Systems and methods for distributing GPS clock to communications devices

• US 20090231191A1
• Filed: 03/17/2008
• Published: 09/17/2009
• Est. Priority Date: 03/17/2008
• Status: Active Grant

• Current Assignee: Taiwan Semiconductor Manufacturing Company Limited
• Original Assignee: Quarterhill Inc. (f/k/a Wi-LAN Inc.)
• Inventors: Wu, Shiquan, Yee, Jung
• Granted Patent: US 8,018,950 B2
• Time in Patent Office: Days
• US Class Current: 342/357.395
• CPC Class Codes: G04G 7/00 Synchronisation radio-controlled time-pieces G04R
• CPC Class Codes: H04J 3/0635 Clock or time synchronisation in a network timer in protocols H04L69/28
• CPC Class Codes: H04J 3/0638 Clock or time synchronisation among nodes; Internode synchronisation synchronization for ring networks H04L12/422; data switching networks with synchronous transmission H04L12/43
• CPC Class Codes: H04J 3/0658 Clock or time synchronisation among packet nodes

Abstract

A method for synchronizing network elements to a global clock derived from the GPS clock acquired by a plurality of base stations. The global clock is distributed to controllers of various networks, and from there to network access devices. The network access devices further distribute the global clock to various wire-line and local wireless networks and from there, to the users served by these networks. The user equipment is enabled with a simple clock discipliner that adjusts the local clock to the global clock, resulting in a reliable synchronization across the converged communication networks.

Claims

5-1. A method as claimed in claim 1, wherein said networked devices include a femto cell provided within a customer premise, said femto cell being comprised of a micro base station (MBS) serving a plurality of wireless-enabled terminals.

9. A timing unit for a micro base station (MBS) connected to a communication network over a wire-line interface, said MBS serving a wireless enabled user terminal over an air interface, said timing unit comprising:

a synchronization unit for synchronizing MBS circuitry at said MBS with a global clock received over said wireline interface and inserting said global clock into a periodic bit sequence sent to said user terminal over said air interface;

a MBS message generator for generating a re-hello message in response to a hello message received from said user terminal;

a time measurement unit for providing MBS timing data and inserting said MBS timing data into said re-hello message; and

a transceiver that transmits said re-hello message to said user terminal and receiving said hello message from said user terminal for triggering said re-hello message generator.

10. A femto cell as claimed in claim 9, wherein said air interface uses a transmission protocols that inherently transmits a periodic bit sequence.

11. A clock discipliner for a wireless-enabled terminal connected in a femto cell, and adapted to correct a deviation Δ

of a local oscillator to a global clock received from a micro base station (MBS), comprising;

a sequence detector for identifying a periodic bit sequence received from said MBS and synchronizing said local oscillator to said global clock received in said periodic bit sequence;

a timing adjustment unit that processes terminal timing data and MBS timing data with a view to determine said deviation Δ and

to adjust the local oscillator with said deviation Δ

;

a hello message generator for generating a hello message at preset intervals; and

a transceiver for transmitting said hello message to said MBS with said terminal timing data and receiving a re-hello message from said MBS with said MBS timing data.

12. A clock discipliner as claimed in claim 11, wherein said terminal timing data includes a time measurement D1 indicative of the time of transmission of the hello message from said terminal and a time measurement D4 indicative of the time of receipt of the re-hello message at said terminal, measured using said local clock.

13. A clock discipliner as claimed in claim 12, wherein said terminal timing data further includes a pre-arranged offset α

between the time of arrival of said sequence at said calculation arrangement and D1.

14. A clock discipliner as claimed in claim 11, wherein said MBS timing data includes a time measurement D2 indicative of the time of receipt of the hello message at said MBS, and a time measurement D3 indicative of the time of transmittal of said re-hello message from said MBS, measured using said global clock.

15. A clock discipliner as claimed in claim 13, wherein said MBS timing data further includes a prearranged offset β

between the time of arrival of a bit of said sequence at said calculation arrangement and D1.

16. A clock discipliner as claimed in claim 13, wherein said calculation arrangement determines said deviation Δ

using said measurement D1 and measurement D4.

17. A method of adjusting a local clock of a wireless-enabled terminal located within the area of coverage of a micro base station (MBS) serving said wireless enabled terminal, to a global clock received in a periodic bit sequence from said MBS, comprising:

synchronizing said local clock to said global clock;

transmitting a hello message;

receiving a re-hello message from said MBS in response to a hello message, said re-hello message comprising MBS timing data; and

determining a time deviation Δ

between said global clock and said local clock using said MBS timing data and terminal timing data.

18. A method as claimed in claim 17, wherein said terminal timing data includes a time measurement D1 indicative of the time of transmission of the hello message and a time measurement D4 indicative of the time of receipt of the re-hello message at said terminal, measured using said local clock.

19. A method as claimed in claim 17, wherein said MBS timing data includes a time measurement D2 indicative of the time of receipt of the hello message at said MBS, and a time measurement D3 indicative of the time of transmittal of said re-hello message from said MBS, measured using said global clock.