Location based handoff for mobile devices
First Claim
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.
1 Assignment
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Accused Products
Abstract
Mobile devices (121, 122, . . . , 12n) are handed off in overlapping cells (181, 182, . . . , 18n) by tracking a velocity (speed and direction) of movement of any number of the mobile devices (121, 122, . . . , 12n). Access points (141, 142, . . . , 14n) are each located in an associated operational cell (181, 182, . . . , 18n) and each operates at a dedicated frequency. The initial signal strengths are measured in advance at predefined locations within a defined space (16) to define signal strengths as location map (42). A nearby initial access point (typically the nearest) and at least two nearby (typically next nearest) access points are assigned for one of the mobile devices (121, 122, . . . , 12n), and the frequencies of each access point identified. A tracking processor (50) periodically scans the frequencies of the nearby access points to determine the location velocity of the mobile device and predict when a handoff will be appropriate. E.g., the actual signal strength measurements between the mobile device and the nearby access points are collected and analyzed to determine a proper time for a handoff of one or more of the nearby access points.
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Citations
16 Claims
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1. A communications system comprising:
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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, and a 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. - View Dependent Claims (2, 3, 4, 5)
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6. In a wireless local area network, a method comprising:
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tracking movement of a selected mobile device within a defined space using wireless access points, each access point having a dedicated frequency different from the dedicated frequency of nearby access points, the tracking including; (a) measuring actual signal strengths at the dedicated frequencies of only a designated subset of the access points neighboring a calculated location of the selected mobile device, (b) calculating an updated location of the mobile device by comparing the measured actual signal strengths with a predefined map of relative signal strengths at predefined locations in the defined space, (c) based on the predefined map and the calculated updated location, identifying from the predefined map an updated designated subset of the access points neighboring the updated calculated location with the strongest signals at the updated calculated location,and (d) periodically repeating steps (a)-(c) such that the mobile unit only scans the dedicated frequencies of the updated designated subset to determine its location; performing wireless communication with the selected mobile device using a communication access point selected from the access points of the updated designated subset; and handing off the selected mobile device from one communication access point to another communication access point based on the predefined map and the updated calculated location. - View Dependent Claims (7, 8, 9, 10, 11)
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12. A communications system comprising:
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a plurality of access points disposed at known locations in a defined space, each access point operating at a dedicated one of a plurlaity of frequencies; a mobile wireless unit movably located within the defined speace, the mobile wireless unit including a memory which stores frequencies of a designated subset of the plurality of frequencies; a computer processor which tracks movement of the mobile wireless unit and reassigning the stored frequencies of the designated subset, the computer processor being programmed to perform the steps of; measuring actual signal strengths at the frequencies of only the stored designated subset of the plurality of frequencies, calculating a location of the mobile wireless unit by comparing the actual signal strengths with a predefined map of relative signal strengths at predefined locations in the defined space; repeating the measuring and calculating step to update the calculated location periodically; updating the stored designated subset of the plurality of frequencies based on the updated calculated location and the map; providing wireless communication service to the mobile wireless unit via a selected communication access point; and handing off the mobile wireless unit from one selected communication access point to another selected communication access point based on the calculated location and the map. - View Dependent Claims (13, 14, 15, 16)
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Specification