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From: Martin Clark on 7 Dec 2005 10:13
I may be using a different version of Simulink and so the prompts might
vary. In any case, the sample time of a constant block must be consistent
with the source (via sample time or frame period). You can set it
explicitly, but that can sometimes be an awkward calculation for complex
systems. An easier way with constants is to use inf. This will be
compatible with any other sample time.


"Ant_Magma" <vcteo1(a)gmail.com> wrote in message
news:1133936245.849953.268760(a)g47g2000cwa.googlegroups.com...
> Bless you Don :D
>
> Thx 4 ur reply Martin.....
> I've did noticed the different sample colors in my model but i didn't
> thought much about it. You mentioned:
>
>>In the DSP Constant blocks "DC" and "Nyquist", set the frame
>>period to inf. The model will then use a single frame rate.
>
> I've checked the help for Constant at mathworks.com. I have to set the
> Output to 'Frame-based' then Sample time will change to Frame period...
>
> Since i dun have matlab in this computer, i'll try it when i get back
> and feedback the results later...
>
> Another question, why set it to inf? Since my bernoulli produces 12
> bits/frame, why not set it to 12 instead of inf?
>


From: Ant_Magma on 7 Dec 2005 20:23
It's solved!! Thx martin for the tip, the model is now working.

I have another series of questions, hope you don't mind....

I've now included the Puncture and Insert Zero block to my model to
obtain a better code rate of 3/4. However, this has lead into another
problem.

As i have mentioned before, my Viterbi decoder is set to Hard decision.
Hard decision works based on 0s & 1s. When i included the puncture
pair, again i get 0.5 BER. However, if i change the decision type in my
Viterbi to Unquantized and add a Unipolar to Biploar Converter (since
unquantized viterbi works on -1 n 1) before the Insert Zero block, it
works perfectly.

I was wondering is there any way to work around the problem? meaning
without using the bipolar converter?

2nd Q:

I obtained somewhere from the help in Simulink that for a 3/4 code rate
the optimum puncture vector is [110110].' correct?
Based on your experience, is there any optimum parameter for
interleaving? rows & columns (i plan to add interleaving after i've
figure out the puncturing)

I've noticed in the Simulink demos (both HiperLAN2 & WLAN802.11a) which
involves OFDM, interleaving is done twice using the Matrix interleaver
and the General block interleaver. Is it just a choice or preference?
Or is there a specific reason to it? And if so, how do i choose the
Elements for the General block interleaver?

Sorry for the barrage of questions....really appreaciate u guy's help...

From: Ant_Magma on 7 Dec 2005 21:38
It's solved!! Thx martin for the tip, the model is now working.

I have another series of questions, hope you don't mind....

I've now included the Puncture and Insert Zero block to my model to
obtain a better code rate of 3/4. However, this has lead into another
problem.

As i have mentioned before, my Viterbi decoder is set to Hard decision.
Hard decision works based on 0s & 1s. When i included the puncture
pair, again i get 0.5 BER. However, if i change the decision type in my
Viterbi to Unquantized and add a Unipolar to Biploar Converter (since
unquantized viterbi works on -1 n 1) before the Insert Zero block, it
works perfectly.

I was wondering is there any way to work around the problem? meaning
without using the bipolar converter?

2nd Q:

I obtained somewhere from the help in Simulink that for a 3/4 code rate
the optimum puncture vector is [110110].' correct?
Based on your experience, is there any optimum parameter for
interleaving? rows & columns (i plan to add interleaving after i've
figure out the puncturing)

I've noticed in the Simulink demos (both HiperLAN2 & WLAN802.11a) which
involves OFDM, interleaving is done twice using the Matrix interleaver
and the General block interleaver. Is it just a choice or preference?
Or is there a specific reason to it? And if so, how do i choose the
Elements for the General block interleaver?

Sorry for the barrage of questions....really appreaciate u guy's help...

From: Ant_Magma on 7 Dec 2005 21:38
It's solved!! Thx martin for the tip, the model is now working.

I have another series of questions, hope you don't mind....

I've now included the Puncture and Insert Zero block to my model to
obtain a better code rate of 3/4. However, this has lead into another
problem.

As i have mentioned before, my Viterbi decoder is set to Hard decision.
Hard decision works based on 0s & 1s. When i included the puncture
pair, again i get 0.5 BER. However, if i change the decision type in my
Viterbi to Unquantized and add a Unipolar to Biploar Converter (since
unquantized viterbi works on -1 n 1) before the Insert Zero block, it
works perfectly.

I was wondering is there any way to work around the problem? meaning
without using the bipolar converter?

2nd Q:

I obtained somewhere from the help in Simulink that for a 3/4 code rate
the optimum puncture vector is [110110].' correct?
Based on your experience, is there any optimum parameter for
interleaving? rows & columns (i plan to add interleaving after i've
figure out the puncturing)

I've noticed in the Simulink demos (both HiperLAN2 & WLAN802.11a) which
involves OFDM, interleaving is done twice using the Matrix interleaver
and the General block interleaver. Is it just a choice or preference?
Or is there a specific reason to it? And if so, how do i choose the
Elements for the General block interleaver?

Sorry for the barrage of questions....really appreaciate u guy's help...

From: Ant_Magma on 7 Dec 2005 21:40
It's solved!! Thx martin for the tip, the model is now working.

I have another series of questions, hope you don't mind....

I've now included the Puncture and Insert Zero block to my model to
obtain a better code rate of 3/4. However, this has lead into another
problem.

As i have mentioned before, my Viterbi decoder is set to Hard decision.
Hard decision works based on 0s & 1s. When i included the puncture
pair, again i get 0.5 BER. However, if i change the decision type in my
Viterbi to Unquantized and add a Unipolar to Biploar Converter (since
unquantized viterbi works on -1 n 1) before the Insert Zero block, it
works perfectly.

I was wondering is there any way to work around the problem? meaning
without using the bipolar converter?

2nd Q:

I obtained somewhere from the help in Simulink that for a 3/4 code rate
the optimum puncture vector is [110110].' correct?
Based on your experience, is there any optimum parameter for
interleaving? rows & columns (i plan to add interleaving after i've
figure out the puncturing)

I've noticed in the Simulink demos (both HiperLAN2 & WLAN802.11a) which
involves OFDM, interleaving is done twice using the Matrix interleaver
and the General block interleaver. Is it just a choice or preference?
Or is there a specific reason to it? And if so, how do i choose the
Elements for the General block interleaver?

Sorry for the barrage of questions....really appreaciate u guy's help...

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