System and method of noise reduction in receiving wireless transmission of packetized audio signals

• US 20040001599A1
• Filed: 06/28/2002
• Published: 01/01/2004
• Est. Priority Date: 06/28/2002
• Status: Active Grant

• Current Assignee: Lucent Technologies, Inc. (Nokia Corporation)
• Original Assignee: Lucent Technologies, Inc. (Nokia Corporation)
• Inventors: Etter, Walter, Sizer, Theodore II, August, Katherine G.
• Granted Patent: US 7,321,559 B2
• Time in Patent Office: Days
• US Class Current: 381/94.1
• CPC Class Codes: G10L 19/005 Correction of errors induced by the transmission channel, if related to the coding algorithm
• CPC Class Codes: H04L 1/0045 Arrangements at the receiver end
• CPC Class Codes: H04L 1/0072 Error control for data other than payload data, e.g. control data

Abstract

A receiver for receiving wireless packetized audio signals having packet headers, and packet payloads including encoded audio signals is provided. The receiver includes an audio decoder for decoding the encoded audio signals into digital audio signals, an audio error detector for detecting impulsive noise in the digital audio signals caused by corrupted payload packets, and a digital signal restoration unit for removing the impulsive noise from the digital audio signals. Further, a method of noise reduction includes the steps of receiving radio frequency packetized audio signals having packet headers, and packet payloads including encoded audio signals and demodulating the RF signals. The method further includes decoding the encoded audio signals into digital audio signals and detecting impulsive noise in the digital audio signals caused by corrupted payload packets. The method further includes removing the impulsive noise by reconstructing the corrupted digital audio signal.

Claims

1. A receiver for receiving wireless packetized audio signals having packet headers, and packet payloads including encoded audio signals, the receiver comprising:

an audio decoder for decoding the encoded audio signals into digital audio signals;

an audio error detector for detecting impulsive noise in digital audio signals caused by corrupted payload packets; and

a digital signal restoration unit for removing the impulsive noise from the digital audio signals.

2. The receiver defined in claim 1 wherein the audio error detector comprises:

a linear prediction (LP) parameter estimator for estimating LP parameters of the digital audio signals;

an LP inverse filter for filtering the digital audio signals using the LP parameters; and

a threshold detector for providing a threshold used in detecting impulsive noise exceeding the threshold.

3. The receiver defined in claim 1 wherein the digital signal restoration unit reconstructs the digital audio signal corresponding to the corrupted payload packet to provide an audio output having reduced noise.

4. The receiver defined in claim 3 wherein the digital signal restoration unit reconstructs the digital audio signal using linear predictor parameters generated by the audio error detector.

5. The receiver defined in claim 3 wherein the digital signal restoration unit generates signal parameters used for reconstructing the digital audio signal.

6. The receiver defined in claim 5 wherein the signal parameters are linear predictor coefficients.

7. The receiver defined in claim 5 wherein the signal parameters are pitch parameters.

8. The receiver defined in claim 3 wherein the audio decoder uses a codec generating linear predictor parameters for decoding the encoded audio signals and the digital signal restoration unit reconstructs the corrupted digital audio signal using the linear predictor parameter coefficients generated by the audio decoder.

9. The receiver defined in claim 3 wherein the wireless packetized audio signal packet headers are channel encoded for noise reduction and further including a channel decoder for decoding the packet headers and for signaling the digital signal restoration unit to reconstruct corrupted digital audio signals.

10. The receiver defined in claim 1 wherein the digital signal restoration unit mutes the digital audio signal corresponding to the corrupted payload packet to provide an audio output having reduced noise.

11. An audio error detector for detecting impulsive noise in packetized digital audio signals caused by corrupted payload packets, the audio error detector comprising:

a linear prediction (LP) parameter estimator for estimating the LP parameter coefficients of the digital audio signals;

an LP inverse filter for filtering the digital audio signals using the LP parameter coefficients; and

a threshold detector for providing a threshold used in detecting impulsive noise exceeding the threshold.

12. A method of noise reduction in wireless transmission of packetized audio signals comprising:

receiving wireless packetized audio signals having packet headers, and packet payloads including encoded audio signals;

decoding encoded audio signals into frames of digital audio signals;

combining the frames into segments of digital audio signals;

detecting impulsive noise in a segment from at least one corrupted frame caused by at least one corrupted payload packet corresponding to the corrupted frame;

removing the impulsive noise from the segment; and

providing audio output.

13. The method of noise reduction defined in claim 12 wherein the step of removing the impulsive noise includes reconstructing the digital audio signal in the at least one corrupted frame.

14. The method of noise reduction defined in claim 13 wherein the reconstructing includes at least one of forward prediction and forward-backward prediction.

15. The method of noise reduction defined in claim 14 wherein the reconstructing comprises switching between forward and forward-backward prediction.

16. The method of noise reduction defined in claim 12 wherein the step of removing the impulsive noise includes muting the impulse noise.

17. The method of noise reduction defined in claim 12 wherein the step of detecting impulsive noise comprises:

estimating LP parameter coefficients of the digital audio signals;

LP inverse filtering the digital audio signals using the LP parameter coefficients; and

providing a threshold for the detection of impulsive noise exceeding the threshold.

18. The method of noise reduction defined in claim 12 wherein the step of detecting impulsive noise comprises modeling the digital audio signals using a Linear Predictor (LP) model wherein the digital audio signals, written as s(i) with time-index i, may be predicted based on the previous K samples, such that

19. The method of noise reduction defined in claim 18 wherein the estimating step comprises using autocorrelation methods to generate the estimated LP parameters â

_j.

20. The method of noise reduction defined in claim 19 further comprising:

comparing the estimation error μ

(i) to a threshold; and

signaling the detection of impulsive noise when the estimation error μ

(i) exceeds the threshold.