FORM 2
The Patent Act 1970
(39 of 1970)
&
The Patent Rules, 2005

COMPLETE SPECIFICATION
(SEE SECTION 10 AND RULE 13)

TITLE OF THE INVENTION

“Untromboned Communication for Multi-networked Simultaneous Alerting and Flexible Pickup”

APPLICANTS:

Name Nationality Address
Alcatel Lucent France 54 rue de la Boétie, 75008 Paris, France

The following specification particularly describes and ascertains the nature of this invention and the manner in which it is to be performed:-

FIELD OF INVENTION
[001] This invention relates to telecommunication networks, and more particularly but not exclusively, to optimum network resource usage during interworking between different telecommunication networks.

BACKGROUND
[002] This section introduces aspects that may be helpful in facilitating a better understanding of the invention. Accordingly, the statements of this section are to be read in this light and are not to be understood as admissions about what is in the prior art or what is not in the prior art.
[003] With increasing usage of internet based telephony, Next Generation Networking (NGN) services using NGN/ IP Multimedia Subsystem (IMS) networks are taking over legacy networks. IMS is an architectural framework for delivering Internet Protocol (IP) multimedia services.
[004] Presently, telecommunication service providers enable users having multiple terminals in different networks to reveal only one number publicly. Telecommunication service providers route a call destined for the public number to all terminals specified by a subscriber. The called user may then answer the call from any one of his terminals. The terminals may include a mobile terminal, fixed line, Session Initiation Protocol (SIP) terminal or a web client. Multiple called user terminals are alerted simultaneously with the help of NGN/IMS network based SIP services but resources on atleast two networks will be used. One of the networks used will be the NGN network triggering service and the other network resource used is the communication path created for alerting the called user terminals. For calls between users belonging to the same network the use of two networks results in wastage of network resources. This wastage of network resources while alerting or in conversation with a terminal in the same network as the calling user is known as tromboning.
[005] Currently switch based parallel switching is employed to overcome tromboning. When a call request is received to a user who has subscribed for parallel ringing service, a switch will be used to simultaneously alert all the terminals of the user. However, switches are unable to provide value added services and simultaneously alerting all the called user terminals in different kinds of networks is also not supported.
[006] Parallel alerting to multiple terminals in different networks is also possible using an SIP based service and the SIP based service should always be triggered through an NGN interface. However, for a call from a mobile terminal to another mobile terminal, the call request will be directed to the NGN network before being sent to the mobile network. Both the signaling channel and media channel for the call would be through the NGN network although the call is not answered by the NGN network terminal which leads to tromboning Customized Application for Mobile network Enhanced Logic (CAMEL) Application Part 4 (CAP4)/Capability Set2 (CS2) may also be used to support multiple call legs in a call and each leg may be controlled separately. On receiving the call request, CAP4/CS2 initiates alerts towards the called user mobile terminal and web clients and a communication path is established between the calling user and the terminal that answered the alert. However, here highly advanced switches with CAP4/CS2 capability is required and currently very few Mobile Switching Centres (MSC’s) support the capability.

SUMMARY
[007] In view of the foregoing, an embodiment herein provides a method for enabling a user to answer a call using a communication terminal chosen from a plurality of communication terminals in different networks. The calling user calls a public number belonging to the called user and the application of the called user initiates independent alerts to the plurality of configured communication terminals in various networks. Timer reset messages are sent periodically to network of the calling user. All the communication terminals are monitored for an answer and the network of the answering terminal is identified. The alerts to all other terminals are cancelled after a communication connection is established between the calling user and the answering terminal of the called user through the network of calling user. While the calling user network may be a Next Generation Network (NGN), a Public Switched Telephone Network (PSTN) or a Public Land Mobile Network (PLMN) but the alerts to the terminals are made using the NGN. The called user have to subscribe to the service of answering the call using a communication terminal chosen from the plurality of communication terminals and the called user should specify the plurality of communication terminals. A check is made to determine if the called user has subscribed for the service of answering the call using a communication terminal chosen from the plurality of communication terminals before initiating call alerts to the plurality of communication terminals. Session Initiation Protocol (SIP) for Internet Protocol (IP) Multimedia Subsystem (IMS) Service Control (ISC) interface and Customized Applications for Mobile networks Enhanced Logic (CAMEL) Application Part (CAP) interface may also be used.
[008] In view of the foregoing, an embodiment herein provides a system for enabling a user to answer a call using a communication terminal chosen from a plurality of communication terminals. The calling user calls a number of a communication terminal belonging to the called user and the network of the called user initiates independent alerts to the plurality of communication terminals. Timer reset messages are sent periodically to network of the calling user. All the communication terminals are monitored for an answer and the network of the answering terminal is identified. The alerts to all the terminals are cancelled after a communication connection is established between the calling user and the answering terminal of the called user through the network. The network may be a Next Generation Network (NGN), a Public Switched Telephone Network (PSTN) or a Public Land Mobile Network (PLMN) and the alerts to the terminals are made using the NGN. The called user may subscribe for the service of answering the call using a communication terminal chosen from the plurality of communication terminals and the called user may specify the plurality of communication terminals. A check is made to determine if the called user has subscribed for the service of answering the call using a communication terminal chosen from the plurality of communication terminals before initiating call alerts to the plurality of communication terminals. Session Initiation Protocol (SIP) Internet Protocol (IP) Multimedia Subsystem (IMS) Service Control (ISC) interface and Customized Applications for Mobile networks Enhanced Logic (CAMEL) Application Part (CAP) interface are used. The system may be configured to send reset timer messages periodically to network of the calling user. These and other aspects of the embodiments herein will be better appreciated and understood when considered in conjunction with the following description and the accompanying drawings.

