Understanding Matlab code - opensource matlab code.

Hi ,

I'm trying to write this matlab code as shown here below and to plot the graphs as shown in below with matlab code implementation shown aswell:

#first

#second

#third - output of the matlab code that's mentioned above:

Unfortuantely when I write the matlab code as mentioned above in first two photos I'm not suceeding to plot the graph as suggested in third photo, can anyone please help me what's wrong with the code? I'm trying exactly to write the matlab code that's mentioned in first two photo and I didn't succeed to run the code successfully .. can please anyone help me on this if he succeed to run the code properly to get the graph that's mentioned in third photo?

Appreciated to attach the code that's used to be more clear and understandable.

Thanks much!

[Walter Roberson]

To be honest, the volunteers are probably not going to type in the code from the image. If you posted your attempt then they might be willing to verify that your code is the same as the image.

[AndresVar]

@Jimmy cho If you search for the code you can find it online. It's just like slides, but the slides is missing the definition of cwords

  cwords=[0 0 0 0 0 0 0;
        0 0 0 1 0 1 1;
        0 0 1 0 1 1 0;
        0 0 1 1 1 0 1;
        0 1 0 0 1 1 1;
        0 1 0 1 1 0 0;
        0 1 1 0 0 0 1;
        0 1 1 1 0 1 0;
        1 0 0 0 1 0 1;
        1 0 0 1 1 1 0;
        1 0 1 0 0 1 1;
        1 0 1 1 0 0 0;
        1 1 0 0 0 1 0;
        1 1 0 1 0 0 1;
        1 1 1 0 1 0 0;
        1 1 1 1 1 1 1];
  

for EbN0dB=-20:

[Jimmy cho]

@AndresVar Thanks much!! Can you please share the code? Really if I find the code or the copied code from photo worked for me then I wouldnt ask for help guys.

Appreciated so much your cooperation

[Jimmy cho]

@AndresVar And I see cwords is defined in the code thats on the photos above so didnt get you what do you mean cwords isnt defined?

Appreciated

[AndresVar]

@Jimmy cho cword is defined but not cwords, I don't understand what the code is doing anyway ... but here it is.

%EbN0dB=input("PLZ ENTER Initial Eb/No (dB) = ");
EbN0dB=-20

EbN0dB = -20

t=1;
for i=1:1:50
    R=4/7; %K=4 and n=3 using Hamming as encoding codes and decoding to overcome errors;
    EbN0=10^(EbN0dB/10);
    sigma=sqrt(1/(2*R*EbN0)); % EbNo=1/2R(sigma)^2
    k=4; % Message Bits
    n=7; % Total Number of Bits
    cwords=[0 0 0 0 0 0 0;
        0 0 0 1 0 1 1;
        0 0 1 0 1 1 0;
        0 0 1 1 1 0 1;
        0 1 0 0 1 1 1;
        0 1 0 1 1 0 0;
        0 1 1 0 0 0 1;
        0 1 1 1 0 1 0;
        1 0 0 0 1 0 1;
        1 0 0 1 1 1 0;
        1 0 1 0 0 1 1;
        1 0 1 1 0 0 0;
        1 1 0 0 0 1 0;
        1 1 0 1 0 0 1;
        1 1 1 0 1 0 0;
        1 1 1 1 1 1 1];
    Nerrs=0; Nblocks=10000;
    for i = 1:Nblocks
        msg=randi([0,1],1,k);
        %**************Encoding*******************************
        cword=[msg mod(msg(1)+msg(2)+msg(3),2)...
            mod(msg(2)+msg(3)+msg(4),2)...
            mod(msg(1)+msg(2)+msg(4),2)];
        s=1-2*cword; % BPSK bit to symbol conversion mapping
        r= s+sigma*randn(1,n); % AWGN CHANNEL rand(1,n) adding guassian noise of variance 1

        % ************Hard Decoding*****************
        b=(r<0); % Thresholg at Zero best for bpsk demod
        dist= mod(repmat(b,16,1)+cwords,2)*ones(7,1);
        [mind1,pos]=min(dist);
        msg_cap1=cwords(pos,1:4);

        %***************Soft Decoding******************
        corr=(1-2*cwords).*r;
        [mind2,pos]=max(corr);
        msg_cap2=cwords(pos,1:4);
        Nerrs=Nerrs+sum(msg~=msg_cap1); % Total Errors
    end
    BER_sim(t)=Nerrs/k/Nblocks; %Bit Error Rate Calculation

