HI Marcus, Even with a file source which I have tried earlier I don't see the hops where I want.
I was trying to do a file transfer experiment first. So I switched to a simple experiment in which I atleast see the hops correctly. If you want I can add the details, grc files of the file transfer experiment too. Thanks, Ajinkya ᐧ On Sat, Aug 27, 2016 at 3:20 AM, Marcus Müller <[email protected]> wrote: > Hi! > > So, first step is to verify that if you used a file source instead of the > USRP source, things work. If that works, move on to determining possible > effects of the physical transmission. > > For that, I'd recommend you use your transmitter as you have it, and on > the receiver side, start with a waterfall diagram over a bandwidth larger > than your transmitter bandwidth. 1MS/s receiver sampling rate should be > pretty OK. Do see the hops in the positions you want? > > Best regards, > > Marcus > > > On 27.08.2016 05:09, Ajinkya D Kadam wrote: > > Hi Marcus, > > I am not using frequency aligning. > > I think your guess about "frequency offset" thing is possible. Since we > are never transmitting on -187Khz but we do observe a signal over there. > > The received signal that we observe is just what is being transmitted. We > are not applying any demodulation or receiver synthesis.I directly connect > the USRPSource --> File Sink. So my real concern is that why is the > receiver not even looking at the transmitter sequence as is ??? > > The goal of the experiment is not to get data through, in which case we > would have to deal with further issues. > > Our goal is to observe the transmitter hopping sequence correctly at the > receiver. > > ᐧ > > On Fri, Aug 26, 2016 at 3:28 PM, Marcus Müller <[email protected]> > wrote: > >> Correct me, but this is 400kS/s – that should really not max out anyone's >> system, unless the spread blocks are really terribly inefficient (I don't >> think they are); please check this, though! >> >> If I'm not mistaken, gr-spread doesn't tune the hardware or anything – it >> just creates a continuous phase stream that changes frequency, in a cyclic >> manner. >> >> My guess is that the receiver is frequency-offset from the transmitter, >> and hence, the demodulator "guesses" the wrong frequencies. Would that be >> possible? >> >> Ajinkya, are you frequency-aligning the two USRPs in any way? >> >> Best regards, >> >> Marcus >> On 26.08.2016 21:22, Dave NotTelling wrote: >> >> I have had issues with scheduling transmissions at ~ 10 ms per hop and >> ending up with transmissions happening on the wrong frequencies. Usually >> it's one channel off. If you slow the system down does everything work >> properly? Also, are you pegging out any single core in your system? I >> have seen lots of issues with scheduling bursts when the CPU utilization is >> high or even a single core that's maxed out. >> >> On Fri, Aug 26, 2016 at 3:00 PM, Ajinkya D Kadam <[email protected]> >> wrote: >> >>> Dave, >>> >>> Thanks for replying. >>> >>> we are hopping every 80ms. >>> ᐧ >>> >>> On Fri, Aug 26, 2016 at 12:32 PM, Dave NotTelling <[email protected]> >>> wrote: >>> >>>> Ajinkya, >>>> >>>> How fast are you hopping? I've had loads of issues with hopping >>>> rapidly and not having the correct frequencies used. >>>> >>>> -Dave >>>> >>>> On Tue, Aug 23, 2016 at 7:16 PM, Ajinkya D Kadam <[email protected] >>>> > wrote: >>>> >>>>> HI All, >>>>> >>>>> I am using gr-spread >>>>> <https://github.com/CIG-SDR/CIG/tree/master/gr-spread> module to >>>>> transmit a signal using FHSS. When I receive the FHSS signal, the received >>>>> signal has a completely different hopping sequence as from the transmitted >>>>> one. I am using USRP N210 for transmission and reception. I am not sure >>>>> why >>>>> this is happening. The transmitted sequence is (frequencies in Khz) >>>>> >>>>> 187.5 >>>>> -12.5 >>>>> 162.5 >>>>> -62.5 >>>>> 62.5 >>>>> 137.5 >>>>> -112.5 >>>>> -37.5 >>>>> 112.5 >>>>> -162.5 >>>>> -137.5 >>>>> -87.5 >>>>> 12.5 >>>>> 37.5 >>>>> 87.5 >>>>> >>>>> and the received sequence is >>>>> >>>>> 37.5 >>>>> 62.5 >>>>> 112.5 >>>>> -187.5 >>>>> 12.5 >>>>> 187.5 >>>>> -37.5 >>>>> 87.5 >>>>> 162.5 >>>>> -87.5 >>>>> 0 >>>>> 137.5 >>>>> -137.5 >>>>> -112.5 >>>>> -62.5 >>>>> 37.5 >>>>> 62.5 >>>>> >>>>> I have created a movie out of the images which plots the IQ, FFT and >>>>> WaterFall plot for the transmitted signal and the received signal using >>>>> the >>>>> "plot_psd_base.py" file in gr-utils. Please have a look at both of them >>>>> here >>>>> <https://drive.google.com/file/d/0B-Ksc0hMVyDVLW11QW1BekJtS0E/view> >>>>> and here >>>>> <https://drive.google.com/file/d/0B-Ksc0hMVyDVSmU4YzlBVXA5ZFE/view?usp=sharing> >>>>> . >>>>> >>>>> Please see the attached files for the flowgraphs, I am using as the >>>>> transmitter and receiver. >>>>> >>>>> I have stored the received and transmitted signal to a file. Since >>>>> these are large files I have uploaded them to google drive here >>>>> <https://drive.google.com/a/nyu.edu/file/d/0B-Ksc0hMVyDVRTdaVTV5ZmhCVkE/view> >>>>> . >>>>> >>>>> Could someone please help me understand the behavior I am observing ? >>>>> >>>>> Is this some sort of synchronization issue ? What am I missing ? >>>>> >>>>> Thanks in advance. >>>>> >>>>> ᐧ >>>>> >>>>> _______________________________________________ >>>>> Discuss-gnuradio mailing list >>>>> [email protected] >>>>> https://lists.gnu.org/mailman/listinfo/discuss-gnuradio >>>>> >>>>> >>>> >>> >> >> >> _______________________________________________ >> Discuss-gnuradio mailing >> [email protected]https://lists.gnu.org/mailman/listinfo/discuss-gnuradio >> >> _______________________________________________ Discuss-gnuradio mailing >> list [email protected] https://lists.gnu.org/mailman/ >> listinfo/discuss-gnuradio > >
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