BRIEF DESCRIPTION OF THE FIGURES
[009] Some embodiments of apparatus and/or methods in accordance with embodiments of the present invention are now described, by way of example only, and with reference to the accompanying drawings, in which:
[0010] Figure 1 schematically illustrates a called user having terminals in different networks, according to an embodiment herein;
[0011] Figure 2 schematically illustrates a flowchart depicting a method to overcome tromboning in NGN networks, according to an embodiment herein;
[0012] Figure 3 schematically illustrates the different layers of the network module, according to an embodiment herein;
[0013] Figure 4 schematically illustrates a diagram depicting the called user answering a call from a PSTN/PLMN terminal, according to an embodiment herein;
[0014] Figures 5a and 5b schematically illustrate a sequence diagram depicting the called user answering a call from a mobile terminal, according to an embodiment herein;
[0015] Figures 6a and 6b schematically illustrate a sequence diagram depicting the called user answering a call from a fixed line terminal, according to an embodiment herein;
[0016] Figure 7 schematically illustrates a diagram depicting the called user answering a call from an IP terminal, according to an embodiment herein; and
[0017] Figure 8a and 8b schematically illustrate a sequence diagram depicting the called user answering a call from an IP terminal, according to an embodiment herein.

DESCRIPTION OF EMBODIMENTS
[0018] The embodiments herein and the various features and advantageous details thereof are explained more fully with reference to the non-limiting embodiments that are illustrated in the accompanying drawings and detailed in the following description. Descriptions of well-known components and processing techniques are omitted so as to not unnecessarily obscure the embodiments herein. The examples used herein are intended merely to facilitate an understanding of ways in which the embodiments herein may be practiced and to further enable those of skill in the art to practice the embodiments herein. Accordingly, the examples should not be construed as limiting the scope of the embodiments herein.
[0019] The embodiments herein achieve a method for adaptively overcoming tromboning in NGN networks by an NGN/IMS network-hosted multi-interfaced application based method. The method facilitates alerting any number of terminals in any number of networks and allows a called user to answer the call from any convenient terminal. Referring now to the drawings, and more particularly to FIGS. 1 through 8, where similar reference characters denote corresponding features consistently throughout the figures, there are shown embodiments.
[0020] When a calling user wishes to communicate with the called user, the calling user sends a call request to the called user. The calling user may initiate the call from a mobile terminal in a PLMN network or from a fixed line terminal in a PSTN network or from a SIP terminal in an NGN/IMS network. If the called user has multiple communication terminals in different networks, the called user may subscribe to a service of answering the call using the communication terminal chosen from the multiple communication terminals. If the called user has subscribed for the service, the method facilitates alerting all the terminals in the different networks and the called user may answer the call from any convenient terminal. For example the called user can answer the call from a mobile terminal in a PLMN network or from a fixed line terminal in a PSTN network or from a SIP terminal in an NGN/IMS network. Various interfaces such as, Interactive Voice Response (IVR), web interface, may be provided for configuring the terminals to be alerted. The method may be triggered in any network and all terminals may be alerted through NGN interface. An independent connection may be initiated by method towards all the terminals in same or different networks through SIP IP multimedia subsystem Service Control interface (ISC) interface in NGN core network. All the alerted terminals may be monitored by the SIP interface to determine the terminal from which the call is answered. On the call being answered, a communication connection may be established to the answering terminal using the network in which the call is answered. The alerts sent to all the terminals are then cancelled by the SIP interface. The called terminal which answered the call could be connected to the calling user through the network interfaces of the calling party. An activity timer, of the Initial Detection Point (IDP) message received by the network for the calling user number, may be manipulated and reset. An IDP indicates initial states in basic call and connection processing where control may be transferred to the Intelligent Network (IN) service. After the connection is established to the relevant terminal, all the other connections that were established for alerting purposes may then be terminated. NGN resources may not be utilized for a call between two users in the same network and thus tromboning is prevented. All the terminals may be alerted simultaneously and the method may be used for calls originating from any network to the call destination in any network.
[0021] Figure 1 schematically illustrates a called user having terminals in different networks. When the calling user 101 wishes to communicate with the called user, the calling user 101 sends a call request to the called user. The call request may be routed to the network module 105 by the calling user network 106. The called user may have multiple terminals in different networks and the called user may subscribe to a service of answering the call using the terminal chosen from the multiple terminals. Various interfaces such as, Interactive Voice Response (IVR), web interface, may be provided for configuring the terminals to be alerted. The multiple terminals may be atleast one of a mobile terminal 102 in PSTN/PLMN 103 network, a fixed line terminal 107 in PSTN/PLMN 103 network and an IP terminal 108 in an NGN 104 network. The network module 105 alerts all the terminals of the called user. The called user may choose to answer the call from any convenient terminal. All the alerted terminals may be monitored to determine the terminal from which the call is answered. The answer may be intercepted and the network of the terminal which answered the call may be identified. A connection may then be established to the answering terminal in the network in which the call is answered using the network of the calling user and the network of the terminal which answered the call. After the connection is established to the answering terminal, all the connections that were established for alerting purposes may then be terminated.
