Re: [Discuss-gnuradio] voice over digital moduation

[Marcus Müller]

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
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> Discuss-gnuradio mailing list
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