Telecommunications – Radiotelephone system – Zoned or cellular telephone system
Reexamination Certificate
1999-03-29
2001-12-11
Bost, Dwayne (Department: 2681)
Telecommunications
Radiotelephone system
Zoned or cellular telephone system
C455S457000, C455S404200
Reexamination Certificate
active
06330454
ABSTRACT:
BACKGROUND
1. Technical Field
The present invention relates generally to wireless communication systems; and more particularly to a wireless communication system that may be accessed via a service control point by a customer application to determine the approximate location of a mobile unit operating within the wireless communication system.
2. Related Art
Cellular wireless communication systems are generally known in the art to facilitate wireless communications within respective service coverage areas. Such wireless communication systems include a “network infrastructure” that facilitates the wireless communications with mobile units operating within a service coverage area. The network infrastructure typically includes a plurality of base stations dispersed throughout the service coverage area, each of which supports wireless communications within a respective cell (or set of sectors). The base stations couple to base station controllers (BSCs), with each BSC serving a plurality of base stations. Each BSC couples to a mobile switching center (MSC) which also couples to the PSTN, the Internet and/or to other MSCs.
A wireless mobile unit operating within the service coverage area communicates with one or more of the base stations. The base stations route the communications to the MSC via a serving BSC. The MSC routes the communications to another subscribing wireless unit via a BSC/base station path (which may be the same BSC/base station path when the communications are with another subscribing unit serviced by the same base station) or via the PSTN/Internet/other network to terminating destination.
Various operating standards have been developed to standardize wireless communications. The wireless communication operating standards include, for example, the Advanced Mobile Phone Service (AMPS) standards, the Global Standards for Mobile Communications (GSMC), the Code Division Multiple Access (CDMA) standards and the Time Division Multiple Access (TDMA) standards. A standard that is employed in North America for interconnectivity of MSCs is the IS-41 standard. These operating standards set forth the technical requirements that facilitate compatible operation between equipment of differing vendors.
Mobile units are used for many differing applications. In many applications, they simply serve as telephones for their users. However, in other applications, they take the place of two-way radios. A particular example of such usage is when mobile units are provided to delivery or service personnel. The mobile units are used primarily for communication between a central office and the worker when the worker is dispatched. In such applications, the central office is frequently interested in the present location of the worker for scheduling purposes and progress updates. To determine a present location of the worker, the central office must call the worker via the mobile unit and request his or her present location. Such technique not only delays the worker but requires a central office person to complete the communication, retrieve the location information and update the worker's status.
Other applications also require location information. For example, when a mobile unit is employed to create a data link between a user and a remote computerized application, the location of the mobile unit is typically required by the remote computerized application, such as automobile navigation services. A technique used to provide the location information is to incorporate a Global Positioning System (GPS) receiver in the automobile, to couple the GPS receiver to a local computer system to record the GPS location of the automobile and to relay the GPS location to the remote computerized application via the mobile unit. Such an application, while appropriate for navigation services since exact coordinates are typically required, is expensive, requires substantial overhead and consumes significant wireless bandwidth.
Thus, there is a need in the art for a system that allows a central location to determine the location of a mobile unit without dedicated overhead or substantial wireless bandwidth consumption.
SUMMARY OF THE INVENTION
Thus, to overcome the shortcomings of the prior systems, among other shortcomings, a wireless communication system constructed according to the present invention interfaces with a Service Control Point (SCP) to provide location information for a serviced mobile unit. In a typical operation, the SCP sends a locate request to a Home Location Register (HLR) of the wireless communication system, requesting the location of the serviced mobile unit. The HLR then accesses a serving Mobile Switching Center (MSC), the serving MSC being identified by the HLR as currently servicing the mobile unit.
Depending upon the particular constraints of the requested operation by the SCP (e.g., immediate locate request or most recent locate request), the serving MSC either retrieves location information for the mobile unit from its Visitor Location Register (VLR) or sends a page to the mobile unit. The mobile unit responds to the page and, based upon the cell/sector from which the mobile unit responded, the serving MSC determines an approximate location of the mobile unit.
With the location information retrieved, the serving MSC then converts the cell/sector identification to longitude and latitude information. The serving MSC may also convert a time-stamp associated with the location information (when the location information was recorded) to a normalized time standard such as Greenwich Standard Time. With this location information determined, the serving MSC provides the information to the requesting SCP. This information may be provided either directly by the serving MSC to the requesting SCP or may be provided via the HLR that receive the request.
In converting the cell/sector identification in which the mobile unit was last located, the serving MSC (or other element of the wireless communication system that performs the conversion) provides the most likely location of the mobile unit within the cell/sector. A typical cell/sector extends across a large geographic area. Resultantly, the mobile unit could reside at any location within its current cell/sector. Thus, in converting the cell/sector ID to a most likely longitude and latitude for the mobile unit, serving MSC makes educated approximations. As one approximation, the serving MSC determines the center of area for the cell/sector and assumes that the mobile unit resides at that location. As another approximation, if cell/sector services a heavily traveled road, for example, the serving MSC determines a mean location on the road and assumes that the mean location is where the mobile unit resides. Other techniques may also be applied to best approximate the mobile unit within the cell/sector from which the mobile unit responded.
Moreover, other aspects of the present invention will become apparent with further reference to the drawings and specification which follow.
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Bost Dwayne
Garlick Bruce
Harrison James
Nortel Networks Limited
West Lewis
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