Leap second and daylight saving time correction for use in a radio controlled clock receiver

• US 8,467,273 B2
• Filed: 03/20/2012
• Issued: 06/18/2013
• Est. Priority Date: 11/15/2011
• Status: Expired due to Fees

• Current Assignee: Grindstone Capital LLC
• Original Assignee: XW LLC
• Inventors: Eliezer, Oren E.
• Primary Examiner(s): Miska, Vit W
• Application Number:
  US13/424,807
• Publication Number:
  US 20130121117A1
• Time in Patent Office: 455 Days
• Field of Search: 368/28, 368/29, 368/27, 329/304, 329/345, 332/144, 332/145
• US Class Current: 368/47
• CPC Class Codes: G04G 7/02 by radio
• CPC Class Codes: G04R 20/10 Tuning or receiving; Circuits therefor

Abstract

A novel and useful system and method for leap second and daylight saving time (DST) correction for use in a radio controlled clock (RCC) receiver. The RCC receiver extracts schedule information from the frame, including the time for the DST transition and whether a leap second needs to be added at the end of this half-year. Linear error correcting coding is used for the leap second and the DST on/off indications, while non-linear error correcting coding (e.g., a look up table) is used for the DST schedule to enhance reception reliability in the presence of noise and interference. The one second/one hour corrections are scheduled to occur when they should take place and the correction is applied exactly when DST or leap second is to go into effect, without having to receive anything around the time of the correction.

Claims

1. A radio receiver method, said method comprising:

receiving a phase modulated (PM), pulse width modulated (PWM)/amplitude shift keyed (ASK) broadcast signal encoded with phase-modulated time information frames;

extracting said time information frames from the phase of said received signal; and

wherein each said time information frame includes a synchronization sequence field, and one or more fields adapted to communicate a schedule for a next daylight-saving time transition, said schedule indicating the specific day for said transition.

2. The method according to claim 1, wherein each said time information frame further comprises an advance leap second notification field indicating whether a leap second is scheduled at the end of a predefined period.

3. The method according to claim 2, wherein a flag is set in response to said advance leap second notification such that when the scheduled leap second is to occur, a 61^st second is added to an appropriate minute, thereby extending said minute by one second.

4. The method according to claim 1, wherein said schedule for daylight-saving transition time is protected using an error correcting code.

5. The method according to claim 1, wherein an hour indication in said daylight-saving time transition schedule field comprises two bits adapted to indicate one of a plurality of possible hours at which daylight-saving time is to go into effect or to end.

6. The method according to claim 1, wherein said daylight saving time (DST) transition schedule is adapted to indicate the time at which the DST is to end if it is already in effect, and the time at which DST is to start, if it is not in effect.

7. The method according to claim 1, wherein the day in said daylight-saving time transition schedule field comprises three bits adapted to indicate one of a plurality of possible days on which daylight-saving time is to go into effect or to end.

8. The method according to claim 1, wherein each said time information frame further comprises at least a one-bit field adapted to indicate whether daylight-saving time is in effect or not.

9. The method according to claim 1, wherein daylight-saving time hour information and said daylight-saving time day information are extracted from said time information frame as a six bit field encoded using an error correction code.

10. The method according to claim 1, further comprising:

extracting daylight-saving time hour information and daylight-saving time day information from said time information frame as a multi-bit field encoded using a nonlinear error correction code;

utilizing a lookup table, constructed a priori and stored in said receiver, to decode said multi-bit field to yield decoded daylight-saving time hour information and daylight-saving time day information.

11. The method according to claim 10, wherein said nonlinear error correction code does not maintain equal Hamming distances between code words.

12. The method according to claim 11, wherein codes with the largest minimum Hamming distance are assigned to daylight-saving time hour information and daylight-saving time day information values most likely to be used.

13. The method according to claim 10, wherein for a received word, comparing the Hamming distance between said received word and all codewords and choosing the codeword from a codebook having a minimum Hamming distance with the received word as its estimated output, wherein if two or more codewords yield the same Hamming distance, selecting the codeword listed earliest in said codebook.

14. A radio receiver method, said method comprising:

receiving a phase modulated (PM), pulse width modulated (PWM)/amplitude shift keyed (ASK) broadcast signal encoded with phase-modulated time information frames;

extracting said time information frames from the phase of the carrier of said modulated received signal, wherein each said time information frame includes a synchronization sequence field, a daylight-saving time hour information field and a daylight-saving time day information field, said daylight-saving time hour information and said daylight-saving time day information comprising a multi-bit field encoded using a nonlinear error correction code; and

utilizing a lookup table, constructed a priori and stored in said receiver, to decode said multi-bit field to yield decoded daylight-saving time hour information and daylight-saving time day information.

