Re: [Discuss-gnuradio] Transmit and Receive hopping Sequence in FHSS (using gr-spread module) mismtach

[Dave NotTelling]

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 <address@hidden> wrote:

Dave, 

Thanks for replying. 

we are hopping every 80ms. 

ᐧ

On Fri, Aug 26, 2016 at 12:32 PM, Dave NotTelling <address@hidden> 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 <address@hidden> wrote:

HI All, 

I am using 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 and here. 

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. 

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

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