[0022] Figure 2 schematically illustrates a flowchart depicting a method to overcome tromboning in NGN 104 networks. When the calling user 101 wishes to communicate with the called user, the calling user 101 sends (201) a call request to the called user. On receiving (202), the call request at the network level, the network checks to determine (202) if the called user has subscribed for service. The service facilitates in alerting multiple terminals in different networks simultaneously. If the called user has not subscribed for the service, the call may proceed (204) as a normal call. If the called user has subscribed for the service, the call request is forwarded (203) to the network module 105. The network module 105 sends (205) alerts to all the terminals in the different networks, which have been specified by the called user. For example, the multiple terminals may comprise of a mobile terminal 102 in PSTN/PLMN 103 network, a fixed line terminal 107 in PSTN/PLMN 103 network and an IP terminal 108 in an NGN 104 network. The called user may choose to answer the call from any convenient terminal. All the alerted terminals may be monitored to identify (207) the terminal from which the call is answered. If the called user answers (206) the call request, a communication connection is then established (209) to the answering terminal in the networkof the subscribed number.. After identifying the answering terminal, the connections that were established for alerting purposes are terminated (208). A communication connection is then established (209) between the answering terminal and the calling user and the call may then proceed (209) with the called user and the calling user 101 communicating with each other.
[0023] Figure 3 schematically illustrates the different layers of the network module. The network module 105 comprises an Interface Control Layer (ICL) 301, Session Control Layer (SCL) 302 and Business Logic Control Layer (BLCL) 303. The ICL 301 handles the various call connection related network messages from network and to network. The ICL 301 comprises of interfaces from different networks and the interfaces may include Intelligent Network Application Part (INAP) interfaces, CAP2/CS1 304 interface and SIP-ISC 305 interface. Interfaces present in the ICL 301 depend on the network of the called user. The interfaces present in the ICL 301 help the ICL 301 interface with the SCL 302 layer, which corresponds to the interfaces present in ICL 301. New interfaces may be added or existing interfaces may be removed from the ICL 301 based on requirements of the vendors or the network. SCL 302 is a layer capable of creating and maintaining multiple call segments in a call that may have atleast two segments. Call segments are created and managed for multiple call segments for active interfaces in the ICL 301 layer. The SCL 302 interfaces with the SIP-ISC 305 interface on the ICL 301 layer and triggers call initiation towards all the called user terminals. BLCL 303 is a layer that provides logic 306 for customizing the way for maintaining information about the terminals to be alerted. The BLCL 303 provides information about the terminals to be alerted and the BLCL 303 manages switching from the call instance created due to the calling user terminal and the call instance created for the purpose of alerting called user terminals. The BLCL 303 helps decide the criterion for selecting the terminals to be alerted. The database 307 in the BLCL 303 maintains information about the terminals to be alerted.
[0024] If the calling user 101 sends a call request to the called user, the network module 105 may be triggered though CAP2 304 interface is the called user is a mobile subscriber. Internally, the CAP interface module of the ICL 301 is triggered. Reset timer messages may be sent in response to initial DP. CAP interface module sends an internal message to the SCL 302 to create call instances and call segments for the terminal of calling user 101 and the BLCL 303 may also be triggered to obtain the list of called user terminals to be alerted. The BLCL 303 identifies the list of terminals to be alerted and sends the list to the SCL 302. On receiving the list of terminals to be alerted, the SCL 302 creates and manages separate call segments for every called user terminal to be alerted. The ICL 301 initiates call attempts towards all the terminals using SIP-ISC 305 interface and all the terminals may be triggered through NGN 104 network. As an example, if one of the terminals is a mobile terminal, a connection message may be sent to the NGN 104 network and the NGN 104 network may pass the connection message to the PLMN network using gateways. Similarly, if one of the terminals is an IP terminal, the IP terminal may be alerted by sending the connection message to the IP terminal through proxies in the NGN 104 network. All the called user terminals in different networks are alerted simultaneously and the called user may choose to answer the call from any one of the terminals.
[0025] When all the terminals are alerted, if the called user answers the call using the mobile terminal, the answer message may be communicated to the network module 105 through the NGN 104 interface. The network module 105 uses the SCL 302 to identify that the call has been answered from the mobile terminal. If the calling user 101 is sending the call request from a mobile terminal, the network module 105 uses the ICL 301 CAP interface module to activate the CAP call instance and sends the connection message towards the Mobile Switching Center (MSC) which initiated the call. The MSC may send the connection message towards the called user mobile terminal. The MSC may then receive a call waiting signal as to the terminal is already engaged due to the alert signal triggered through the NGN interface. The network module 105 then sends a disconnection towards the mobile terminal for the call triggered on NGN interface. The network module 105 also cancels the alert signals sent to all the other terminals. Now the call waiting to the mobile terminal from the network module 105 CAP gets connected to the calling user 101.
