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Re: [Discuss-gnuradio] False Packets for benchmark TX/RX


From: Yahya Ezzeldin
Subject: Re: [Discuss-gnuradio] False Packets for benchmark TX/RX
Date: Wed, 5 Dec 2012 03:15:37 +0200

I tried offsetting the carrier frequency (playing at the RX side) but still ALL the packets are Ok=False.

Can this be related to the distance between the nodes, I mean is there some kind of typical distance for the nodes placement for the benchmark?

Best Regards,
--
Yahya Ezzeldin



On Wed, Dec 5, 2012 at 2:52 AM, Marcus D. Leech <address@hidden> wrote:
On 04/12/12 07:47 PM, Yahya Ezzeldin wrote:
I am pretty aware this had been covered in alot of question in the Mailing List but after going through alot of them I am unable to find a solution.

Currently,  I am trying to establish the benchmark connection between two USRP 1 nodes. Both Laptop stations have GnuRadio 3.6.2 installed on Ubuntu 12.04.

Now the facts:
****************

1) The codes I use at Node 1 is :
       ./benchmark_tx.py -f 900M -m gmsk -r 250k --tx-amplitude=0.5 --tx-gain=20
    The codes I use at Node 2 is :
       ./benchmark_rx.py -f 900M -m gmsk -r 250k --rx-gain=15

2) I edited the threshold in the receive_path.py from 30 to -70. This is based on the FFT_plot that I get when transmitting the packets. Is this wrong ?

Inline image 2

3) My USRPs are placed approx. 50cm apart.

4) I get this as output on Node 2 when running benchmark_rx command

ok = False  pktno =  215  n_rcvd =    1  n_right =    0
ok = False  pktno =  217  n_rcvd =    2  n_right =    0
ok = False  pktno =  219  n_rcvd =    3  n_right =    0
ok = False  pktno =  221  n_rcvd =    4  n_right =    0
ok = False  pktno =  165  n_rcvd =    5  n_right =    0
ok = False  pktno =  230  n_rcvd =    6  n_right =    0
ok = False  pktno =  227  n_rcvd =    7  n_right =    0
ok = False  pktno =  233  n_rcvd =    8  n_right =    0
ok = False  pktno =  239  n_rcvd =    9  n_right =    0
ok = False  pktno =  236  n_rcvd =   10  n_right =    0
ok = False  pktno =  252  n_rcvd =   11  n_right =    0
ok = False  pktno =  240  n_rcvd =   12  n_right =    0
ok = False  pktno =  241  n_rcvd =   13  n_right =    0
ok = False  pktno =  246  n_rcvd =   14  n_right =    0
ok = False  pktno =  243  n_rcvd =   15  n_right =    0
ok = False  pktno =  225  n_rcvd =   16  n_right =    0



I hope anyone can guide me as to what to do regarding this 


Best Regards,
--
Yahya Ezzeldin
_______________________________________________ Discuss-gnuradio mailing list address@hidden https://lists.gnu.org/mailman/listinfo/discuss-gnuradio
The usual reason for this is frequency-offset between RX and TX.  In the 'real world' this is a constant problem,
  which is why complete, market-ready, radio-based digital comms systems have a frequency locking mechanism
  in the receiver.

Try offseting the RX frequency in small amounts in either direction, and see if you can get good packets.



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

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