Telecommunications – Radiotelephone system – Zoned or cellular telephone system
Reexamination Certificate
1998-06-10
2004-09-28
Kuntz, Curtis (Department: 2643)
Telecommunications
Radiotelephone system
Zoned or cellular telephone system
C455S436000, C455S437000
Reexamination Certificate
active
06799046
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Technical Field
The present invention relates to a method and system for servicing a wireless communication network in general, and in particular to a method and system for servicing a mobile telephone communication network. Still more particularly, the present invention relates to a method and system for locating a mobile telephone within a cellular telephone communication network.
2. Description of the Prior Art
In a cellular telephone communication network, the service area is divided into multiple cells, with each cell being served by a base station. During normal operation, when a mobile telephone (or mobile station) is moved from one cell to another within the cellular telephone communication network while the mobile telephone has an active connection, the cell currently servicing the mobile telephone will have to perform a hand-off operation during which the mobile telephone is instructed to tune to a new channel served by the base station of the cell into which the mobile telephone is entering.
In the prior art, the selection of a target cell for hand-off is typically based upon a comparison of the received signal strength indication (RSSI) at different neighboring cells, and the cell having the highest RSSI will be selected. However, this simplistic selection algorithm suffers from a lack of accuracy due to the fluctuations of RSSI from shadowing losses in multi-path fading. As a result, suboptimal target cells are often selected, which leads to further unnecessary hand-offs soon thereafter.
Generally speaking, a hand-off operation may be facilitated if the location of a mobile telephone within the cellular telephone communication network is known to the base station performing the hand-off. In addition to location triggered hand-off, there are also other reasons for determining the location of the mobile telephone within the cellular telephone communication network. For example, in order to manage the mobile telephone traffic within the network more efficiently, the telephone service provider needs to know the approximate location of each mobile telephone having an active connection. Furthermore, the ability to locate a mobile telephone within the cellular telephone communication network with an adequate accuracy can also find application in mobile telephone location services, which provide the location information of a mobile telephone to an authorized service subscriber, even if the mobile telephone does not have an active connection.
Aside from the telephone servicing end, it is also desirable to locate mobile telephone users who are making calls. For example, a chief problem with servicing request for a 911-emergency service is that emergency service providers, such as police, generally do not know the location of the mobile telephone user calling the emergency number because of the mobile nature of the telephone. This problem is exacerbated in situation in which the mobile telephone user who called the emergency number cannot provide enough location information to allow the emergency service provider to dispatch emergency services to the location of the call. Thus, there are numerous strong incentives to determine the location of the mobile telephone within the cellular telephone communication network.
Nevertheless, previously installed cellular systems had little capability in this regard. For example, in an Advanced Mobile Phone Service (AMPS) system, a user can be located within a cell by determining which base station antenna is being utilized to service the user. However, a cell can be as large as 3-5 miles in radius, making this information practically useless. While there are other alternative solutions, such as the use of a Global Positioning System (GPS) unit at each mobile telephone, or the use of triangulation algorithm on a transmitting mobile telephone, these and similar approaches are often too costly, if they can even provide a satisfactory result. Consequently, it is desirable to provide an improved method for estimating the location of a mobile telephone within a cellular telephone communication network that is both reliable and cost effective.
SUMMARY OF THE INVENTION
In view of the foregoing, it is therefore an object of the present invention to provide an improved method for servicing a wireless communication network.
It is another object of the present invention to provide an improved method and system for servicing a mobile telephone communication network.
It is yet another object of the present invention to provide an improved method and system for locating a mobile telephone within a cellular telephone communication network.
In accordance with a preferred embodiment of the present invention, a mobile telephone communication network has multiple cells, with each of the cells having a base station coupled to at least one antenna. A cell is initially divided into a number of sections. A location information and a signal information, such as a received signal strength indication, is then collected at each of the sections within the cell. The collected location information and signal information are subsequently processed into a signal information profile database. Utilizing the signal information profile database, the section within the cell at which a mobile telephone is located can be determined.
All objects, features, and advantages of the present invention will become apparent in the following detailed written description.
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Crane John D.
Dillon & Yudell LLP
Kuntz Curtis
Nortel Networks Limited
Taylor Barry W
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