Symmetric pilot processing for robust timing offset and frequency offset estimation in receivers

Abstract

Timing and frequency offset processing in sub-carriers is performed in an Integrated Services Digital Broadcasting-Terrestrial (ISDB-T) a receiver system. Sub-carriers are divided into two sub-sets, where the sub-sets contain an equal number of sub-carriers. Subsequently bad sub-carriers are removed, if present, from first sub-set of the sub-sets, and corresponding sub-carriers from a second sub-set of the sub-sets are also removed. Further, a phase difference on each sub-carrier from each sub-set is computed, and mean phase differences of each of the sub-sets are computed. Furthermore, frequency offset is computed by averaging the mean phase differences of the sets.

What is claimed is: 
     
       1. A method of computing timing and frequency offset in sub-carriers in an Integrated Services Digital Broadcasting-Terrestrial (ISDB-T) a receiver system, said method comprising:
 storing said sub-carriers in a storage device; 
 using a processor for dividing said sub-carriers into two sub-sets, using a processor, wherein said the sub-sets comprise an equal number of sub-carriers; 
 removing bad sub-carriers from a first sub-set of said sub-sets; 
 removing sub-carriers from a second sub-set of said sub-sets that correspond to said bad sub-carriers from said first sub-set of said subsets sub-sets; 
 computing a phase difference on each sub-carrier from each sub-set responsive to the removing steps; 
 computing mean phase differences of each of said sub-sets responsive to the computing step; and 
 computing a timing offset and a frequency offset in said sub-carriers using the computed mean differences. 
 
     
     
       2. The method of  claim 1 , wherein said frequency offset in said sub-carriers is computed by summing said mean phase differences of said sub-sets. 
     
     
       3. The method of  claim 1 , wherein said timing offset in said sub-carriers is computed by calculating the a difference of said mean phase differences of said sub-sets. 
     
     
       4. The method of  claim 1 , wherein a bad sub-carrier occurs when a magnitude of a received signal in said sub-carrier is smaller than a predetermined threshold level. 
     
     
       5. The method of  claim 1 , wherein said sub-carriers from said second sub-set of said sub-sets that correspond to said bad sub-carriers from said first sub-set of said subsets sub-sets are bad sub-carriers. 
     
     
       6. The method of  claim 1 , wherein said sub-carriers from said second sub-set of said sub-sets that correspond to said bad sub-carriers from said first sub-set of said subsets sub-sets are good sub-carriers. 
     
     
       7. The method of  claim 6 , wherein a good sub-carrier occurs when a magnitude of a received signal in said sub-carrier is equal to or larger than a predetermined threshold level. 
     
     
       8. A non-transitory program storage device readable by computer, tangibly embodying a program of instructions executable by said computer to perform a method of computing timing and frequency offset in sub-carriers in an Integrated Services Digital Broadcasting-Terrestrial (ISDB-T) a receiver system, said method comprising:
 using a processor for dividing said sub-carriers into two sub-sets, using a processor, wherein said the sub-sets comprise an equal number of sub-carriers; 
 removing bad sub-carriers from a first sub-set of said sub-sets; 
 removing sub-carriers from a second sub-set of said sub-sets that correspond to said bad sub-carriers from said first sub-set of said subsets sub-sets; 
 computing a phase difference on each sub-carrier from each sub-set responsive to the removing steps; 
 computing mean phase differences of each of said sub-sets responsive to the computing step; and 
 computing a timing offset and a frequency offset in said sub-carriers using the computed mean differences. 
 
     
     
       9. The program storage device of  claim 1 , wherein said frequency offset in said sub-carriers is computed by summing said mean phase differences of said sub-sets. 
     
     
       10. The program storage device of  claim 1 , wherein said timing offset in said sub-carriers is computed by calculating the a difference of said mean phase differences of said sub-sets. 
     
     
       11. The program storage device of  claim 1 , wherein a bad sub-carrier occurs when a magnitude of a received signal in said sub-carrier is smaller than a predetermined threshold level. 
     
     
       12. The program storage device of  claim 1 , wherein said sub-carriers from said second sub-set of said sub-sets that correspond to said bad sub-carriers from said first sub-set of said subsets sub-sets are bad sub-carriers. 
     
     
       13. The program storage device of  claim 1 , wherein said sub-carriers from said second sub-set of said sub-sets that correspond to said bad sub-carriers from said first sub-set of said subsets sub-sets are good sub-carriers. 
     
     
       14. The program storage device of  claim 13 , wherein a good sub-carrier occurs when a magnitude of a received signal in said sub-carrier is equal to or larger than a predetermined threshold level. 
     
     
       15. An apparatus for computing timing and frequency offset in sub-carriers in an Integrated Services Digital Broadcasting-Terrestrial (ISDB-T) a receiver system, said apparatus comprising:
 a storage device for storing said sub-carriers; 
 a processor for dividing said sub-carriers into two sub-sets, wherein said the sub-sets comprise an equal number of sub-carriers; 
 digital logic means for removing bad sub-carriers from a first sub-set of said sub-sets; 
 digital logic means for removing sub-carriers from a second sub-set of said sub-sets that correspond to said bad sub-carriers from said first sub-set of said subsets sub-sets; 
 means for computing a phase difference on each sub-carrier from each sub-set; 
 means for computing mean phase differences of each of said sub-sets; and 
 means for computing a timing offset and a frequency offset in said sub-carriers using the computed mean differences. 
 
     
     
       16. The apparatus of  claim 15 , wherein said frequency offset in said sub-carriers is computed by summing said mean phase differences of said sub-sets. 
     
     
       17. The apparatus of  claim 15 , wherein said timing offset in said sub-carriers is computed by calculating the a difference of said mean phase differences of said sub-sets. 
     
     
       18. The apparatus of  claim 15 , wherein a bad sub-carrier occurs when a magnitude of a received signal in said sub-carrier is smaller than a predetermined threshold level. 
     
     
       19. The apparatus of  claim 15 , wherein said sub-carriers from said second sub-set of said sub-sets that correspond to said bad sub-carriers from said first sub-set of said subsets sub-sets are bad sub-carriers. 
     
     
       20. The apparatus of  claim 15 , wherein said sub-carriers from said second sub-set of said sub-sets that correspond to said bad sub-carriers from said first sub-set of said subsets sub-sets are good sub-carriers, wherein a good sub-carrier occurs when a magnitude of a received signal in said sub-carrier is equal to or larger than a predetermined threshold level. 
     
     
       21. The method of claim 1, wherein said receiver comprises a mobile television receiver. 
     
     
       22. The program storage device of claim 8, wherein said receiver comprises a mobile television receiver. 
     
     
       23. The apparatus of claim 15, wherein said receiver comprises a mobile television receiver.