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Re: [Discuss-gnuradio] OFDM packets
From: |
Crespi Floriana |
Subject: |
Re: [Discuss-gnuradio] OFDM packets |
Date: |
Fri, 29 Feb 2008 16:29:13 +0100 |
User-agent: |
Internet Messaging Program (IMP) 3.2.6 |
Scrive Eric Blossom <address@hidden>:
> On Thu, Feb 28, 2008 at 12:51:18PM +0100, Crespi Floriana wrote:
> > Hi,
> > I have a problem with OFDM system.
> > I transmit OFDM signal at 2.4 GHz, but I receive half of the total packets.
> > Moreover, only half of the packets received are correct.
> > CRC controller is perfect but i want a ber estimate, so I change the
> > payload (binary file) and I receive check bit by bit.
> > The result of my alteration test is similar than CRC test.
> > I have a lot of frequency offset, therefore I change manually the frequency
> > receiver.
> > I use revision 6845 and RFX 2400.
> > Example with crc:
> > The final packet I receive:
> > ok: False pktno 4602 n_rcvd 1300 n_right 83
> >
> > Why can't i get all the packets?
> > Could you help me??
> >
> > I'm testing OFDM system without USRP and none of the packets are lost.
> >
> > Thanks a lot.
> >
>
> Hi Crespi,
>
> You have neglected to tell us virtually anything about your problem.
> Could you please tell us:
>
> which version of GNU Radio? trunk, tarball (which one), etc?
> what operating system, distribution and architecture?
> the command line you issued
> any modifications you may have made to distributed code?
> anything else that might be relevant
>
>
> Thanks,
> Eric
>
>
Hi, thank you for your reply.
I use:
* Linux K-Ubuntu 7.04
*Gnuradio Trunk 6845
The command are :
--TX--
sudo python benchmark_ofdm_tx.py -f 2.442e9 -T A --tx-amplitude 10000
--RX--> sudo python benchmark_ofdm_rx.py -f 2.4419899e9 -T A
(occuped tones, size packet and fft are default value)
Important: If I don't change Rx frequency it can't receive!!
I change the payload. I upload file to the code and I calculate its lenght.
Number packets= (lenght file/ size packets)+1
Before my modification I tested ofdm system and the result is similar then after
modification.
The trial simulation (without USRP and antennas) is perfect. I Receive all
packets and they are correct.
I tested with coax for estimate channel problem but the result is similar to
real channel. I thought the problem was the channel but this experiment reject
my theory.
I don't find the problem because my alteration code don't change the core code.
This is my result. final packet
===================================================================================
Trial simulation
ok: True pktno: 4609 n_rcvd: 4610 n_right: 4610
bit right 14750243
bit wrong 0.0
===================================================================================
All correct
===================================================================================
Coax
ok: False pktno: 4000 n_rcvd: 1300 n_right: 830
bit right 2109817
bit wrong 2050183
===================================================================================
Thank you a lot for your help.
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