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
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Colby B. 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 G.
Research Assistant
Communications and Signal Processing Lab
Oklahoma State University
http://cspl.okstate.edu
[email protected]
[email protected]
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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 G. <
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
To confirm, you were able to receive 802.11b using the USRP2?
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Colby B. 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 G.
Research Assistant
Communications and Signal Processing Lab
Oklahoma State University
http://cspl.okstate.edu
[email protected]
[email protected]
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