Hi Nikos, you're absolutely right with respect to it just being a bus bandwidth limitation: Gigabit ethernet can only carry 1Gbit/s, and with 16 bit per I and Q part, 31.25 Megasamples would be the maximum rate you could get through; adding a bit of overhead (it's not that much, roughly 40B overhead per 1450B payload, so roughly 2.7%), this gets reduced to roughly 30 MS/s, and including the fact that an average NIC isn't always using the cable to its fullest extent, that might be even less. So another reason why this isn't a GNU Radio issue is that 30MS/s is not a rate supported by the USRP: sampling rates need to be master_clock_rate/N, N being a natural number. That master clock rate is fixed to 100MHz on N210, so the only possible rates are
100MS/s (impossible over Gigabit Ethernet), 50MS/s (only possible with 8bit samples), 33.333MS/s (only possible with 8bit samples, but bad, because 3 is an odd decimation, and anti-aliasing filter performance is much worse for these), 25MS/s, 20MS/s, and so on. UHD will print a warning that the rate is impossible and that a "close by" rate was used. Best regards, Marcus _______________________________________________ Discuss-gnuradio mailing list Discuss-gnuradio@gnu.org https://lists.gnu.org/mailman/listinfo/discuss-gnuradio
