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Method of addressing messages and communications system

  • US 7,760,677 B2
  • Filed: 06/01/2005
  • Issued: 07/20/2010
  • Est. Priority Date: 02/19/1998
  • Status: Expired due to Fees
First Claim
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1. A method of communicating between an interrogator and one or more radio frequency identification (RFID) devices, the method comprising:

  • placing the devices in communication range of the interrogator, wherein each of the devices accommodates a first predetermined number of bits to be used for a respective first value;

    causing the devices to select random values, wherein each of the devices chooses random values independently of random values selected by other devices;

    transmitting a signal from the interrogator requesting devices having first values within a specified group of one or more values to respond, the specified group being less than the entire set of values having the first number of bits;

    receiving the signal at the devices, and in response, each of the devices respectively determining if their respective first value falls within the specified group and, if so, sending a respective reply including a respective random value to the interrogator within a randomly selected time slot of a number of slots, and, if not, not sending a reply; and

    determining with the interrogator if collisions occurred between devices that sent the respective reply and, if so, adjusting the number of slots.

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