ber_QAM.m

function ber=ber_QAM(EbN0dB,M,AWGN_or_Rayleigh)
% Find ananlytical BER of Mary QAM in AWGN or Rayleigh channel
% EbN0dB=EbN0dB: Energy per bit-to-noise power[dB] for AWGN channel
%       =rdB: Average SNR(2*sigma Eb/N0)[dB] for Rayleigh channel
% M = Modulation order (Constellation size)  

% MIMO-OFDM Wireless Communications with MATLAB¢ç   Yong Soo Cho, Jaekwon Kim, Won Young Yang and Chung G. Kang
% 2010 John Wiley & Sons (Asia) Pte Ltd

% http://www.wiley.com//legacy/wileychi/cho/

N= length(EbN0dB);  sqM= sqrt(M); 
a= 2*(1-power(sqM,-1))/log2(sqM);  b= 6*log2(sqM)/(M-1);
if nargin<3,  AWGN_or_Rayleigh='AWGN';  end
if lower(AWGN_or_Rayleigh(1))=='a', ber = a*Q(sqrt(b*10.^(EbN0dB/10)));
 else   rn= b*10.^(EbN0dB/10)/2; ber = 0.5*a*(1-sqrt(rn./(rn+1)));
end