific services (i.e., for Call Waiting [CW] and for Three-Way Calling [3WC]). 
         [0042]    The overall processing associated with a Call Waiting invocation is partitioned into five segments, as highlighted in  FIG. 6  and briefly discussed below. 
         [0043]    1. When an incoming call arrives for a CW subscriber with an existing active CS call, the CW Application Server (AS) sends a WIN CCDIR message to the MSC. The DisplayText parameter is used to deliver a textual message to the CW subscriber (i.e., a notification of an additional incoming call, including the calling party identity), used as a CW notification. The BillingiD parameter identifies the specific existing call to which the message is associated. The MSC performs the requested actions, i.e., delivering text to be displayed via the handset, and responds back to the CW AS. 
         [0044]    2. Upon receiving the incoming call notification, the CW subscriber decides to invoke CW, e.g., via a flash signal. The handset detects this event and generates a Flash with Information message, containing a special digit string that is used to designate the user-requested event. The MSC receives this message and detects that a corresponding WIN trigger, e.g., All_Calls, is armed. The MSC then sends an ORREQ message to the designated SCP (i.e., to the CW AS depicted in  FIG. 6 ), containing the corresponding feature control digits. The CW AS uses the received digits to determine the appropriate (CW) logic to invoke. In this case, the CW AS responds with an orreq message that instructs the MSC to abort its processing, while leaving the existing call intact. 
         [0045]    3. The CW AS initiates procedures to establish a connection from the new incoming caller to the target CW subscriber (e.g., using Third-Party Call Control [3PCC] logic in the IMS domain). The CW AS also places the prior connection (between the CW subscriber and the original connected party) on hold (e.g., via re-INVITE procedures in the IMS domain). 
         [0046]    Based on the above processing, the CW subscriber is connected to the new incoming call and the original call is placed on hold. 
         [0047]    Further processing (associated with subsequent CW logic) is partitioned into the final two segments, as depicted in  FIG. 6 . 
         [0048]    4. The CW subscriber can toggle between the set of active and held calls via flash signals. The handset detects this event and generates a Flash with Information message, containing a special digit string that is used to designate the user-requested event. The MSC receives this message and detects that a corresponding WIN trigger (e.g., All_Calls) is armed. The MSC sends an ORREQ message to the designated SCP (i.e., to the CW AS), containing the corresponding feature control digits. The CW AS uses the received digits to determine the appropriate (CW) logic to invoke. The CW AS responds with an orreq message that instructs the MSC to abort its processing, while leaving the existing call intact. 
         [0049]    5. The CW AS initiates procedures to re-establish the original call to the target CW subscriber and to place the connection between the CW subscriber and the new incoming call on hold (e.g., using re-INVITE procedures in the IMS domain). 
         [0050]    Based on the above processing, the CW logic is able to toggle the active/held states of the connections between the CW subscriber and the new/original calls. 
         [0051]      FIG. 7  illustrates how the current invention may be applied for Three Way Calling (3WC). In this flow, a Media Resource Function (MRF) is used to provide the network-based bridging functionality for this service. 
         [0052]    The overall processing (associated with the 3WC invocation) is partitioned into four segments, as shown in  FIG. 7  and described below. 
         [0053]    1. The 3WC subscriber establishes an active call with another party (“Party  1 ”). Once this call is established, the 3WC subscriber decides to invoke 3WC (e.g., via entry of address digits for the additional party [“Party  2 ”]). The handset detects this event and generates a Flash with Information message, containing a digit string that includes the address of Party  2 . The MSC receives this message and detects that a corresponding WIN trigger (e.g., All_Calls) is armed. The MSC therefore sends an ORREQ message to the designated SCP (i.e., to the 3WC AS shown in the figure), containing the corresponding digits. The 3WC AS uses the received digits to determine the appropriate (3WC) logic to invoke. In this case, the 3WC AS responds with an orreq message that instructs the MSC to abort its processing, while leaving the existing call intact. 
         [0054]    2. The 3WC AS initiates procedures to establish a connection from the 3WC subscriber to a Media Resource Function (MRF), e.g., using 3PCC logic in the IMS domain. The 3WC AS instructs the MRF to [a] establish a connection from the 3WC subscriber toward the target party (Party  2 ) and [b] place the existing connection from the 3WC subscriber toward the original connected party on hold (e.g., via 3PCC and re-INVITE procedures in the IMS domain). 
         [0055]    Based on the above processing, the 3WC subscriber is connected (via the MRF) to Party  2 , and the original call leg toward Party  1  is placed on hold. 
         [0056]    Subsequent processing associated with the 3WC service, used to bridge the three parties together, is partitioned into two additional segments as briefly discussed below. 
         [0057]    3. The 3WC subscriber requests to be bridged together with Parties  1  and  2 . The handset detects this event and generates a Flash with Information message, containing a special digit string that is used to designate the user-requested event. The MSC receives this message and detects that a corresponding WIN trigger (e.g., All_Calls) is armed. The MSC then sends an ORREQ message to the designated SCP (i.e., to the 3WC AS), containing the corresponding feature control digits. The 3WC AS responds with an orreq message that instructs the MSC to abort its processing, while leaving the existing call intact. 
         [0058]    4. The received digits are used to determine the appropriate (3WC) logic to invoke. The 3WC AS initiates procedures to bridge together the three call legs (to the 3WC subscriber, to Party  1 , and to Party  2 ) via the MRF to establish the three-way call (e.g., via 3PCC and re-INVITE procedures in the IMS domain). 
         [0059]    While there has been described and illustrated a method and system for supporting feature control signaling between a user handset and a network-based service platform when the user handset is served by circuit switched access based on the use of WIN triggers, it will be apparent to those skilled in the art that modifications and variations are possible without deviating from the spirit and broad scope of the present invention which shall be limited solely by the scope of the claims appended hereto.