Forum: GNU Radio Symbol rates. USRP2 vs USRP1

Announcement (2017-05-07): www.ruby-forum.com is now read-only since I unfortunately do not have the time to support and maintain the forum any more. Please see rubyonrails.org/community and ruby-lang.org/en/community for other Rails- und Ruby-related community platforms.
F8c67168687ff78ffe36b97ad5764f66?d=identicon&s=25 Colby Boyer (Guest)
on 2009-04-22 22:36
(Received via mailing list)
Hi all,

As some of you know, I am working on porting the BBN 802.11b code to the
USRP2.  I understand that the ADC/DAC rates are higher than the USRP1.
What
are the effects, if any, on the rate at which symbol are sent through
the
air? I am suspect that this could be the reason I cannot decode sent
packets.

Colby
D9b2772a9387f5dbe010dbc0c3a93f8d?d=identicon&s=25 Douglas Geiger (Guest)
on 2009-04-23 00:17
(Received via mailing list)
-----BEGIN PGP SIGNED MESSAGE-----
Hash: SHA1

Colby Boyer wrote:
> Hi all,
>
> As some of you know, I am working on porting the BBN 802.11b code to the
> USRP2.  I understand that the ADC/DAC rates are higher than the USRP1. What
> are the effects, if any, on the rate at which symbol are sent through the
> air? I am suspect that this could be the reason I cannot decode sent
> packets.
>
> Colby
>

Main change I had to do when I was working on it was the samples/baud. I
only had it recognizing very high SNR 1 and 2Mbps packets.
 Doug

- --
Doug Geiger
Research Assistant
Communications and Signal Processing Lab
Oklahoma State University
http://cspl.okstate.edu
douglas.geiger@okstate.edu
doug.geiger@ieee.org
-----BEGIN PGP SIGNATURE-----
Version: GnuPG v1.4.9 (Cygwin)
Comment: Using GnuPG with Mozilla - http://enigmail.mozdev.org

iD8DBQFJ75c/gfOzzR5bXIgRAmHfAJ4iANMn3cFMUJRXH6+3jtYS0+7DmQCeL7or
RdX3Vm2+66ESDf+TB+yxcsY=
=Okof
-----END PGP SIGNATURE-----
F8c67168687ff78ffe36b97ad5764f66?d=identicon&s=25 Colby Boyer (Guest)
on 2009-04-23 01:31
(Received via mailing list)
What changes did you have to make to the sample/baud rate?

How high is high SNR? 10dB? 15dB?

I can only establish communication within simulation. When I try to
transmit
stuff over the air, it fails.

On Wed, Apr 22, 2009 at 3:16 PM, Douglas Geiger <
D4f6aa720f15aa01a59fa77c9ac7ee46?d=identicon&s=25 Valerio, Danilo (Guest)
on 2009-04-23 10:26
(Received via mailing list)
Hi Colby!

In the RX path the difference in the adc rate should be compensated by
the fact that you multiplied the decim by a factor of 1.5.
[In your bbn_80211b_rx.py (line 98)]

In the TX path Andrea figured out that:

Rate = 2 * [FPGA_processing_rate / (spb*interp_rate)]

The BBN guys suggested to use spb=4 and interp_rate=32 for communicating
with a wifichipset.
In fact, with USRP1:
2 * [64 MS/s / (4 S/bit * 32)] = 1 Mbps

On the contrary, in USRP2 the FPGA_processing_rate is 100 MS/s.
Therefore, in order to transmit at 1 Mbps, we need to set the
(spb*interp_rate) accordingly:

e.g.
2 * [100 MS/s / (4 S/bit * 48)] = 1Mbps.

We were wondering how it is possible that spb=4 can represent a barker
sequence.
We have tried some different combinations of spb and interp_rate (e.g.
spb=8 and interp=24), so that the result is always 1 Mbps.
But we still have no success.
By "no success", I mean that the wifi chipset monitoring the air
receives frames that seem to be randomly generated.

Any suggestions?
Anyway, thanks for uploading your branch. ;-)

Danilo
F8c67168687ff78ffe36b97ad5764f66?d=identicon&s=25 Colby Boyer (Guest)
on 2009-04-23 22:15
(Received via mailing list)
To confirm, you were able to receive 802.11b using the USRP2?
D9b2772a9387f5dbe010dbc0c3a93f8d?d=identicon&s=25 Douglas Geiger (Guest)
on 2009-04-24 00:47
(Received via mailing list)
-----BEGIN PGP SIGNED MESSAGE-----
Hash: SHA1

Colby Boyer wrote:
> To confirm, you were able to receive 802.11b using the USRP2?
>

Yes, only at 1 and 2Mbps (DSSS w/Barker Code) rates.
 Doug

- --
Doug Geiger
Research Assistant
Communications and Signal Processing Lab
Oklahoma State University
http://cspl.okstate.edu
douglas.geiger@okstate.edu
doug.geiger@ieee.org
-----BEGIN PGP SIGNATURE-----
Version: GnuPG v1.4.9 (Cygwin)
Comment: Using GnuPG with Mozilla - http://enigmail.mozdev.org

iD8DBQFJ8HgugfOzzR5bXIgRAjDZAJ4+VwTHn00cgcVvprerq2hjUVm1dgCfWL+b
7UCtnKv189WcVW9kelHN4hQ=
=NSwp
-----END PGP SIGNATURE-----
This topic is locked and can not be replied to.