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Location based handoff for mobile devices

  • US 7,840,227 B2
  • Filed: 03/30/2005
  • Issued: 11/23/2010
  • Est. Priority Date: 04/06/2004
  • Status: Active Grant
First Claim
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1. A communications system comprising:

  • a plurality of mobile wireless units movably located within a defined space of a wireless local area network;

    a plurality of fixed access points disposed at known locations in the defined space, each access point operating at a dedicated frequency different from the dedicated frequency of its nearest neighbor access points;

    a means for tracking movement of at least one mobile unit within the defined space including;

    a memory storing a map of the access points and relative signal strengths of signals from the access points at predefined locations in the defined space,a means for scanning identified scanning frequencies of access points nearby a selected one of the mobile wireless units to measure actual signal strengths between the selected mobile unit and each of the nearby access points, anda means for calculating a location of the selected mobile unit relative to the map by comparing the actual signal strengths with the map of relative signal strengths at predefined locations in the defined space;

    a means for assigning the nearby access points with strongest signals at the calibrated location to the selected mobile unit based on the map of relative strengths in the defined space and communicating the dedicated frequencies of the nearby access points to the selected mobile unit;

    wherein the tracking means tracks the movement of the selected mobile unit by periodically scanning the frequencies of the assigned access points adjacent the calculated location and predicts future locations of the selected mobile unit;

    wherein the assigning means assigns the nearby access points based on the predicted location of the selected mobile unit and the map;

    wherein the scanning means only scans the frequencies of the assigned nearby access points.

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