Telecommunications – Radiotelephone system – Zoned or cellular telephone system
Reexamination Certificate
1997-09-30
2001-02-13
Hunter, Daniel S. (Department: 2749)
Telecommunications
Radiotelephone system
Zoned or cellular telephone system
Reexamination Certificate
active
06188905
ABSTRACT:
TECHNICAL FIELD
This invention relates to a dynamic channel allocation scheme for a mobile communications network and, more particularly, to a scheme for maintaining uninterrupted service in a mobile network.
BACKGROUND OF THE INVENTION
Most existing mobile communication systems incorporate a cellular architecture in which geographical areas are divided into cells. Each cell contains a base station for interfacing mobile units in the cell to a mobile switching center (MSC) and a backbone wired network. The MSC connects the base stations together for communication therebetween and to provide communication with the public switched network. A base station is equipped with radio transceivers that enable rf communications over available frequency channels with mobile units in the cell.
In the area where two neighboring cells intersect, the cells overlap to form a handover region. Handover typically occurs when the signal strength or quality of a connection between a mobile unit and a base station falls below a predetermined threshold. This generally occurs when the mobile unit enters the handover region at the edge of a cell. As the mobile unit moves from one cell to another, an ongoing call involving the mobile unit is handed off from a channel in the current cell to an available channel in the next cell. However, if no channel is available in the next cell, the call drops (i.e., terminates) because the mobile unit moves out of range of the base station of the current cell. Since handover requests for channels come without warning, often wireless resources are not available when needed and calls get dropped.
Dropping calls significantly effects the service quality for cellular customers. In mobile communications systems, it is important that mobile units with an established radio connection on a radio channel are able to maintain that connection when moving from one cell to another cell. Accordingly, there is a need in the art to minimize the number of calls dropped due to handover failure.
SUMMARY OF THE INVENTION
The present invention overcomes the shortcomings of the prior art by providing a scheme which allows essentially uninterrupted cellular service to subscribers. Specifically, the present invention provides an intelligent profile based dynamic channel allocation service feature for individual subscribers.
The present invention exploits the predictability of repetitive travel behavior to anticipate usage. If a mobile unit's instantaneous location is known by the mobile communications network, then that knowledge can be used by the network to anticipate the real time needs of the mobile unit across the network. Thus, scarce and expensive wireless resources can be managed more effectively to maximize their usage and improve the grade of service (GoS) to all end-users.
People commute from their homes to their work locations in the morning and vice versa in the evening generally traveling the same route with a few alternatives. Another group of subscribers who travel the same general route at the same general time includes sales people who regularly go to appointments or see a client. These subscribers commonly make telephone calls and pass through a number of cells during their trip. Thus, an ongoing call involving an individual subscriber is typically subjected to multiple handovers. One of the objects of the present invention is to provide a service feature in the form of uninterrupted service to subscribers who repeatedly travel the same route when using their mobile unit during a particular time period. Another object of the present invention is to implement the service feature transparently to the subscribers without involving redesign of system hardware requirements.
To avoid dropping calls involving the aforementioned subscribers, it is critical to ensure that a free channel is available in the next cell when handover occurs. One of the objects of the present invention is to create profiles of subscribers which include statistical information such as data related to the timing and route regularly traveled. A profile can be createl by geographically tracking the subscribers. In addition, statistics can be compiled to account for diversions resulting from problems such as road congestion and weather.
Another object of the present invention is to utilize a subscriber's profile to anticipate a subscriber's movement along the route and particularly movement from one cell to another. Thus, the subscriber's profile allows the mobile communications system to intelligently allocate channels before entry of the subscriber into the handover region, thereby ensuring that an ongoing call is not dropped. Implementation of the service feature does not burden channel resources since the actual route of a preferred subscriber is followed and channel resources are dynamically allocated on a real time basis once the new cell service area has been accurately determined.
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Agrawal Dharma P.
Agrawal Prathima
Rudrapatna Ashok N.
AT&T Corp.
Banner & Witcoff , Ltd.
Hunter Daniel S.
Nguyen Thuan T.
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