Object cluster detection and estimation
First Claim
1. A method of estimating a number of physical objects clustered together, wherein each object includes wireless communication circuitry capable of receiving and transmitting radio frequency (RF) signals, the method comprising:
- causing each of a plurality of physical objects to generate a radio frequency (RF) transmission during a respective transmission timeslot;
by each physical object, generating Received Signal Strength Indication (RSSI) values for the RF transmissions received by that respective physical object from the other physical objects, such that each physical object receives a transmission from, and generates an RSSI value for, every other physical object of the plurality of physical objects;
by a node, collecting and collectively analyzing the RSSI values generated by the plurality of physical objects, wherein collectively analyzing the RSSI values comprises applying a clustering algorithm; and
estimating how many of the plurality of physical objects are clustered together based on the collective analysis of the RSSI values generated by the plurality of physical objects.
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Abstract
A vehicle tracking system includes a wheel unit containing RF communication circuitry. The wheel units communicate with fixed nodes of a monitoring system. In some embodiments, the wheel units are placed on shopping carts and are used to track the shopping carts in a vicinity of a store. The system may implement a variety of tracking-relating features, including detecting unauthorized store exit events, estimating the number of shopping carts that are clustered together, and inhibiting shopping cart theft.
109 Citations
24 Claims
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1. A method of estimating a number of physical objects clustered together, wherein each object includes wireless communication circuitry capable of receiving and transmitting radio frequency (RF) signals, the method comprising:
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causing each of a plurality of physical objects to generate a radio frequency (RF) transmission during a respective transmission timeslot; by each physical object, generating Received Signal Strength Indication (RSSI) values for the RF transmissions received by that respective physical object from the other physical objects, such that each physical object receives a transmission from, and generates an RSSI value for, every other physical object of the plurality of physical objects; by a node, collecting and collectively analyzing the RSSI values generated by the plurality of physical objects, wherein collectively analyzing the RSSI values comprises applying a clustering algorithm; and estimating how many of the plurality of physical objects are clustered together based on the collective analysis of the RSSI values generated by the plurality of physical objects. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 22, 23, 24)
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13. A system for detecting clusters of objects, comprising:
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a plurality of wireless communication devices that are configured for attachment to respective movable objects; and an external system configured to communicate bi-directionally with the wireless communication devices; wherein the wireless communication devices are configured to (1) generate RF transmissions during respective transmission timeslots, (2) measure signal strengths of the RF transmissions received from the other wireless communication devices, such that each wireless communication device receives, and measures a signal strength of, a transmission from every other wireless communication device of said plurality, and (3) report said signal strengths to the external system; wherein the external system is programmed to collectively analyze the reported signal strengths using a clustering algorithm and, based on said analysis, estimate how many of the wireless communication devices are clustered together. - View Dependent Claims (14, 15, 16, 17, 18, 19, 20, 21)
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Specification