Hi I'm a Spanish Telecommunitacion Engineering student in his last year and I'm doing my final degree project related to USRP2.One part of this project is the measurement of the channel usage in the Wi-Fi band (2,4GHz and 5.2GHz).
I've built the next flow graph: [USRP2 source (i.e. freq = 2.4G)]-->[Head]-->[FFT Filter]-->[Complex to Mag^2]-->[Stream to vector] --> [TCP sink(client)] The TCP server converts the message received from the USRP2 into a float, using numpy library: value_measured = numpy.fromstring (stream_received_from_usrp2, numpy.float32) Result: I launch the flow graph and I wait unit it finishes. The measured data is an array of float numbers. I work out the maximum value and the average of all the floats and I use this values to decide whether the channel is busy or not. If I choose a really busy Wi-Fi channel (ie: channel 1, @ 2.412GHz), the obtained results are (acording to the gaining, decimation,... values I've chosen): MAX Value = 434.435 Average = 1.4530 But, if I choose an empty Wi-Fi channel, the obtained results are: MAX Value = 2.839 Average = 0.34955 I've repeated this many times and probably it's not a accurate way to measure 'how busy is the channel' but I'm able to test if there are Wi-Fi transmissions. BUT, I've the following question/problem: The TCP server (which receives the USRP2's measurements) doesn't receive the same amount of data in consecutive measures. I mean, if I run the graph, the number of samples that sends to the TCP server isn't always the same. I thought that I could fix this value with the Head Block, but obviously I'm wrong. How could I fix the value of the measured data? I've thought to do this without sockets, recording this values directly from USRP2 to a "variable sink". I can get it with a graphical sink but not with a non-graphical sink. I hope someone can tell me if I'm wrong or not with this method, or I should improve it. Thank you for your time, Juan Ramon Gutierrze _______________________________________________ Discuss-gnuradio mailing list [email protected] http://lists.gnu.org/mailman/listinfo/discuss-gnuradio
