OFDM Implementation

GNU Radio
21

Try this
cd /usr/share/gnuradio/examples/ofdm/
benchmark_ofdm_tx.py -h

Don’t forget the spaces (just copy & paste should work)

22

Thanks Johnny yah that worked …it is showing me different options for
OFDM… so for this particular benchmark_ofdm file the signal processing
blocks are displaying in GNU Radio companion or is there anything else i
have to do to make the block diagram of the system? thank you so much
for
your quick response and valuable information…
Really appriciate that johnny.
Thanks.

Tuan Ta-2 wrote:

benchmark_ofdm_tx.py -h

is the output:
/usr/share/gnuradio/examples/ofdm/benchmark_ofdm_rx.pyc
/usr/share/gnuradio/examples/ofdm/benchmark_ofdm_tx.pyc

My benchmark_ofdm code is not in /usr/local/bin so when you get to

.
when i enter this comand i get this result
sumitstop wrote:
-f

analyzer for the center frequency of the ofdm signal.
u can change the bandwidth of the ofdm signal by changing the no of

yah i have replaced the GMSK modulator and demodulator with OFDM
get
to
really appriciate your help because i have only few time left for

what

Demodulator right. but they didnot use any modulator any where
C++

waqasme wrote:
and

Waq.

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23

hello, well i followed the same steps and now i can see the different
options
by typing that command benchmark_ofdm_py. -h … now am done up till
that
now i asked my supervisor to provide me the extra USRP so hopefully i
will
get it soon from him. till that time i am just try to understand how it
works . i have one question reagarding the OFDM signal block processing
diagram like which we can create in GNU Radio companion. For this
particular
benchmark_OFDM is there any block diagram or blocks i have to create in
GNU
radio companion? and one more question do i need 1 USRP1 device or two
to
transmit and recieve? please let me know the procedure how to setup . i
am
assuming it is connected through USB interface what else is required to
make
a proper setup? thanks once again for your help. Thanks to u and
johnny…
Please advise…

sumitstop wrote:

help.
hp@ubuntu:~$ benchmark_ofdm_tx.py-h

after that u can run these files by typing ./benchmark_ofdm_tx.py -f
now run the transmitter again with the same frequency.

Also you mentioned this command ( benchmark_ofdm.py -h ) is that a
you.

benchmark programs are quite good to start with…

Hi Sumit,
Somebody already told me about this benchmark file. but its just C++

through some modifications as written in umit,

transmission and reception via USRP. i will really appriciate if

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24

Hello sumit,
I am trying to make OFDM trasmitter and reciever block diagram( with
signal
processing blocks available in GNU Radio) in GNU Radio companion. As my
supervisor asked me to make simulation first in GNU radio software then
move
on to USRP. i have made this basic simulation model for OFDM transmitter
which consists of:
Random source, Interleave, packet encoder, OFDM modulator, throttle and
FFT
sink block . by using these signal blocks iam getting the flow graph of
OFDM
transmitter. but now i want to make OFDM reciever as well. i tried the
same
technique in reverse order with OFDM demodulator ,packet decoder,
deinterlever , throotle and scope sink but its not showing any signal .
please if you know how to design or make the OFDM transmitter and
reciever
in GNU Radio companion software please guide me or let me know…
Thanks in advance.

Regards,

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25

Hi,
sorry my internet was down for almost 12 hrs… so whts the situation
now.are you able to transmit and receive …

waqasme wrote:

hp@ubuntu:~$ directory/usr/local/bin
No such file or directory. how to access that directory? do i need to run

and benchmark_ofdm_tx.py -h
spectrum analyzer for the center frequency of the ofdm signal.

one i have found has input and output as well for probe avg mag 2
like how to make this OFDM tranmission and reception via USRP. iam

http://pwnhome.files.wordpress.com/2011/04/simple_transceiver1.png

And sorry to mention in the last mail that i will be suing USRP 1 .

in the design. Now i am confused what blocks i have to replace with

may i know what daughter boards do you have…

to, and i tried to implement that OFDM transmitter part. This

Sumit Kr.
Research Assistant
Communication Research center
IIIT Hyderabad
India

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26

Hey Marcus this was very very informative.This offset was really killing
me
every time when I was running the OFDM example.I think I need to order
some
GPSDO :slight_smile:

Marcus D. Leech wrote:

Watch out for the frequency offset, it killed the system for me. If
what you’ll experience in real-world systems, and real-world channels.

around is typically not a complete system in this regard. In
Physics, it turns out, is a harsh mistress…

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Sumit Kr.
Research Assistant
Communication Research center
IIIT Hyderabad
India

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27

dont use random source… packet encoder is already in the ofdm block
in the
gnuradio-companion. so need not to include.also try to put the
screen-shot
of ur block diagram.

waqasme wrote:

of OFDM transmitter. but now i want to make OFDM reciever as well. i tried
the same technique in reverse order with OFDM demodulator ,packet decoder,
deinterlever , throotle and scope sink but its not showing any signal .
please if you know how to design or make the OFDM transmitter and reciever
in GNU Radio companion software please guide me or let me know…
Thanks in advance.

