Hi Abhinav, point of timing recovery like you do it is that there's no IQ samples that *exactly and reliably* correspond to the symbol timing; that's why you need timing recovery. The question here is: what do you actually need? The IQ samples before timing recovery aren't useful to the decoder.
Just to assure you: AGC2 doesn't modify the number of samples, it just multiplies with a factor that changes so that average power stays the same. Best regards, Marcus On 01/25/2016 06:26 PM, abhinav narain wrote: > Hi All, > > My problem is that above calculation sort of works, and isn't it exact. > I have the following preable of 32 > bits [1,0,1,0,1,1,0,0,1,1,0,1,1,1,0,1,1,0,1,0,0,1,1,0,0,1,1,1,0,1,0,1]. > This can be seen in badpreamble.png, where for some reason I have > trailing 0s or noise and the > start of preamble is missing. > > If I shift the position to 8 bits lag in the bit file and then > plot(8shiftedpreamble.png), the corresponding > IQ samples using above logic, it is almost right (alhough sitll not right. > > Any suggestions how to get the exact IQ samples ? > Thanks, > Abhinav > > On Sun, Jan 24, 2016 at 11:03 AM, abhinav narain > <[email protected] <mailto:[email protected]>> wrote: > > Hi all, > This might be too simple, but I wanted to confirm as I am not sure > how the > blocks manipulate the IQ samples and how AGC works, does it add more > samples for compensating the noise average or not. > > I have a flowgraph(image attached) which dumps the IQ samples and > the bits after using Polyphase Clock Sync. I want to find exact IQ > samples corresponding to > a specific preamble in the bitsequence I have obtained in the output > file. > Let say the starting position of sample is= P, the sample rate=S > ksps, samples \ > per symbol=Y. > > Is it correct to assume that the index of iq samples corresponding to > preamble in the IQ file will be at index P*Y ? > If preamble size is 32 bits then there will be 32*Y of them ? > > Thanks, > Abhinav > > > > > _______________________________________________ > Discuss-gnuradio mailing list > [email protected] > https://lists.gnu.org/mailman/listinfo/discuss-gnuradio
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