Blind correlation for high precision ranging of coded OFDM signals

• US 20050251844A1
• Filed: 02/28/2005
• Published: 11/10/2005
• Est. Priority Date: 02/02/2001
• Status: Abandoned Application

• Current Assignee: Rosum Corporation (Liberty Broadband Corp.)
• Original Assignee: Rosum Corporation (Liberty Broadband Corp.)
• Inventors: Omura, Jimmy K., Martone, Massimiliano, Rabinowitz, Matthew, Spilker, James J. Jr.
• Application Number:
  US11/068,570
• Publication Number:
  US 20050251844A1
• Time in Patent Office: Days
• US Class Current: 725/118
• CPC Class Codes: H04L 27/2662 Symbol synchronisation
• CPC Class Codes: H04L 27/2678 using cyclostationarities, e.g. cyclic prefix or postfix

Abstract

An apparatus having a corresponding method and computer program comprises a front end to receive an orthogonal frequency division modulation (OFDM) signal comprising a plurality of OFDM symbols each comprising N samples and a cyclic prefix comprising M of the N samples, wherein M<N; a buffer to store the cyclic prefix for one of the OFDM symbols; and a correlator to generate a correlation output based on the cyclic prefix and the one of the OFDM symbols.

Claims

1. An apparatus comprising:

a front end to receive an orthogonal frequency division modulation (OFDM) signal comprising a plurality of OFDM symbols each comprising N samples and a cyclic prefix comprising M of the N samples, wherein M<

N;

a buffer to store the cyclic prefix for one of the OFDM symbols; and

a correlator to generate a correlation output based on the cyclic prefix and the one of the OFDM symbols.

2. The apparatus of claim 1, further comprising:

a synchronizer to identify boundaries of the OFDM symbols.

3. The apparatus of claim 1, further comprising:

an accumulator to accumulate the correlation output for a plurality of the OFDM symbols.

4. The apparatus of claim 3, wherein the correlator comprises:

a fast Fourier transform (FFT) engine.

5. The apparatus of claim 1, wherein:

the correlator generates frequency-domain representations of the one of the OFDM symbols and the cyclic prefix for the one of the OFDM symbols, generates a product of the frequency-domain representations; and

generates a time-domain representation of the product.

6. The apparatus of claim 1, wherein:

a location of the apparatus is determined based upon the correlation output.

7. The apparatus of claim 1, further comprising:

a ranging unit to determine a location of the apparatus based upon the correlation output.

8. The apparatus of claim 1, further comprising:

a demodulator to demodulate the OFDM signal based upon the correlation output.

9. The apparatus of claim 1, wherein the OFDM signal comprises at least one of the group consisting of:

a European Telecommunications Standards Institute (ETSI) Digital Video Broadcasting-Terrestrial (DVB-T) signal;

a ETSI Digital Video Broadcasting-Handheld (DVB-H) signal; and

a Japanese Integrated Services Digital Broadcasting-Terrestrial (ISDB-T) signal.

10. A method comprising:

receiving an orthogonal frequency division modulation (OFDM) signal comprising a plurality of OFDM symbols each comprising N samples and a cyclic prefix comprising M of the N samples, wherein M<

N;

storing the cyclic prefix for one of the OFDM symbols; and

generating a correlation output based on the cyclic prefix and the one of the OFDM symbols.

11. The method of claim 10, further comprising:

identifying boundaries of the OFDM symbols.

12. The method of claim 10, further comprising:

accumulating the correlation output for a plurality of the OFDM symbols.

13. The method of claim 10, wherein generating a correlation output based on the cyclic prefix and the one of the OFDM symbols comprises:

generating frequency-domain representations of the one of the OFDM symbols and the cyclic prefix for the one of the OFDM symbols;

generating a product of the frequency-domain representations; and

generating a time-domain representation of the product.

14. The method of claim 10, wherein:

a location is determined based upon the correlation output.

15. The method of claim 10, further comprising:

determining a location based upon the correlation output.

16. The method of claim 10, further comprising:

demodulating the OFDM signal based upon the correlation output.

17. The method of claim 10, wherein the OFDM signal comprises at least one of the group consisting of:

a European Telecommunications Standards Institute (ETSI) Digital Video Broadcasting-Terrestrial (DVB-T) signal;

a ETSI Digital Video Broadcasting-Handheld (DVB-H) signal; and

a Japanese Integrated Services Digital Broadcasting-Terrestrial (ISDB-T) signal.

18. An apparatus comprising:

front end means for receiving an orthogonal frequency division modulation (OFDM) signal comprising a plurality of OFDM symbols each comprising N samples and a cyclic prefix comprising M of the N samples, wherein M<

N;

buffer means for storing the cyclic prefix for one of the OFDM symbols; and

correlator means for generating a correlation output based on the cyclic prefix and the one of the OFDM symbols.

19. The apparatus of claim 18, further comprising:

means for identifying boundaries of the OFDM symbols.

20. The apparatus of claim 18, further comprising:

means for accumulating the correlation output for a plurality of the OFDM symbols.

21. The apparatus of claim 20, wherein the correlator means comprises:

means for performing a fast Fourier transform (FFT).

22. The apparatus of claim 18, wherein:

the correlator means generates frequency-domain representations of the one of the OFDM symbols and the cyclic prefix for the one of the OFDM symbols, generates a product of the frequency-domain representations; and

generates a time-domain representation of the product.

23. The apparatus of claim 18, wherein:

a location of the apparatus is determined based upon the correlation output.

24. The apparatus of claim 18, further comprising:

means for determining a location of the apparatus based upon the correlation output.

25. The apparatus of claim 18, further comprising:

means for demodulating the OFDM signal based upon the correlation output.

26. The apparatus of claim 18, wherein the OFDM signal comprises at least one of the group consisting of:

a European Telecommunications Standards Institute (ETSI) Digital Video Broadcasting-Terrestrial (DVB-T) signal;

a ETSI Digital Video Broadcasting-Handheld (DVB-H) signal; and

a Japanese Integrated Services Digital Broadcasting-Terrestrial (ISDB-T) signal.