Re: [Discuss-gnuradio] Bandwidth switching per symbol

Hi,

Thanks a lot for your reply!

This is exactly what I was looking for!
Would you by any chance have an idea in what C level files I could
manipulate the interpolation?

best regards and thank you,
Bjorn

Zitat von "Matthias Wilhelm" <wilhelm@informatik.uni-kl.de>:

> Hi,
>
> i think this would be hard on the python level, you would need to
> notify the python code after each symbol to make adjustments, which
> will lead to latency between symbols ...
>
> (As I understand you want to keep the chipping sequences, but change
> the sampling rate used for each symbol. You can have the same effect
> by changing the interpolation between samples, keeping the rate
> constant, and oversampling small bandwidths. )
> For this, I would suggest that you add a "per packet schedule" that
> specifies the bandwidth of each symbol, and hack the C code to
> follow the schedule, changing the interpolation between chips for
> each symbol.
> Something like send_802_15_4_pkt (packet, "1,2,8,2,4,1"), meaning
> 1MChips/s for the first symbol, 2MChips/s (the default) for the
> second, then 8MChips/s, etc. The benefit is that you can go on
> working on the packet level in python.
> On the C side, you would need to run the flow graph at 16MSamples
> (to get 2 samples per chip @ 8MChips/s, basically fast enough to
> support the largest bandwidth you want), and decide for each symbol
> the necessary interpolation to generate the specified bandwidth
> (e.g., 16 samples/chip @1MChips/s).
>
> Regards,
> Matthias
>
>
> Am 27.07.2011 um 13:31 schrieb bjoernm@ee.ethz.ch:
>
>> Hi,
>>
>> I'm currently using the UCLA ZigBee Phy implementation by Thomas
>> Schmid and I need to
>> change the Bandwidth of the used wireless channel on a per symbol basis.
>>
>> I managed to change it on a per packet basis, which can be done on
>> the python level
>> (tunnel.py, usrp_transmit_path.py etc.). Well now, I need to do the
>> same thing, but on a
>> per symbol basis, which (up to my knowledge) is not possible from
>> the python level...
>>
>> Does anyone have an idea how I could do that? (Changing the Bitrate
>> of the USRP after
>> each symbol (e.g. after sending 32 modulated bits (actually chips)))
>>
>> I would be very happy for any help or suggestions!
>> Thanks a lot!
>>
>> best regards,
>> Bjorn
>>
>>
>>
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>

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