Telecommunications – Radiotelephone system – Emergency or alarm communication
Reexamination Certificate
1999-07-29
2002-08-13
Maung, Nay (Department: 2681)
Telecommunications
Radiotelephone system
Emergency or alarm communication
C455S003050, C455S426100
Reexamination Certificate
active
06434377
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a procedure as defined in the preamble of claim
1
.
The invention applies to a wireless local loop (WLL) in which subscriber's stations are connected via a radio link over a base transceiver station to an access node (AN) and from the access node to a local exchange over a standard V
5
interface, in which the subscriber ports are identified by means of an L
3
address.
In a GSM-based mobile network (GSM, Global System for Mobile Communications), it is possible to make a so-called emergency call even if the subscriber cannot be identified in the service network concerned (emergency setup). An emergency call can also be made from a mobile station containing no subscriber identification module (SIM). Subscribers connected to a local exchange via a V
5
interface consistent with the ETS 300 347-1 standard are identified by their L
3
address both in the local exchange and in the access node. The L
3
address is an individual number for the subscriber port in the V
5
interface. L
3
address (Layer
3
address) refers to a layer
3
address according to the OSI model (Open Systems Interconnection).
When a subscriber in a GSM network cannot be served by his/her own network but is within the coverage area of a base transceiver station linked to a GSM based WLL access node, or if the subscriber is in his/her proper network but the subscriber identification module SIM fails, preventing the use of TMSI (Temporary Mobile Subscriber Identity) or IMSI (International Mobile Subscriber Identity) data for call setup, it is possible that the person will try to call a common emergency number if there is an emergency situation. The call will founder on the L
3
address because the calling subscriber cannot be identified in the subscriber identification procedure, or authentication procedure, and the subscriber therefore has no L
3
address available.
In a prior-art procedure, successful setup of an emergency call is ensured by defining non-existent extra subscribers in the local exchange and access node. In a situation where an unidentified subscriber is trying to call a common emergency number, the call is set up over a V
5
interface using the identification data of a non-existent subscriber.
A problem with this prior-art procedure is that it increases the size of the subscriber database.
The object of the invention is to eliminate the above-mentioned drawback.
A specific object of the invention is to disclose a procedure that enables a call originated by an unidentified and/or undefined subscriber in a mobile network to be set up over a V
5
interface without the need to create non-existent subscribers in the local exchange.
SUMMARY OF THE INVENTION
The procedure of the invention is characterised by what is presented in claim
1
.
According to the invention, an emergency call to a predetermined emergency number attempted by a subscriber unidentified and/or undefined in the local exchange is detected during an emergency call and subscriber identification procedure, and a free L
3
address is selected and the unidentified subscriber's emergency call is set up using this free L
3
address over a V
5
interface in accordance with the ordinary call setup procedure.
In an embodiment of the procedure, the free L
3
address is a normal L
3
address of an existing subscriber.
In an embodiment of the procedure, the free L
3
address is a predetermined value in the V
5
/L
3
address range, and this value has been reserved for the setup of emergency calls, to be used for emergency calls made by unidentified subscribers.
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Altera Law Group LLC
Maung Nay
Nokia Corporation
Vuong Quochien B.
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