15. The method according to claim 14, wherein a code with the largest minimum Hamming distance is assigned to daylight-saving time hour information and daylight-saving time day information most likely to be transmitted.

16. The method according to claim 14, wherein codes with the largest minimum Hamming distance are assigned to those daylight-saving time hour information and daylight-saving time day information values most likely to be used.

17. The method according to claim 14, wherein codes with the smallest minimum Hamming distance are assigned to those daylight-saving time hour information and daylight-saving time day information values least likely to be used.

18. The method according to claim 14, wherein a code-word having the largest minimum Hamming distance from all other code-words is assigned to the multi-bit field that represents a daylight-saving time hour of 2 AM and daylight-saving time day of the first Sunday of November for the end of the DST period and the second Sunday of March for the beginning of the DST period.

19. The method according to claim 14, wherein code words having the second largest minimum Hamming distance are assigned to multi-bit field values that represent a daylight-saving time hour of 2 AM.

20. A radio receiver, comprising:

a receiver circuit operative to receive a phase modulated (PM), pulse width modulation (PWM)/amplitude shift keyed (ASK), broadcast signal encoded with phase-modulated time information frames;

a frame extractor operative to extract said time information frames from the phase of the carrier of said received signal, wherein each said time information frame includes a synchronization sequence field, daylight saving time (DST) hour information and DST day information, said DST hour information and said DST day information comprising a multi-bit field encoded using a nonlinear error correction code; and

a lookup table constructed a priori and stored in said radio receiver, said lookup table used to extract and decode said multi-bit field to yield decoded DST hour and day information.

21. The receiver according to claim 20, wherein code-words with the largest minimum Hamming distance are assigned to daylight saving time (DST) hour information and DST day information values most likely to be used.

22. The receiver method according to claim 20, wherein an error correcting code-word having the largest minimum Hamming distance is assigned to a multi-bit field that represents a daylight saving time (DST) hour of 2 AM and DST day of the first Sunday of November for the end of the DST duration and the second Sunday of March for the beginning of the DST duration.

23. The receiver according to claim 20, wherein each said time information frame further comprises a leap second field indicating whether a leap second is scheduled at the end of the current predefined period.

24. A time-keeping device, comprising:

a receiver circuit operative to receive a phase modulated (PM), pulse width modulation (PWM)/amplitude shift keyed (ASK), broadcast signal encoded with phase-modulated time information frames;

a frame extractor operative to extract said time information frames from the phase of the carrier of said received signal, wherein each said time information frame includes a synchronization sequence field, daylight saving time (DST) schedule information including DST hour information and DST day information, said DST hour information and said DST day information comprising a multi-bit field encoded using a nonlinear error correction code;

a lookup table constructed a priori and stored in said radio receiver, said lookup table used to extract and decode said multi-bit field to yield decoded DST hour and day information;

a time correction module operative to correct the time indicated by said device by one hour forward at the instance represented by said daylight saving time (DST) schedule field while DST is not in effect, and wherein the time indicated by said device is corrected by one hour backwards when DST is in effect, said one hour correction preformed based on said DST schedule being received any time before the transition is to occur.

25. The time-keeping device according to claim 24, wherein the daylight saving time (DST) field is extracted from the time information frame twice a year, once during the DST period, in order to determine when it is to end, and once outside of the DST period, in order to determine when the next DST period is to begin, thereby conserving receiver power consumption.

26. The time-keeping device according to claim 25, wherein one of said two receptions occurs in April or May.

27. The time-keeping device according to claim 25, wherein one of said two receptions occurs in November.

28. The time-keeping device according to claim 24, further comprising means for repeating reception of said DST schedule information in the event it is received in error, whereby repeated reception increases the confidence in the extracted data.

29. The time-keeping device according to claim 24, wherein said time correction module is operative to enable said time keeping device to schedule a one hour correction to an appropriate day and time without relying on receiving said correction information on that day.

30. The time-keeping device according to claim 24, wherein a flag is set in response to said advance leap-second notification, such that when the scheduled leap-second is to occur, a 61^st second is added to an appropriate minute, thereby extending said minute by one second.