Regards,

Sumit Kr.
Research Assistant
Communication Research center
IIIT Hyderabad
India

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28

10-64 MHz

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

-JM

29

What frequency does the USRP1 want to see on its “ext clk” input?

10 MHz or 64 MHz?

@(^.^)@ Ed

30

Hi everyone,
I am trying to test signal tranmit by using OFDM modulator via USRP1
and i
am getting this error message . Does anyone know what does it mean?or
how to
fix this problem. i connected one usrp1 with usb cable to my laptop just
to
check the transmission. it shows the signal in FFT sink but when i add
USRP
sink it gives me this error. i am not sure how to confirm that wheater
it is
tranmsitting the signal or not. Any help will be appriciated

Error: failed to enable realtime scheduling.
usrp: failed to find usrp[0]
Traceback (most recent call last):
File “/home/lefteris/top_block.py”, line 98, in
tb = top_block()
File “/home/lefteris/top_block.py”, line 51, in init
self.usrp_simple_sink_x_0 = grc_usrp.simple_sink_c(which=0,
side=“A”)
File
“/usr/lib/python2.6/dist-packages/grc_gnuradio/usrp/simple_usrp.py”,
line 91, in init
self._make_usrp(which=which, nchan=1)
File “/usr/lib/python2.6/dist-packages/grc_gnuradio/usrp/common.py”,
line
28, in _make_usrp
def _make_usrp(self, *args, **kwargs): self._u =
self._usrp_args[0](*args, **kwargs)
File “/usr/lib/python2.6/dist-packages/gnuradio/usrp/usrp_swig.py”,
line
2469, in sink_c
return _usrp_swig.sink_c(*args, **kwargs)
RuntimeError: can’t open usrp

Thanks…
waq.

Tuan (Johnny) Ta wrote:

benchmark_ofdm_tx.py -h

is the output:
/usr/share/gnuradio/examples/ofdm/benchmark_ofdm_rx.pyc
/usr/share/gnuradio/examples/ofdm/benchmark_ofdm_tx.pyc

My benchmark_ofdm code is not in /usr/local/bin so when you get to

.
when i enter this comand i get this result
sumitstop wrote:
-f

analyzer for the center frequency of the ofdm signal.
u can change the bandwidth of the ofdm signal by changing the no of

yah i have replaced the GMSK modulator and demodulator with OFDM
get
to
really appriciate your help because i have only few time left for

what

Demodulator right. but they didnot use any modulator any where
C++

waqasme wrote:
and

Waq.

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31

Hi everyone,
I am trying to test signal tranmit by using OFDM modulator via USRP1
and i
am getting this error message . Does anyone know what does it mean?or
how to
fix this problem. i connected one usrp1 with usb cable to my laptop just
to
check the transmission. it shows the signal in FFT sink but when i add
USRP
sink it gives me this error. i am not sure how to confirm that wheater
it is
tranmsitting the signal or not. Any help will be appriciated

Error: failed to enable realtime scheduling.
usrp: failed to find usrp[0]
Traceback (most recent call last):
File “/home/lefteris/top_block.py”, line 98, in
tb = top_block()
File “/home/lefteris/top_block.py”, line 51, in init
self.usrp_simple_sink_x_0 = grc_usrp.simple_sink_c(which=0,
side=“A”)
File
“/usr/lib/python2.6/dist-packages/grc_gnuradio/usrp/simple_usrp.py”,
line 91, in init
self._make_usrp(which=which, nchan=1)
File “/usr/lib/python2.6/dist-packages/grc_gnuradio/usrp/common.py”,
line
28, in _make_usrp
def _make_usrp(self, *args, **kwargs): self._u =
self._usrp_args[0](*args, **kwargs)
File “/usr/lib/python2.6/dist-packages/gnuradio/usrp/usrp_swig.py”,
line
2469, in sink_c
return _usrp_swig.sink_c(*args, **kwargs)
RuntimeError: can’t open usrp

Thanks…
waq.

Tuan (Johnny) Ta wrote:

benchmark_ofdm_tx.py -h

is the output:
/usr/share/gnuradio/examples/ofdm/benchmark_ofdm_rx.pyc
/usr/share/gnuradio/examples/ofdm/benchmark_ofdm_tx.pyc

My benchmark_ofdm code is not in /usr/local/bin so when you get to

.
when i enter this comand i get this result
sumitstop wrote:
-f

analyzer for the center frequency of the ofdm signal.
u can change the bandwidth of the ofdm signal by changing the no of

yah i have replaced the GMSK modulator and demodulator with OFDM
get
to
really appriciate your help because i have only few time left for

what

Demodulator right. but they didnot use any modulator any where
C++

waqasme wrote:
and

Waq.

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