[TangerineSDR] Simulating the Tangerine using Red Pitaya

[Phil Erickson]

Hi Bill,

  I have a couple questions:

a)  Are the dropped frames randomly spaced in time, or are they sequential?
b)  Have you done the phase coherence check yet by feeding in a sine wave
tone?  That would be important.

73
Phil W1PJE

73
Phil W1PJE


On Tue, Jul 23, 2019 at 1:15 PM Engelke, Bill via TangerineSDR <
tangerinesdr at lists.tapr.org> wrote:

> I finally have a simulation which I believe is faithful to the design
> target for the speed of the Tangerine.
>
>
>
> The Red Pitaya (in HPDSDR emulation mode) is able to output 2 (I/Q)
> channels, each at 48 ksps (for a total output of 96 ksps).  To simulate 192
> ksps, in Digital RF we specify 192,000 as sample rate, duplicate the data 8
> times, and save each buffer twice. Data output is 96,000 x (2 data saves) X
> (2 antennas) X (8 bands) X (8 bytes per sample) = 24,576,000 bytes/sec.
> The msec/file is set to 4000; so every 4 seconds, the system outputs a file
> of size 98,311,608 bytes. Since the payload is 98,304,000 bytes, we see
> that Digital RF adds very little overhead.  The compression is set to zero,
> so missing data is not removed (if it occurs); the system will save NaN
> (not a number) in the missed values.
>
>
>
> Speed test results:
>
>
>
> Every buffer save introduces enough delay to make the program miss a few
> buffers (even when saving to ramdisk).  The percentage of missed data is
> quite small; for example, in today’s benchmark, we have the following:
>
>
>
> buffer# sent
>
> buffer# saved
>
> buffers sent
>
> buffers missed
>
> percent lost
>
> success rate
>
> missed data (microseconds)
>
> 5425
>
> 5409
>
> 5425
>
> 16
>
> 0.29%
>
> 99.71%
>
> 12000
>
> 10766
>
> 10757
>
> 5341
>
> 9
>
> 0.17%
>
> 99.83%
>
> 6750
>
> 16107
>
> 16098
>
> 5341
>
> 9
>
> 0.17%
>
> 99.83%
>
> 6750
>
> 21469
>
> 21440
>
> 5362
>
> 29
>
> 0.54%
>
> 99.46%
>
> 21750
>
> 26803
>
> 26801
>
> 5334
>
> 2
>
> 0.04%
>
> 99.96%
>
> 1500
>
> 32151
>
> 32135
>
> 5348
>
> 16
>
> 0.30%
>
> 99.70%
>
> 12000
>
> 37499
>
> 37484
>
> 5348
>
> 15
>
> 0.28%
>
> 99.72%
>
> 11250
>
> Total   à
>
> 37499
>
> 96
>
> 0.26%
>
> 99.74%
>
> 72000
>
>
>
>
>
>
>
> It is interesting to note that, during this test, I started the drf mirror
> utility, which copies the data from ramdisk to spinning disk (I found that
> setting the process priority of drf to -5 [higher than pihpsdr] was
> necessary to get the data save to work.  It was able to keep up with the
> amount of data being moved, so I conclude that this is a workable solution;
> the science users will have to weigh in on whether this amount of data loss
> is acceptable. I’m not sure how to speed this system up any further with
> this hardware.  Attached is source code for the part of pihpsdr which I
> modified to save the Dgitial RF data; if anybody spots any bug, I am
> interested to know,.
>
>
>
>
>
> W. D. Engelke (Bill), Asst. Research Engr. AB4EJ
>
> Center for Advanced Public Safety
>
> Cyber Hall
>
> The University of Alabama
>
> Tuscaloosa, AL 35487
>
> Desk: (205) 348-7244
>
> Mobile: (205) 764-3099
>
>
> --
> TangerineSDR mailing list
> TangerineSDR at lists.tapr.org
> http://lists.tapr.org/mailman/listinfo/tangerinesdr_lists.tapr.org
>


-- 
----
Phil Erickson
phil.erickson at gmail.com
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