I had a couple of questions about the carrier sensing functionality of the USRP2 and the BBN 802.11 code. When we call the carrier_sensing function and it returns a value in dB, how does the USRP2 sample its data?
I know that it takes an average of the samples of the channel by using an IIR filter with the parameter alpha = 0.001. I calculated the sample period to be approximately 10 usec. Does the USRP2 actually sample faster (i.e. 1 usec), filter/decimate the data before returning a value every 10 usec?
How fast can the USRP2 actually sample data?
Does anyone suggest a value for alpha? With the given alpha, the carrier sensing block is storing values of the channel on the order of 10s of msec ago. Packets should last about 1-2 msec, so storing information for that long does not make a lot of sense.