Re: [Discuss-gnuradio] Simultaneously send data and store it in file with high sample rate

[Tom Rondeau]

On Sun, Mar 24, 2013 at 9:54 PM, john jade <address@hidden> wrote:
> Hi Martin,
> Thanks a lot. I am using gr-digital narrowband examples,with little bit of
> changes in the code.I am still not able to get full sample rate of 25MHz.At
> max i am getting 2MHz sample rate.
> I attached my code ,can you please let me know what might be the reason.Is
> it because of processing time or some other reason.
>
> parameters i am passing from terminal
> sudo python test.py -f 5.825e9 --rx-freq 5.825e9 --tx-gain 31.5 --rx-gain
> 31.5  -m dbpsk -a="serial=ECR13W5UP" -r 1e6
>
> if i try to change -r(bit rate)   to  >2e6  i am getting overflow.
>
> Thanks.

John,

The ability to process data in a software radio application is
directly proportional to the sampling rate used. The higher the
sampling rate, the more computational power required. As you increase
the computational load on your application, each block takes longer to
process data, and at some point, your application can take too much
time, which means that the data flowing from the USRP to the host is
coming too fast to be processed, so it gets dropped.

A digital receiver is a complex set of algorithms used to properly
synchronize (in time, frequency, and phase not to mention any
multipath distortions) the incoming signal. This is much more complex
than just drawing the signal in a GUI.

So in other words, you shouldn't expect to be able to handle those
kinds of bandwidth with the digital receiver. Now, there's a lot more
optimization that can be done to make those algorithms more
computationally efficient in order to continue increasing the
potential symbol rate.

Tom


> On Fri, Mar 22, 2013 at 7:07 PM, Martin Luelf <address@hidden> wrote:
>>
>> > Hi Martin,
>> >
>> > Can you please show me an example.. How to write connect statement?
>> >
>> > Thanks
>> >
>> >
>> > On Thu, Mar 21, 2013 at 6:26 PM, Martin Luelf <address@hidden> wrote:
>> >
>> >> > Hi,
>> >> > How to simultaneously transmit data to usrp and also store it in a
>> >> file.?
>> >> > I
>> >> > ran two separate flow graphs.But i want to have a sample rate of
>> >> 25Mhz.Is
>> >> > it possible to do it.
>> >> >
>> >> > I want the same thing in receiver side also(simultaneously detect the
>> >> > packet  and store the data)
>> >> >
>> >> > I am using USRPN210 and Ubuntu 12.04
>> >> >
>> >> > Thanks.
>> >>
>> >> Hi,
>> >>
>> >> you can connect a block's output to as many inputs as you want. So take
>> >> tha last block in your chain that generates your signal and connect it
>> >> both to a uhd sink (which will make the USRP transmitt the signal) and
>> >> a
>> >> file sink (which will write the same samples to a file).
>> >>
>> >> Same goes for the receiver side. If you use GRC just add another
>> >> connection from a block's out port to another ones in port and the
>> >> output
>> >> will be send to both blocks.
>> >>
>> >> Yours
>> >> Martin
>> >>
>>
>> Hi,
>>
>> first of all please make sure that you reply to the list rather than to
>> the individual persons, or CC the list so that answers are also available
>> for anyone who might have a similar question in the future.
>>
>> The question how to do a block connect is confusing me a bit. Maybe there
>> is a misunderstanding? You should already have done block connections when
>> setting up your flowgraphs.
>>
>> Anyway what I mean is a standard connection of two GNURadio blocks, so in
>> GRC it might look like this (I know I am not an ASCII artist, sorry)
>>
>>                  |---->(Your signal processing block)
>> (UHD Source)-----|
>>                  |---->(File Sink)
>>
>> This should lead to python code like this
>>
>> ##################################################
>> # Blocks
>> ##################################################
>> self.uhd_usrp_source_0 = uhd.usrp_source(...)
>> self.yourblock_0 = yourmodule.yourblock(...)
>> self.file_sink_0 = gr.file_sink(gr.sizeof_gr_complex*1, ...)
>> ##################################################
>> # Connections
>> ##################################################
>> self.connect((self.uhd_usrp_source_0, 0), (self.file_sink_0, 0))
>> self.connect((self.uhd_usrp_source_0, 0), (self.yourblock_0, 0))
>>
>> Yours
>> Martin
>>
>
>
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