Re: [Discuss-gnuradio] voice over digital moduation

Hi Atif,

nice question!
so, I'm a bit bit confused by your resampling and your "multiply with
signal source". Can you explain what the sampling rates of your USRP
is?

And: if you resample something to 200 kS/s, then the unambiguously
representable frequencies are -100kHz to + 100kHz.

Since your OFDM signal doesn't have 0Hz bandwidth, I'm almost certain
that it's then a very bad idea to shift it by 100 kHz. Add some Qt GUI
frequency sinks throughout your flowgraph to see why!

Best regards,
Marcus

On Thu, 2017-11-09 at 20:22 -0800, Atif Javed wrote:
> Hi
>
> I have been working with Gnuradio and USRP N200 for about a month now and about all this time I have never succeeded in transmitting digital voice via USRP. My Proposed approach is like
>
> audio source--->CVSD encoder---->OFDM mod------>rational resample to 200k------->multiply with signal source (100k)------>USRP sink
>
> on the receiver side
>
> USRP source------> multiply with signal source (100k)----------..rational resample to 48k ------->low pass filter----->OFDM demod------>CVSD decoder ------->audio sink
>
>
> I have also used a built in flowgraph of OFDM voice attached within where i get zero output with encoder (codec 2). If the encoder is disabled, the output works just fine.
> Any kind of assistance in this regard would be much appreciated.
>
> Regards
> ATIF JAVED
> _______________________________________________
> Discuss-gnuradio mailing list
> Discuss-gnuradio@gnu.org
> https://lists.gnu.org/mailman/listinfo/discuss-gnuradio