Re: OFDM on USRP2

Dear Tom,

Do you mind sharing your code for usrp n210 ?

I am new on gnuradio and usrp and I am not able to find a python example
to
perform packet transmission.

Thank you

Vanessa

Tom R. wrote:

It supports both USRPs and the UHD driver. I get pretty bad
Or was it receive only? And in any case did UHD print and warnings about

Tom

Guanbo

be run on a USRP2? I have seen previous posts of this, however the

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On Mon, May 30, 2011 at 5:05 AM, vanITA1082
[email protected]wrote:

Vanessa

You can find lots of examples from my gr_apps github repo:

For direct cloning:
git://github.com/trondeau/gr_apps.git

Note, some of these are just basic utilities while others are more
“works-in-progress” type projects.

Tom

On 05/31/2011 10:15 AM, vanITA1082 wrote:

Vanessa

Dont know what state they’re in:

./gnuradio-examples/python/ofdm
./gnuradio-examples/python/ofdm/ofdm_mod_demod_test.py
./gnuradio-examples/python/ofdm/plot_ofdm.m
./gnuradio-examples/python/ofdm/ofdm_sync.m
./gnuradio-examples/python/ofdm/benchmark_ofdm_rx.py
./gnuradio-examples/python/ofdm/benchmark_ofdm_tx.py
./gnuradio-examples/python/ofdm/gr_plot_ofdm.py
./gnuradio-examples/python/ofdm/benchmark_ofdm.py
./gnuradio-examples/python/ofdm/ofdm_sync_pn.m


Marcus L.
Principal Investigator
Shirleys Bay Radio Astronomy Consortium

Yes, but they do not work with UHD which is the only way to use my USRP
N210

Marcus D. Leech wrote:

examples?
./gnuradio-examples/python/ofdm/ofdm_mod_demod_test.py


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Thanks.

However we are trying to transmit a packet from a usrp n210 to another
usrp
n210 and we are searching for examples do to this simple operation.

How is it possible that are not out there? Do you know any source of
simple
examples?

Thanks

Vanessa

Tom R. wrote:

to
GitHub - trondeau/gr_apps: GNU Radio applications

http://www.cs.ucsb.edu/~veljko/downloads/ofdm_example.tar.gz
control
I found issues with the UHD code in setting the sample rates. When you

Veljko

The codes are attached.

Michael R.

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On Wed, 2011-06-01 at 00:50 -0700, vanITA1082 wrote:

Yes, but they do not work with UHD which is the only way to use my USRP N210

I just pushed a branch with UHD versions of the OFDM apps:

git://github.com/bistromath/gnuradio.git

It’s in the uhd_ofdm branch. This is untested code, so use at your own
risk. I just wanted to illustrate to people how easy it is to move stuff
over to UHD. Check the git diffs for a guide on the things that change.
Basically the largest change is saying “uhd.usrp_source” instead of
“usrp_source”, and use sample rate instead of decimation/interpolation
factors. These changes apply to ALL the USRP examples, not just the OFDM
stuff.

Note that this doesn’t fix any lingering bitrot which may be in there –
I haven’t tried the OFDM examples in a while. I’ll get a chance to test
them in a day or so.

–n

On Thu, Jun 9, 2011 at 1:24 AM, vanITA1082
[email protected] wrote:

Hi Vanessa,

One thing you might also have to change is the tx-amplitude in
transmit_path.py. I wasn’t having any success until I changed the
range from 0 <= AMPL < 32768 to 0 <= AMPL <= 1.

I’m interested in whether you have any success with this. I’m
currently able to send something that looks like OFDM, but unable to
demodulate it.

Thanks,
Morgan

Thank you!

I found 2 errors in benchmark_ofdm_tx.py:

line 63 should be “sink”
line 69 should be “samp_rate”

Thanks again
Vanessa

Nick F.-4 wrote:

risk. I just wanted to illustrate to people how easy it is to move stuff
–n

n210 and we are searching for examples do to this simple operation.

./gnuradio-examples/python/ofdm/ofdm_sync_pn.m
http://www.sbrac.org


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I am going more deeply into the OFDM example, however I cannot figure
out
which is the bit rate of the usrp.
I mean, I know and I can set the bit rate of my application but how fast
the
packets are sent out by the usrp?
How can I evaluate the throughput on the wireless link?

Thanks

Vanessa

Morgan R.-2 wrote:

On Wed, 2011-06-01 at 00:50 -0700, vanITA1082 wrote:
Basically the largest change is saying “uhd.usrp_source” instead of

Dont know what state they’re in:

http://old.nabble.com/OFDM-on-USRP2-tp30638994p31807479.html
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On Thu, 2011-06-09 at 01:24 -0700, vanITA1082 wrote:

Thank you!

I found 2 errors in benchmark_ofdm_tx.py:

line 63 should be “sink”
line 69 should be “samp_rate”

Thanks. In addition, check out the messages Morgan R. just posted,
he found that the transmit_path multiplier should be reduced since UHD
expects amplitudes <1.0 while gr-usrp expects amplitudes up to +32767.
This is lines 66-67 of transmit_path.py.

–n

On 20/06/2011 10:05 AM, vanITA1082 wrote:

I am going more deeply into the OFDM example, however I cannot figure out
which is the bit rate of the usrp.
I mean, I know and I can set the bit rate of my application but how fast the
packets are sent out by the usrp?
How can I evaluate the throughput on the wireless link?

Thanks

Vanessa
The USRP knows nothing about packets or modulation or any of the
higher-level concepts you seek.

The USRP/USRP2/N2XX are, conceptually, digitizers that digitize the
baseband output of the RF chain, and present it to the
host at a fixed sample rate. Conversely, they take digital samples
from the host, and convert them into baseband analog signals
for the RF hardware to transmit.

Any given modulation waveform (whether it’s OFDM, or BPSK, or NBFM, or
whatever) occupies a certain bandwidth, and you chose
the sample rate to accomodate the bandwidth of the signal.