    %**** QoS Varifying and Updating to Transmitter *******
    if(Nerrs>4000)
        %disp('Increasing SNR ');
        EbN0dB=EbN0dB+1;
    else EbN0dB=EbN0dB-1;
        %disp('Decreasing SNR ');
    end
    %disp([EbN0dB R BER_sim(t) Nerrs k*Nblocks]);
    y(t)=10*log(BER_sim(t)); %log BER
    t=t+1;
end
x=1:1:50;
plot(x,BER_sim,'ro');
title(' BER PLOT');
xlabel('Iterations Adapting EbNo');
ylabel('BER(dB)');
legend('Adaptive EbNo');
grid on;

[Jimmy cho]

@AndresVar thanks much appreciated !! .. I will explain in detail what is the purpose of that to share my knowledge to you aswell.

but first could you please try to compile that code that you shared me above but only with one change instead of if(Nerrs>4000)

replace it please by if(Nerrs>2000) ?

MUCH thanks if you can share me the plot that you'll get with the new changes of Nerrs value as suggested above.

@AndresVar much thanks !

[Walter Roberson]

%EbN0dB=input("PLZ ENTER Initial Eb/No (dB) = ");
EbN0dB=-20

EbN0dB = -20

t=1;
for i=1:1:50
    R=4/7; %K=4 and n=3 using Hamming as encoding codes and decoding to overcome errors;
    EbN0=10^(EbN0dB/10);
    sigma=sqrt(1/(2*R*EbN0)); % EbNo=1/2R(sigma)^2
    k=4; % Message Bits
    n=7; % Total Number of Bits
    cwords=[0 0 0 0 0 0 0;
        0 0 0 1 0 1 1;
        0 0 1 0 1 1 0;
        0 0 1 1 1 0 1;
        0 1 0 0 1 1 1;
        0 1 0 1 1 0 0;
        0 1 1 0 0 0 1;
        0 1 1 1 0 1 0;
        1 0 0 0 1 0 1;
        1 0 0 1 1 1 0;
        1 0 1 0 0 1 1;
        1 0 1 1 0 0 0;
        1 1 0 0 0 1 0;
        1 1 0 1 0 0 1;
        1 1 1 0 1 0 0;
        1 1 1 1 1 1 1];
    Nerrs=0; Nblocks=10000;
    for i = 1:Nblocks
        msg=randi([0,1],1,k);
        %**************Encoding*******************************
        cword=[msg mod(msg(1)+msg(2)+msg(3),2)...
            mod(msg(2)+msg(3)+msg(4),2)...
            mod(msg(1)+msg(2)+msg(4),2)];
        s=1-2*cword; % BPSK bit to symbol conversion mapping
        r= s+sigma*randn(1,n); % AWGN CHANNEL rand(1,n) adding guassian noise of variance 1

        % ************Hard Decoding*****************
        b=(r<0); % Thresholg at Zero best for bpsk demod
        dist= mod(repmat(b,16,1)+cwords,2)*ones(7,1);
        [mind1,pos]=min(dist);
        msg_cap1=cwords(pos,1:4);

        %***************Soft Decoding******************
        corr=(1-2*cwords).*r;
        [mind2,pos]=max(corr);
        msg_cap2=cwords(pos,1:4);
        Nerrs=Nerrs+sum(msg~=msg_cap1); % Total Errors
    end
    BER_sim(t)=Nerrs/k/Nblocks; %Bit Error Rate Calculation

    %**** QoS Varifying and Updating to Transmitter *******
    if(Nerrs>2000)
        %disp('Increasing SNR ');
        EbN0dB=EbN0dB+1;
    else EbN0dB=EbN0dB-1;
        %disp('Decreasing SNR ');
    end
    %disp([EbN0dB R BER_sim(t) Nerrs k*Nblocks]);
    y(t)=10*log(BER_sim(t)); %log BER
    t=t+1;
end
x=1:1:50;
plot(x,BER_sim,'ro');
title(' BER PLOT');
xlabel('Iterations Adapting EbNo');
ylabel('BER(dB)');
legend('Adaptive EbNo');
grid on;

[Jimmy cho]

@AndresVar by the way I need you to do that on purpose which the idea and the concept that's behind the code will be really explicit and then I can explain to you by the two explames the purpose and the logic behind ..

it's really wonderful.