Transcript Basic Concepts - Gunadarma University

Design Simulation of adaptive filter
algorithm (LMS and NLMS) for
acoustic echo cancellation
Name
: Arum Tri Iswari Purwanti
NPM
: 10407165
Department
: Electrical Engineering
Supervisor
: Raden Supriyanto SSi., SKom., MSc.
CONTENTS
INTRODUCTION
DESIGN AND IMPLEMENTATION
RESULT AND ANALYSIS
CONCLUSION
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INTRODUCTION
Echo from the environment automatically added
to the signal. In the real world application like
hand-free communication, the echo can make
the conversation impossible in the extreme
condition.
3
INTRODUCTION

Acoustic echo occur when an audio signal is
reverberated in a real environment, resulting in
the original intended signal plus attenuated and
delay time.
Figure 1.1 Reverberation of the signal
4
INTRODUCTION

When the signal is received by a system, its
output will come out through the loudspeaker to
the free environment.

The signal is reverberated in the environment
and back into the system via microphone input.
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DESIGN AND IMPLEMENTATION

The method used to cancel the echo signal is
known as
ADAPTIVE FILTERING
Least Mean Square
(LMS)
Algorithm
Normalized Least Mean Square
(NLMS)
Algorithm
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Least Mean Square (LMS) Algorithm
Each iteration of the LMS algorithm requires 3
distinct steps in this order:

Output of the FIR filter, y(n) is calculated using

The value of the error estimation is calculated
using
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Least Mean Square (LMS) Algorithm

The tap weights of the FIR vector are updated in
preparation for the next iteration, by
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Normalized Least Mean Square (NLMS)
Algorithm
Each iteration of the NLMS algorithm requires
these steps in the following order:

Output of the adaptive filter is calculated.

An error signal is calculated as the difference
between the desired signal and the filter output.
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Normalized Least Mean Square (NLMS)
Algorithm

The step size value for the input vector is
calculated.

The filter tap weights are updated in preparation
for the next iteration.
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DESIGN AND IMPLEMENTATION
The parameters are :

Error Estimation

Mean Square Error (MSE)

Echo Return Loss Enhancement (ERLE)

Attenuation

Accuracy Percentage
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DESIGN AND IMPLEMENTATION

The configuration of an Acoustic Echo Cancellation
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DESIGN AND IMPLEMENTATION

H(n) the impulse response between loudspeaker and
microphone

d(n) the desired signal which is obtained by convolving
the input signal with the impulse response of acoustic
environment

y(n) the echo replica which is created at the output of
the adaptive filter

e(n) error from the different between desired signal
and the echo replica, e(n)=d(n)-y(n)
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DESIGN AND IMPLEMENTATION
Figure 1.2 Overall system
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DESIGN AND IMPLEMENTATION

To generate the desired signal, it can be done
by convolving between the wav file input and
the manipulation of the real impulse response.

To filter the echo, two algorithms (LMS and
NLMS) will be compared each other based on
their steps.

Each parameter will be calculated to know the
better the algorithm between the LMS algorithm
and the NLMS algorithm.
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RESULT AND ANALYSIS
Based on the parameters :

Error Estimation
16
RESULT AND ANALYSIS

Mean Square Error (MSE)
17
RESULT AND ANALYSIS

ERLE, Attenuation, Accuracy Percentage, and
Complexity
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CONCLUSION

Both algorithms can cancel the echo with its
own algorithm.

The NLMS algorithm has so many advantages
than the LMS algorithm such as the smaller
values of error estimation, MSE, and attenuation
and the higher values of ERLE and accuracy
percentage.
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CONCLUSION

The LMS algorithm also has the advantages
such as the smaller value of complexity and
better stability.

To implement the algorithm of adaptive filter for
echo cancellation, the NLMS algorithm is better
than the LMS algorithm
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THANK YOU
FOR YOUR ATTENTION
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