Determining the geographical location from which an emergency call originates in a packet-based communications network
View Patent ↗In order that emergency service vehicles can be dispatched to the correct destination promptly, accurate information about the location of the caller is needed. Another problem concerns routing emergency calls to the correct destination. For emergency calls a universal code is used such as 911 in North America and 112 in Europe. This universal code cannot be used to identify the destination of the call. These problems are particularly acute for nomadic communications systems such as voice over internet protocol communications networks. That is because user terminals change network location. These problems are solved by enabling the geographical location of the emergency caller to be determined by entities within a packet-based network without the need for modification of existing emergency services network infrastructure.
1. A method of providing a routing key for routing an emergency call from a packet-based communications network node to an emergency services network node in a switched telephone network, the packet-based communications network comprising an access part and a core part, said method comprising the steps, performed at a node of the core part of the packet-based communications network, of:
(i) requesting, during the emergency call, a node in the access part of the packet-based communications network to determine a current geographical location of a terminal from which the emergency call originates;
(ii) receiving information about the determined current geographical location from the node in the access part of the packet-based communications network;
(iii) generating a routing key on the basis of the received information and pre-specified information about geographical locations served by particular emergency service network nodes; and
(iv) storing said generated routing key together with the received information at the node in the core part of the packet-based communications network.
2. A method as claimed in claim 1 wherein said step (ii) further comprises receiving a call-back number from which the emergency call originates.
3. A method as claimed in claim 1 which further comprises providing the stored information to the switched telephone network for receipt by a public safety answering point (PSAP).
4. A method as claimed in claim 3 wherein said stored information is provided via an E2 interface.
5. A computer program stored on a computer readable medium and arranged to control a location gateway server in a packet-based communications network in order to carry out the method of claim 1 .
6. A method of routing an incoming emergency call in a packet-based communications network to an appropriate emergency services answering point in a switched telephone network, the packet-based communications network comprising an access part and a core part, said method comprising:
(I) at a packet-based call server in the core part of the packet-based communications network, receiving the emergency call;
(ii) requesting a node in the access part of the packet-based communications network to determine a current geographical location of a terminal from which the emergency call originates;
(iii) at a location gateway server in the core part of the packet-based communications network, receiving information about the determined current geographical location from the node in the access part of the packet-based communications network and using that to generate a routing key;
(iv) at the call server, routing the emergency call using the generated routing key; and
(v) storing said generated routing key together with the received information at the location gateway server.
7. A method as claimed in claim 6 wherein said information is received at the location gateway server as a result of polling a location information server in the access part of the packet-based communications network.
8. A method as claimed in claim 6 wherein said packet-based communications network is a voice over internet protocol network.
9. A method as claimed in claim 6 wherein said terminal is a nomadic entity.
10. A method as claimed in claim 6 which further comprises making the stored information accessible to an automatic location identification node in an emergency services network.