BER Calculation of BPSK for custom demodtalor IP core

Hello All,

I am new to MATLAB. I have my own BPSK demodulator IP core. I have transmitter which transmit the data at 4.8ksps and modulate the signal through channel and noisy signal becomes the input to reciever. Receiver demodulates the signal and producing sequence of recovered bits. Up to this all process done through the instrument and the RF+FPGA board. I just want to comapre the received bits to be transmitted bits and tally up the errors using matlab. How could i do this?

Kindly guide me.

Thank you.

Answer 1

[Awais Saeed]

use biterr() and semilogy() to find bit errors and to plot BER curve

clc
clear
close all
% generate data to send
x = 4*rand(1,10000);
x(x<=3) = 0;
x(x>3) = 1;

% Add AWGN, compute BER for the received data
SNR=0:30;
for i=1:length(SNR)
    y = awgn(x,i);
    % Threshold detection
    y(y<=0.5) = 0;
    y(y>0.5) = 1;
    % Compute bit error of received and transmitted data
    [num(i),err(i)] = biterr(x,y);
end
% plot BER curve
semilogy(SNR,err,'r-')
ylabel('BER');
xlabel('SNR');

Answer 2

[brahmi shah]

Hello @Awais Saeed

Thank you for your reply.

I want to verify my demodulator ip by calculating ber of TX and RX data. And i have one fix pattern (1011010110) which is going to be transmit by instrument and recieved by board which has demodulator ip. for this should i use above mentioned code by you?

[Awais Saeed]

Unfortunately, I am not aware of that. As to your question

"I just want to comapre the received bits to be transmitted bits and tally up the errors using matlab. How could i do this?"

you can get the idea how to compare transmitted data (x) and recevied data (y), that is by using biterr() function. In modulation schemes, usually we want a BER curve and I have also showed how to get one.

[brahmi shah]

@Awais Saeed

Thank you for your reply.

Can please guide me if i want to give input as a file instead of random bits is this possible?

[Awais Saeed]

Yes. Read your file and extract the data. See the documentation of importdata() and uigetfile() for detail.

[brahmi shah]

a = myfunction(txdata.txt);

b = myfunction(Rxdata.txt);

[num,ratio]= biterr(a,b);

function out = myfunction(inFile)

fid = fopen(inFile, 'rt'); %open your text file for reading

fclose(fid); %close your files.

end

Is this correct?

[Awais Saeed]

[Input_file] = uigetfile('paste path to your file-containing folder','MultiSelect','on');
x = importdata(Input_file); % this is your transmitting data

% do your operations on x
% after performing operations, you will have recieved data as y
% Now compute error as

[num(i),err(i)] = biterr(x,y);

% if you are adding AWGN with different
% SNR values, then use biterr() in a loop
% as shown in my first answer

[brahmi shah]

Hello @Awais Saeed

As you said (% do your operations on x) what should i do here? i am not getting any idea

Kindly guide me

Thank you.