[0026] When all the terminals are alerted and if the called user answers the call using the IP terminal, the answer message may be communicated to the network module 105 through the NGN 104 interface. The network module 105 uses the SCL 302 to identify that the call has been answered from the IP terminal. If the calling user 101 is sending the call request from a mobile terminal, the network module 105 uses the ICL 301 CAP interface module to activate the CAP call instance and sends the connection message towards the MSC which initiated the call. The MSC triggers the relevant softswitch handling the calls to the IP terminal and the IP terminal may be reached through the softswitch. The MSC may then receive a call waiting signal as to the terminal is already engaged due to the call accepted for alert signal triggered through the NGN interface. The network module 105 then sends a disconnection towards the IP terminal terminal for call triggered through NGN interface. The network module 105 also cancels the alert signals sent to all the other terminals. When the alerting call towards the IP terminal has been disconnected, the call waiting to the mobile terminal from the network module 105 CAP gets connected to the calling user 101.
[0027] Figure 4 schematically illustrates a diagram depicting the called user answering a call from a PSTN/PLMN terminal. When the calling user 101 wants to communicate with the called user, the calling user 101 sends a call request to the called user. The calling user 101 may be in a PSTN/PLMN 103 network or in an NGN 104 network. A Mobile Switching Center (MSC) or a Service Switching Point (SSP) 401 in the network of called user 102 sends an IDP to the network module 105. The network module 105 sends call request messages to all the terminals of the called user. SCL 302 and BLCL 303 in the network module 105 determine the called user terminals to be alerted depending on whether the called user has subscribed for the service or not. If the called user has subscribed for the service and has multiple terminals in different networks, the call request may be sent to all the terminals in the different networks. For example, the multiple terminals may be atleast one of a mobile terminal 102 in PLMN 103 network, a fixed line terminal 107 in PSTN 103 network and an IP terminal 108 in an NGN 104 network. A softswitch 402 in the NGN 104 relays the request message to the PSTN/PLMN 103 terminals through the MSC/SSP 401 and to the called user IP terminal 108. The network module 105 sends a reset activity timer message to the network of calling user 101 to prevent the activity timer in the network of calling user 101 from expiring. The called user may choose to answer the call from any convenient terminal. If the network module 105 determines a ringing in the called user terminal, the network module 105 ignores the ringing and waits for more notifications. If the called user answers the call from the fixed line terminal, the MSC/SSP 401 sends a connect message to the MSC/SSP 401 and the MSC/SSP 401 sends an answer message to the softswitch 402. The softswitch 402 then sends a 200 OK message to the network module 105. On receiving the 200 OK message, the network module 105 sends a message to the MSC/SSP 401 to connect the answering fixed line terminal to the calling user 101 terminal. The MSC/SSP 401 sends a setup message to the answering fixed line terminal to setup the call between the calling and the called users. The network module 105 also sends messages to the softswitch 402 to cancel the alert messages that were sent to the called user terminals. The softswitch 402 sends a release message to the called user PSTN/PLMN 103 terminals through the MSC/SSP 401 and a cancel message to the called user IP terminal 108. The calling and the called users may then communicate with each other using the communication connection that was established between the calling user 101 terminal and the called user terminal 107.
[0028] Figures 5a and 5b schematically illustrate a sequence diagram depicting the called user answering the call from a mobile terminal. When calling user 101 wants to communicate with the called user, the calling user 101 sends a call request to the called user. The calling user 101 may be in a PSTN/PLMN 103 network or in an NGN 104 network. The network of the called user 102 sends an IDP to the network module 105. ICL 301 then starts (501) a context for the call request to keep track of the activities during the call. ICL 301 prepares (502) the message to be sent to the service logic in the network module 105 and the message indicates the reception of the call request. The message may then be sent to SCL 302 and BLCL 303. SCL 302 and BLCL 303 determine (503) the called user terminals to be alerted depending on whether the called user has subscribed for the service or not. If the called user has subscribed for the service, SCL 302 and BLCL 303 prepares (505) a message to be sent to the CAP interface logic and the message may indicate the CAP interface logic to hold the IDP. SCL 302 and BLCL 303 also send a reset activity timer message to ICL 301. ICL 301 then sends (504) the reset activity timer message to the network of the calling user 101. If the IDP on CAP does not receive a response, the activity timer in the calling user 101 network may expire. The reset activity timer message is sent to the network of calling user 101 to prevent the activity timer in the network of the calling user 101 from expiring and hereby maintaining the transaction. The activity timer is a transaction timer for timing the response for the IDP request.
