2007/6/11, Teun <[EMAIL PROTECTED]>:
Hi Guys, I tried searching the forum, but I still got some problems which I don't fully understand. To my knowledge, the receiving ADC Rate is 64 MSamples/second, at a granuality of 14 bits/sample. This would make it possible to have a total system bandwith of 32 Mhz (Nyquist), which is enough for example 802.11 standards. However, samples are transfered to the PC, using the USB bus. The usual I/O handling of the USB bus is 16 bits I and 16 bits Q signals, which means that you require 4 bytes per complex sample. The raw data rate for the USB is 480Mbit/s, but due to overhead it is possible to get only about 320Mbit/s, which is about 40Mbyte/s. Summing everything up, it is possible to transfer 40M/4 = 10Msamples/second over the USB bus, which means that you can only check a system with a bandwith of approximately 10Mhz. Am I right about this? If this is true, the limiting factor is the USB bus, not the ADC's on the USRP. Is it possible to use some sort of 1Gbit ethernet connection for the USRP? I know this wouldn't help that much, but It would make it possible to achieve the 802.11 standards (Channels of 20Mhz). Is this possible or are other things like CPU speed/PC memory becoming an issue?
Correct me if I am wrong, but in the usrp_rx_cfile.py script there is an option to transfer 8-bit samples across the USB. With this option enable, it should be possible to increase the BW at the expense of the resolution. -- Trond Danielsen _______________________________________________ Discuss-gnuradio mailing list [email protected] http://lists.gnu.org/mailman/listinfo/discuss-gnuradio
