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Viterbi decoding questions.

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kelvin_sg

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how to do puncturing in viterbi

I am a little puzzled with puncturing in viterbi algorithm.
What's the difference bwteen soft/hard decision.


Soft decision,
bits->1/2 convolutional encoding->QPSK---->Demod->quantize to 0~63->viterbi decoding

Is this soft decision? Where do I put depuncture?
bits->1/2 convolutional encoding->puncture to 3/4->serial-parallel->QPSK---->
---->filter->Demod->quantize to 0~63->viterbi decoding(?)

Is this hard decision?
bits->1/2 convolutional encoding->puncture to 3/4->serial-parallel->QPSK---->
---->filter->Demod->quantize to 0~63->deciding 00, 01, 10, 11->parallel-serial->
(depunct)insert 0s->viterbi decoding.

Or is this hard decision?
bits->1/2 convolutional encoding->puncture to 3/4->serial->BPSK---->
---->filter->Demod->deciding 0, 1 (antipodal)->(depunct)insert 0s->
viterbi decoding.

Thank you!
 

kelvin_sg

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veterbi depuncture

Anyone can shed some light on this question?
THanks in advance!
 

firephenix405

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depuncture algorithm

simply speaking, hard decision is to decide the output of modulation to be 0 or 1.
soft decision give more bits to quantize the output.

kelvin_sg said:
I am a little puzzled with puncturing in viterbi algorithm.
What's the difference bwteen soft/hard decision.


Soft decision,
bits->1/2 convolutional encoding->QPSK---->Demod->quantize to 0~63->viterbi decoding

Is this soft decision? Where do I put depuncture?
bits->1/2 convolutional encoding->puncture to 3/4->serial-parallel->QPSK---->
---->filter->Demod->quantize to 0~63->viterbi decoding(?)

Is this hard decision?
bits->1/2 convolutional encoding->puncture to 3/4->serial-parallel->QPSK---->
---->filter->Demod->quantize to 0~63->deciding 00, 01, 10, 11->parallel-serial->
(depunct)insert 0s->viterbi decoding.

Or is this hard decision?
bits->1/2 convolutional encoding->puncture to 3/4->serial->BPSK---->
---->filter->Demod->deciding 0, 1 (antipodal)->(depunct)insert 0s->
viterbi decoding.

Thank you!
 

abaidullah

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in hard decison the result is 0 or 1 and is used by the demod

where as in the soft-decison the decoder ouptuts a number of bits (3, 4, ... etc.) and the quantization is done decide the bits.
 

alzomor

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Hi

As I under stood hard decision gives you a final decision about the received bit and
But in soft decision you get a number represents the probability that the received digit is 1 or 0

you can check the last part of this article
http://www.complextoreal.com/chapters/convo.pdf

Salam
Hossam Alzomor
www(.)i-g(.)org
 

kelvin_sg

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Previously I think I also understood as alzomor's, i.e. in soft decision, i quantize a 1/2 CC result and quantize demod output and calculate the square root distance from the CC data point and use that in the add-compare-select..

Now I have a question, for punctured codes, how do I insert the 0s in such a decoding process?
 

MrJiang

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in my opinion there are two kinds of soft dicision for viterbi: soft input and hard output, soft input and soft output.

for puncture, you should insert the 0s before decoding according to the puncture pattern.
 

    kelvin_sg

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alzomor

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I think If you do depuncture at Tx you should do puncturing at the RX

But what makes you change you opinion about soft decision

Salam
Hossam Alzomor
www(.)i-g(.)org
 

kelvin_sg

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MrJiang said:
in my opinion there are two kinds of soft dicision for viterbi: soft input and hard output, soft input and soft output.

for puncture, you should insert the 0s before decoding according to the puncture pattern.
then for punctured codes, it will be soft inut/hard output?
or both?

Basically I am confused, in soft decoding, how is depuncturing incoperated?

Added after 1 minutes:

alzomor said:
I think If you do depuncture at Tx you should do puncturing at the RX

But what makes you change you opinion about soft decision

Salam
Hossam Alzomor
www(.)i-g(.)org
still confused over the question, usually one puncture in TX, depuncture in RX am I right?
 

MrJiang

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in my opinion, depuncture is just adding zeros on the position that punctured at TX.
if the codes input is soft, it is still soft output.

in the viterbi decoder, these zeros will be treated as error codes.
 

samuraign

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do demapping(hard or soft)
insert zeros

then do ur metric calculation and ACS(add compare select)
 

abaidullah

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MrJiang said:
in my opinion, depuncture is just adding zeros on the position that punctured at TX.
if the codes input is soft, it is still soft output.

in the viterbi decoder, these zeros will be treated as error codes.
the puncturing is the process in which we don't transmit some of the bits ... and the receiver end we add zeros at these locations
 

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