Telecommunications – Radiotelephone system – Special service
Reexamination Certificate
1998-05-06
2001-06-12
Legree, Tracy (Department: 2681)
Telecommunications
Radiotelephone system
Special service
C455S436000, C455S461000, C455S426100
Reexamination Certificate
active
06246872
ABSTRACT:
FIELD OF THE INVENTION
The invention relates to a method and mobile switching centre for handling a dropped connection between a mobile station and a mobile switching centre in a cellular communications system.
BACKGROUND OF THE INVENTION
Mobile communications systems typically consist of a mobile switching centre connected to a number of basestation controllers, each basestation controller controlling a number of basestation transceivers each located in a respective cell. A first connection can be established between a mobile station located in a particular cell and the mobile switching centre by establishing a traffic channel (RF link) between the basestation transceiver in the particular cell, and a corresponding channel from the basestation transceiver through the relevant basestation controller to the mobile switching centre. A call between a mobile terminal and a second terminal (which may be a wireless terminal, a wireline terminal, or an inter-mobile switching centre agent for example) is connected when a second connection from the mobile switching centre to the second terminal is made, and the first and second connections are bridged.
In the normal course of events, a traffic channel is assigned through a traffic channel assignment procedure and then communications over the assigned traffic channel commence. This “normal course of events” includes handoff, conversation mode, mobile origination and mobile termination scenarios. In a handoff, a traffic channel assignment is sent and the mobile starts communicating with a new basestation over a new traffic channel. In conversation mode the mobile simply continues to communicate over the assigned channel. In a mobile origination, a traffic channel is assigned as a result of a user of the mobile originating a call and then communications over the traffic channel commence. In a mobile termination, a traffic channel is assigned as a result of another party making a call to the mobile terminal, and then communications over the assigned traffic channel commence.
In any of the above scenarios, the traffic channel may be lost after the successful completion of the traffic channel assignment. This may be due to failure to connect to the newly assigned traffic channel as in the case of a handoff, mobile origination or mobile termination, or simply due to the failure to maintain communications over the traffic channel after it has been connected. In existing systems, when a traffic channel is dropped in any of the above-identified circumstances, the entire call is torn down meaning that the second connection to the second terminal is also disconnected, and either the caller or the callee must redial the other party's number to be reconnected.
One problem with this situation is that dropped calls and connect failures are annoying to customers. More importantly, any time that a call is dropped or fails to be connected, there exists the possibility that the parties involved will not bother to attempt to reconnect, and this represents lost revenue to the operating companies.
Another drawback with dropped calls is that some of them may be emergency calls such as 911 calls and a person making such a call may not have the opportunity to attempt it again should the call be dropped.
SUMMARY OF THE INVENTION
It is an object of the invention to obviate or mitigate one or more of the above identified disadvantages.
According to a first broad aspect, the invention provides in a communications system, wherein a call connection between a first mobile terminal and a connection entity comprises a first connection over an assigned traffic channel between the mobile terminal and a mobile switching centre and a second connection between the mobile switching centre and the connection entity, wherein said first connection may be lost after successfully assigning said traffic channel, a method of recovering from such a lost first connection comprising the steps of: a) maintaining said second connection; b) paging the first mobile terminal to determine its location; c) establishing a new first connection between the mobile terminal and the mobile switching centre; and d) bridging the second connection with said new first connection thereby re-connecting the call.
According to another broad aspect, the invention provides a mobile switching centre for use in a communications system, wherein a call connection between a first mobile terminal and a connection entity comprises a first connection over an assigned traffic channel between the mobile terminal and the mobile switching centre and a second connection between the mobile switching centre and the connection entity, wherein said first connection may be lost after said traffic channel has been successfully assigned, the mobile switching centre comprising: a) a connection holding mechanism for maintaining said second connection after said first connection is lost; b) a paging mechanism for paging the first mobile terminal to determine its location; c) connection establishment circuitry for coordinating the establishment of a new first connection between the mobile terminal and the mobile switching centre; and d) connection bridging circuitry for bridging the second connection with said new first connection thereby re-connecting the call.
REFERENCES:
patent: 5153902 (1992-10-01), Buhl et al.
patent: 5369681 (1994-11-01), Boudreau et al.
patent: 5566225 (1996-10-01), Haas
patent: 5566236 (1996-10-01), MeLampy et al.
patent: 5590177 (1996-12-01), Vilmur et al.
patent: 5752185 (1998-05-01), Ahuja
patent: 5995830 (1999-11-01), Amin et al.
patent: 6032040 (2000-02-01), Choy et al.
Lee Henry
Lewis Len
Legree Tracy
Nortel Networks Limited
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