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