Time Stamp Replication Within a Wireless Network

• US 20150326331A1
• Filed: 05/11/2015
• Published: 11/12/2015
• Est. Priority Date: 05/09/2014
• Status: Active Grant

• Current Assignee: Imagination Technologies Limited (Imagination Technologies Group Ltd.)
• Original Assignee: Imagination Technologies Limited (Imagination Technologies Group Ltd.)
• Inventors: Knowles, Ian
• Granted Patent: US 10,009,132 B2
• Time in Patent Office: Days
• US Class Current: 1/1
• CPC Class Codes: H04J 3/065 using timestamps
• CPC Class Codes: H04J 3/0664 unidirectional timestamps
• CPC Class Codes: H04J 3/0673 using intermediate nodes, e.g. modification of a received timestamp before further transmission to the next packet node, e.g. including internal delay time or residence time into the packet
• CPC Class Codes: H04R 2227/005 Audio distribution systems for home, i.e. multi-room use
• CPC Class Codes: H04R 2420/07 Applications of wireless loudspeakers or wireless microphones
• CPC Class Codes: H04R 27/00 Public address systems circuits for preventing acoustic reaction H04R3/02; circuits for distributing signals to loudspeakers H04R3/12; monitoring or testing arrangements for public address systems H04R29/007; amplifiers H03F
• CPC Class Codes: H04W 56/0015 one node acting as a reference for the others

Abstract

Time stamp replication within wireless networks is described. In an embodiment, a wireless station receives an input time stamp and uses this input time stamp to generate an output time stamp. The wireless station transmits the output time stamp to wireless stations in one of a number of groups which make up the wireless network. The output time stamp is generated to compensate for delays between receiving the input time stamp and transmitting the output time stamp such that output time stamp which is transmitted at a time T corresponds to the value that the input time stamp would have had if it had been received at time T (and not at a time earlier than T). This may, therefore, reduce or eliminate independent time stamp errors and jitter caused by multiple disparate systems and processes.

Claims

1. A method comprising:

receiving an input time stamp at a first wireless station in a wireless network, the wireless network comprising two or more groups of wireless stations;

storing a data pair comprising the received input time stamp and a value associated with a local clock at the first wireless station when the input time stamp was received;

calculating an output time stamp by extrapolating from at least two stored data pairs; and

transmitting a frame comprising the output time stamp to wireless stations within one of the groups.

2. A method according to claim 1, wherein receiving an input time stamp comprises:

receiving a frame comprising an input time stamp; and

extracting the input time stamp from the received frame.

3. A method according to claim 1, wherein the first wireless station comprises a counter, the method further comprising:

incrementing the counter based on said local clock at the wireless station.

4. A method according to claim 1, wherein the frame comprising an input time stamp is received via a first communication interface and the frame comprising the output time stamp is transmitted via a second communication interface.

5. A method according to claim 4, wherein the wireless station comprises a single communication interface which operates as both the first and second communication interfaces.

6. A method according to claim 1, wherein the input time stamp is:

an original time stamp generated by an access point in the wireless network;

or

a time stamp received from a master station in another group and generated by the master station based on an input time stamp received by the master station.

7. A method according to claim 1, wherein the input time stamp is a time stamp received from a master station in another group and generated by the master station based on an input time stamp received by the master station and wherein the input time stamp received by the master station is an original time stamp generated by an access point in the wireless network.

8. A method according to claim 1, wherein the frames are beacon frames.

9. A method according to claim 1, wherein the wireless station is a Wi-Fi™

station.

10. A method according to claim 1, wherein the wireless station is a wireless speaker.

11. A wireless station comprising:

a local clock;

a first communication interface arranged to receive an input time stamp and to store a data pair comprising the received input time stamp and a value associated with the local clock when the input time stamp was received;

a time stamp correction module arranged to calculate an output time stamp by extrapolating from two stored data pairs; and

a second communication interface arranged to transmit the output time stamp to wireless stations in one of a plurality of groups in a wireless network.

12. A wireless station according to claim 11, wherein the input time stamp is received in a frame and the first communication interface is arranged to extract the input time stamp from the received frame.

13. A wireless station according to claim 11, further comprising a counter, wherein the value is a value of the counter incremented based on the local clock.

14. A wireless station according to claim 11, comprising an interface module arranged to operate as both the first and the second communication interfaces.

15. A wireless station according to claim 11, wherein one of the first and the second communication interfaces is a wireless interface or wherein both the first and the second communication interfaces are wireless interfaces.

16. A wireless station according to claim 11, wherein both the first and the second communication interfaces are wireless interfaces and wherein the first and second communication interfaces operate on different channels within a single frequency band.

17. A wireless station according to claim 11, wherein both the first and the second communication interfaces are wireless interfaces and wherein the first and second communication interfaces operate in different frequency bands.

18. A wireless station according to claim 11, wherein the first communication interface is a wired interface.

19. A non-transitory computer readable storage medium having stored thereon computer readable instructions that, when processed at a computer system for generating a manifestation of an integrated circuit, cause the computer system to generate a manifestation of an integrated circuit comprising:

a counter;

a first communication interface arranged to receive an input time stamp and to store a data pair comprising the received input time stamp and a value of the counter when the input time stamp was received;

a time stamp correction module arranged to calculate an output time stamp by extrapolating from two stored data pairs; and

a second communication interface arranged to transmit the output time stamp to wireless stations in one of a plurality of groups in a wireless network.