[0029] If the called user has multiple terminals in different networks the call request may be sent to all the terminals in the different networks. For example, the multiple terminals may comprise of a mobile terminal 102 in PLMN 103 network, a fixed line terminal 107 in PSTN 103 network and an IP terminal 108 in an NGN 104 network. The called user may choose to answer the call from any convenient terminal. SCL 302 and BLCL 303 also prepare (507) a message for the SIP-ISC 305 interface logic to tell SIP-ISC 305 to send an alert to the first called user terminal. The message is sent to ICL 301. On receiving the message from SCL 302 and BLCL 303, ICL 301 activates (506) the events to wait for an answer. ICL 301 may then send (508) a SIP invitation towards the first called user terminal. If ICL 301 determines a ringing in the called user terminal, ICL 301 ignores (509) the ringing and waits for more notifications. SCL 302 and BLCL 303 may also prepare (5011) a message for the SIP-ISC 305 interface logic to tell SIP-ISC 305 to send an alert to the other called user terminal. The message is also sent to ICL 301. On receiving the message from SCL 302 and BLCL 303, ICL 301 activates (5010) the events to wait for an answer. ICL 301 then sends (5012) an SIP invitation towards the other called user terminal. If ICL 301 determines a ringing in the called user terminal, ICL 301 ignores (5013) the ringing and waits for more notifications. If the called user answers the call from the mobile terminal, the mobile network sends a 200 OK message to the network module 105. 200 OK is a Hyper Text Transfer Protocol (HTTP) response status code and indicates that the request was successful. On receiving the 200 OK message, ICL 301 reports (5014) the event to SCL 302 and BLCL 303 and sends an acknowledgement to the network of the mobile terminal. On receiving the event notification, SCL 302 and the BLCL 303 determine that the called user has chosen (5015) to answer the call from the mobile terminal. SCL 302 and BLCL 303 then prepare (5017) a message to indicate the CAP interface logic to make a connection with the mobile terminal. SCL 302 and BLCL 303 send the connection message to ICL 301. The ICL 301 then sends (5016) the connect message to the mobile network. A communication connection is made between the mobile terminal of the called user and the calling user 101. SCL 302 and the BLCL 303 may prepare (5018) a message to tell the SIP-ISC 305 interface logic to close the call context towards the mobile terminal. Call context comprises the call activity status, timers, alert signal and any other signal or information needed for communication between two communication terminals. The message is sent to ICL 301. ICL 301 prepares (5019) a SIP message to close the call alert towards the mobile terminal. ICL 301 sends the message towards the mobile network and the mobile network may respond by sending a 200 OK message to ICL 301. SCL 302 and BLCL 303 also prepare (5021) a message to indicate the SIP-ISC 305 interface logic to close the call context towards the other terminals. The message is sent to ICL 301. ICL prepares (5020) a SIP message to close the call alert towards the other terminals. ICL 301 sends the message towards the other terminals and the other terminals may respond by sending a 200 OK message to ICL 301. On receiving a response from the other terminals, ICL 301 closes (5022) the context towards other terminals.
[0030] Figures 6a and 6b schematically illustrates a sequence diagram depicting the called user answering the call from a fixed line terminal. When the calling user 101 wants to communicate with the called user, the calling user 101 sends a call request to the called user. The calling user 101 may be in a PSTN/PLMN 103 network or in an NGN 104 network. The network of called user 102 sends an IDP to the network module 105. ICL 301 then starts (601) a context for the call request to keep track of the activities during the call. ICL 301 prepares (602) the message to be sent to the service logic in the network module 105 and the message indicates the reception of the call request. The message may then be sent to SCL 302 and BLCL 303. SCL 302 and BLCL 303 determine (603) the called user terminals to be alerted depending on whether the called user has subscribed for the service or not. SCL 302 and BLCL 303 prepare (605) a message to be sent to the CAP interface logic and the message may indicate the CAP interface logic to hold the IDP. SCL 302 and BLCL 303 also send a reset activity timer message to ICL 301. ICL 301 then sends (604) the reset activity timer message to the network of the calling user 101. If the IDP on CAP does not receive a response, the activity timer in the calling user 101 network may expire. The reset activity timer message is sent to the network of calling user 101 to prevent the activity timer in the network of calling user 101 from expiring. If the called user has multiple terminals in different networks the call request may be sent to all the terminals in the different networks. For example, the multiple terminals may be atleast one of a mobile terminal 102 in PLMN 103 network, a fixed line terminal 107 in PSTN 103 network and an IP terminal 108 in an NGN 104 network. The called user may choose to answer the call from any convenient terminal. SCL 302 and BLCL 303 also prepare (607) a message for the SIP-ISC 305 interface logic to tell SIP-ISC 305 to send an alert to the first called user terminal. The message is sent to ICL 301. On receiving the message from SCL 302 and BLCL 303, ICL 301 activates (606) the events to wait for an answer. ICL sends (608) a SIP invitation towards the first called user terminal. If ICL 301 determines a ringing in the called user terminal, ICL 301 ignores (609) the ringing and waits for more notifications. SCL 302 and BLCL 303 also prepare (6011) a message for the SIP-ISC 305 interface logic to tell SIP-ISC 305 to send an alert to the other called user terminal. The message is also sent to ICL 301. On receiving the message from SCL 302 and BLCL 303, ICL 301 activates (6010) the events to wait for an answer. ICL 301 then sends (6012) an SIP invitation towards the other called user terminal. If ICL 301 