FREQUENCY DOMAIN FEEDBACK CHANNEL ESTIMATION FOR AN INTERFERENCE CANCELLATION REPEATER INCLUDING SAMPLING OF NON CAUSAL TAPS

• US 20100284447A1
• Filed: 05/10/2010
• Published: 11/11/2010
• Est. Priority Date: 05/11/2009
• Status: Abandoned Application

• Current Assignee: Qualcomm, Inc.
• Original Assignee: Qualcomm, Inc.
• Inventors: Gore, Dhananjay Ashok, Wang, Michael Mao, Proctor, James Arthur JR., Barriac, Gwendolyn Denise, Tian, Tao
• Application Number:
  US12/776,957
• Publication Number:
  US 20100284447A1
• Time in Patent Office: Days
• US Class Current: 375/211
• CPC Class Codes: H04B 7/15585 by interference cancellation
• CPC Class Codes: H04L 25/022 of frequency response
• CPC Class Codes: H04L 25/0226 sounding signals per se

Abstract

A method for estimating a feedback channel for a wireless repeater uses frequency domain channel estimation on samples of a pilot signal and samples of a receive signal. The pilot signal samples may be delayed to align the largest channel tap to a given reference time. A time domain feedback channel is generated by retaining both the causal taps and the non-causal taps of the channel estimate.

Claims

1. A method for estimating a feedback channel for a wireless repeater in a wireless communication system, the wireless repeater having a first antenna and a second antenna to receive a receive signal and transmit an amplified signal, the receive signal being a sum of a remote signal to be repeated and a feedback signal resulting from the feedback channel between the first and second antenna of the wireless repeater, the method comprising:

using blocks of N samples of the amplified signal as a pilot signal;

using blocks of N samples of the receive signal;

estimating the feedback channel between the first antenna and the second antenna using frequency domain channel estimation using samples of the pilot signal and samples of the receive signal;

generating a time domain feedback channel estimate from the frequency domain channel estimation, the time domain feedback channel estimate having N taps; and

retaining M1 causal taps and M2 non-causal taps in the time domain feedback channel estimate, the M1 causal taps being the first M1 taps of the channel estimate and the M2 non-causal taps being the last M2 taps of the channel estimate.

2. The method of claim 1, further comprising:

before estimating the feedback channel, introducing a delay to the samples of the pilot signal to align the largest channel tap of the feedback channel to a first reference time; and

estimating the feedback channel in frequency domain using samples of the delayed pilot signal and samples of the receive signal.

3. The method of claim 1, wherein estimating the feedback channel between the first antenna and the second antenna using frequency domain channel estimation comprises performing Fast Fourier transform (FFT) operations on blocks of N samples of the pilot signal and the receive signal.

4. The method of claim 1, wherein the sum of M1 and M2 is less than N.

5. The method of claim 1, further comprising:

setting channel taps in the time domain channel estimate outside of the M1 causal taps and the M2 non-causal taps to zero.

6. The method of claim 5, further comprising:

setting channel taps in the time domain channel estimate from M1+1 to N−

M2−

1 to zero.

7. The method of claim 1, wherein retaining M1 causal taps and M2 non-causal taps in the time domain feedback channel estimate comprises:

circularly convolving the time domain feedback channel estimate with a filter having a length of L and a delay greater than M2 to generate a composite channel estimate, the filter indicative of filtering applied to the receive signals; and

retaining L+M1−

1 channel taps of the composite channel estimate to retain the M1 causal taps and M2 non-causal taps.

8. The method of claim 1, further comprising:

scaling the M1 causal taps and M2 non-causal taps in the time domain feedback channel estimate using a set of correction scaling factors.

9. The method of claim 8, wherein each of the correction scaling factor is a function of a tap index and N.

10. A machine-readable medium comprising instructions, which, when executed by a machine, cause the machine to perform operations, the instructions comprising:

using blocks of N samples of an amplified signal as a pilot signal;

using blocks of N samples of a receive signal;

estimating the feedback channel between a first antenna and a second antenna of a wireless repeater using frequency domain channel estimation and using samples of the pilot signal and samples of the receive signal;

generating a time domain feedback channel estimate from the frequency domain channel estimation, the time domain feedback channel estimate having N taps; and

retaining M1 causal taps and M2 non-causal taps in the time domain feedback channel estimate, the M1 causal taps being the first M1 taps of the channel estimate and the M2 non-causal taps being the last M2 taps of the channel estimate.

