OFDM Transmiter and receiver by using USRP1

Hello all,
I am trying to transmitt and recieve OFDM signal Via USRP1 board. I made
basic simulation in GNU radio a signal source block and then interleave
and
then OFDM modulator and then channel model block then usrp1 sink and fft
sink to see the output…In FFT sink at the end it shows proper square
like
OFDM signal but on the other hand in spectrum analyser it shows only one
peak sine wav signal not OFDM. I tried to play with the setiings but
couldnot get the desired ofdm signal output. This is just tranmitter
setup
and i attched with spectrum anlyzer but i dinot get OFDM signal . iam
only
getting simple sine wave in the spectrum analyser. I tried with simple
random sourse block and then DQPSK modulator and Usrp sink then it
worked it
shows sine wave signal in out put at spectrum analyser.Please any body
know
how to fix this problem or any solution ??? For reciever part i will use
the
same block in reverse order with ofdm demodulator… All suggestions are
appriciated.
Looking forward to it…

Thanks in advance…
waq.

View this message in context:
http://old.nabble.com/OFDM-Transmiter-and-receiver-by-using-USRP1-tp32662445p32662445.html
Sent from the GnuRadio mailing list archive at Nabble.com.

On 10/16/2011 12:29 PM, waqasme wrote:

random sourse block and then DQPSK modulator and Usrp sink then it worked it
shows sine wave signal in out put at spectrum analyser.Please any body know
how to fix this problem or any solution ??? For reciever part i will use the
same block in reverse order with ofdm demodulator… All suggestions are
appriciated.
Looking forward to it…

Thanks in advance…
waq.
More specificity is usually required to allow people to help you.
Posting your (GRC-produced) flow-graph would help.

From your description it’s hard for anyone to help you.


Marcus L.
Principal Investigator
Shirleys Bay Radio Astronomy Consortium
http://www.sbrac.org

Hi Marcus,

As i mentioned the flow graph signal blocks i have used in gnu radio
companion from that i am getting this out put on FFT sink in GNU radio
companion simulation flowgraph which is similar like this

and i have used RF cable to connect from USRP1 TX board to the spectrum
analyser RF out put and i am getting the output like this

In spectrum analyser iam getting noise and only 1 peak in the middle
which
does not look like ofdm signal.
I insert both the images above so you can have a look and please let me
know
what could be the problem.
I have used 2.4GHz frequency and i am using USRP1 board . i hope the
above
too diagrams help you to understand my problem.

Thanks and Regards,

Marcus D. Leech wrote:

peak sine wav signal not OFDM. I tried to play with the setiings but
the

Discuss-gnuradio mailing list
[email protected]
https://lists.gnu.org/mailman/listinfo/discuss-gnuradio

http://old.nabble.com/file/p32663266/fft%2Bofdm_spectrum.jpg
http://old.nabble.com/file/p32663266/fft%2Bofdm_spectrum.jpg
http://old.nabble.com/file/p32663266/fft%2Bofdm_spectrum.jpg
fft+ofdm_spectrum.jpg
http://old.nabble.com/file/p32663266/ofdm_spec.gif

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On 10/16/2011 05:55 PM, waqasme wrote:

Hi Marcus,

As i mentioned the flow graph signal blocks i have used in gnu radio
companion from that i am getting this out put on FFT sink in GNU radio
companion simulation flowgraph which is similar like this

If you’re trying to embed images, it’s not working, and the de-embedded
ones on the bottom show only
the spectrum of something typical of OFDM, and a spectrum-analyser
output that looks like it was
set up to sweep from 10Hz to 5GHz (is that what you had in mind?),
which would produce only a sharp
peak in the middle.

We still don’t know what your flow-graph(s) look like.


Marcus L.
Principal Investigator
Shirleys Bay Radio Astronomy Consortium
http://www.sbrac.org

/home/hp/Desktop/spectrumoutput.jpeg
http://old.nabble.com/file/p32675018/spectrumoutput.jpeg spectrumoutput.jpeg

Block diagram in GNU radio
/home/hp/Documents/finaltesting.grc
http://old.nabble.com/file/p32675018/finaltesting.grc finaltesting.grc

Your flow-graph appears to be badly confused about bandwidths and
interpolations and sample rates
–an interpolation ratio on your USRP1 sink of 100e6 is almost
certainly not what you had in mind.

You probably need to learn more about all of that, and get some better
notions of how the OFDM
modulator block works. At the very least you’ll need to
fractionally-interpolate the baseband
up to some sample rather that can reasonably be further interpolated
by the USRP1 hardware.

Given how simple this graph currently is, I’d strongly suggest that
you upgrade your “world” to UHD,
since your investment in the “old world” is still rather small.


Principal Investigator
Shirleys Bay Radio Astronomy Consortium
http://www.sbrac.org

On Oct 18, 2011, at 11:18 AM, “Marcus D. Leech” [email protected]
wrote:

interpolations and sample rates
Given how simple this graph currently is, I’d strongly suggest that
you upgrade your “world” to UHD,
since your investment in the “old world” is still rather small.


Principal Investigator
Shirleys Bay Radio Astronomy Consortium

As of last night, the ‘next’ branch of GNU Radio (if you are using git)
has the OFDM code and examples rewritten using UHD.