determines a ringing in the called user terminal, ICL 301 ignores (6013) the ringing and waits for more notifications. If the called user answers the call from the fixed line terminal, the fixed line network sends a 200 OK message to the network module 105. On receiving the 200 OK message, ICL 301 reports (6014) the event to SCL 302 and the BLCL 303 and sends an acknowledgement to the network of the fixed line. On receiving the event notification, SCL 302 and BLCL 303 determine that the called user has chosen (6015) to answer the call from the fixed line terminal. SCL 302 and BLCL 303 then prepare (6017) a message to indicate the CAP interface logic to make a connection with the fixed line terminal. SCL 302 and BLCL 303 send the connection message to ICL 301. ICL 301 sends (6016) the connect message to the fixed line network. A communication connection is made between the fixed line terminal of the called user and the calling user 101. SCL 302 and BLCL 303 also prepare (6018) a message to indicate the SIP-ISC 305 interface logic to close the call context towards the fixed line terminal. The message is sent to the ICL 301. ICL 301 prepares (6019) a SIP message to close the call alert towards the fixed line terminal. ICL 301 sends the message towards the fixed line network and the fixed line network may respond by sending a 200 OK message to ICL 301. SCL 302 and BLCL 303 also prepare (6021) a message to indicate the SIP-ISC 305 interface logic to close the call context towards the other terminals. The message is sent to ICL 301. ICL 301 prepares (6020) a SIP message to close the call alert towards the other terminals. ICL 301 sends the message towards the other terminals and the other terminals may respond by sending a 200 OK message to ICL 301. On receiving a response from the other terminals, ICL 301 closes (6022) the context towards the other terminals.
[0031] Figure 7 schematically illustrates a diagram depicting the called user answering a call from an IP terminal. When the calling user 101 wants to communicate with the called user, the calling user 101 sends a call request to the called user. The calling user 101 may be in a PSTN/PLMN 103 network or in an NGN 104 network. A Mobile Switching Center (MSC) or a Service Switching Point (SSP) 401 in the network of called user 102 sends an IDP to the network module 105.. The network module 105 sends call request messages to all the terminals of the called user. SCL 302 and BLCL 303 in the network module 105 determine the called user terminals to be alerted depending on whether the called user has subscribed for the service or not. If the called user has subscribed for the service and has multiple terminals in different networks, the call request may be sent to all the terminals in the different networks. For example, the multiple terminals may be atleast one of a mobile terminal 102 in PLMN 103 network, a fixed line terminal 107 in PSTN 103 network and an IP terminal 108 in an NGN 104 network. A softswitch 402 in the NGN 104 relays the request message to the PSTN/PLMN 103 terminals through the MSC/SSP 401 and to the called user IP terminal 108. The network module 105 sends a reset activity timer message to the network of calling user 101 to prevent the activity timer in the network of calling user 101 from expiring. The called user may choose to answer the call from any convenient terminal. If the network module 105 determines a ringing in the called user terminal, the network module 105 ignores the ringing and waits for more notifications. If the called user answers the call from the IP terminal, the IP terminal sends a 200 OK message to the network module 105 through the softswitch 402. On receiving the 200 OK message, the network module 105 sends a message to the MSC/SSP 401 to connect the answering IP terminal to the calling user 101 terminal. The MSC/SSP 401 then sends an invitation message to the IP terminal to setup the call between the calling and the called users through the softswitch 402. The network module 105 also sends messages to the softswitch 402 to cancel the alert messages that were sent to the called user terminals. The softswitch 402 sends a release message to the called user PSTN/PLMN 103 terminals through the MSC/SSP 401 and a cancel message to the called user IP terminal 108. The calling and the called users may then communicate with each other using the communication connection that was established between the calling user 101 terminal and the called user IP terminal 108.
[0032] Figures 8a and 8b schematically illustrates a sequence diagram depicting the called user answering the call from an IP terminal. When the calling user 101 wants to communicate with the called user, the calling user 101 sends a call request to the called user. The calling user 101 may be in a PSTN/PLMN 103 network or in an NGN 104 network. The network of called user 102 sends an IDP to the network module 105. ICL 301 then starts (801) a context for the call request to keep track of the activities during the call. ICL 301 then prepares (802) a message to be sent to the service logic in the network module 105, where the message indicates reception of the call request. The message is then sent to SCL 302 and BLCL 303. SCL 302 and BLCL 303 determine (803) the called user terminals to be alerted depending on whether the called user has subscribed for the service or not. SCL 302 and BLCL 303 prepare (805) a message to be sent to the CAP interface logic and the message may indicate the CAP interface logic to hold the IDP. SCL 302 and BLCL 303 also sends a reset activity timer message to ICL 301. ICL 301 then sends (804) the reset activity timer message to the network of the calling user 101. If the IDP on CAP does not receive a response, the activity timer in the calling user 101 network may expire. The reset activity timer message is sent to the network of calling user 101 to prevent the activity timer in the network of calling user 101 from expiring. If the called user has multiple terminals in different networks the call request is sent to all the terminals in the different networks. For example, the multiple terminals may be atleast one of a mobile terminal 102 in PLMN 103 