Convintrlv: What is the best way to implement convintrlv for one packet?

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Dylan
Dylan 2024-8-27
回答： Shivam Gothi 2024-8-27
openExample('comm/DigitalVideoBroadcastingTerrestrialExample','supportingFile','commdvbt.slx')
I have been using this example as a reference to build a DVBT simulation on Matlab with code rather than a simulink block diagram. One problem I have encountered is that I seem to have to zero pad the convolutional interleaver by a lot to be able to have enough data for the deinterelaver to recreate the original message.
simple example to show what I mean:
nrows = 3
slope = 1
x = [1 2 3 4 5 6 7 8 9 10];
x_prime = convintrlv(x,nrows,slope) = [1 0 0 4 2 0 7 5 3 10]
x = convdeintrlv(x_prime,nrows,slope) = [0 0 0 0 0 0 1 2 3 4]
Obviously it is decoding the message but theres a delay and Id have to introduce a delay to get the whole picture. So then I pad with zeros.
x = [x 0 0 0 0 0 0];
x_prime = convintrlv(x,nrows,slope) = [1 0 0 4 2 0 7 5 3 10 8 6 0 0 9 0]
x = convdeintrlv(x_prime,nrows,slope) = [0 0 0 0 0 0 1 2 3 4 5 6 7 8 9 10]
Cool, but now my message has turned from a length 10 packet to a length 16 packet and this will affect later subsystems. What is a good way to solve for this?
I know in the DVBT example I showed at the top there is a buffer command. I'm not sure how to implement it, though.

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Shivam Gothi
Shivam Gothi 2024-8-27
Hello,
I see that you are working on implementing convintrlv and convdeintrlv using MATLAB code. However, it seems that the delay introduced in output signal and the zero-padding stages are not ideal for your requirements.
While implementing convintrlv and convdeintrlv, the delay is inhereritant and we cannot do any thing to remove.
But there is a work-around for this.
To implement it as a MATLAB code, you can automate the process of padding extra zeros to input signal and removing the excess zeros from the output signal by defining a "user defined function".
I have made two user defined functions in files "UserDefined_convintrlv.m" and "UserDefined_convdeintrlv.m". They are attached with the answer.
You can use them as shown below:
x = [1 2 3 4 5 6 7 8 9];
x_prime=UserDefined_convintrlv(x,3,1);
the output of above code is:
Now, again se the user defined function "UserDefined_convdeintrlv" as shown in below code:
x=UserDefined_convdeintrlv(x_prime,3,1)
The output of above command is attached below:
In this way you can get rid of manuall adding the zeros. Also, the output generated by "convdeintrlv" is free from any delay.
I have tested both the user defined functions for different values of "nRows" and "slope". I found that it is working.
I am also attaching the code of "UserDefined_convintrlv.m" and "UserDefined_convdeintrlv.m", in case the attached files failed to open.
%User defined function for convintrlv. Save the file with name "UserDefined_convintrlv.m"
function out = UserDefined_convintrlv(x,nRows,slope)
zeros_to_be_padded=zeros(1,nRows*(nRows-1)*slope);
x=[x zeros_to_be_padded];
out = convintrlv(x,nRows,slope);
end
%User defined function for convdeintrlv. Save the file with name "UserDefined_convdeintrlv.m"
function out = UserDefined_convdeintrlv(x,nRows,slope)
zeros_to_be_removed=nRows*(nRows-1)*slope;
temp_out = convdeintrlv(x,nRows,slope);
out = temp_out(zeros_to_be_removed+1:end);
end
"REMEMBER TO PLACE THE "UserDefined_convintrlv.m" and "UserDefined_convdeintrlv.m" FILES IN THE SAME WORKING DIRECTORY.
I hope this helps...

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