Autoregressive signal processing for repeater echo cancellation
A method and apparatus to address multipath interference in a communication system is provided. The method comprises measuring an error signal in a signal path of the repeater, wherein the error signal contains desired communication signals, noise signals, and multipath coupling interference signals, computing a power spectrum of the measured error signal, and estimating a response of the multipath coupling interference by processing the power spectrum of the measured error signal using autoregressive estimation in the frequency domain. The method further comprises computing a plurality of FIR filter coefficients from the estimated response and applying the plurality of filter coefficients to an adjustable filter that generates a cancellation signal used to at least partially mitigate the multipath coupling interference signals.
1. A method of mitigating multipath coupling interference in a communication system comprising:
measuring an error signal in a signal path of the communication system, wherein the error signal contains desired communication signals, noise signals, and multipath coupling interference signals;
computing a power spectrum of the measured error signal;
estimating a response of the multipath coupling interference by processing the power spectrum of the measured error signal using autoregressive estimation in a frequency domain that is performed using linear prediction in the frequency domain by minimizing, at a discrete set of frequencies, a prediction error power associated with the measured error signal;
computing a plurality of FIR filter coefficients from the estimated response;
applying the plurality of filter coefficients to an adjustable filter that generates a cancellation signal used to at least partially mitigate the multipath coupling interference signals.
2. The method of claim 1 , wherein the autoregressive estimation estimates the response of the multipath coupling interference by minimizing the power spectrum of the measured error signal.
3. The method of claim 1 , further comprising:
identifying a first set of frequencies where the power spectrum of the measured error signal is predominately associated with the noise signals.
4. The method of claim 3 , wherein the response of the multipath coupling interference is estimated by processing the power spectrum of the measured error signal using autoregressive estimation in the frequency domain at the first set of frequencies.
5. The method of claim 3 , further comprising:
identifying a second set of frequencies where the power spectrum of the measured error signal is predominately associated with the noise signals as well as the desired communication signals,
estimating a power spectrum of the measured error signal at the frequencies in the second set of frequencies using the power spectrum values associated with the first set of frequencies, and
forming a combined power spectrum which is composed of the power spectrum of the measured error signal at the frequencies in the first set of frequencies and the estimated power spectrum at the frequencies in the second set of frequencies.
6. The method of claim 5 , wherein the response of the multipath coupling interference is estimated by processing the combined power spectrum using autoregressive estimation in the frequency domain.
7. The method of claim 1 , wherein the communication system is a signal repeating system.
8. The method of claim 7 , wherein the signal repeating system is one of a repeater or a distributed antenna system.
9. The method of claim 7 , further comprising:
transmitting the error signal via an antenna of the signal repeating system.
10. The method of claim 1 , wherein the communication system is a same frequency signal repeating system.
11. The method of claim 1 , wherein the communication system is a frequency translating signal repeating system.
12. The method of claim 1 , wherein applying the plurality of filter coefficients is performed in a digital domain.
13. The method of claim 1 , wherein applying the plurality of filter coefficients is performed in an analog domain.
14. An apparatus, comprising:
an adjustable filter; and
processing circuitry coupled to the adjustable filter, the processing circuitry configured to:
measure an error signal in a signal path of the apparatus, wherein the error signal contains desired communication signals, noise signals, and multipath coupling interference signals;
compute a power spectrum of the measured error signal;
estimate a response of the multipath coupling interference by processing the power spectrum of the measured error signal using autoregressive estimation in a frequency domain that is performed using linear prediction in the frequency domain by minimizing, at a discrete set of frequencies, a prediction error power associated with the measured error signal;
compute a plurality of FIR filter coefficients from the estimated response; and
apply the plurality of filter coefficients to the adjustable filter to generate a cancellation signal used to at least partially mitigate the multipath coupling interference signals.
15. The apparatus of claim 14 , wherein the autoregressive estimation estimates the response of the multipath coupling interference by minimizing the power spectrum of the measured error signal.
16. The apparatus of claim 14 , wherein the processing circuitry is further configured to identify a first set of frequencies where the power spectrum of the measured error signal is predominately associated with the noise signals.
17. The apparatus of claim 16 , wherein the response of the multipath coupling interference is estimated by processing the power spectrum of the measured error signal using autoregressive estimation in the frequency domain at the first set of frequencies.
18. The apparatus of claim 16 , wherein the processing circuitry is further configured to identify a second set of frequencies where the power spectrum of the measured error signal is predominately associated with the noise signals as well as the desired communication signals, estimate a power spectrum of the measured error signal at the frequencies in the second set of frequencies using the power spectrum values associated with the first set of frequencies, and form a combined power spectrum which is composed of the power spectrum of the measured error signal at the frequencies in the first set of frequencies and the estimated power spectrum at the frequencies in the second set of frequencies.
19. The apparatus of claim 18 , wherein the response of the multipath coupling interference is estimated by processing the combined power spectrum using autoregressive estimation in the frequency domain.
20. The apparatus of claim 14 , wherein the apparatus is a signal repeating system.
21. The apparatus of claim 20 , wherein the signal repeating system is one of a repeater or a distributed antenna system.
22. The apparatus of claim 21 , further comprising:
an antenna,
wherein the processing circuitry is further configured to transmit the error signal via the antenna.
23. The apparatus of claim 22 , wherein the apparatus is a same frequency signal repeating system.
24. The apparatus of claim 14 , wherein the apparatus is a frequency translating signal repeating system.
25. The apparatus of claim 14 , wherein the processing circuitry is configured to apply the plurality of filter coefficients to the adjustable filter in a digital domain.
26. The apparatus of claim 14 , wherein the processing circuitry is configured to apply the plurality of filter coefficients to the adjustable filter in an analog domain.