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 <ajinkya.ka...@nyu.edu>
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
>
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