Hi everybody,
I am using USRP N200 and the antenna is VERT2450.
One system sends the “input” file (in repeat mode)after ofdm
modulation.The
other system receives this and demodulates and saves to a “output” file.
The
input file can be any text file.
This grc is for sending
0fdm_sender.grc
http://gnuradio.4.n7.nabble.com/file/n49746/0fdm_sender.grc
This grc is for receiving
ofdm_receiver.grc
http://gnuradio.4.n7.nabble.com/file/n49746/ofdm_receiver.grc
When I run both these I could be able to receive the file.
Now the problem is that I could able to receive the file for only
2.45Ghz,
2.455Ghz ,2.46Ghz center frequencies of source and sink USRP’s but I
could
not be able to receive for other frequencies say 2.456Ghz,2.457GHz etc
(The
center frequencies are changed in both sender and receiver files ,both
USRP
sink and source)
If I use the given example in the source code i.e, the benchmark_tx.py
and
benchmark_rx.py with the above parameters I could be able to send and
receive at all frequencies even 2.456Ghz and 2.457Ghz.
So I could not understand why this is happening so.
I checked in the list whether this question is answered earlier or not
but
couldn’t find it.So if it is already present ,give that link and I am
extremely sorry for it.
Thanks in advance
Regards,
Chaitanya
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On 08/04/2014 08:42 PM, chaitanya wrote:
Hi everybody,
I am using USRP N200 and the antenna is VERT2450.
Which d’board?
Now the problem is that I could able to receive the file for only 2.45Ghz,
2.455Ghz ,2.46Ghz center frequencies of source and sink USRP’s but I could
not be able to receive for other frequencies say 2.456Ghz,2.457GHz etc (The
center frequencies are changed in both sender and receiver files ,both USRP
sink and source)
So, at 2.45 GHz it works reliably? And not at all for the rest? I’d
triple-check you really are setting the freq on both tx and rx (and not
just changing a variable that isn’t propagated to the devices, for
example). There’s no frequency-specific code in the OFDM stuff.
And of course make sure there’s no interference on those other
frequencies.
M
Thanks for the reply
Which d’board?
SBX Board (Rev 5.1)
So, at 2.45 GHz it works reliably? And not at all for the rest?
Yes,this is what exactly I want to say.It is reliable at 2.45GHz ,
2.455GHz
and 2.46GHz.
For other frequencies it is not reliable.
I’d triple-check you really are setting the freq on both tx and rx (and not
just changing a variable that isn’t propagated to the devices, for
example).
The variable change is propagated to the device.I used the GUI FFT SINK
to
verify that.
There’s no frequency-specific code in the OFDM stuff.
I did not understand this statement.
What I am changing is the center frequencies of USRP source and sink in
grc.
In the benchmark_tx and benchmark_rx , I am changing using -f option.
And of course make sure there’s no interference on those other frequencies.
I am sure there is no interference
chaitanya
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Hi Martin,
thanks for reply
Wait, so it does work for more than one frequency? Where exactly does it
not work?
Yes,it worked for more than one frequency .They are 2.45GHz ,2.455GHz
and
2.46GHz.
It did not work(that means not reliable) for
2.451GHz,2.452GHz,2.453GHz,2.454GHz and also between 2.456 to 2.459GHz.
Put in another way: The OFDM code is agnostic of the actual frequency.
There is nothing in the OFDM code that will make it work better at one
frequency than another.
Yeah, I also expected that. Thats why i posted this question.It should
work
for all frequencies but its not working, I don’t know why.
Please if possible once try running those ofdm_sender.grc and
ofdm_receiver.grc at 2.45Ghz and also at 2.452Ghz.And observe the FFT
sink.
chaitanya
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FFT sink at the receiver or attached to the transmitter GRC?
Your GRCs don’t work for me. With which version of GNU Radio were they
built?
On 08/06/2014 03:26 PM, chaitanya wrote:
Thanks for the reply
Which d’board?
SBX Board (Rev 5.1)
So, at 2.45 GHz it works reliably? And not at all for the rest?
Yes,this is what exactly I want to say.It is reliable at 2.45GHz , 2.455GHz
and 2.46GHz.
For other frequencies it is not reliable.
Wait, so it does work for more than one frequency? Where exactly does it
not work?
I’d triple-check you really are setting the freq on both tx and rx (and not
just changing a variable that isn’t propagated to the devices, for
example).
The variable change is propagated to the device.I used the GUI FFT SINK to
verify that.
There’s no frequency-specific code in the OFDM stuff.
I did not understand this statement.
Put in another way: The OFDM code is agnostic of the actual frequency.
There is nothing in the OFDM code that will make it work better at one
frequency than another.
M
Hi Marcus
Thanks for reply
Your GRCs don’t work for me. With which version of GNU Radio were they
built?
one is version 3.6.5.1 and the other one is version 3.7.2.1.
