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[Discuss-gnuradio] USRP2 Carrier Sensing using Raw Samples

From: Miklos Christine
Subject: [Discuss-gnuradio] USRP2 Carrier Sensing using Raw Samples
Date: Wed, 2 Dec 2009 19:17:07 -0800


I recently ran an experiment using the USRP2 to collect I&Q samples using usrp2_rx_cfile.py. I want to detect when the an 802.11b channel is busy using these raw samples.
I've seen the use of the filter y[n] = alpha*x[n] + (1-alpha)*y[n-1] with alpha as 0.001 in the carrier sensing BBN 802.11 code. The default threshold was set to 30 dB.
I've imported the data to Matlab and calculated the magnitude squared of each sample and ran it through this filter, but it appears that the data does not match the packets that I sent.

The carrier sensing code might correspond to the USRP, but are there any direct changes I would need to make for the USRP2 to use the carrier sensing code?

I've read through this post:
but it deals with the USRP at the FPGA level.

Anyone have any suggestions?

Miklos Christine


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