Telecommunications – Radiotelephone system – Zoned or cellular telephone system
Utility Patent
1998-12-21
2001-01-02
Le, Thanh Cong (Department: 2749)
Telecommunications
Radiotelephone system
Zoned or cellular telephone system
C455S456500, C455S517000, C455S067150
Utility Patent
active
06169903
ABSTRACT:
FIELD OF THE INVENTION
This invention relates in general to wireless communication systems, and more specifically to a method and apparatus for determining a location at which a subscriber unit is positioned.
BACKGROUND OF THE INVENTION
Many forms of wireless communication systems are in use today. Both one-way (outbound only) systems, such as one-way paging systems, and two-way (outbound and inbound) systems, such as two-way messaging systems, abound. Subscriber unit position measurement is a desirable feature, as is a reliable estimation of the quality of the connection (Quality of Service) between the subscriber unit and the base station transmitters that are closest to the subscriber unit. The former opens the possibility of a large number of applications, and the latter forms the basis for optimized targeted delivery of messages.
A problem that exists in many of today's wireless communication systems is a lack of sufficiently accurate subscriber unit location determination and a further lack of adequate Quality of Service measurement. This problem is particularly severe in systems utilizing frequency shift keyed (FSK) modulation.
Thus, what is needed is a method and apparatus in a wireless communication system for determining a location at which a subscriber unit is positioned. Preferably, the method and apparatus will also provide an improved Quality of Service measurement. In addition, it is highly desirable that the method and apparatus be suitable for operation in FSK systems.
SUMMARY OF THE INVENTION
An aspect of the present invention is a method in a wireless communication system for determining a location at which a sub-scriber unit is positioned. The method comprises the steps of defining a plurality of sub-areas within a coverage area of the wireless communication system, and positioning a plurality of transmitters within ones of the plurality of sub-areas, each transmitter positioned at a transmitter location. The method further comprises the step of programming a memory, in at least one of the subscriber unit and a controller of the wireless communication system, with a plurality of unique transmitter identifiers and a corresponding plurality of transmitter locations; and periodically transmitting a locator signal from the plurality of sub-areas during a plurality of time slots coordinated such that, within a sub-area, no more than one transmitter transmits during each of the plurality of time slots, the locator signal comprising one of the plurality of unique transmitter identifiers for identifying a transmitter from which the locator signal is sent. The method further comprises the steps of monitoring, by the subscriber unit, the locator signal to determine a plurality of propagation delays between the subscriber unit and ones of the plurality of transmitters received; and estimating, by one of the subscriber unit and the controller, the location of the subscriber unit from the plurality of propagation delays and the plurality of transmitter locations corresponding to the plurality of unique transmitter identifiers received.
Another aspect of the present invention is a controller in a wireless communication system for facilitating a determination of a location at which a subscriber unit is positioned. The controller comprises a network interface for receiving a message, and a processing system coupled to the network interface for processing the message. The processing system comprises a memory programmed with a plurality of unique transmitter identifiers. The controller further comprises a base station interface coupled to the processing system for controlling a plurality of transmitters to transmit the message. The processing system is programmed to define a plurality of sub-areas within a coverage area of the wireless communication system, ones of the sub-areas including the plurality of transmitters, each transmitter positioned at a transmitter location; and to periodically control the plurality of transmitters to transmit a locator signal from the plurality of sub-areas during a plurality of time slots coordinated such that, within a sub-area, no more than one transmitter transmits during each of the plurality of time slots. The locator signal comprises one of the plurality of unique transmitter identifiers for identifying a transmitter from which the locator signal is sent.
Another aspect of the present invention is a subscriber unit in a wireless communication system for facilitating a determination of a location at which the subscriber unit is positioned. The subscriber unit comprises a receiver for receiving wirelessly transmitted information, and a processing system for processing the wirelessly transmitted information. The processing system is programmed to control the receiver to monitor a locator signal that is periodically transmitted from a plurality of transmitters within ones of a plurality of sub-areas defined within a coverage area of the wireless communication system, each transmitter positioned at a transmitter location. The locator signal is transmitted during a plurality of time slots coordinated such that, within a sub-area, no more than one transmitter transmits during each of the plurality of time slots. The locator signal comprises one of a plurality of unique transmitter identifiers for identifying a transmitter from which the locator signal is sent. The processing system is further programmed to determine from the locator signal a plurality of propagation delays between the subscriber unit and ones of the plurality of transmitters received.
REFERENCES:
patent: 5369681 (1994-11-01), Boudreau et al.
patent: 5475863 (1995-12-01), Simpson et al.
patent: 5845213 (1998-12-01), Sumner et al.
Dorenbosch Jheroen Pieter
Souissi Slim
Breeden R. Louis
Cong Le Thanh
Motorola Inc.
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