Hi, I'm simulating various code rate LDPC codes in AWGN channel. I'm not sure how I should scale the gaussian r. v. for adding the noise when I include the rate R of the LDPC code. In theory, this should be the square root of the variance. As I have below, I'm dividing by 2*R. Is this right? Or should I be multiplying by R? sigma=sqrt((10.^(-SNRdB/10))/(2*R)); If someone could help me with this or know where I could get the answer that would be great!!! Thanks, Eric