hello everybody
what the customer have specified us for making viterbi decoding
includes some units that i want to know about
"SOFT SLICER"
what it is doing is converting 10 bits I and Q inputs to
two 3-bits output pair....any idea what it is....
and can someone provide some insight on "Node Synchronizer" used for
viterbi decoder...please provide some web links(one that dont ask for
money.. ;) ) if possible...

Posted by julius●March 22, 20072007-03-22

On Mar 22, 12:42 am, "khurram712" <khurram...@hotmail.com> wrote:

> hello everybody
>
> what the customer have specified us for making viterbi decoding
>
> includes some units that i want to know about
>
> "SOFT SLICER"
>
> what it is doing is converting 10 bits I and Q inputs to
>
> two 3-bits output pair....any idea what it is....
>
> and can someone provide some insight on "Node Synchronizer" used for
> viterbi decoder...please provide some web links(one that dont ask for
> money.. ;) ) if possible...

No idea what a "node synchronizer" is, but the
"soft slicer" is one that gives the probabilities
for one symbol (say -1) versus another (say +1).
Let's simplify by assuming BPSK (sending -1 or +1).
You see a noisy version y[n] = x[n] + z[n],
x[n] is the transmitted symbols, z[n] is white
Gaussian noise. If you know the mean/variance
of z[n], then from the observed y[n] you can
compute (with some abuse of notation):
p(y[n] | x[n]=1) and p(y[n] | x[n]=-1).
Using Bayesian rule etc you can find
p( x[n]=1 | y[n]=Y), p( x[n]=-1 | y[n]=Y).
In many cases you only care about the ratio of the
log of the two quantities above. Look up "log
likelihood ratio".
This is probably what a "soft slicer" is.
The customer needs to tell you what format exactly
he/she wants.
Julius

100% of our work is cutting-edge DSP
We are a small, high tech, sonar-processing company that develops state-of-the-art sonar, signal processing software systems used in naval aircraft.
Tasks:
* 60-75% signal processing algorithm development
* 25% real time code development in C++ Full relocation will be provided for the right candidate (e.g. relocation package up to $20,000).