It totally depends on where you implement the latency sensitive components. I believe the best USB can do is a minimum of 100us, and that probably the theoretical minimum. If you need 80-120 us latency, you will definitely need to move the latency sensitive components to the FPGA.
Here are a couple more references related to latency in GNUradio and the USRP: G. Nychis, T. Hottelier, Z. Yang, S. Seshan, P. Steenkiste, "Enabling MAC Protocol Implementations on Software-Defined Radios", NDIS 2009 K. Tan, J. Zhang, J. Fang, H. Liu, Y. Ye, S. Wang, Y. Zhang, H. Wu, W. Wang, G. Voelker, "Sora: High Performance Software Radio using General Purpose Multi-core Processors" Tim ------------------------------------------- Timothy R. Newman, Ph.D. Wireless @ Virginia Tech 447 Durham Hall Blacksburg, VA 24061 Phone: 540-231-2041 ________________________________________ From: discuss-gnuradio-bounces+trnewman=vt....@gnu.org [discuss-gnuradio-bounces+trnewman=vt....@gnu.org] On Behalf Of Rushikesh Khasgiwale [rushikesh.khasgiw...@mavs.uta.edu] Sent: Sunday, September 20, 2009 5:17 PM To: gnuradio Subject: [Discuss-gnuradio] USB latency problem I tried to use the usrp for implementing rfid protocols, however the USB latency is causing a bottleneck and I cannot generate and send the reply packet before the timeout(I need to send the reply within 80-120 us). upon reading Thomas Schimd's paper(http://nesl.ee.ucla.edu/document/show/242), it seems that I may have to do processing on the fpga itself instead of sending data over usb. Has anyone else faced a similar problem? CTS packets in 802.11 use functionality similar to mine, so maybe those who implemented it can help me. thanks -rushikesh _______________________________________________ Discuss-gnuradio mailing list Discuss-gnuradio@gnu.org http://lists.gnu.org/mailman/listinfo/discuss-gnuradio _______________________________________________ Discuss-gnuradio mailing list Discuss-gnuradio@gnu.org http://lists.gnu.org/mailman/listinfo/discuss-gnuradio
