Telecommunications – Radiotelephone system – Zoned or cellular telephone system
Reexamination Certificate
1999-03-31
2001-10-23
Hunter, Daniel (Department: 2684)
Telecommunications
Radiotelephone system
Zoned or cellular telephone system
C455S517000, C455S561000
Reexamination Certificate
active
06308073
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates generally to wireless telecommunications systems and, more particularly, to wireless telecommunications systems that are capable of determining and/or tracking the precise location of a remote or mobile station, and to methods used within such systems. In addition, the present invention is directed to wireless telecommunications systems and methods for providing the speed and direction of movement of a mobile station.
BACKGROUND OF THE INVENTION
Mobile and cellular telephones have come into common use today. Such equipment enables the provision of convenient telecommunications services to persons traveling in a vehicle or otherwise remote from traditional stationary telephone equipment.
To provide these services, cellular and mobile wireless communications systems generally employ a number of remote stations (often referred to as mobile stations or customer premises radio units) and one or more stationary units or base stations. The remote stations generally have the ability to establish communications links with the base stations, and the base stations are capable of establishing one or more communications links with a public service telephone network (PSTN), thus enabling the user of a remote station to communicate remotely with conventional telephones or other remote stations connected to the network.
The remote station typically comprises a cellular phone including a battery-operated transmitter/receiver, or a mobile phone, a similar device which is fixed to an object, usually an automobile. However, it is not uncommon, particularly in rural communities, for remote units to comprise stationary customer premises radio units (CPRUs). To initiate a telephone call on the public service telephone network (PSTN), a remote station will generally establish a communications link with a base station and the base station, often via a base station controller, cluster controller or control station, will establish a communications link with the public service telephone network. An exemplary wireless telecommunications system is described in U.S. Pat. No. 5,497,424, entitled “Spread Spectrum Wireless Telephone System,” which is hereby incorporated by reference.
While providing convenient telephone services, present wireless telecommunications systems have limitations. Unlike traditional stationary telephones, in which the location of the telephone is inherent in the telephone number assigned to it, remote stations operating within a wireless environment do not have such information available. Moreover, because remote stations often have the ability to move and to establish communications with many base stations as they move through a network of communications cells, absent the use of global positioning systems (GPSs), there is presently no way to know the precise location of a remote station, unless the user of the remote station is somehow able to provide that information.
For example, if a mobile station user needs emergency assistance, the user may use the mobile station to call 911 or otherwise seek help. If the user knows his or her precise location, that information may be conveyed to emergency personnel allowing aid to be rendered fairly quickly. If, however, the user is lost or is somehow incapacitated, for example, if the user is rendered unconscious after initiating a call, information concerning the user's location may not be obtained, substantially increasing the likelihood that the user will not receive the needed emergency assistance.
In addition, if a remote station is lost or stolen, there is presently no practical way for the owner of the remote station or the wireless network service provider to locate the remote station.
Thus, there is a substantial need for a wireless telecommunications system that is capable of determining the precise location of a remote station.
SUMMARY OF THE INVENTION
The present invention is directed to a wireless telecommunications system having the ability to identify or determine the location of a remote unit or remote station, and to methods used within such systems.
In one innovative aspect, the present invention is directed to a wireless telecommunications system having the ability to determine the location of a remote station using principals of triangulation or intersecting spheres. For example, to determine the location of a remote station, a wireless telecommunications system in accordance with the present invention may determine the propagation delays in signals transmitted between the remote station and a plurality of base stations, convert the respective propagation delay times to corresponding distances, and use principals of triangulation or intersecting spheres to locate the remote station.
In one preferred embodiment, a remote station may reference a base station selection table, as is done during conventional handoff procedures; determine which base stations (preferably three) are likely to be within a range of communication of the remote station; and establish communications links with the identified base stations. The base stations may then determine the propagation delays inherent in transmissions between the remote station and the respective base stations, and provide the propagation delay data back to the remote station. The remote station may then use the determined propagation delays to calculate distances to the respective bases stations. The calculated distances then may be transmitted to one or more of the respective base stations in the form of an “assist request” message and, thereafter, may be conveyed to a locator unit or to emergency personnel. Alternatively, the determined distances or propagation delays may be used by the remote station to identify the position of the remote station, and the position information may be forwarded on to one of the respective base stations. Irrespective of the specific hardware that performs the position determination, the distances from the respective base stations may be plotted as radii from the locations of the base stations within a digital map of the relevant area, and principals of triangulation or intersecting spheres may be used to, thereafter, identify the location, or possible locations, of the remote station.
Those skilled in the art will understand that the format of the information is not an issue, as the requisite calculations may be performed using time (propagation delay) or distance information. It will also be understood that, depending upon the design criteria relevant to a given wireless telecommunications system, the propagation delay and/or distance calculations may be done within the remote station, the base stations or further back within the wireless communications system, for example, within a base station controller, cluster controller, or enhanced services processor.
Additional information, such as the speed of the mobile station and the direction in which it is moving, is also obtainable in accordance with the present invention. In one presently preferred embodiment, a series of signals may be communicated between the mobile station and the base stations, as already described, with each series providing the location of the mobile station at a particular point in time. Thus, the location of the mobile station as a function of time may be determined, which is then converted into desired information such as speed and direction.
Accordingly, it is an object of the present invention to provide a wireless communications system that is capable of determining the location of a remote station or remote unit without the use of a global positioning system (GPS)
It is another object of the present invention to provide improved methods for locating a remote station within an area of a wireless communications network.
It is still another object of the present invention to provide a system and/or method for tracking and/or determining the direction and rate of travel of a mobile station within an area of a wireless communications system.
Other objects and features of the present invention will become apparen
Gavette Sherman L.
Petty John H.
Hunter Daniel
Lyon & Lyon LLP
Nguyen Thuan T.
Xircom Wireless, Inc.
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