Method and apparatus for receiving a wideband signal in the presence of multipath channel imperfections and frequency offset

• US 7,035,358 B1
• Filed: 02/23/2001
• Issued: 04/25/2006
• Est. Priority Date: 02/23/2001
• Status: Expired due to Fees

• Current Assignee: Intel Corporation
• Original Assignee: ArrayComm LLC (Ygomi LLC)
• Inventors: Sankaran, Sundar G., Petrus, Paul
• Primary Examiner(s): Corrielus, Jean B.
• Application Number:
  US09/792,002
• Time in Patent Office: 1,887 Days
• Field of Search: 375/342, 375/344, 375/346, 375/350, 375/348, 375/285, 375/229, 375/231, 455/173.1, 455/182.2, 455/192.2
• US Class Current: 375/344
• CPC Class Codes: H04L 2027/003 at baseband only
• CPC Class Codes: H04L 2027/0038 using an equaliser
• CPC Class Codes: H04L 25/03012 operating in the time domain H04L25/03165, H04L25/03178 take precedence
• CPC Class Codes: H04L 27/0014 Carrier regulation of chaotic carriers H04L27/001; for multicarrier receivers H04L27/2657

Abstract

Payload reconstructing methods and apparatuses from wideband signals in the presence of multipath channel imperfections and frequency offset are disclosed. In one embodiment, a method in accordance with the teachings of the present invention includes receiving a signal, estimating a frequency offset of the received signal, performing frequency offset compensation on the received signal in response to the estimated frequency offset, performing equalization compensation on the received signal in response to the frequency offset compensated signal, and outputting payload information included in the received signal in response to the equalized frequency compensated received signal.

Claims

1. A method, comprising:

receiving a signal;

estimating a frequency offset of the received signal, wherein estimating the frequency offset comprises coarsely estimating the frequency offset of the received signal and finely estimating the frequency offset of the received signal, wherein coarsely estimating the frequency offset of the received signal comprises;

estimating a plurality of equalizer filter coefficients for a plurality of hypothetical coarse frequency offsets using at least squared error technique; and

selecting one of the plurality of hypothetical coarse frequency offsets corresponding to a lowest least squared error as a coarse estimation of the frequency offset;

performing frequency offset compensation on the received signal in response to the estimated frequency offset;

performing equalization compensation on the received signal in response to the frequency offset compensated signal; and

outputting payload information included in the received signal in response to the equalized frequency compensated received signal.

2. The method of claim 1 wherein the received signal includes the payload information between first and second training sequences included in the received signal, the method further comprising estimating the start of said received first training sequence included in the received signal.

3. The method of claim 2 wherein estimating the start of the first training sequence comprises correlating the received first training sequence with a reference first training sequence.

4. The method of claim 1 further comprising performing sample rate conversion on the equalized frequency compensated signal.

5. The method of claim 1 further comprising performing residual frequency offset and amplitude change compensation on the received signal after performing equalization compensation on the received signal.

6. The method of claim 1 wherein finely estimating the frequency offset of the received signal comprises:

performing equalization compensation on a received first training sequence included in the received signal in response to the coarse estimate of the frequency offset of the received signal;

dividing the equalized received first training sequence by a reference first training sequence;

calculating a magnitude spectrum at a plurality frequencies of a result of the division of the equalized received first training sequence by the reference first training sequence; and

selecting one of the plurality of frequencies corresponding to a highest magnitude spectrum calculation as a fine estimation of the frequency offset.

7. The method of claim 1 wherein performing equalization compensation on the received signal comprises estimating equalizing filter coefficients in response to a frequency offset compensated received first training sequence.

8. An apparatus, comprising:

an antenna to receive a signal; and

a payload regenerator coupled to the antenna to receive the signal, the payload regenerator to compensate the received signal for frequency offset by coarsely estimating the frequency offset and then finely estimating the frequency offset, and to equalize the frequency compensated received signal to generate payload information included in the received signal, wherein the payload regenerator is coupled to finely estimate the frequency offset by equalizing a first training sequence included in the received signal in response to the coarse estimate of the frequency offset of the received signal, dividing the equalized received first training sequence by a reference first training sequence, calculating a magnitude spectrum at a plurality frequencies of a result of the division of the equalized received first training sequence by the reference first training sequence and selecting one of the plurality of frequencies corresponding to said highest magnitude spectrum calculation as a fine estimation of the frequency offset.

