Encoding and decoding methods for high-precision time transfer and encoding and decoding devices therefor

Patent metadata

Field	Value
Publication number	US-9537576-B2
Application number	US-201414562000-A
Country	US
Kind code	B2
Filing date	Dec 5, 2014
Priority date	Aug 7, 2013
Publication date	Jan 3, 2017
Grant date	Jan 3, 2017

Abstract

A format for modified IRIB-G time code, with added message fields while preserving pulse width coding rule of the standard IRIG-B time code, having a time interval field for carrying time interval between the local time signal and a received time signal, and a user-defined or padded field for carrying user-defined time and/or control messages. An encoding and a decoding methods and devices for high-precision time transfer, where the modified IRIG-B time code carries more messages, and enabling transmission of timing messages and testing messages of two-way time comparison via a single message channel at the same time, which reduces fluctuation due to encoding and decoding manipulation and correlation with working frequencies via exact synchronization between the on-times of the output encoded time code and the transmitted time signal, and between the on-times of the output decoded time signal and the input time code, and improves precision of time transfer.

First claim

We claim:

1. A method for encoding a modified IRIG-B time code for high-precision time transfer, comprising
generating modified IRIG-B time code frames in an encoding device, each of the frames comprising N number of code elements, N denoting an integer larger than 100, at a code element rate of N bits per second, having fields of a standard TRIG-B time code, a time interval field, a user-defined or padded field, and an ending code element;
defining, by the encoding device, three code element values for the frames, wherein the three code element values have pulse width encoding and include a ‘0’ code element at duration of 20% of an index count, a ‘1’ code element at duration of 50% of the index count, and a ‘P’ code element at duration of 80% of the index count;
preserving definitions of the first 99 code elements and the last code element in the standard IRIG-B time pulse width encoding rule in each of the frames, and then compressing width of the code elements of the standard IRIG-B by the encoding device;
adding message fields between the 100th code element and (N−1)th code element by the encoding device, the added message fields including:
the time interval field which starts at the 100 th code element of each of the frames for carrying a time interval between a local time signal and a received time signal, the first code element of the time interval is the 100 th code element of each of the frames and denotes an advance or a delay, with remaining code elements of the time interval denotes a time interval measure value in unit of picoseconds;
the user-defined or padded field which is subsequent to the time interval field for carrying user-defined time, control messages, or both, with the code element values ‘1’, ‘0’, or both, filling up a bit of an un-used code element; and
the ending code element is the last code element of each of the frames and is fixed as a ‘P’ code element; and

transmitting the modified IRIG-B time code frames from the encoding device via space channels, electric cables, or optical fiber.

2. The method for high-precision time transfer using the modified IRIG-B time code frame according to claim 1 , further comprising
commencing counting when a code generation hardware module, within the encoding device, detects a transmitted 1PPS signal, said 1PPS signal being transmitted by space channels, electric cables, or optical fiber from a reference clock, obtaining a sequence number of a current code element, selecting a corresponding code element for encoding based on the sequence number of the current code element, a current time message, and a time interval message as measured locally, generating a non-synchronous modified IRIG-B time code frame, and transmitting the non-synchronous modified IRIG-B time code frame to a code synchronization module through an electric path;
triggering a time synchronization enabling signal with a pulse width smaller than that of the ‘P’ code element when the code generation module counts to the Nth code element at its electric low-level, and transmitting said time synchronization enabling signal to a synchronization signal generation module through an electric path, where N is for a last code element;
generating a synchronization signal synchronous with a rising edge of the transmitted 1PPS signal and with a pulse width smaller than that of the ‘P’ code element when the synchronization signal generation module And the transmitted 1PPS signal received from the reference clock with the time synchronization enabling signal, and transmitting said synchronization signal to a code synchronization module through an electric path; and
Oring the non-synchronous modified IRIG-B time code frame with the synchronization signal by the code synchronization module, and outputting a modified IRIG-B time code frame synchronous with the local 1PPS signal through an electric interface.

3. A decoding method for high-precision time transfer using a modified IRIG-B time code, comprising
receiving, by a decoding device, at least one modified IRIG-B time code frame, the modified IRIG-B time code frame being generated and transmitted according to claim 1 ;
commencing counting, by the decoding device, when a reference marker identification module detects a reference marker for timer message from the received modified IRIG-B time code frame, that is, detecting two consecutive reference code elements ‘P’, where a rising edge of a second ‘P’ code element is a 1PPS reference, obtaining a sequence number of a current code element, restoring a value of each code element subsequent to an identification bit of the reference marker based on a pulse width coding rule, and transmitting said value to a metadata parser module;
generating, by the decoding device, a mask signal with the pulse width smaller than that of the ‘P’ code element when the reference marker identification module counts to an Nth code element at its electric low-level, and outputting the mask signal to a pulse per second parser module;
outputting a time and control message, a time interval message, and a user-defined message based on a definition in a field of the modified IRIG-B time code frame by the metadata parser hardware module within the decoding device; and
Anding a signal of the received modified IRIG-B time code frame with the mask signal by the pulse per second parser module, and outputting a 1PPS signal synchronous with an on-time of the received modified IRIG-B time code frame by the decoding device,
wherein the signal of the modified IRIG-B time code frame is sent by space channels, electric cables, or optic fiber.

4. An encoding device, comprising
a code generation hardware module being configured to:
detect a 1PPS signal transmitted by space channels, electric cable, or optical fiber from a reference clock,
commence counting, obtain a sequence number of a current code element, select a code element for encoding based on the sequence number of the code element, a current time message, and a time interval message measured locally, and output a first signal for code synchronization, and
trigger a second signal and output the second signal for synchronous signal generation upon counting a Nth code element,

a synchronization signal generation hardware module connected to the code generation module, the synchronization signal generation module being configured to:
receive the second signal from the code generation module and the 1PPS signal,
Anding the second signal with the 1PPS signal to be transmitted, generate a third signal that is synchronous with the 1PPS signal, and
output the third signal for code synchronization, and

a code synchronization hardware module connected to the code generation module and to the synchronization signal generation module, respectively, the code synchronization module being configured to:
receive the first signal from the code generation module and to the third signal from the synchronization signal generation module, and
Oring the first signal with the third signal to output a fourth signal that is an IRIG-B time code frame synchronous with the 1PPS signal,

wherein the transmitted 1PPS signal, the time message, the time interval message, and the user-defined message are admitted in the code generation module; the code generation module is respectively connected with the synchronization signal generation module and the code synchronization module;
the transmitted 1PPS signal is admitted and Anded in the synchronization signal generation module with the second signal of a synchronization enabling signal generated in the code generation module to have the third signal as a result signal; and
the result signal is admitted and outputted by the code synchronization module to be the fourth signal of a synchronous modified IRIG-B time code frame.

5. A decodin

Assignees

• Univ Shanghai Jiaotong

Inventors

• Wu Guiling
• Hu Liang
• Shen Jianguo
• Zou Weiwen
• Chen Jianping

Classifications

• H04L1/00

  Arrangements for detecting or preventing errors in the information received {(correcting synchronisation H04L7/00)} · CPC title

• H04B10/524 Primary

  Pulse modulation · CPC title

• G01S19/00

  Satellite radio beacon positioning systems; Determining position, velocity or attitude using signals transmitted by such systems · CPC title

• H04L25/4902

  Pulse width modulation; Pulse position modulation · CPC title

• H04L25/00

  Baseband systems · CPC title