for j=1:length(N)
A = 0.5.*(randn(3,3, N) +(1i) * randn(3,3, N));
end
Why are you overwriting all of A in each loop iteration?
You are creating A as a 3 x 3 x 10 array each time.
C = log2(det(I + (P/N)*(A*A')));
Reminder: the * operator is only valid when one of the sides is a scalar, or both sides are either vectors or 2D arrays with the number of columns of the first operand being the same as the number of rows of the second operand. Your 3 x 3 x 10 array is not 2D so * cannot be used with it.
N = 10;
SNRdB=0:2:20;
[...]
semilogy(SNRdB,C_eigen,'ro-','lineWidth',.5);
I would suggest to you that you should not be assigning a constant N, and should instead be using
N = length(SNRdB);
I would further suggest to you that you should be using
for j=1:N
A = 0.5.*(randn(3,3) +(1i) * randn(3,3));
C = log2(det(I + (P/N)*(A*A')));
C_eigen(j) = something having to do with C
end
