sir this code showing me error..plz help me out..

function cdmamodem(user1,user2,snr_in_dbs) % >>>multiple access b/w 2 users using DS CDMA % >>>format is : cdmamodem(user1,user2,snr_in_dbs) % >>>user1 and user2 are vectors and they should be of equal length % >>>e.g. user1=[1 0 1 0 1 0 1] , user2=[1 1 0 0 0 1 1],snr_in_dbs=-50 % >>>or snr_in_dbs=50 just any number wud do % Waqas Mansoor % NUST , Pakistan

close all user1=[1 0 0 1 1 0]; user2=[1 1 0 1 0 0]; %% to convert the binary sequences to bipolar NRZ format length_user1=length(user1); length_user2=length(user2);

for i=1:length_user1 if user1(i)==0 user1(i)=-1; end end

for i=1:length_user2 if user2(i)==0 user2(i)=-1; end end

fc=1; %%carrier frequency eb=2; %% energy per bit tb=1; %% time per bit of message sequence

%%% CDMA transmitter for user1 t=0.01:0.01:tb*length_user1; %0.01 %%plotting base band signal for user1 basebandsig1=[]; for i=1:length_user1 for j=0.01:0.01:tb%0.01 if user1(i)==1 basebandsig1=[basebandsig1 1]; else basebandsig1=[basebandsig1 -1]; end end end

figure plot(basebandsig1) axis([0 100*length_user1 -1.5 1.5]); title('original binary sequence for user1 is')

%%%% BPSK MODULATION FOR USER 1 bpskmod1=[]; for i=1:length_user1 for j=0.01:0.01:tb bpskmod1=[bpskmod1 sqrt(2*eb)*user1(i)*cos(2*pi*fc*j)]; end end length(bpskmod1) figure plot(bpskmod1) %axis([0 100*length_user1 -2 2]); title(' BPSK signal for user 1 is')

%% plot fft of BPSK sequence % figure % plot(real(fft(bpskmod1))) % title('FFT of BPSK signal for user1 is')

%% PN generator for user1 %% let initial seed for user1 is 1000 seed1=[1 -1 1 -1]; %convert it into bipolar NRZ format spreadspectrum1=[]; pn1=[];

for i=1:length_user1 for j=1:10 %chip rate is 10 times the bit rate pn1=[pn1 seed1(4)]; if seed1 (4)==seed1(3) temp=-1; else temp=1; end seed1(4)=seed1(3); seed1(3)=seed1(2); seed1(2)=seed1(1); seed1(1)=temp; end % spreadspectrum1=[spreadspectrum1 user1(i)*pn1]; end

% each bit has 100 samples. and each pn chip has 10 samples. there r % 10 chip per bit there fore size of pn samples and original bit is same

pnupsampled1=[]; len_pn1=length(pn1); for i=1:len_pn1 for j=0.1:0.1:tb if pn1(i)==1 pnupsampled1=[pnupsampled1 1]; else pnupsampled1=[pnupsampled1 -1]; end end end length_pnupsampled1=length(pnupsampled1); sigtx1=bpskmod1.*pnupsampled1;

figure plot(sigtx1) %axis([0 100*length_user1 -2 2]); title(' spread spectrum signal transmitted for user 1 is')

%% plot fft of BPSK sequence figure plot(real(fft(sigtx1))) title('FFT of spread spectrum signal transmitted for user1 is')

% rxcode1=pnupsampled1.*sigtx1; % figure % plot(rxcode1) % %axis([0 100*length_user1 -2 2]); % title(' spread spectrum signal transmitted for user 1 is')

%%% CDMA transmitter for user2 t=0.01:0.01:tb*length_user2; %0.01 %%plotting base band signal for user2 basebandsig2=[]; for i=1:length_user2 for j=0.01:0.01:tb%0.01 if user2(i)==1 basebandsig2=[basebandsig2 1]; else basebandsig2=[basebandsig2 -1]; end end end

figure plot(basebandsig2) axis([0 100*length_user2 -1.5 1.5]); title('original binary sequence for user2 is')

%%%% BPSK MODULATION FOR USER 2 bpskmod2=[]; for i=1:length_user2 for j=0.01:0.01:tb bpskmod2=[bpskmod2 sqrt(2*eb)*user2(i)*cos(2*pi*fc*j)]; end end figure plot(bpskmod2) %axis([0 100*length_user2 -2 2]); title(' BPSK signal for user 2 is')