11. A computer-readable medium including program code stored thereon, comprising:

program code to use blocks of N samples of an amplified signal as a pilot signal;

program code to use blocks of N samples of a receive signal;

program code to estimate the feedback channel between a first antenna and a second antenna of a wireless repeater using frequency domain channel estimation and using samples of the pilot signal and samples of the receive signal;

program code to generate a time domain feedback channel estimate from the frequency domain channel estimation, the time domain feedback channel estimate having N taps; and

program code to retain M1 causal taps and M2 non-causal taps in the time domain feedback channel estimate, the M1 causal taps being the first M1 taps of the channel estimate and the M2 non-causal taps being the last M2 taps of the channel estimate.

12. A wireless repeater, comprising:

a first antenna and a second antenna configured to receive a receive signal and transmit an amplified signal, the receive signal being a sum of a remote signal to be repeated and a feedback signal resulting from a feedback channel between the first antenna and the second antenna; and

a channel estimation module configured to estimate the feedback channel between the first antenna and the second antenna using frequency domain channel estimation and using a signal indicative of the amplified signal as a pilot signal and using blocks of N samples of the pilot signal and blocks of N samples of the corresponding receive signal, to generate a time domain feedback channel estimate from the frequency domain channel estimation, and to retain M1 causal taps and M2 non-causal taps in the time domain feedback channel estimate, the M1 causal taps being the first M1 taps of the channel estimate and the M2 non-causal taps being the last M2 taps of the channel estimate.

13. The wireless repeater of claim 12, further comprising:

a delay element configured to introduce a delay to samples of the amplified signal to align the largest channel tap of the feedback channel to a first reference time, the channel estimation module using the delayed amplified signal as the pilot signal.

14. The wireless repeater of claim 12, wherein the channel estimation module is configured to estimate the feedback channel between the first antenna and the second antenna using frequency domain channel estimation by performing Fast Fourier transform (FFT) operations on blocks of N samples of the pilot signal and the receive signal.

15. The wireless repeater of claim 12, wherein the sum of M1 and M2 is less than N.

16. The wireless repeater of claim 12, wherein the channel estimation module is further configured to set channel taps in the time domain channel estimate outside of the M1 causal taps and the M2 non-causal taps to zero.

17. The wireless repeater of claim 16, wherein the channel estimation module is further configured to set channel taps in the time domain channel estimate from M1+1 to N−

M2−

1 to zero.

18. The wireless repeater of claim 12, wherein the channel estimation module is further configured to circularly convolve the time domain feedback channel estimate with a filter having a length of L and a delay greater than M2 to generate a composite channel estimate, the filter indicative of filtering applied to the receive signals, to retain L+M1−

1 channel taps of the composite channel estimate to retain M1 causal taps and M2 non-causal taps in the time domain feedback channel estimate.

19. The wireless repeater of claim 12, wherein the channel estimation module is further configured to scaling the M1 causal taps and M2 non-causal taps in the time domain feedback channel estimate using a set of correction scaling factors.

20. The wireless repeater of claim 19, wherein each of the correction scaling factor is a function of a tap index and N.

21. A wireless repeater, comprising:

first and second means configured to receive a receive signal and transmit an amplified signal, the receive signal being a sum of a remote signal to be repeated and a feedback signal resulting from a feedback channel between the first and second means; and

third means for estimating the feedback channel between the first and second means using frequency domain channel estimation and using a signal indicative of the amplified signal as a pilot signal and using blocks of N samples of the pilot signal and blocks of N samples of the corresponding receive signal, for generating a time domain feedback channel estimate from the frequency domain channel estimation, and for retaining M1 causal taps and M2 non-causal taps in the time domain feedback channel estimate, the M1 causal taps being the first M1 taps of the channel estimate and the M2 non-causal taps being the last M2 taps of the channel estimate.