Conversational bearer negotiation
First Claim
1. A method of setting up a call between first and second nodes of a communication system, said call extending across a circuit switched access network available to the first node and a packet switched backbone network, the networks being interconnected by at least one Media Gateway, the method comprising:
- 1) sending a call initiation message from the first node to the second node via a control node over a packet switched access network available to the first node;
2) at the control node, obtaining from a Home Subscriber Server the identity of a Media Gateway Control Function controlling that Media Gateway which will terminate the circuit switched call for the first node;
3) establishing a circuit switched call between the first node and said Media Gateway;
4) sending from the control node to the first node over the packet switched access network, a circuit switched access number associated with the identified Media Gateway Control Function;
5) calling said access number from the first node, and as part of the call set-up procedure communicating the identity of the Media Gateway selected to terminate the call to the Media Gateway Control Function;
6) terminating the circuit switched call at the selected Media Gateway; and
7) sending an update message from the first node to the second node over the packet switched access network, the Media Gateway Control Function incorporating into the update message an IP address of said selected Media Gateway.
1 Assignment
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Accused Products
Abstract
A method of setting up a call between first and second nodes of a communication system when the call extends across a circuit switched access network and a packet switched backbone network interconnected by a Media Gateway. A control node obtains from a Home Subscriber Server, the identity of a Media Gateway Control Function controlling that Media Gateway which will terminate the call within the circuit switched access network. The first node calls an access number notified to it by the Media Gateway Control Function, and as part of the call setup procedure, the identity of the Media Gateway selected to terminate the call is communicated to the second node.
35 Citations
20 Claims
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1. A method of setting up a call between first and second nodes of a communication system, said call extending across a circuit switched access network available to the first node and a packet switched backbone network, the networks being interconnected by at least one Media Gateway, the method comprising:
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1) sending a call initiation message from the first node to the second node via a control node over a packet switched access network available to the first node; 2) at the control node, obtaining from a Home Subscriber Server the identity of a Media Gateway Control Function controlling that Media Gateway which will terminate the circuit switched call for the first node; 3) establishing a circuit switched call between the first node and said Media Gateway; 4) sending from the control node to the first node over the packet switched access network, a circuit switched access number associated with the identified Media Gateway Control Function; 5) calling said access number from the first node, and as part of the call set-up procedure communicating the identity of the Media Gateway selected to terminate the call to the Media Gateway Control Function; 6) terminating the circuit switched call at the selected Media Gateway; and 7) sending an update message from the first node to the second node over the packet switched access network, the Media Gateway Control Function incorporating into the update message an IP address of said selected Media Gateway. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17)
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18. A method of operating a Serving Call State Control Function of an IP Multimedia Subsystem to set up a call from a first client terminal to a second client terminal, the method comprising:
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receiving a SIP INVITE message from the first client terminal over a packet switched access network, the INVITE being identified as requiring the setting up of a circuit switched call from the first client terminal; forwarding the SIP INVITE message to a second client terminal; sending a query to a Home Subscriber Server in order to identify a Media Gateway Control Function which controls that Media Gateway which will be selected to terminate the circuit switched call from the first client terminal; sending a SIP REFER message from the Serving Call State Control Function to the first client terminal over the packet switched access network, said SIP REFER message including a circuit switched access number associated with the identified Media Gateway Control Function, which sets up the circuit switched call when the client terminal calls the circuit switched access number; and forwarding a SIP update message received from the first client terminal to the second client terminal over the packet switched access network, wherein the SIP update message includes an IP address of the selected Media Gateway incorporated into the SIP update message by the Media Gateway Control Function.
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19. A method of operating a Media Gateway Control Function arranged to control a Media Gateway which provides a user plane interface between a circuit switched network and a packet switched backbone network, the method comprising:
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receiving a SIP INVITE message from a first client terminal via a Serving Call State Control Function of an IP Multimedia Subsystem, wherein the SIP INVITE message is initiating a call from the first client terminal to a second client terminal; in response to receipt of said SIP INVITE message, selecting a call back telephone number from a pool of numbers allocated to the Media Gateway Control Function; sending the selected number to the first client terminal in a SIP message; answering a subsequent call from the first client terminal to the selected number including receiving the identity of the Media Gateway which will terminate the circuit switched call for the first client terminal as part of the call set-up procedure; incorporating into a SIP update message an IP address of the selected Media Gateway; sending the SIP update message to the Serving Call State Control Function for forwarding to the second client terminal; and informing the Media Gateway of the IP address of the second client terminal.
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20. A method of setting up a call between a first node and a second node in a communication system, wherein the first node has access to both a circuit switched access network and a packet switched access network, and the call is set up across the circuit switched access network and a packet switched backbone network, the networks being interconnected by an originating Media Gateway, the method comprising:
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utilizing packet switched signaling to identify the originating Media Gateway and an originating Media Gateway Control Function controlling the originating Media Gateway and to provide a telephone number for the originating Media Gateway Control Function to the first node; establishing a circuit switched call leg between the first node and the originating Media Gateway Control Function; sending an IP address of the originating Media Gateway from the originating Media Gateway Control Function to the second node via a terminating Media Gateway Control Function; establishing a packet switched call leg between the originating Media Gateway and the terminating Media Gateway; and through-connecting the call to the second node.
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Specification