LDPC function 可以改变消息的长度吗？ 如何？

Question

This is MATLAB code about LDPC (Low Density Parity Check). Could I change the length of data ? and how?

ldpcEncoder = comm.LDPCEncoder;
data = logical(randi([0 1],32400,1));
% Transmit and receive LDPC coded signal data
    encData = ldpcEncoder(data);

I try to change the length of data , but MATLAB always warns that "Input must be a column vector of length K , the message length." Is this length of data is fixed?

Answer 1

The input of the LDPC codes should be always of length K , otherwise, the parity matrix would change and the code would be different. When you create an LDPCEncoder object in MATLAB, you are defining the K and N lengths, so the input data can't change.

Answer 2

Yes, you can. You can create your comm.LDPCEncoder with certain parity check matrix in the following way:

comm.LDPCEncoder(ParityCheckMatrix) 

For example, if you want to generate a DVB-S2 encoder for a code rate of 1/2, the code will be:

p = dvbs2ldpc(1/2);
enc = comm.LDPCEncoder(p);