I am back with a question related to my OFDM Transceiver System that I am designing where I use DUC and DDC. I could get rid of the high BER problem. I realized that the problem was due to the phase error occuring between the transmitter and the receiver side as I saw the constellation diagram at the receiver rotating constantly. So to get rid of this, I obtained the phase difference between the transmitter and the receiver and I rotated the complex signal with the obtained phase error. However, I feel this is only an ideal method to get rid of the phase error. I read about the phase error compensation techniques but those are mostly when there is a noise in the channel. But in my case, I still haven't added any noise in the channel. I suspect the phase error is either because of the DUC and the DDC, or because of the pulse shaping filters that I used after OFDM modulator.
So I was wondering if anyone could tell me why is this phase error occuring even without a noisy channel, and what can I do to mitigate the phase error with some estimation.
I have attached the screenshot of my system along with the waveforms obtained. Below are the specs -
Random Integer Generator Specs
Set Size - 2
Initial Seed - 37
Sample Time - 1/1e6
Samples per frame - 20
OFDM Modulator Specs
FFT length - 32
Number of guard bands - [6;5]
Insert DC Null - Checked
Cyclic Prefix Length - 16
Number of OFDM symbols - 1
Number of transmitted antennas - 1
Raised Cosine Transmit Filter Specs
Rolloff factor - 0.2
Filter span in symbols - 8
Output samplers per symbol - 4
Linear amplitude filter gain - 1
DIgital Up- Converter Specs
Interpolation factor - [2 8]
Minimum order filter design - Yes
Two-sided bandwitdth - 2.4 e6
Passband ripple - 0.05 dB
Stopband ripple - 90 dB
Center Frequency - 30e6
Input sample rate - 9.6e6
Digital Down-Converter Specs
Decimation factor - [8 2]
Minimum order filter design - Yes
Two-sided bandwitdth - 2.4 e6
Passband ripple - 0.05 dB
Stopband ripple - 90 dB
Center Frequency - 30e6
Input sample rate - 153.6e6
Thank you in advance!