I have to generate a pair of orthogonal codes to multiply with two QAM modulated signals in cooperative communication. How to generate this?
The simplest way to get an orthogonal code dictionary is to generate a Hadamard/Walsh matrix. All the rows and columns of this matrix are mutually orthogonal. You can use a couple of its rows or columns as your codes. Please remember that the size of the matrix (and hence the length of the code) can only be a power of 2, for example N = 4, 8, 16, 32,64,....
The code is simple: for example for N=64-length codes:
C = hadamard(64);
code1 = C(: , 3); % the code will be a vertical column
code2 = C(:,11);
The simplest way to get an orthogonal code dictionary is to generate a Hadamard/Walsh matrix. All the rows and columns of this matrix are mutually orthogonal. You can use a couple of its rows or columns as your codes. Please remember that the size of the matrix (and hence the length of the code) can only be a power of 2, for example N = 4, 8, 16, 32,64,....
The code is simple: for example for N=64-length codes:
C = hadamard(64);
code1 = C(: , 3); % the code will be a vertical column
code2 = C(:,11);
In case you were using Simulink, try running this demo model and see how things happen by observing the scopes and changing the parameters.
Before you run, make sure you enter the following parameters in the workspace first:
PG = 128; % Processing gain
bit_rate = 1e6;
Tb = 1/bit_rate;
chip_rate = bit_rate*PG;
Tc = 1/chip_rate;
Tstop = 10*Tb;
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