I'm trying to implement a MIMO receiver using the 4 RF
chains of the N310. To test the timing of the system, at
the transmitter I'm simply sending a short pulse from one
transmit antenna of one USRP. At the receiver it looks
like there is up to a ~20 ms delay/offset between the
pairs of antennas 0/1 and 2/3 and that this delay changes
each time I restart my GNURadio flowgraph. I can see
the delay both in GNURadio GUI Time Sink and in actual
samples that I write to file. I've tried various pulse
widths and sampling rates at both the tx and rx, and it
seems invariant to these.
I'd really like to be able to synchronize the 4 RF
chains in time simultaneously. Is that possible?