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Beacon synchronization in wifi based systems

  • US 9,125,152 B2
  • Filed: 08/16/2011
  • Issued: 09/01/2015
  • Est. Priority Date: 08/16/2011
  • Status: Expired due to Fees
First Claim
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1. A wireless device comprising:

  • a transceiver for transmitting and receiving messages to and from an access point, the wireless device having a sleep mode from which a device application wakes up to perform actions and the transceiver may turn on to listen for beacons from the access point to transmit and receive packets; and

    a scheduling system which schedules each application wake up and transceiver turn-on time, the scheduling system comprising a clock drift estimator and wake up adjustment procedure which determines an expected clock drift from a history of synchronization errors calculated with each beacon reception, wherein each synchronization error is computed as the difference between a wireless device actual beacon arrival time and the wakeup time;

    wherein the scheduling system schedules the wakeup time such that;


    tbIdeal

    t
    bWakeup

    du+E where tbIdeal is an ideal beacon time, tbWakeup is beacon reception wakeup time, Δ

    du is device-up period and E reflects the expected clock drift;

    wherein the scheduling system schedules the wakeup time independent of timestamps associated with beacons.

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