OFDM Carrier Frequency Recovery

Question

re ib 2012-10-11

0
链接

此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/50493-ofdm-carrier-frequency-recovery

I used your example " syncCarrierFreqMSKSignalRecovery" to construct my model and apply it for QPSK system,it works . but when i applied it to OFDM-QPSK , it doesn't work.

Your matlab code for Single carrier system is

freqOffset = 0; 
phaseOffset = 0;
hPFO = comm.PhaseFrequencyOffset('FrequencyOffset', freqOffset, ... 'PhaseOffset', phaseOffset, ... 'SampleRate', samplesPerSymbol/Ts);
rx_signal1l = step(hPFO,tx_signal);
   rx_signal = rx_signal1l.';
hDelayInstFreq = dsp.Delay;
hMovAve = dsp.DigitalFilter('TransferFunction','FIR (all zeros)', ... 'Numerator', ones(1,100)/100);
hCumSum = dsp.CumulativeSum('Dimension','Channels (running sum)', ... 'FrameBasedProcessing', true);
%%Calculate the frequency shift estimate
P = 2;
currInstFreq = rx_signal.^(2*P);
prevInstFreq = step(hDelayInstFreq, currInstFreq);
freqShiftEst1 = currInstFreq .* conj(prevInstFreq);
% Average over 1 frame
freqShiftEst = mean(freqShiftEst1);
% Moving average over 100 frames
freqShiftEst = step(hMovAve, freqShiftEst);
freqShiftEst = angle(freqShiftEst) / (2*P);
% Convert digital frequency to Hertz
freqShiftEst = freqShiftEst / (2*pi*Ts);
%%Apply frequency correction
freqCorr = repmat(-freqShiftEst*Ts, samplesPerFrame, 1);
% Calculate cumulative phase shift
freqCorr = step(hCumSum, freqCorr);
% Apply frequency shift correction
rxSym = rx_signal .* exp(1i*2*pi*freqCorr);

Kindly advice , how to modify the previous code to use with OFDM System

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Walter Roberson 2012-10-15

Who is "your" in "your example" ?

Please expand on "does not work" ?

re ib 2012-10-20

There is an example in Matlab help examples named "syncCarrierFreqMSKSignalRecovery" that deals with frequency offset , AWGN for QPSK. i want to used it to make OFDM- QPSK based. how can i modify this example?

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