FREQUENCY OFFSET ACQUISITION METHOD AND APPARATUS THEREOF

• US 20100266076A1
• Filed: 04/13/2010
• Published: 10/21/2010
• Est. Priority Date: 04/15/2009
• Status: Active Grant

• Current Assignee: Realtek Semiconductor Corp.
• Original Assignee: Realtek Semiconductor Corp.
• Inventors: He, Wei-Hung
• Granted Patent: US 9,001,940 B2
• Time in Patent Office: Days
• US Class Current: 375/344
• CPC Class Codes: H04L 27/2613 Structure of the reference signals
• CPC Class Codes: H04L 27/2657 Carrier synchronisation
• CPC Class Codes: H04L 27/2676 Blind, i.e. without using known symbols

Abstract

A frequency offset acquisition method includes: receiving a specific sequence signal transmitted through a channel; shifting a frequency of the specific sequence signal at a plurality of different frequencies in frequency domain to thereby generate a plurality of shifted sequence signals respectively; and determining an estimated frequency offset value between a transmitter and a receiver according to the shifted sequence signals.

Claims

1. A frequency offset acquisition method, comprising:

receiving a specific sequence signal transmitted through a channel, and storing the specific sequence signal in a storage unit;

shifting a frequency of the specific sequence signal at a plurality of different frequencies in frequency domain to thereby generate a plurality of shifted sequence signals, respectively; and

determining an estimated frequency offset value between a transmitter and a receiver according to the plurality of shifted sequence signals.

2. The method of claim 1, wherein the step of determining the estimated frequency offset value according to the plurality of shifted sequence signals comprises:

performing a correlation operation upon an original sequence signal and each shifted sequence signal to generate a plurality of operation results, respectively; and

determining the shifted sequence signal according to the plurality of operation results;

wherein the original sequence signal is outputted to the channel by the transmitter, and the original sequence signal corresponds to the specific sequence signal.

3. The method of claim 2, wherein the original sequence signal is a pseudorandom noise sequence signal.

4. The method of claim 2, wherein the step of performing the correlation operation upon the original sequence signal and each shifted sequence signal to generate the plurality of operation results comprises:

for each shifted sequence signal, performing a cyclic correlation operation upon the original sequence signal and the shifted sequence signal to generate an operation result including a plurality of correlation values; and

the step of determining the estimated frequency offset value according to the plurality of operation results comprises;

performing an absolute value operation upon the plurality of correlation values included in each operation result to generate a plurality of corresponding absolute values, and choosing a specific absolute value among the plurality of absolute values, wherein the specific absolute value is an extreme value among the plurality of absolute values; and

determining the estimated frequency offset value according to an extreme value among a plurality of specific absolute values which correspond to the plurality of operation results, respectively.

5. The method of claim 4, further comprising:

utilizing the estimated frequency offset value to perform a frequency offset calibration upon the specific sequence signal to generate a calibrated sequence signal;

choosing a plurality of partial sequence signals among the calibrated sequence signals; and

updating the frequency offset value according to the plurality of partial sequence signals and the original sequence signal.

6. The method of claim 5, wherein a correlation value corresponding to the specific absolute value is generated from a cyclic correlation operation of the original sequence signal and the shifted sequence signal according to a reference point, and the step of updating the frequency offset value comprises:

performing the cyclic correlation operation of the original sequence signal and the shifted sequence signal according to the reference point, respectively, thereby generating a plurality of corresponding operation results; and

updating the frequency offset value according to the plurality of operation results.

7. The method of claim 5, wherein the step of choosing the plurality of partial sequence signals among the calibrated sequence signals comprises:

choosing a first partial sequence signal r′

(n1) and a second partial sequence signal r′

(n2) among the preliminarily calibrated sequence signal r′

(k);

wherein k is an integer no larger than K and no smaller than zero, n1 is an integer no larger than K−

m and no smaller than zero, n2 is an integer no larger than K and no smaller than K−

m, K is an integer, and the parameter m is a predetermined value.

8. The method of claim 1, wherein the step of determining the estimated frequency offset value between the transmitter and the receiver according to the plurality of shifted sequence signals comprises:

referring to the plurality of shifted sequence signals, and determining the estimated frequency offset value between the transmitter and the receiver both complying with a time domain synchronous orthogonal frequency division multiplexing (TDS-OFDM) specification.

9. A frequency offset acquisition apparatus, comprising:

a receiving unit, for receiving a specific sequence signal transmitted through a channel,

a processing unit, coupled to the receiving unit, for shifting a frequency of the specific sequence signal at a plurality of different frequencies in frequency domain to thereby generate a plurality of shifted sequence signals, respectively; and

a determining unit, coupled to the processing unit, for determining an estimated frequency offset value between a transmitter and a receiver according to the plurality of shifted sequence signals.

10. The apparatus of claim 9, wherein the determining unit performs a correlation operation upon an original sequence signal and each shifted sequence signal to generate a plurality of operation results, respectively, and determines the shifted sequence signal according to the plurality of operation results;

the original sequence signal is outputted to the channel by the transmitter; and

the original sequence signal corresponds to the specific sequence signal.

11. The apparatus of claim 10, wherein the original sequence signal is a pseudo random noise sequence signal.

12. The apparatus of claim 10, wherein for each shifted sequence signal, the determining unit performs a cyclic correlation operation upon the original sequence signal and the shifted sequence signal to generate an operation result including a plurality of correlation values;

for each operation result, the determining unit performs an absolute value operation upon the plurality of correlation values included in each operation result to generate a plurality of corresponding absolute values, and chooses a specific absolute value among the plurality of absolute values, where the specific absolute value is an extreme value among the plurality of absolute values; and

the determining unit determines the estimated frequency offset value according to an extreme value among a plurality of specific absolute values which correspond to the plurality of operation results, respectively.

13. The apparatus of claim 12, further comprising:

a calibration unit, coupled to the determining unit, for utilizing the estimated frequency offset value to perform a frequency offset calibration upon the specific sequence signal to generate a calibrated sequence signal;

a choosing unit, coupled to the calibration unit, for choosing a plurality of partial sequence signals among the calibrated sequence signals; and

an updating unit, coupled to the choosing unit, for updating the frequency offset value according to the plurality of partial sequence signals and the original sequence signal.

14. The apparatus of claim 13, wherein a correlation value corresponding to the specific absolute value is generated by the determining unit performing a cyclic correlation operation upon the original sequence signal and the shifted sequence signal according to a reference point;

and the updating unit performs the cyclic correlation operation of the original sequence signal and the shifted sequence signal according to the reference point, respectively, to thereby generate a plurality of corresponding operation results, and updates the frequency offset value according to the plurality of operation results.

15. The apparatus of claim 13, wherein the choosing unit chooses a first partial sequence signal r′

(n1) and a second partial sequence signal r′

(n2) among the preliminarily calibrated sequence signal r′

(k), where k is an integer no larger than K and no smaller than zero, n1 is an integer no larger than K−

m and no smaller than zero, n2 is an integer no larger than K and no smaller than K−

m, K is an integer, and the parameter m is a predetermined value.

16. The apparatus of claim 13, wherein the specific sequence signal complies with a time domain synchronous orthogonal frequency division multiplexing specification.