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Self calibration of signal strength location system

A signal and target positioning technology, which is applied in the field of target positioning system and can solve the problems such as the change of transmission power cannot be solved.

Active Publication Date: 2006-09-06
SYMBOL TECH INC
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

This calibration requires each mobile unit to perform a special calibration procedure when it is brought into service and, unless the mobile unit is recalibrated, does not account for changes in transmit power as the mobile unit or its battery ages

Method used

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  • Self calibration of signal strength location system
  • Self calibration of signal strength location system

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Embodiment Construction

[0012] Referring to the diagram of FIG. 1, there is schematically shown a wireless local area network system 10 operating in accordance with a protocol such as IEEE standard 802.11. The system 10 of FIG. 1 includes a computer 12 acting as a server and connected by a wired network to access points 14, 18, 20, wherein the access points 14, 18, 20 are arranged at fixed locations within an area such as schools, factories or hospitals. In addition to providing wireless communication between the server computer 12 and one or more mobile units 16 via access points 14, 18, 20 associating the mobile units 16, the system 10 also provides for locating mobile units within an area. Features.

[0013] In system 10, the location of a mobile unit is determined by receiving signals from the mobile unit at a plurality of access points and measuring the received signal strength, such as through the RSSI functionality of a standard 802.11 receiver. The system may first be calibrated to form a d...

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Abstract

A system for locating mobile units in a data communications system based on signal strength measurements of mobile unit transmissions is calibrated for variations in mobile unit transmitter power by determining range of a mobile unit from an access point using two way time ranging. The time ranging is compared to the value for range based on signal strength and a correction value for the mobile unit is updated based on the difference between range based on time ranging and the range based on signal strength.

Description

[0001] priority statement [0002] This application claims all benefit of Provisional Application Serial No. 60 / 473096 filed May 23, 2003 and assigned to the same assignee as this application. Background technique [0003] The present invention relates to object location systems, and more particularly to systems having multiple access points in which mobile units communicate with the access points using a wireless data communication protocol such as IEEE Standard 802.11. The invention particularly relates to systems in which the location of a mobile unit is determined by measuring the strength of signals transmitted by the mobile unit which are received by an access point to estimate the distance of the mobile unit from the access point. The term "access point" as used in this application applies to access points contemplated by standard 802.11 or other standards that interface a computer or wired network to a wireless medium and also to RF ports and Cell Controller, which is...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): H04B17/00G01SG01S5/14H04Q7/00
CPCG01N33/6842
Inventor C·泽格林D·P·戈伦
Owner SYMBOL TECH INC