Hello, I am trying to make a simple FFT flow chart using a RFNoC FFT block and a signal source as input. I am finding that the maximum FFT size I can use is limited by the MTU of my Ethernet connection. While connected to the 1GB Ethernet I had a MTU of 1500 and was able to use an FFT size of 1024 but if I tried to use 2048 I would get a timeout on chan0 error message, similar to this case http://comments.gmane.org/gmane.comp.hardware.usrp.e100/13915 . I was able to increase the FFT size to 1024 because I stayed in the RFNoc layer to display data instead of moving back up to the host. If I move up to the host layer then I am limited to FFT size of 512 like the previous case.
I switched to a 10GB connection which supports a MTU of 9000. This gave me a new max FFT size of 2048 if I stay in the RFNoC layer and 1024 if I move back up to the host layer. To do this I had to edit the code for the RFNoC block like in this case http://comments.gmane.org/gmane.comp.hardware.usrp.e100/16564. In that example it is mentioned that it may be possible to break up larger FFTs into multiple packets and recombine them. I am wondering if there is a way to increase the FFT size past 2048 with a limited MTU. It aslo seems that the max packet size for the USRP is 8000 so increasing the MTU further may be of little use. FInally I am wondering if it is possible to have an FFT size up to 8192 and if not, will it be in the future? I have attached my flowchart below
example.grc
Description: application/gnuradio-grc
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