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On 11/22/2020 10:30 AM, Cameron Matson
wrote:
Marcus,
Yes it was all coming out of the same uhd_source object. I
think I was able to resolve the issue for now by setting the
"Sync" parameter to "unknown PPS" which I believe is
using the White Rabbit Ethernet based timing synchronization
which we have connected at one of the SFP ports, though I need
to dig in a bit more into the API.
I agree 20 ms is *HUGE*; is it unexpected even without an
external timing source? Should I still be concerned?
Thanks,
Cameron
Actually, this isn't unexpected. For architectural reasons, there
is a timstamp clock for each RF chain in th device--those clocks
need to b synchronized, so a "set_time_next_pps" will take care of
that.
On 11/20/2020 11:49 AM, Rob Kossler wrote:
Hi Cameron,
Yes, this is possible. I'm not too familiar with
gnuradio but in the end you need to use a "timed
start" to the receive streams.
Rob
Hello all,
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?
Thanks
Cameron Matson
Cameron:
Can you share a simple Gnu Radio flow-graph that displays
this behavior? A 20ms offset is *HUGE*. Are all 4 streams
being streamed out
of the same uhd_source object?
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