Telecommunications – Radiotelephone system – Emergency or alarm communication
Reexamination Certificate
1998-11-06
2001-05-29
Hunter, Daniel (Department: 2749)
Telecommunications
Radiotelephone system
Emergency or alarm communication
C455S433000, C455S432300, C455S436000, C455S414200
Reexamination Certificate
active
06240284
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Technical Field of the Invention
This invention relates to telecommunication systems and, more particularly, to a system and method of handling emergency calls from roaming mobile stations in a radio telecommunications network.
2. Description of Related Art
When a mobile subscriber initiates an emergency call such as a 911 call, the call is connected through a serving mobile switching center (MSC) to an end office (EO) known as a Public Safety Answering Point (PSAP). There may be situations in which the call is then prematurely disconnected. This disconnection may be due to the subscriber hanging up, loss of radio signal, border rescan problems, loss of the subscriber's mobile station (MS) during an attack, or other reasons. Current and previous versions of TR45.2 (PN 3581) state that under these circumstances, the serving MSC attempts to reestablish the call. In other words, the serving MSC pages for the MS, and if a page response is received, an alert signal is sent to the responding MS. If the alert signal is answered, the call is reconnected to the PSAP.
However, in existing networks, it is currently not possible to reconnect the emergency MS under certain circumstances. For example, the emergency MS may immediately originate another call to a different destination before the emergency call can be reconnected to the PSAP. Also, the MS may have been operating near the border of the serving MSC when the emergency call was dropped, and by the time the serving MSC attempts to reestablish the call the MS may have travelled into a bordering MSC. In this case, the emergency call cannot be reestablished.
There are no known prior art teachings of a solution to the aforementioned deficiency and shortcoming. In order to overcome the disadvantage of existing solutions, it would be advantageous to have a system and method of handling emergency calls in a radio telecommunications network in which an emergency MS is reconnected to the PSAP following a premature disconnection. The invention would reconnect the call to the PSAP even if the emergency MS attempts to originate a different call, or if the emergency MS has travelled into the service area of a bordering MSC.
SUMMARY OF THE INVENTION
In one aspect, the present invention is a method in a radio telecommunications network of reconnecting an emergency call between a mobile station with an emergency (emergency MS) and a public safety answering point (PSAP) when the call has been disconnected before the call was finished. The network includes a serving mobile switching center (MSC) serving the emergency MS, and a home location register (HLR) that stores features and subscription data for the emergency MS. The method comprises the steps of activating a hotlining feature in the HLR when the emergency call is begun, determining that the emergency call was disconnected before the call was finished, determining that the emergency MS attempts to access the network after the emergency call was disconnected, and automatically connecting the emergency MS to the PSAP.
The network may include a plurality of MSCs, and the emergency MS may register in a second MSC other than the serving MSC after the hotlining feature has been activated. The method then includes the steps of notifying the HLR that the emergency MS has registered in the second MSC, determining in the HLR that the emergency MS has an unfinished emergency call, and instructing the second MSC to connect the emergency MS to the PSAP.
If the emergency MS registers within the service area of a second MSC other than the serving MSC before the hotlining feature has been activated, the method includes the steps of sending a registration notification (REGNOT) message from the second MSC to the HLR, sending a registration cancellation (REGCANC) message from the HLR to the previous serving MSC identifying the emergency MS, and sending a return REGCANC message from the previous serving MSC to the HLR identifying that the emergency MS has an unfinished emergency call and providing a PSAP number to the HLR. This is followed by sending a qualification directive (QUALDIR) message from the HLR to the second MSC with the PSAP number and instructions to connect the emergency MS to the PSAP. Thereafter, when a registration or a call origination is received from the emergency MS in the second MSC, the call is automatically connected to the appropriate PSAP.
In another aspect, the present invention is a system in a radio telecommunications network for reconnecting an emergency call between an emergency MS and a PSAP when the call has been disconnected before the call was finished. The system comprises means within the HLR for activating a hotlining feature for the emergency MS when the emergency call is begun, means within the serving MSC for determining that the emergency call was disconnected before the call was finished, means within the serving MSC for determining that the emergency MS attempts to access the network after the emergency call was disconnected, and means within the serving MSC for automatically connecting the emergency MS to the PSAP.
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patent: 5596625 (1997-01-01), LeBlanc
patent: 5598460 (1997-01-01), Tendler
patent: 5689548 (1997-11-01), Maupin et al.
patent: 5712900 (1998-01-01), Maupin et al.
patent: 5797093 (1998-08-01), Houde
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patent: WO 97/21314 (1997-06-01), None
patent: WO 97/28659 (1997-08-01), None
patent: WO 97/44971 (1997-11-01), None
Bugnon Jacques
Nguyen Binh
Hunter Daniel
Le Lana
Smith ,Danamraj & Youst, P.C.
Telefonaktiebolaget L M Ericsson (publ)
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