METHOD AND SYSTEM FOR AN OFDM JOINT TIMING AND FREQUENCY TRACKING SYSTEM

• US 20100027691A1
• Filed: 08/01/2008
• Published: 02/04/2010
• Est. Priority Date: 08/01/2008
• Status: Active Grant

• Current Assignee: Avago Technologies International Sales Pte Limited (Broadcom, Inc.)
• Original Assignee: Broadcom Corporation (Broadcom, Inc.)
• Inventors: Kent, Mark
• Granted Patent: US 8,559,296 B2
• Time in Patent Office: Days
• US Class Current: 375/260
• CPC Class Codes: H04L 27/265 Fourier transform demodulators, e.g. fast Fourier transform [FFT] or discrete Fourier transform [DFT] demodulators H04L27/26524 takes precedence
• CPC Class Codes: H04L 27/2657 Carrier synchronisation
• CPC Class Codes: H04L 27/2662 Symbol synchronisation
• CPC Class Codes: H04L 27/2675 Pilot or known symbols

Abstract

Aspects of a method and system for an OFDM joint timing and frequency tracking system may include tracking carrier frequency and symbol timing in an Orthogonal Frequency Division Multiplexing (OFDM) signal based on at least a reference symbol set. A receiver frequency and timing may be adjusted based on the tracked carrier frequency and symbol timing. The carrier frequency may be tracked by generating an output signal as a function of a frequency offset Δf, and the symbol timing may be tracked by generating an output signal as a function of a guard time Δt_g. The received OFDM signal may be fast Fourier transformed to generate the reference symbol (RS) set. The receiver frequency and timing may be adjusted coarsely prior to fine adjustment. The coarse receiver frequency and the timing adjustment may be based on processing a primary synchronization signal and a secondary synchronization signal.

Claims

1. A method for processing communication signals, the method comprising:

tracking carrier frequency and symbol timing in an Orthogonal Frequency Division Multiplexing (OFDM) signal based on at least a reference symbol set; and

adjusting a receiver frequency and timing based on said tracked carrier frequency and symbol timing.

2. The method according to claim 1, comprising tracking said carrier frequency by generating an output signal as a function of a frequency offset Δ

f.

3. The method according to claim 1, comprising tracking said symbol timing by generating an output signal as a function of a guard time Δ

t_g.

4. The method according to claim 1, comprising Fast Fourier Transforming said received OFDM signal to generate said reference symbol (RS) set.

5. The method according to claim 1, comprising finely adjusting said receiver frequency and said timing.

6. The method according to claim 5, comprising coarsely adjusting said receiver frequency and said timing prior to said fine adjustment.

7. The method according to claim 6, comprising generating said coarse receiver frequency and said timing adjustment based on processing a primary synchronization signal and a secondary synchronization signal.

8. The method according to claim 1, wherein said reference symbol set comprises a plurality of time-frequency slots.

9. The method according to claim 8, wherein said plurality of time-frequency slots changes according to a time-frequency shift and pseudo-noise sequence that modulates said reference symbol set.

10. The method according to claim 1, wherein said OFDM signal conforms with a Universal Mobile Telecommunications Standards (UMTS) long-term evolution (LTE) signal.

11. The method according to claim 1, comprising controlling adjustment of said receiver frequency via a receiver frequency oscillator (TXCO).

12. The method according to claim 1, comprising controlling adjustment of said timing via a timing generator.

13. A system for processing communication signals, the system comprising:

one or more circuits operable to, at least;

track carrier frequency and symbol timing in an Orthogonal Frequency Division Multiplexing (OFDM) signal based on a reference symbol set; and

adjusts a receiver frequency and timing based on at least said tracked carrier frequency and symbol timing.

14. The system according to claim 13, wherein said one or more circuits track said carrier frequency by generating an output signal as a function of a frequency offset Δ

f.

15. The system according to claim 13, wherein said one or more circuits track said symbol timing by generating an output signal as a function of a guard time Δ

t_g.

16. The system according to claim 13, wherein said one or more circuits Fast Fourier Transforms said received OFDM signal to generate said reference symbol (RS) set.

17. The system according to claim 13, wherein said one or more circuits finely adjusts said receiver frequency and said timing.

18. The system according to claim 17, wherein said one or more circuits coarsely adjusts said receiver frequency and said timing prior to said fine adjustment.

19. The system according to claim 18, wherein said one or more circuits generates said coarse receiver frequency and said timing adjustment based on processing a primary synchronization signal and a secondary synchronization signal.

20. The system according to claim 13, wherein said reference symbol set comprises a plurality of time-frequency slots.

21. The system according to claim 20, wherein said plurality of time-frequency slots changes according to a time-frequency shift and pseudo-noise sequence that modulates said reference symbol set.

22. The system according to claim 13, wherein said OFDM signal conforms with a Universal Mobile Telecommunications Standards (UMTS) long-term evolution (LTE) signal.

23. The system according to claim 13, wherein said one or more circuits controls adjustment of said receiver frequency via a receiver frequency oscillator (TXCO).

24. The system according to claim 13, wherein said one or more circuits controls adjustment of said timing via a timing generator.