Hello,
I am trying to implement a MIMO bursty
transmission on USRP X310 with 2 CBX daughterboards using GNU Radio.
In order to make both antennas to start transmission synchronously I
set up the time spec in the USRP Sink code usrp_sink_impl.cc:
_metadata.time_spec = get_time_now() +
::uhd::time_spec_t(epsilon);
where epsilon is 1ms fixed delay. This
fixed delay is a problem, because of the GNU Radio time jitter, i.e.
in one case epsilon is too small and the burst is late (LLLL), in
another case epsilon is too large and the USRP just wastes time for
waiting.
I want to minimize the waiting time,
and make the USRP to start transmission simultaneously as soon as the TX chains of
both antennas have some data to transmit. One option is making
changes in the X310 FPGA image. My question however is, can I
minimize the waiting time just by changing the GNU Radio code or
settings?
Thank you in advance,
Dmitry.