srinivas naga vutukuri wrote: > Hi, > > I am transmitting the sinusoidal wave form (IQ samples), in the > following methods, and found that when i stem plot in the MATLAB both > the input wave form data on one USRP2 and the received data on another > USRP2, initially the waveform is exactly fitting (i mean overlapping), > and after certain samples, it starts ie., in the input wave form and the > output data waveform drifting slightly and at the end samples both the > waveforms overlaps perfectly. Why this slight drifting is happening when > transmitting the I Q samples from one USRP2 to another USRP2. > > 1st method: > > I used, tx_samples.cc and receive_streaming_samples.cc. > > 2nd method: > > Using the GRC, created a signal source, and file sink and usrp2 sink > on One PC and another PC usrp2 source and file source. So plotting both > the input stored samples and output received samples, observed the above > mentioned drift of mismatch of samples of the waveform and again at the > end and start it perfectly matches or overlaps. > > > Kindly help me in understanding this phenomena, why this is happening on > raw data (IQ) samples sending. But this never happens, when i checked > with the benchmark_rx.py and benchmark_tx.py used (as internally these > two are using GMSK modulation, sync work and packets framing method). > Is it possible that this is due to a phase/frequency- drift between the two units? I think benchmark_rx implements a PLL (Costas- loop) for frequency/phase- offsets, and might (don't remember) as well implement a form of early- late- gate loop (Optimized Müller & Müller algorithm) for time- synchronizing the samples.
I don't know if the phenomena you see is due to this, but it might... BR //Mattias _______________________________________________ Discuss-gnuradio mailing list Discuss-gnuradio@gnu.org http://lists.gnu.org/mailman/listinfo/discuss-gnuradio