Leap Second and Daylight Saving Time Correction in a Radio Controlled Clock Receiver

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.

What is claimed is: 
     
         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 . 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.   
     
     
         6 . The method according to  claim 5 , 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. 
     
     
         7 . The method according to  claim 5 , 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. 
     
     
         8 . The method according to  claim 5 , 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. 
     
     
         9 . The method according to  claim 5 , 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. 
     
     
         10 . The method according to  claim 5 , 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. 
     
     
         11 . 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.   
     
     
         12 . The receiver according to  claim 11 , 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. 
     
     
         13 . The receiver method according to  claim 11 , 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. 
     
     
         14 . The receiver according to  claim 11 , 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.