simulation-for-several-modulation.zip_ask

% Various routines that simulate or compute aspects of digital communication systems % % Simulate matched filter receiver figure(1); N = 100; noise_amp = 3; signal_set = 'bpsk2'; % either 'bpsk1', 'bpsk2', 'ask', or 'fsk' bits = ['1', '0', '1', '0', '0', '1']; % if strcmp(signal_set, 'bpsk1') signal1 = ones(1,N); signal0 = -signal1; elseif strcmp(signal_set, 'bpsk2') signal1 = sqrt(2)*sin(2*pi*2*[0:N-1]/N); signal0 = -signal1; elseif strcmp(signal_set,'fsk') signal1 = sqrt(2)*sin(2*pi*2*[0:N-1]/N); signal0 = sqrt(2)*sin(2*pi*3*[0:N-1]/N); elseif strcmp(signal_set, 'ask'); signal1 = ones(1,N); signal0 = zeros(1,N); else perror(sprintf('Unknown signal set %s\n',signal_set)); end color0='r';color1='b'; x = []; xcolor = []; for n=1:length(bits) x=[x eval(strcat('signal',bits(n)))]; xcolor = [xcolor eval(strcat('color',bits(n)))]; end % Send signal through white noise channel r = x + noise_amp*randn(1,length(x)); % Run matched filters y1=filter(signal1(N:-1:1),1,r); y0=filter(signal0(N:-1:1),1,r); % Graphics subplot(211) t=[0:length(r)-1]; plot(t,r,'k');hold on a = axis; xp=x*(0.75*max(abs([a(3) a(4)])/max(x))); for n=1:length(bits) plot(t((n-1)*N+1:n*N),xp((n-1)*N+1:n*N),[xcolor(n) '--']); h = text((n-1)*N+N/2,max(xp),bits(n)); set(h,'fontsize',16);set(h,'color',xcolor(n)); end for n=N*[1:length(bits)],h=line([n n],a(3:4));set(h,'linestyle','--');end h=title('Received signal');set(h,'fontsize',18); hold off subplot(212) plot(t,y0,color0,t,y1,color1) a = axis; for n=1:length(bits) if y1(n*N)>= y0(n*N) h = text(n*N-10,.75*a(4),'1'); set(h,'fontsize',16);set(h,'color',color1); if bits(n) == '0' set(h,'fontweight','bold'); end else h = text(n*N-10,.75*a(4),'0'); set(h,'fontsize',16);set(h,'color',color0); if bits(n) == '1' set(h,'fontweight','bold'); end end end for n=N*[1:length(bits)],h=line([n n],a(3:4));set(h,'linestyle','--');end h=title('Matched Filter Output');set(h,'fontsize',18); % % Compute Pr[e] curves % figure(2) snrdb = [-10:.5:12]; snr = 10.^(snrdb/10); p_bpsk = Q(sqrt(2*snr)); p_fsk = Q(sqrt(snr)); h=semilogy(snrdb,p_bpsk,snrdb,p_fsk,'r--');grid;axis([-10 12 10^(-8) 1]) set(gca,'fontsize',18); h=xlabel('Signal-to-Noise Ratio (dB)');set(h,'fontsize',18); h=ylabel('Bit Error Probability');set(h,'fontsize',18); legend('BPSK','FSK'); % % Error Correction (Repetition Code) % figure(3) snrdb = [-10:.5:12]; snr = 10.^(snrdb/10); p_bpsk = Q(sqrt(2*snr)); pb_bpsk = p_bpsk; pb_rep = 1-(1-p_bpsk).^3-3*p_bpsk.*(1-p_bpsk).^2; p_31 = Q(sqrt(2*3*snr)); % 3 times longer transmission time pb_31 = p_31; semilogy(snrdb,pb_bpsk,'b-',snrdb,pb_31,'r--',snrdb,pb_rep,'k-.'); grid;axis([-10 12 10^(-15) 1]) set(gca,'fontsize',18); h=xlabel('Signal-to-Noise Ratio (dB)');set(h,'fontsize',18); h=ylabel('Block Error Probability');set(h,'fontsize',18); legend('No ECC','3 Times Longer Bit Interval','Length 3 Repetition Code') title('Repetition Code (3,1)') % % (7,4) Hamming Code Performance Curves % figure(4) snrdb = [-10:.5:12]; snr = 10.^(snrdb/10); p_bpsk = Q(sqrt(2*snr)); pb_uc = 1-(1-p_bpsk).^4; p_74 = Q(sqrt(2*7/4*snr)); % 7/4 longer transmission time pb_74 = 1-(1-p_74).^4; pb_hamming = 1-(1-p_bpsk).^7-7*p_bpsk.*(1-p_bpsk).^6; semilogy(snrdb,pb_uc,'b-',snrdb,pb_74,'r--',snrdb,pb_hamming,'k-.'); grid;axis([-10 12 10^(-15) 1]); set(gca,'fontsize',18); legend('Uncoded','7/4 Longer Bit Interval','Hamming Code'); h=xlabel('Signal-to-Noise Ratio (dB)');set(h,'fontsize',18); h=ylabel('Block Error Probability');set(h,'fontsize',18); title('(7,4) Hamming Code Performance'); % % Capacity Calculations % figure(5) p=[0:.01:.5]; C=1+p.*log2(p)+(1-p).*log2(1-p); C(1) = 1; subplot(211) plot(p,C) set(gca,'fontsize',18);grid h = xlabel('Error Probability');set(h,'fontsize',18); h = ylabel('Capacity (bits)');set(h,'fontsize',18); subplot(212) C=1+p_bpsk.*log2(p_bpsk)+(1-p_bpsk).*log2(1-p_bpsk); plot(snrdb,C); set(gca,'fontsize',18);grid;legend('Capacity using BPSK') h = xlabel('Signal-to-Noise Ratio (dB)');set(h,'fontsize',18); h = ylabel('Capacity (bits)');set(h,'fontsize',18);