network, a fixed line terminal 107 in PSTN 103 network and an IP terminal 108 in an NGN 104 network. The called user may choose to answer the call from any convenient terminal. SCL 302 and BLCL 303 also prepare (807) a message for the SIP-ISC 305 interface logic to indicate the SIP-ISC 305 to send an alert to the first called user terminal. The message is sent to ICL 301. On receiving the message from SCL 302 and BLCL 303, ICL 301 activates (806) the events to wait for an answer. ICL 301 then sends (808) an SIP invitation towards the first called user terminal. If ICL 301 determines a ringing in the called user terminal, ICL 301 ignores (809) the ringing and waits for more notifications. SCL 302 and BLCL 303 also prepare (8011) a message for the SIP-ISC 305 interface logic to indicate the SIP-ISC 305 to send an alert to the other called user terminal. The message is also sent to ICL 301. On receiving the message from SCL 302 and BLCL 303, ICL 301 activates (8010) the events to wait for an answer. ICL 301 then sends (8012) an SIP invitation towards the other called user terminal. If ICL 301 determines a ringing in the called user terminal, ICL 301 ignores (8013) the ringing and waits for more notifications. If the called user answers the call from the IP terminal, the IP network sends a 200 OK message to the network module 105. On receiving the 200 OK message, ICL 301 reports (8014) the event to SCL 302 and BLCL 303 and sends an acknowledgement to the network of the IP terminal. On receiving the event notification, SCL 302 and BLCL 303 determine that the called user has chosen (8015) to answer the call from the IP terminal. SCL 302 and BLCL 303 then prepare (8017) a message to indicate the CAP interface logic to make a connection with the IP terminal. SCL 302 and BLCL 303 send the connection message to ICL 301. ICL 301 then sends (8016) the connect message to the IP network. A communication connection is made between the IP terminal of the called user and the calling user 101. SCL 302 and BLCL 303 also prepare (8018) a message to indicate the SIP-ISC 305 interface logic to close the call context towards the IP terminal. The message is sent to ICL 301. ICL 301 prepares (8019) a SIP message to close the call alert towards the IP terminal. ICL 301 sends the message towards the IP network and the IP network may respond by sending a 200 OK message to ICL 301. SCL 302 and BLCL 303 also prepare (8021) a message to indicate the SIP-ISC 305 interface logic to close the call context towards the other terminals. The message is sent to ICL 301. ICL 301 prepares (8020) a SIP message to close the call alert towards the other terminals. ICL 301 sends the message towards the other terminals and the other terminals may respond by sending a 200 OK message to ICL 301. On receiving a response from the other terminals, ICL 301 may close (8022) the context towards the other terminals.
[0033] Embodiments disclosed herein helps in untromboned communication between the calling user 101 and the called user having multiple terminals in different networks. NGN 105 resources are not utilized for a call between users belonging to the same network. All the terminals of the called user are alerted simultaneously. There is no dependency on the network or on the switch and there is no need for inter-working between network nodes from different vendors. The user may add terminals to or remove terminals from the list of terminals to be alerted whenever the user wants to update the list.
[0034] The description and drawings merely illustrate the principles of the invention. It will thus be appreciated that those skilled in the art will be able to devise various arrangements that, although not explicitly described or shown herein, embody the principles of the invention and are included within its spirit and scope. Furthermore, all examples recited herein are principally intended expressly to be only for pedagogical purposes to aid the reader in understanding the principles of the invention and the concepts contributed by the inventor(s) to furthering the art, and are to be construed as being without limitation to such specifically recited examples and conditions. Moreover, all statements herein reciting principles, aspects, and embodiments of the invention, as well as specific examples thereof, are intended to encompass equivalents thereof.
[0035] The functions of the various elements shown in the FIGs 1 to 8, including any functional blocks labeled as “processors”, may be provided through the use of dedicated hardware as well as hardware capable of executing software in association with appropriate software. When provided by a processor, the functions may be provided by a single dedicated processor, by a single shared processor, or by a plurality of individual processors, some of which may be shared. Moreover, explicit use of the term “processor” or “controller” should not be construed to refer exclusively to hardware capable of executing software, and may implicitly include, without limitation, digital signal processor (DSP) hardware, network processor, application specific integrated circuit (ASIC), field programmable gate array (FPGA), read only memory (ROM) for storing software, random access memory (RAM), and non volatile storage. Other hardware, conventional and/or custom, may also be included. Similarly, any switches shown in the FIGS. are conceptual only. Their function may be carried out through the operation of program logic, through dedicated logic, through the interaction of program control and dedicated logic, or even manually, the particular technique being selectable by the implementer as more specifically understood from the context.
[0036] It should be appreciated by those skilled in the art that any block diagrams herein represent conceptual views of illustrative circuitry embodying the principles of the invention. Similarly, it will be appreciated that any flow charts, flow diagrams, state transition diagrams, pseudo code, and the like represent various processes which may be substantially represented in computer readable medium and so executed by a computer or processor, whether or not such computer or processor is explicitly shown.

