QAM.rar_16 QAM _M-QAM_QAM 信号_QAM信号_星座图 QAM

function [p]=cm_sm41(snr_in_dB) % [p]=cm_sm41(snr_in_dB) % CM_SM41 finds the probability of error for the given % value of snr_in_dB, SNR in dB. N=10000; d=1; % min. distance between symbols Eav=10*d^2; % energy per symbol snr=10^(snr_in_dB/10); % SNR per bit (given) sgma=sqrt(Eav/(8*snr)); % noise variance M=16; % Generation of the data source follows. for i=1:N, temp=rand; % a uniform R.V. between 0 and 1 dsource(i)=1+floor(M*temp); % a number between 1 and 16, uniform end; % Mapping to the signal constellation follows. mapping=[-3*d 3*d; -d 3*d; d 3*d; 3*d 3*d; -3*d d; -d d; d d; 3*d d; -3*d -d; -d -d; d -d; 3*d -d; -3*d -3*d; -d -3*d; d -3*d; 3*d -3*d]; for i=1:N, qam_sig(i,:)=mapping(dsource(i),:); end; % received signal for i=1:N, [n(1) n(2)]=gngauss(sgma); r(i,:)=qam_sig(i,:)+n; end; % detection and error probability calculation numoferr=0; for i=1:N, % Metric computation follows. for j=1:M, metrics(j)=(r(i,1)-mapping(j,1))^2+(r(i,2)-mapping(j,2))^2; end; [min_metric decis] = min(metrics); if (decis~=dsource(i)), numoferr=numoferr+1; end; end; p=numoferr/(N);