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AMI_BER_FINAL.m
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AMI_BER_FINAL.m
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%%
% Intergrated Communication System
close all;
clear all;
clc;
%% Parameters
Nbits = 1000; % Number of bits generated
Rbits = 1000; % bps
Ts = 1/Rbits;
% SNR
SNR = [5 6 7 8 9 10 11 12 ];
lenSNR = length(SNR);
Nthres = 100;
% RRC filter
rr = 0.35; % RRC roll-off factor
Nup = 4; % Upsampling rate
rgd = 4; % RRC group delay
Rsam = Nup*Rbits;
Nb2d = 1; % sample to start down-sampling
% valid values: 1:Nup
Npre = 2*rgd*Nup; % Length of preamble bits
pre_pat = zeros(1,Npre); % create the preamble pattern
pre_pat(1:2:Npre) = 1;
pre_pat(Npre) = 1;
% DAC
Bdac = 8;
DRdac = 2; % DAC dynamic range, in Volts
% Arrays initialization
errors = zeros(1, lenSNR);
Ber = zeros(1,lenSNR);
Sym = zeros(Nbits,1);
Sam_dac = zeros(Nbits*Nup,1);
% Calculate RRC coefficients
disp('SRRC filter - Channel output');
rcosSpec = fdesign.pulseshaping(Nup, 'Square Root Raised Cosine', 'Nsym,beta', 2*rgd, rr);
rcosFlt = design(rcosSpec);
rcosFltcoefs = rcosFlt.Numerator/max(rcosFlt.Numerator);
%% Modulator Model
disp('AMI Modulator ....');
disp(' ');
for m=1:lenSNR
cnt = 0;
fprintf('\nSNR = %3.2f dB', SNR(m));
while errors(m) < Nthres
cnt=cnt+1;
Sym = zeros(Nbits,1);
Sam_dac = zeros(Nbits*Nup,1);
for ns = 1:(Nbits+Npre)
if ns <= Npre
Bits(ns) = pre_pat(ns);
else
Bits(ns) = randi([0, 1]); % New bit
end
% AMI modulation
flag=0;
for i=1:length(Bits)
if Bits(i)==0
Sym(i)=0;
else
if flag==0
Sym(i)=1;
flag=1;
else
Sym(i)=-1;
flag=0;
end
end
end
%RRC
SNup(2*Nup*rgd+(ns-1)*Nup+1:2*Nup*rgd+ns*Nup) = [Sym(ns) zeros(1, Nup-1)]; % Insert (Nup-1) zeros
for mn=1:Nup % Pulse shape (Direct FIR)
len = 2*Nup*rgd+ns*Nup;
tmp = SNup(len+mn-Nup-2*Nup*rgd:len+mn-Nup);
Sam_dac((ns-1)*Nup+mn) = sum(tmp.*rcosFltcoefs);
end
end
Sam_dac = Sam_dac';
%% Channel
Ps = sum(Sam_dac.^2)/length(Sam_dac);
Pn = Ps/(10^(SNR(m)/10));
ch_noise = sqrt(Pn)*(sqrt(2*log(1./(1-rand(1,length(Sam_dac)))))).*cos(2*pi*rand(1,length(Sam_dac)));
% fprintf('\nAWGN noise added. SNR = %3.1f dB', 10*log10(Ps/Pn));
Sam_adc = Sam_dac + ch_noise;
%% Rx
Sam_rrc = filter(rcosFltcoefs, 1, Sam_adc);
%% Inverse AMI
sym_rx = Sam_rrc(Nb2d:Nup:end);
sym_rx2=sym_rx;
for ns=1:length( sym_rx2);
abs1=abs( sym_rx2(ns)+1);
abs2=abs( sym_rx2(ns));
abs3=abs( sym_rx2(ns)-1);
y=min([abs1 abs2 abs3]);
if y==abs1
sym_rx2(ns)=-1;
elseif y==abs2
sym_rx2(ns)=0;
else
sym_rx2(ns)=1;
end
end
for j=1:length( sym_rx2)
if sym_rx2(j)==0
bits_rx(j)=0;
else
bits_rx(j)=1;
end
end
%%
% Correlation
t1 = (0:length(Bits)-1)/Rbits;
t2 = (0:length(bits_rx)-1)/Rbits;
[acor,lag] = xcorr(Bits,bits_rx);
[~,I] = max(abs(acor));
lagDiff = lag(I);
timeDiff = lagDiff/Rbits;
BitsExcor = bits_rx(abs(lagDiff)+1:end);
%%
sum2=0;
for ns=1:length(BitsExcor)
sum2=sum2+bitxor(BitsExcor(ns),Bits(ns));
end
errors(m) = errors(m) + sum2;
end
%Ber
Ber(m) = errors(m)/(cnt*Nbits);
fprintf(' BER = %3.2e', Ber(m));
fprintf(' No of Bits = %d Errors = %d\n', cnt*Nbits, errors(m));
end
%% Display
% % Scope
%
% % fprintf('\nSNR = %3.1d dB',SNR);
%
%
% scrsz = get(0,'ScreenSize');
% figure('Position', [50 50 scrsz(3)-100 scrsz(4)-200]);
% set(gcf, 'color', 'white');
% FontSize = 11;
% set(gcf,'DefaultLineLineWidth',1);
% set(gcf,'DefaultTextFontSize', FontSize, 'DefaultAxesFontSize', FontSize, 'DefaultLineMarkerSize', FontSize);
%
%
%
% ax(1) = subplot(6,1,1);
% stem((0:length(Sym)-1)*Ts, Bits);
% ylabel('Bits');
% title(['SNR = ',num2str(SNR)]);
%
% grid on
%
% ax(2) = subplot(6,1,2);
% stem((0:length(Sym)-1)*Ts, Sym);
% ylabel('Sym');
% grid on
%
% ax(3) = subplot(6,1,3);
% plot((0:length(Sam_dac)-1)*Ts/Nup, Sam_dac);
% hold on;
% plot((0:length(Sam_adc)-1)*Ts/Nup, Sam_adc, '-r');
%
% legend('Sam dac','Sam adc');
%
% grid on
%
% ax(4) = subplot(6,1,4);
% plot((0:length(Sam_rrc)-1)*Ts/Nup, Sam_rrc, '-o', 'MarkerSize', 4);
% ylabel('Sam rrc');
%
% grid on
%
% ax(5) = subplot(6,1,5);
% stem((0:length(sym_rx)-1)*Ts, sym_rx2);
% ylabel('Sym rx');
%
% grid on
%
% ax(6) = subplot(6,1,6);
% stem((0:length(BitsExcor)-1)*Ts, BitsExcor);
% ylabel('BitsExcor');
% grid on
%
%
%
% linkaxes(ax,'x');
%%
% Scope
scrsz = get(0,'ScreenSize');
figure('Position',[scrsz(4)/20 scrsz(4)/8 scrsz(3)/2 6*scrsz(4)/8]);
set(gcf, 'color', 'white');
FontSize = 13;
set(gcf,'DefaultLineLineWidth',2);
set(gcf,'DefaultTextFontSize', FontSize, 'DefaultAxesFontSize', FontSize, 'DefaultLineMarkerSize', FontSize);
semilogy(SNR, Ber, '.-');
grid on;
axis([min(SNR)-1 max(SNR)+1 1e-6 1]);
xlabel('SNR [dB]');
ylabel('BER');
text(4.2, 0.014, 'AMI', 'Color', 'b')