How to implement a system for having SNR of the signal to be 80 dB at the receiving end??

i have done this way. I don't know whether this is right or wrong. x=randsrc(2,1); h=1/sqrt(2)*(randn(2,2)+1j*randn(2,2)); noise=(1/(sqrt(2)))*(1/10^8)*(randn(2,1)+1j*randn(2,1)); r=h*x+n;