I guess I was a little bit too quick with my answer... In more detail:
> 2) You have done frequency correction manually: did you do this by > looking at the DC subcarrier (no power transmitted here) in the > received signal prior to OFDM demod? > Frequency synchronization in OFDM is very crucial, because the OFDM > symbol rate is small! To see why, try to understand the effect of a > small frequency error at the output of the FFT demodulator. The fractional offset (0.35) was found manually by look at the cross-correlation in the frequency domain and taking df = (left_of_max - right_of_max) / (left_of_max+right_of_max). Should be correct, shouldn't it? > 3) You have found the beginning of the frame manually. In your matlab > code you posted there is a variable "start_resamp" that indicates this. > How do you know that the begining of frame is not BETWEEN two samples? > in other words there is no fine timing synchronization. I wonder what > the effect of a small timing error is at the output of the FFT demodulator. I didn't quite understand what you are saying until I though about it: This should be equivalent to a small modulation in the frequency domain? I just simulated that by: % simulate fractional offset d_resamp = d_resamp .* exp(j*linspace(0,2*pi*0.1,length(d_resamp)).'); No effect - after all I did resampling before. Jens _______________________________________________ Discuss-gnuradio mailing list Discuss-gnuradio@gnu.org http://lists.gnu.org/mailman/listinfo/discuss-gnuradio
