Line coding - NTNU

Decoding of partial response
? c k - c k-1
c k - c k-1
c k - c k-1
c k-1
c k-1
Digital Communication, Line codes and scrambling
IET, NTNU
27
Precoding of partial response (duobinary)
Precoder
Convert to
bipolar
b k = 0,1 d k = 0,1
0 to -1
c k = ±1 a k ˆ
+
1 to +1
z -1 z -1
Digital Communication, Line codes and scrambling
Duobinary
coding
b k
= 0 d k
= d k1
c k
= c k1
a k
= c k
+ c k1
=±2 b ˆ
k
= 0
b k
=1 d k
d k1
c k
c k1
a k
= c k
+ c k1
= 0 b ˆ
k
=1
3-level
decision
Decoding depends only on current received signal sample ):
no error propagation.
Precoding may be used also for modified duobinary and dicode.
IET, NTNU
b k
28