Variable step-sized modifications increase the speed of convergence the equalizer. Low complexity reduction is achieved by utilizing a sign operator in the adaptation algorithm. Robust against noisy channel.

1. Performance of Variable Step-Size
Dithered Signed-Error CMA for
Blind Equalization
Jusak Jusak
Dr. Zahir M. Hussain
Prof. Richard Harris

2. What is blind equalization ?
Conventional
equalization
filter
Blind
equalization
filter
source channel equalizer detector sink
pilot signal
adaptation
algorithm
source channel equalizer detector sink
adaptation
algorithm

3. Constant Modulus Algorithm (CMA)
It penalizes deviations from the output of a filter.
 
2
n
n y
y 
 
cma
cma = error function
yn = output of a filter
 = dispersion constant
      cma
r
f
f 
 n
n
n 

1

4. Reduced Complexity CMA (1)
Signed-Error CMA:
Transfer multiplications bulk update in CMA to
Sign operators (quantized to –1 or +1).
 
 
2
sign n
n y
y 

 
 cma
se
Lack of robustness properties of CMA

5. Reduced Complexity CMA (2)
Dithered Signed-Error CMA
Modification of SE-CMA by incorporating
controlled noise (so-called dither) in order to give
more precise quantization.
 
 
n
n
n d
y
y
cma
dse 


 



2
sign
Inherit robustness properties of CMA

6. Our proposed Algorithm
It increases the convergence speed of dithered
signed-error CMA.
HOW ??????
       
 
n
n
p
n d
y
R
y
n
n
n r
f
f 

 



 2
sgn
.
1
Variable step-size

7. Results (1)
BPSK signal, noiseless channel

8. Results (2)
BPSK signal, noisy channel (SNR = 30 dB)

9. Results (3)
8-PAM signal, noiseless channel

10. Conclusions
Variable step-sized modifications increase the
speed of convergence the equalizer.
Low complexity reduction is achieved by utilizing
a sign operator in the adaptation algorithm.
Robust against noisy channel.

11. The End