Re: [Discuss-gnuradio] sampling rate of tx_sampless.cc and rx_streaming_sampless.cc

[John Orlando]

<snip>
> If what you really mean is that you have a host PC generated sample
> stream at 15.36 Msps and need to transmit it with the USRP2, then yes,
> you'd set the USRP2 FPGA interpolation to 6, then fractionally
> resample from 15.36 Msps to 16 Msps on the host.
>
> Depending on what the last DSP processing stage in your application
> is, you may be able to "fold" this resampling into the prior stage.
> For example, if the last step in your signal processing chain is a
> spectral shaping filter, like a root-raised-cosine filter, then you
> can reimplement this using a polyphase resampler and use the output
> filter taps there.  This would combine the filter and resampling
> operation in one block and eliminate the need for a very high CPU
> resampling block.
>
> Where does the figure of 15.36 Msps come from?

Just a guess, but that sounds like 4x the UMTS chip rate (which is
3.84 Mchips/sec).  If this is the case, there is an RRC filter at the
last DSP stage typically, so your suggestion for folding this
re-sampling in is spot-on.

-- 
Regards,
John Orlando
CEO/System Architect
Epiq Solutions
www.epiq-solutions.com