Beacon synchronization in wifi based systems

摘要

A wireless device comprises a transceiver and a scheduling system. The transceiver transmits and receives messages to and from an access point, and has a sleep mode from which it occasionally wakes at wakeup times to listen for beacons from the access point. The scheduling system schedules wakeup times according to historical beacon synchronization data.

主权项

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−tbWakeup=Δdu+E where tbIdeal is an ideal beacon time, tbWakeup is beacon reception wakeup time, Δdu 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.