Method and apparatus for time synchronisation in wireless networks
AssigneeImagination Technologies Limited
InventorIan R. Knowles
Life of this patent
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Abstract
A wireless media distribution system is provided comprising an access point (6) for broadcasting media and a plurality of stations (2) for reception and playback of media. Each station is configured for receiving and decoding a timestamp in a beacon frame transmitted repeatedly from the access point. This is used to control the output signal of a station physical layer clock (12) which is then used as a clock source for an application layer time synchronisation protocol. This application layer time synchronisation protocol can then be used in the station to control an operating system clock (8) for regulating playback of media.
Claims20
A wireless station comprising:
- a physical layer clock;
- and
- receive and decode circuitry for repeatedly receiving and decoding a broadcast beacon frame and a timestamp included therein, wherein the physical layer clock comprises:
- an oscillator configured to generate a clocking signal,
- a counter configured to increment in dependence on the clocking signal,
- an error calculation unit configured to determine an error between a current counter value and a received value in the timestamp, and
- a rate adjustment module configured to adjust the clocking signal in dependence on the determined error and provide the adjusted clocking signal to the counter;
- wherein the receive and decode circuitry is configured to overwrite the counter with the received value in the timestamp.
A wireless station comprising:
- a physical layer clock;
- and
- receive and decode circuitry for repeatedly receiving and decoding a broadcast beacon frame and a timestamp included therein, wherein the physical layer clock comprises:
- an oscillator configured to generate a clocking signal,
- a counter configured to increment in dependence on the clocking signal,
- an error calculation unit configured to determine an error between a current counter value and a received value in the timestamp, and
- a rate adjustment module coupled between the oscillator and the counter and configured to adjust the clocking signal in dependence on the determined error and provide the adjusted clocking signal to the counter.
A method for synchronising a physical layer clock of a wireless station to a physical layer clock of an access point, the method comprising:
- repeatedly receiving and decoding a broadcast beacon frame and a timestamp included therein;
- generating a clocking signal;
- incrementing a counter in dependence on the generated clocking signal;
- determining an error between a current counter value and a received value in the timestamp;
- adjusting the clocking signal in dependence on the determined error and providing the adjusted clocking signal to the counter;
- and
- overwriting the counter with the received value in the timestamp.
Dependencies are inferred from the claim text.