%% plot fft of BPSK sequence % figure % plot(real(fft(bpskmod2))) % title('FFT of BPSK signal for user2 is')

%% PN generator for user2 %% let initial seed for user2 is 1000 seed2=[-1 1 -1 1]; %convert it into bipolar NRZ format spreadspectrum2=[]; pn2=[];

for i=1:length_user2 for j=1:10 %chip rate is 10 times the bit rate pn2=[pn2 seed2(4)]; if seed2 (4)==seed2(3) temp=-1; else temp=1; end seed2(4)=seed2(3); seed2(3)=seed2(2); seed2(2)=seed2(1); seed2(1)=temp; end % spreadspectrum2=[spreadspectrum2 user2(i)*pn2]; end pnupsampled2=[]; len_pn2=length(pn2); for i=1:len_pn2 for j=0.1:0.1:tb if pn2(i)==1 pnupsampled2=[pnupsampled2 1]; else pnupsampled2=[pnupsampled2 -1]; end end end length_pnupsampled2=length(pnupsampled2); sigtx2=bpskmod2.*pnupsampled2;

figure plot(sigtx2) %axis([0 100*length_user2 -2 2]); title(' spread spectrum signal transmitted for user 2 is')

%% plot fft of BPSK sequence figure plot(real(fft(sigtx2))) title('FFT of spread spectrum signal transmitted for user2 is')

% rxcode2=pnupsampled2.*sigtx2; % figure % plot(rxcode2) % %axis([0 100*length_user2 -2 2]); % title(' spread spectrum signal transmitted for user 2 is')

%%%%%%%%%%%%%%%signal by adding the above 2 signals%%%%%%%%%%% composite_signal=sigtx1+sigtx2;

%%%%%%%%%%%%%AWGN CHANNEL%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% composite_signal=awgn(composite_signal,snr_in_dbs); %% SNR of % dbs %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

%%%%%%%%%%%%%DMODULATION FOR USER 1%%%%%%%%%%%%%%%%%%%% rx1=composite_signal.*pnupsampled1; figure plot(rx1)

%%%% BPSK DEMODULATION FOR USER 1 demodcar1=[]; for i=1:length_user1 for j=0.01:0.01:tb demodcar1=[demodcar1 sqrt(2*eb)*cos(2*pi*fc*j)]; end end bpskdemod1=rx1.*demodcar1; figure plot(bpskdemod1) title('o/p of bpsk demod for user 1 is ') len_dmod1=length(bpskdemod1); sum=zeros(1,len_dmod1/100); for i=1:len_dmod1/100 for j=(i-1)*100+1:i*100 sum(i)=sum(i)+bpskdemod1(j); end end sum;

 rxbits1=[]; 
 for i=1:length_user1 
    if sum(i)>0 
        rxbits1=[rxbits1 1]; 
    else 
        rxbits1=[rxbits1 0]; 
    end 
 end 
rxbits1

%%%%%%%%%%%%%DMODULATION FOR USER 2%%%%%%%%%%%%%%%%%%%% rx2=composite_signal.*pnupsampled2; figure plot(rx2)

%%%% BPSK DEMODULATION FOR USER 2 demodcar2=[]; for i=1:length_user2 for j=0.01:0.01:tb demodcar2=[demodcar2 sqrt(2*eb)*cos(2*pi*fc*j)]; end end bpskdemod2=rx2.*demodcar2; figure plot(bpskdemod2) title('o/p of bpsk demod for user 2 is ') len_dmod2=length(bpskdemod2); sum=zeros(1,len_dmod1/100); for i=1:len_dmod2/100 for j=(i-1)*100+1:i*100 sum(i)=sum(i)+bpskdemod2(j); end end sum;

 rxbits2=[]; 
 for i=1:length_user2 
    if sum(i)>0 
        rxbits2=[rxbits2 1]; 
    else 
        rxbits2=[rxbits2 0]; 
    end 
 end 
rxbits2

[Walter Roberson]

http://www.mathworks.com/matlabcentral/answers/13205-tutorial-how-to-format-your-question-with-markup

Also, we will not be able to help you unless you indicate what error the code is showing.