9. The apparatus of claim 8 further comprising a converter coupled between the antenna and the payload regenerator.

10. The apparatus of claim 9 wherein the converter comprises:

a down converter to convert the signal from a broadband radio frequency (RF) signal to a baseband signal; and

an analog to digital (A/D) converter to convert the baseband signal from analog to digital, the payload regenerator receiving the received signal through an output of the A/D converter.

11. The apparatus of claim 9 wherein the converter comprises:

a down converter to convert the signal from a broadband radio frequency (RF) signal to an intermediate frequency signal;

an analog to digital (A/D) converter to convert the intermediate frequency signal from analog to digital; and

a digital down converter coupled to the A/D converter to convert the digitized intermediate frequency signal to a digital baseband signal, the payload regenerator receiving the received signal through an output of the digital down converter.

12. The apparatus of claim 8 wherein the payload regenerator comprises any one of a digital signal processor (DSP), microprocessor, field programmable gate array (FPGA) or application specific integrated circuit (ASIC) to generate the payload information included in the received signal.

13. The apparatus of claim 8 wherein the payload regenerator comprises storage to store the received signal.

14. The apparatus of claim 8 wherein the payload regenerator is coupled to estimate a start of a first training sequence included in the received signal by correlating the first training sequence included in the received signal with a reference first training sequence.

15. The apparatus of claim 8 wherein the payload regenerator is coupled to coarsely estimate the frequency offset by estimating a plurality of equalizer filter coefficients for a plurality of hypothetical coarse frequency offsets using a least squared errors technique and selecting one of the plurality of hypothetical coarse frequency offsets corresponding to a lowest least squared error as a coarse estimation of the frequency offset.

16. The apparatus of claim 8 wherein the payload regenerator is coupled to compensate for residual frequency offset and amplitude change in the received signal after the received signal is equalized and frequency compensated.

17. A machine-readable medium having stored thereon instructions, which when executed cause:

a signal to be received;

a frequency offset of the received signal to be estimated, wherein to estimate the frequency offset comprises coarsely estimating the frequency offset of the received signal and finely estimating the frequency offset of the received signal, wherein coarsely estimating the frequency offset of the received signal comprises;

estimating a plurality of equalizer filter coefficients for a plurality of hypothetical coarse frequency offsets using a least squared error technique; and

selecting one of the plurality of hypothetical coarse frequency offsets corresponding to a lowest least squared error as a coarse estimation of the frequency offset;

frequency offset compensation to be performed on the received signal in response to the estimated frequency offset;

equalization compensation to be performed on the received signal in response to the frequency offset compensated signal; and

payload information included in the received signal to be output in response to the equalized frequency compensated received signal.

18. The machine-readable medium of claim 17 wherein the received signal includes the payload information between first and second training sequences included in the received signal, the machine-readable medium having stored thereon further instructions, which when executed cause the start of said received first training sequence included in the received signal to be estimated.

19. The machine-readable medium of claim 18 wherein the frequency offset of the received signal being estimated comprises correlating the received first training sequence with a reference first training sequence.

20. The machine-readable medium of claim 17 wherein further instructions are stored on the machine-readable medium, which when executed cause sample rate conversion to be performed on the equalized frequency compensated signal.

21. The machine-readable medium of claim 17 wherein further instructions are stored on the machine-readable medium, which when executed cause residual frequency offset and amplitude change compensation to be performed on the received signal after equalization compensation is performed on the received signal.

22. The machine-readable medium of claim 17 wherein finely estimating the frequency offset of the received signal comprises:

performing equalization compensation on a received first training sequence included in the received signal in response to the coarse estimate of the frequency offset of the received signal;

dividing the equalized received first training sequence by a reference first training sequence;

calculating a magnitude spectrum at a plurality frequencies of a result of the division of the equalized received first training sequence by the reference first training sequence; and

selecting one of the plurality of frequencies corresponding to the highest magnitude spectrum calculation as a fine estimation of the frequency offset.

23. The machine-readable medium of claim 17 wherein the equalization compensation performed on the received signal comprises estimating equalizing filter coefficients in response to a frequency offset compensated received first training sequence.