US 6,720,922 B2Granted

Radio-frequency badge for location measurement

AssigneeMicrosoft Corporation

InventorsLyndsay Williams, Roger M. Needham

Life of this patent

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Abstract

A system and process for determining the location of persons and objects using transmitters (TXs) that transmit location messages to at least one receiver connected to a computer, in a network of computers. The TXs are small, battery-powered, radio frequency transmitters carried by the person or object whose location is being tracked. The location message signals are picked up by one or more receivers (RXs) scattered throughout an environment. Each TX transmits a code with a unique identifier, and each RX also has a unique identifier. The RXs measure the signal strength of each location message transmission. Each RX is connected to a computer, which is in turn connected to a network. The RX computers send the data messages including the TX identifier, radio signal strength, and RX identifier to a central computer via the network. The central computer uses this information to determine the location of the TXs.

Claims39

Dependent claims

A location tracking system for determining the location of persons and objects using transmitters that transmit location messages to at least one receiver connected to a computing device in a network of computing devices, comprising:

a plurality of battery-powered, radio frequency (RF), transmission-capable only transmitters (TXs), each of which is carried by the person, or attached to the object, whose location is to be determined;
at least one RF receiver (RX), each of which receives location messages transmitted by TXs within signal range of the RX;
at least one computing device, each of which is in communication with a different one of the RX and receives data messages from the RX each of which is generated using a location message received from a TX;
a centralized computing device which is in communication with each of the computing devices associated with a RX via said network, wherein said centralized computing device determines the location each of person carrying a TX or object having an attached TX, using data derived from data messages forwarded to it from a computing device associated with a RX.

1 more element

Dependencies are inferred from the claim text.

Facts

Application: 10/112,217Filed 29 Mar 2002
Published: US 2003/0184475 A12 Oct 2003
Granted: 13 Apr 2004
Term ends: Not estimatedThe source records don’t support an estimate.

Classification8 codes

G01S 5/14
Using radio waves: determining absolute distances from a plurality of spaced points of known location
G01C 21/20
Navigation; Navigational instruments not provided for in groups G01C1/00 - G01C19/00: instruments for performing navigational calculations
G01S 5/017
Determining conditions which influence positioning, e.g. radio environment, state of motion or energy consumption: detecting state or type of motion
G01S 5/019
Determining conditions which influence positioning, e.g. radio environment, state of motion or energy consumption: energy consumption