I think the device addr in usrp sink and source should be changed.And
also
the file path in file sink and source should be changed according to ur
system.
Thinking about this, that was a bad question from my side.
Since the ofdm_mod doesn’t even know about the center frequency, the
signal generated digitally is always the same, so you can only be
looking at the rx side’s abs(FFT).
yeah,at rx side only
Would be nice if you had a description of what happens or a screenshot
uploaded somewhere!
These are the screen shots of FFT at 2.45GHz and 2.455GHz center
frequencies.
2_45GHz.png http://gnuradio.4.n7.nabble.com/file/n49851/2_45GHz.png
2_455GHz.png http://gnuradio.4.n7.nabble.com/file/n49851/2_455GHz.png
These are the screen shots of FFT at 2.452GHz and 2.454GHz center
frequencies.
2_452GHz.png http://gnuradio.4.n7.nabble.com/file/n49851/2_452GHz.png
2_454GHz.png http://gnuradio.4.n7.nabble.com/file/n49851/2_454GHz.png
Ok, you’re seeing frequency selective behaviour. This can happen for a
myriad of reasons, among these interference and multipath propagation.
You’re excluding interference as a reason on an ISM band, so I presume
you’re working with a direct cable between tx and rx or in an anechoic
chamber; thus multipath can’t be the reason, either.
No , I am not working with a cable between tx and rx or not in an
anechoic
chamber.But I can say there is no interference (as on ISM band) because
when
I run the benchmark_tx.py and benchmark_rx.py files ,then most of the
packets are being received (i.e, n_right value is near to n_rcvd ) even
at
2.452 and 2.454GHz center frequencies.
chaitanya
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On 08/07/2014 03:32 PM, chaitanya wrote:
Hi Marcus
Thanks for reply
Your GRCs don’t work for me. With which version of GNU Radio were they
built?
one is version 3.6.5.1 and the other one is version 3.7.2.1.
I think the device addr in usrp sink and source should be changed.And also
the file path in file sink and source should be changed according to ur
system.
Ah, so you’re using the old OFDM components, I guess. Not what I was
assuming.
What’s your UHD version?
These are the screen shots of FFT at 2.45GHz and 2.455GHz center
frequencies.
2_45GHz.png http://gnuradio.4.n7.nabble.com/file/n49851/2_45GHz.png
2_455GHz.png http://gnuradio.4.n7.nabble.com/file/n49851/2_455GHz.png
These are the screen shots of FFT at 2.452GHz and 2.454GHz center
frequencies.
2_452GHz.png http://gnuradio.4.n7.nabble.com/file/n49851/2_452GHz.png
2_454GHz.png http://gnuradio.4.n7.nabble.com/file/n49851/2_454GHz.png
Posting this earlier would have helped. Your rx spectrum is pretty
screwed up at these frequencies. I can’t say why, but I’d like to get
the version issues sorted out first.
Also, I recommend using the new OFDM subsystem. Refer to the manual for
details.
Cheers,
Martin
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Thinking about this, that was a bad question from my side.
Since the ofdm_mod doesn’t even know about the center frequency, the
signal generated digitally is always the same, so you can only be
looking at the rx side’s abs(FFT). Would be nice if you had a
description of what happens or a screenshot uploaded somewhere!
Ok, you’re seeing frequency selective behaviour. This can happen for a
myriad of reasons, among these interference and multipath propagation.
You’re excluding interference as a reason on an ISM band, so I presume
you’re working with a direct cable between tx and rx or in an anechoic
chamber; thus multipath can’t be the reason, either.
Greetings,
Marcus
On 07.08.2014 11:24, Marcus M. wrote:
,2.455GHz and 2.46GHz. It did not work(that means not reliable)
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Thanks for reply
What’s your UHD version?
3.5.3 and 3.7.1
Ah, so you’re using the old OFDM components, I guess. Not what I was
assuming.
Also, I recommend using the new OFDM subsystem. Refer to the manual for
details.
I did not understand this. Are you asking me to use the latest version
of
gnuradio.
Chaitanya
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There are “old style” OFDM blocks in GNU Radio, and “new style”
blocks, which are cooler, more versatile and cleaner.
On 08.08.2014 16:23, chaitanya wrote:
version of gnuradio.
Chaitanya
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Hi Chaitanya,
in GRC there is a category called OFDM with the new style blocks. Also
in [pathtognuradiosource]/gr-digital/examples/ofdm configured
flowgraphs are provided for reference.
Just to make that sure, I’m refering to GNU Radio 3.7.
happy hacking
Johannes
On 08.08.2014 18:16, chaitanya wrote:
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Thanks for reply
There are “old style” OFDM blocks in GNU Radio, and “new style”
blocks, which are cooler, more versatile and cleaner.
Where can i get that. Can you please name the "new style " OFDM blocks.
chaitanya
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Also, there’s the manual.
M
