Forum: GNU Radio OFDM

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unknown (Guest)
on 2007-02-12 22:57
(Received via mailing list)
I'm pretty new to gnu radio and I want to transmit an OFDM signal using
different modulation types (BPSK, QPSK, and 64-QAM).  The concept is
pretty simple: read data, map it to a specified constellation map, and
then send it through an IFFT.  I don't know if this code already exists
but I could use some help.

Nick
Johnathan C. (Guest)
on 2007-02-13 01:28
(Received via mailing list)
removed_email_address@domain.invalid wrote:

> I'm pretty new to gnu radio and I want to transmit an OFDM signal
> using different modulation types (BPSK, QPSK, and 64-QAM).  The
> concept is pretty simple: read data, map it to a specified
> constellation map, and then send it through an IFFT.  I don't know if
> this code already exists but I could use some help.

There is work underway in this area to create a parameterized OFDM
modulator/demodulator pair, but it is incomplete and not yet merged into
the trunk.  You can see the code in:

http://gnuradio.org/trac/browser/gnuradio/branches...

These examples depend on C++ elsewhere in the tree in this developer
branch so they won't run as-is. You can, however, see how the transmit
path is put together.

By the way, you're right--the modulator is the easy part.  It's the
receiver synchronization that always turns out to be the black magic
part. (Why is this always glossed over? :-)

Johnathan C.
Corgan Enterprises LLC
http://corganenterprises.com
Tom R. (Guest)
on 2007-02-13 03:52
(Received via mailing list)
Johnathan C. wrote:
> There is work underway in this area to create a parameterized OFDM
> receiver synchronization that always turns out to be the black magic
> part. (Why is this always glossed over? :-)
>
> Johnathan C.
> Corgan Enterprises LLC
> http://corganenterprises.com

As Johnathan said, we've pretty much got the modulator and demodulator
done. A few of us will be working next week on pulling it all together
and finishing the synchronization. With any luck and the alignment of
the Zodiac (or whatever astrological/mythological concept you want to
wish on), we'll get this merged into the trunk by the end of next week.

 From there, hack away and make improvements.

Tom
Robert McGwier (Guest)
on 2007-02-16 01:30
(Received via mailing list)
The OFDM work has begun under my (n4hy) branch.  Next week it will
continue as I travel to Virginia Tech to work with Tom, Matt, and others
on this and other work.

When we have an OFDM transceiver and can drive one of the Flexible
boards from Matt on the air,  we will move it into the trunk so we can
add FEC, interleaving, etc.  easily and learn how Achilleas work needs
to be optimized (if at all) to be used with this code.

Bob
(ARS  N4HY)

removed_email_address@domain.invalid wrote:
>
>


--
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TAPR, Packrats, NJQRP, QRP ARCI, QCWA, FRC. ARRL SDR WG Chair
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