Hybrid timing for a GNSS receiver

• US 9,571,262 B2
• Filed: 12/31/2015
• Issued: 02/14/2017
• Est. Priority Date: 12/31/2014
• Status: Active Grant

• Current Assignee: Iposi, Inc.
• Original Assignee: Iposi, Inc.
• Inventors: Kurby, Christopher Neil
• Primary Examiner(s): Huang, David S
• Application Number:
  US14/985,744
• Publication Number:
  US 20160269170A1
• Time in Patent Office: 411 Days
• Field of Search: 375/355, 375/356, 375/362
• US Class Current: 1/1
• CPC Class Codes: G01S 19/05 providing aiding data
• CPC Class Codes: H03L 7/06 using a reference signal applied to a frequency- or phase-locked loop
• CPC Class Codes: H03L 7/0807 concerning mainly a recovery circuit for the reference signal
• CPC Class Codes: H04L 43/16 Threshold monitoring
• CPC Class Codes: H04L 7/0012 by comparing receiver clock with transmitter clock
• CPC Class Codes: H04L 7/0025 interpolation of clock signal

Abstract

Synchronization of a time base at a local clock to a reference time. Initially, correction data (e.g., synchronization data) may be derived from packet data received over an asynchronous packet-switched network (e.g., the internet). Correction data derived from the packet data may be used to correct at least a portion of the time base (e.g., a frequency component). In turn, once the time base is corrected (e.g., to better than a predetermined quality threshold), the source of synchronization data may change to an alternate (e.g., more accurate source) such as positioning signals from a positioning system. In this regard, the corrected time base may be used to assist in acquiring such positioning signals to allow for higher accuracy correction. Furthermore, use of the positioning system may allow for correction of a phase of the time base (e.g., to align the phase to the positioning system. In turn, an accurate time base may be utilized (e.g., for location determination using the positioning system) and/or other contexts such as a downstream communication operation. For instance, a device employing the synchronization techniques described herein may be an LTE base station used to facilitate downstream communication with another device by use of the synchronized time base.

Claims

1. A system for synchronizing a local clock at a device, comprising:

a local reference oscillator operative to generate a time base for the device;

a network interface device in operative communication with an asynchronous packet-switched communication network to receive a synchronization data communication of synchronization data from the asynchronous packet-switched communication network;

a positioning system receiver operative to receive at least on positioning system signal from a positioning system; and

a synchronization module in operative communication with the network interface module and the positioning system receiver and configured to synchronize the local reference oscillator using the synchronization data communication from the network interface module in a first time period and the at least one positioning system signal from the positioning system receiver in a second time period;

wherein the positioning system receiver acquires the at least one positioning system signal based on the local reference oscillator in the first period in which the local reference oscillator is corrected using the synchronization data communication from the network interface device.

2. The system of claim 1, wherein the second time period is subsequent to the first time period and the at least one position system signal is acquired using the local reference oscillator corrected using the synchronization data communication from the network interface device.

3. The system of claim 1, wherein the synchronization module comprises a network synchronization module operative to generate first synchronization data from the synchronization data communication and a positioning system synchronization module operative to generate second synchronization data from the at least one positioning system signal.

4. The system of claim 3, wherein the synchronization module comprises at least one switch for selection of the first synchronization data or the second synchronization data for use in correction of the local oscillator.

5. The system of claim 4, wherein the system comprises a coarse time adjustment module operative to vary a voltage supplied to the local reference oscillator and a fine time adjustment module comprising a dividing module operative to alter a counter value corresponding to a pulse per second output of the time base.

6. The system of claim 3, wherein the positioning system receiver is a Global Navigation Satellite System (GNSS) receiver, and wherein the second synchronization data comprises frequency and phase synchronization data.

7. The system of claim 6, wherein the positioning system receiver comprises an integration module for integration of signals during acquisition, wherein an integration time period is in phase with the positioning system based on synchronization of the local reference oscillator by the second synchronization data.

8. The system of claim 1, further comprising:

a quality assessment module operative to compare a corrected time base based on the synchronization data from the network interface device to a quality threshold.

9. A method for providing time and frequency synchronization data to a Global Navigation Satellite System (GNSS) receiver, comprising;

receiving, via a connection to a packet-based network of computers, packet data containing information about the current time;

deriving time and frequency information from the received packet data;

receiving RF signals from a global navigation satellite, the RF signals containing information about the current time;

deriving time and frequency information from the signals from the global navigation satellite; and

switching between the time and frequency information derived from the received packet data and the time and frequency information derived from the global navigation satellite as the time and frequency provided to and used by the GNSS receiver.

10. A method as defined in claim 9, further including using the time and frequency information derived from the received packet data to prime the operation of deriving time and frequency information from the signals from the global navigation satellite.

11. A method as defined in claim 9, further including determining if the time and frequency information derived from the received packet data has errors less than a predetermined threshold.

12. A method as defined in claim 11, further including switching from the time and frequency information derived from the received packet data to the time and frequency information derived from the global navigation satellite once the error is determined to be less than the predetermined threshold.

13. A method for correction of a time base at a device, comprising:

receiving a synchronization data communication comprising first synchronization data at the receiver from an asynchronous packet-switched communication network;

correcting at least a frequency component of the time base to generate a frequency corrected time base at the device based on the first synchronization data received from the asynchronous packet-switched communication network;

acquiring at least one positioning system signal utilizing the frequency corrected time base; and

synchronizing the frequency component and a phase component of the time base utilizing the at least one positioning system signal to generate a frequency and phase corrected time base.

14. The method of claim 13, further comprising:

utilizing the frequency and phase corrected time base to integrate received positioning signals over an integration period, wherein the integration period is in phase relative to the positioning signals received.

15. The method of claim 13, further comprising:

comparing the frequency corrected time base to a threshold quality prior to the acquiring, wherein the frequency corrected time base is utilized in the acquiring only when the accuracy of the frequency corrected time base exceeds the threshold quality.

16. The method of claim 13, further comprising:

detecting a loss of acquisition of any positioning signal system;

continuing to operate the device using the time base without correction.

17. The method of claim 16, further comprising repeating the method at a predetermined time period after the detecting.

18. The method of claim 13, further comprising:

utilizing the frequency and phase corrected time base in connection with a downstream communication operation.