Matlab code for Baseband frequency offset and correction

frequency offset matlab

Hi to all experts,

I am very new in this topic. I am writing a matlab simulation program for baseband QPSK modulation signal through AWGN channel. I would like to seek all your helps of how to add in frequency offset in my code and how to correct it..

I had read some info on it.. There are people writing in this way for frequency offset:

A = 1; %symbol
Amod = exp (j*(2*pi*A/4 + pi/4)); %QPSK signal
f_offset = exp (j*2*pi*0.1); %assume 0.1 is the normalised frequency offset
A_noisy = awgn(Amod, 3, 'measured'); %assumed in EbNo=3dB
A_foffset = A_noisy*f_offset;

This is the correct way to do a frequency offset or is there other way??and how can i do the correction assumed that I do not know what is the frequency offset. Hope you can help. Thanks in advance.

frequency offset estimation matlab

I can't understand your code, and maybe I am wrong but it is probably the code is completely wrong.

At least there should be a modulation signal such as random bit sequence. And then the bit sequence is modulated with QPSK format on a carrier. Then the frequency offset should be added to the carrier. You can assume the carrier is 0 Hz.

The frequency offset correction can be done with a costas loop, which is introduced in many digital communication book.

Added after 11 seconds:

I can't understand your code, and maybe I am wrong but it is probably the code is completely wrong.

At least there should be a modulation signal such as random bit sequence. And then the bit sequence is modulated with QPSK format on a carrier. Then the frequency offset should be added to the carrier. You can assume the carrier is 0 Hz.

The frequency offset correction can be done with a costas loop, which is introduced in many digital communication book.

carrier frequency offset matlab

Hi hi, thanks for replying.

hmmm..you are right..I wrote these lines only for a single bit modulation. My original codes are

A=randint(1,10000,4); % 10000 data bits
Am=pskmod(A,4); % QPSK modulation
t=0:1/10000:1-1/10000; % time frame
f_offset=exp(j*2*pi*0.1*t); % frequency offset=0.1
Af=Am.*f_offset; % frequency offset of QPSK modulation
An=awgn(Af,3,'measured'); % add in noise

Can I ask by doing these, is it frequency offset my original data bits?

I tried one method which I found from the webpage of estimating the frequency offset but do not really understand it. The code was as follow:

yk=conj(Am).*An; % assumed the receiver know what are the data bits.
zk=10000/(2*pi).*angle(An(2:end).*conj(An(1:end-1)));
% estimating the frequency offset..This part I do not understand at all. In the webpage it say that the I can get estimate what is the frequency offset, but I can't get the frequency offset of 0.1. So hope you can advise me how really does it work.

As for coastas loop, I had read abt it, but I dun really understand as well. Maybe you and briefing explained to me..Hope you can spend some previous time of urs to guide me. Thank you so much.

Best Regards