Thanks for reply. My plan is to extend the usrp_spectrum_sense.py: grab its output data and let a py script find the best available frequency in the data; then put this frequency into the usrp2_source block of file transmitter. In such case, my py script would contain two top_block and the second one, file transmitter, would run after the first one stops. Is this possible? When you say threading, do you mean two top_block?
Speaking of DySPAN, I will look into that. Really thanks. On Sat, May 7, 2011 at 8:55 PM, Tom Rondeau <trondeau1...@gmail.com> wrote: > On Fri, May 6, 2011 at 4:34 PM, Yang <yyl....@gmail.com> wrote: > >> Hi all, >> >> I am recently doing a project on gnu radio and usrp2. My goal is to >> implement DSA: let Tx sense some bands, choose available one by energy >> detection, then tune the usrp2 to this frequency and transmit a signal. >> >> This might sound quite simple and basic for you, but I find it very hard >> to get started. I have tried some ways: >> >> 1. To write blocks for GRC: >> I have written a energy detection block find no way to realize the band >> switching function. Also, my energy detection block can only sense the >> signal USRP2 received from a fixed frequency (i.e. from usrp2_source block). >> How could I change the frequency during the detection? I cannot think of a >> way to make the one-way flow of GRC to do some feedback functions. >> >> 2. To extend/modify usrp_spectrum_sense.py: >> I cannot figure out what is going on in gr_bin_statistic block (even with >> the detailed explanation from Firas): dose it just copy data from FFT and >> window block and save them in a .dat file? If it can generate the raw file, >> what is happening in the main_loop and m.data? Is m.data a file too? >> >> Sorry for so much words but I feel I am totally lost in scripts. I am >> still new to this and I cannot find a place to dive into and get work done. >> I believe there should be some quite simple and straightforward way to >> realize DSA. Would anyone point a way for me to go? >> >> Any help would be appreciated. Thank you. >> -- >> Yang >> Sent with Sparrow <http://www.sparrowmailapp.com> >> > > > The IEEE DySPAN conference (which just finished) has had many demos and > papers about realizing DSA using GNU Radio. If you have access to the IEEE > proceedings, you should find various references to people who have built GNU > Radio programs for this purpose, at least as far back as the 2007 > conference. You might find some useful ideas from any papers published or > the websites of the demonstrators. > > Having done some of this myself, I would say that you could have a thread > operating in Python that is waiting for a message from a GNU Radio sink > block. The message would contain some information about the spectrum usage > that you could then use to retune the USRP sink. So the retuning is done in > the Python domain and not directly from a GR block. > > A more complicated (but possibly more elegant) method would be to use the > message passing interface. You would set it up so that a work function would > make some decision on the free channel that would send a message to the USRP > sink to change frequencies. The most difficult part of this is due to our > lack of documentation and examples of using the messages. > > Tom > > > >
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