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List:       gnuradio-discuss
Subject:    [Discuss-gnuradio] Problem with receiving data sent through ofdm transmitter (tx_ofdm)
From:       Qurat-Ul-Ann Akbar <quratulannakbar2015 () u ! northwestern ! edu>
Date:       2016-12-16 23:30:33
Message-ID: CAJwfNj0ruESi1EaBda3eYJGwZYBnjpCuF3T+wBe49v66E+mLZw () mail ! gmail ! com
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[Attachment #2 (multipart/alternative)]


Hello,

I am using the OFDM transmitter and receiver blocks to send random data
through USRP N210 coupled with an RFX2400 and XCVR 2450 daughter boards.
The transmitter and the receiver are on different machines and I am using
2.435G as the center frequency. There are a few issues:

1. I use uhd_fft to see the spectrum on both the transmitter and receiver.
Even before I start sending my data I see a peak close to 2.435G on both
the transmitter and receiver. Is it because WiFi transmits in this range as
well?

2. When I start sending data I can see a rectangular shaped spectrum being
sent and received through uhd_fft but nothing is actually seen on the
frequency and time sink in GNU Radio. I have tried reducing gain on the
sender side and its 0 db now and also the amplitude multiply const and it
is 0.05 now. But still no effect. When I change the gain on receiver side
nothing really happens at 0 db but around 40 you see a slight rise in the
frequency spectrum and around 60 db it starts giving errors like :

INFO: Detected an invalid packet at item 48 and it gives after 48 items


Sometimes this happens even before I start my transmitter.  I do not
see anything being received in any of the cases.


I have attached my transmitter and receiver flowgraphs. And also
screenshots of my uhd_fft spectrum.

Can anyone please tell me what the problem is ? I would really appreciate
it.

Best,
Annie

[Attachment #5 (text/html)]

<div dir="ltr">Hello,<div><br></div><div>I am using the OFDM transmitter and receiver \
blocks to send random data through USRP N210 coupled with an RFX2400 and XCVR 2450 \
daughter boards. The transmitter and the receiver are on different machines and I am \
using 2.435G as the center frequency. There are a few \
issues:</div><div><br></div><div>1. I use uhd_fft to see the spectrum on both the \
transmitter and receiver. Even before I start sending my data I see a peak close to \
2.435G on both the transmitter and receiver. Is it because WiFi transmits in this \
range as well?  </div><div><br></div><div>2. When I start sending data I can see a \
rectangular shaped spectrum being sent and received through uhd_fft but nothing is \
actually seen on the frequency and time sink in GNU Radio. I have tried reducing gain \
on the sender side and its 0 db now and also the <font face="arial, helvetica, \
sans-serif">amplitude multiply const and it is 0.05 now. But still no effect. When I \
change the gain on receiver side nothing really happens at 0 db but around 40 you see \
a slight rise in the frequency spectrum and around 60 db it starts giving errors like \
:</font></div><div><font face="arial, helvetica, \
sans-serif"><br></font></div><div><pre style="color:rgb(0,0,0);margin:0em"><font \
face="arial, helvetica, sans-serif">INFO: Detected an invalid packet at item 48 and \
it gives after 48 items</font></pre><pre style="color:rgb(0,0,0);margin:0em"><font \
face="arial, helvetica, sans-serif"><br></font></pre><pre style="margin:0em"><font \
color="#000000" face="arial, helvetica, sans-serif">Sometimes</font><font \
face="arial, helvetica, sans-serif"><font color="#000000"> this happens even before I \
start my transmitter.  I do not see anything being received in any of the cases. \
</font></font></pre></div><div>  </div><div>I have attached my transmitter and \
receiver flowgraphs. And also screenshots of my uhd_fft \
spectrum.</div><div><br></div><div>Can anyone please tell me what the problem is ? I \
would really appreciate it.  \
</div><div><br></div><div>Best,</div><div>Annie</div><img \
src="http://t.sidekickopen68.com/e1t/o/5/f18dQhb0S7ks8dDMPbW2n0x6l2B9gXrN7sKj6v5dq_jN6 \
3K5dvd_KNjW3LyyZ81pctGFW1dsDB71k1H6H0?si=5925899090264064&amp;pi=2745a127-1900-429a-8906-9b89fc7437c4" \
style="display:none!important" height="1" width="1"></div>

--001a11438022de68fa0543cef424--


["uhd_fft_aftertransmission_TRANSMITTER.png" (image/png)]
["uhd_fft_beforetransmission_TRANSMITTER.png" (image/png)]

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