Devin, Then you are not taking the problem from the right perspective... First, you have to know the bandwidth you need for your application ( mainly "fmax"). This will define your sampling rate. Then, you have to set your decimation factor depending on the amount of data resulting from the previous choice. On a "fast" pc running Linux, an avg around 30 msps can be achieved. Not tested with Beagleboard yet.
Then.... processing : you need to have one thread reading the USB stream from the USRP and filling a buffer. you need a second thread performing the fft and doing the decision. the good question now is : what is the frequency resolution you need ( this will set the fft size .... and time needed to compute that). I would suggest you start by estimating FFT size, then evaluate the time you have to compute that. But maybe I am completely wrong and in fact you do not need real time processing... ???? sylvain 2010/6/21 devin kelly <[email protected]> > Sylvain, > > Sorry for not being clear. I was just trying to say that, the higher the > decimation rate the more data I have to process, I wasn't talking about > decimating twice. > > So would I'd like to do is record samples for 0.5 to 0.75 seconds (for > example), then do some processing on those samples for the remaining, 0.25 > to 0.5 seconds, and repeat. The processing I'm thinking of is taking an > FFT, making a decision, then recording it to non-volatile storage. So my > question is, to do processing like I described, what sort of decimation > rates can I choose? > > Devin > > > On Mon, Jun 21, 2010 at 9:01 AM, devin kelly <[email protected]> wrote: > >> >> What about a more reasonable decimation rate, like 32 or 64... Could I >> collect samples 50%-75% of the time and then process that data the rest of >> the time? >> >> Thanks again, >> Devin >> >> >> On Fri, Jun 18, 2010 at 10:09 AM, devin kelly <[email protected]> wrote: >> >>> Hello, >>> >>> I'm interested in doing a project with the Beagle Board and the USRP1, >>> along with using gnu radio. My lab doesn't have a Beagle Board or USRP1 >>> (only USRP2s), so I need a few questions answered before I commit to this >>> platform. >>> >>> What type of performance can I expect from the Beagle Board? I'm mostly >>> interested in doing FFTs with some comparatively small processing on that >>> data, is this possible? >>> >>> What sort of decimation rates can I use and expect near real time >>> performance for this application? I have a few (albeit several years old) >>> machines that struggle with just taking an FFT with a decimation rate of >>> around 8. This is on the USRP2 as well. >>> >>> Any advice at all is appreciated. >>> Devin >>> >> >> > > > -- > http://users.wpi.edu/~dkelly/ >