CLAIMS
What is claimed is:
1. A method for enabling a called user to answer a call using a communication terminal chosen from a plurality of communication terminals belonging to a plurality of networks, wherein a calling user calls a communication terminal belonging to said called user, said method further comprising steps of
initiating independent connections to said plurality of communication terminals on a calling user calling said called user;
checking for a answer from any one communication terminal from said plurality of communication terminals;
identifying network to which said communication terminal belongs, on said called user answering said communication terminal;
connecting said communication terminal to said calling user through said network; and
canceling said independent connections.

2. The method, as claimed in claim 1, wherein said network is one of
a Next Generation Network (NGN);
a Public Switched Telephone Network (PSTN); and
a Public Land Mobile Network (PLMN).

3. The method, as claimed in claim 1, wherein said independent connections are made using NGN.
4. The method, as claimed in claim 1, wherein said called user specifies said plurality of communication terminals.

5. The method, as claimed in claim 1, wherein said called user subscribes to a service of answering said call using said communication terminal chosen from said plurality of communication terminals.

6. The method, as claimed in claim 1, wherein said method further comprises of checking if said called user has subscribed to a service of answering said call using said communication terminal chosen from said plurality of communication terminals, before initiating independent connections to said plurality of communication terminals.

7. The method, as claimed in claim 1, wherein said method uses a Session Initiation Protocol (SIP) Internet Protocol (IP) Multimedia Subsystem (IMS) Service Control (ISC) interface.

8. The method, as claimed in claim 1, wherein said method uses a Customized Applications for Mobile networks Enhanced Logic (CAMEL) Application Part (CAP) interface.

9. The method, as claimed in claim 1, wherein said method uses an Intelligent Network Application Part (INAP) interface.

10. The method, as claimed in claim 1, wherein timer reset messages are sent periodically to network of said calling user.

11. A system for enabling a user to answer a call from a calling user using a communication terminal chosen from a plurality of communication terminals belonging to a plurality of networks, wherein said calling user calls said plurality of communication terminals belonging to said called user, said system further comprising of atleast one means configured for
initiating independent connections to said plurality of communication terminals on a calling user calls said called user;
checking for a answer from any one communication terminal from said plurality of communication terminals;
identifying network to which said communication terminal belongs, on said called user answering said communication terminal;
connecting said communication terminal to said calling user through said network; and
canceling said independent connections.

12. The system, as claimed in claim 11, wherein said network is one of
a Next Generation Network (NGN);
a Public Switched Telephone Network (PSTN); and
a Public Land Mobile Network (PLMN).

13. The system, as claimed in claim 10, wherein said system is configured to check if said called user has subscribed to answer said call using said communication terminal chosen from said plurality of communication terminals, before initiating independent connections to said plurality of communication terminals.

14. The system, as claimed in claim 10, wherein said system is configured to use a Session Initiation Protocol (SIP) Internet Protocol (IP) Multimedia Subsystem (IMS) Service Control (ISC) interface.

15. The system, as claimed in claim 10, wherein said system is configured to send reset timer message periodically to network of said calling user.

Dated this 8th June 2009

Dr. Kalyan Chakravarthy
Patent Agent

ABSTRACT
A system and method for enabling a user to answer a call using a communication terminal chosen from a plurality of communication terminals. The calling user calls a number of a communication terminal belonging to the called user and the network of the called user initiates independent alerts to the plurality of communication terminals. All the communication terminals are monitored for an answer and the network of the answering terminal is identified. A communication connection is established between the calling user and the answering terminal of the called user through the network. The alerts to the other terminals are then cancelled. The network may be a Next Generation Network (NGN), a Public Switched Telephone Network (PSTN) or a Public Land Mobile Network (PLMN) and the alerts to the terminals are made using the NGN.

FIG. 2