Tom

hi Marcus,

I am attaching the screen shots and also block diagram of transmitter…
right now i am just trying to look for transmission of OFDM signal via
usrp1. As i mentioned earlier in the fft scope plot in gnu radio i see
the
typical ofdm signal but on the other hand in usrp sink on the spectrum
analyser i saw only simple sine wave peak. please have a look and let me
know if there is something else do i need to do to generate the proper
ofdm
signal on the spectrum analyser.

/home/hp/Desktop/spectrumoutput.jpeg
http://old.nabble.com/file/p32675018/spectrumoutput.jpeg
spectrumoutput.jpeg

Block diagram in GNU radio
/home/hp/Documents/finaltesting.grc
http://old.nabble.com/file/p32675018/finaltesting.grc finaltesting.grc

Please have a look and suggest me how to fix this problem in order to
see
the proper ofdm signal on spectrum analyser as well?? Do i need and firm
ware update or sumthing on FPGA on usrp1 ???
Looking forward to hear from you.

Thanks for your help.
Cheers.

Marcus D. Leech wrote:


View this message in context:
http://old.nabble.com/OFDM-Transmiter-and-receiver-by-using-USRP1-tp32662445p32675018.html
Sent from the GnuRadio mailing list archive at Nabble.com.

Hello Marcus thanks for your reply… Well the problem is there is not
much
documentation available on internet on usurp … Also I am quite new to
gnu
radio and usrp1 … I tried to play with interpolation and decimation
settings but didnot get the desired ofdm signal … I am not sure what
else I
can do to fix this problem . If u know any documentation regarding that
please do let me know . U mentioned about UHd but I could not find any
UHd
blocks in gnu radio … As I saw in one example someone use UHd … Iam
using
Ubuntu 10.10 and gnu radio companion 3.2.2 version … I will really
appreciate if u can guide me how to setup the settings or specs i need
for
usrp 1 … Thanks and regards…

Marcus D. Leech wrote:

know if there is something else do i need to do to generate the proper
/home/hp/Documents/finaltesting.grc
fractionally-interpolate the baseband


View this message in context:
http://old.nabble.com/OFDM-Transmiter-and-receiver-by-using-USRP1-tp32662445p32677135.html
Sent from the GnuRadio mailing list archive at Nabble.com.

Hello Marcus thanks for your reply… Well the problem is there is not
much
documentation available on internet on usurp … Also I am quite new to
gnu
radio and usrp1 … I tried to play with interpolation and decimation
settings but didnot get the desired ofdm signal … I am not sure what
else I
can do to fix this problem . If u know any documentation regarding that
please do let me know . U mentioned about UHd but I could not find any
UHd
blocks in gnu radio … As I saw in one example someone use UHd … Iam
using
Ubuntu 10.10 and gnu radio companion 3.2.2 version … I will really
appreciate if u can guide me how to setup the settings or specs i need
for
usrp 1 … Thanks and regards…

Marcus D. Leech wrote:

know if there is something else do i need to do to generate the proper
/home/hp/Documents/finaltesting.grc
fractionally-interpolate the baseband


View this message in context:
http://old.nabble.com/OFDM-Transmiter-and-receiver-by-using-USRP1-tp32662445p32677136.html
Sent from the GnuRadio mailing list archive at Nabble.com.

Hello Marcus thanks for your reply… Well the problem is there is not
much
documentation available on internet on usurp … Also I am quite new to
gnu
radio and usrp1 … I tried to play with interpolation and decimation
settings but didnot get the desired ofdm signal … I am not sure what
else I
can do to fix this problem . If u know any documentation regarding that
please do let me know . U mentioned about UHd but I could not find any
UHd
blocks in gnu radio … As I saw in one example someone use UHd … Iam
using
Ubuntu 10.10 and gnu radio companion 3.2.2 version … I will really
appreciate if u can guide me how to setup the settings or specs i need
for
usrp 1 … Thanks and regards…

Marcus D. Leech wrote:

know if there is something else do i need to do to generate the proper
/home/hp/Documents/finaltesting.grc
fractionally-interpolate the baseband


View this message in context:
http://old.nabble.com/OFDM-Transmiter-and-receiver-by-using-USRP1-tp32662445p32677138.html
Sent from the GnuRadio mailing list archive at Nabble.com.

usrp 1 … Thanks and regards…

Try using:

http://www.sbrac.org/files/build-gnuradio

On your Ubuntu platform. It will build and install everything required
for a modern
UHD-supporting Gnu Radio environment.

While I agree that documentation is sparse, the problems with your
flow-graph indicate to me
problems at a conceptual level. Have you looked at the GRC Tutorials?

www.csun.edu/~skatz/katzpage/sdr_project/sdr/grc_tutorial1.pdf

Also:

http://gnuradio.org/redmine/projects/gnuradio/wiki/Tutorials

And:

http://gnuradio.org/redmine/projects/gnuradio/wiki/HowToUse

And:

http://gnuradio.org/redmine/projects/gnuradio/wiki/GNURadioCompanion

And:

http://gnuradio.org/redmine/projects/gnuradio/wiki/TutorialsWritePythonApplications

But if you don’t really have a clear notion of what interpolation and
decimation are all about, none of
the above will be of much help. You need a basic introduction to
Digital Signal Processing, and
going down the Gnu Radio path isn’t a substitute for such background.

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