% define parameters
N = 3;		% (2*N)^2 - QAM

% create QAM symbol stream
B = BitStream(20004);
x = BitToSymbolStream(B,N);
X = QAM_Mod(x,N);

% add noise at specified SNR level
SNR = 20;
sigma_x = std(X);
noise = (randn(1,length(X)) + sqrt(-1)*randn(1,length(X)))/sqrt(2);
X = X + sigma_x*10^(-SNR/20)*noise;

% recovery of bit stream
y = QAM_Demod(X,N);
B2 = SymbolToBitStream(y,N);

% determining the number of bit errors and BER
BER = norm(B-B2,1)/length(B);
disp(sprintf('BER = %f %',BER*100));