[amsat-bb] Small Sat SDR Paper + Outernet + BY70-1
skristof at etczone.com
skristof at etczone.com
Mon Jan 16 20:26:01 UTC 2017
I sure hope we never have to know any of this to talk on a satellite. If
so, my Arrow antenna becomes a multi-hot dog skewer.
On 2017-01-16 15:01, John Toscano wrote:
> I found the paper on CPU & FPGA performance in satellite communications to
> be very interesting, and mostly very well-done. However there seemed to be
> some obvious places in the paper where the authors could have better
> conveyed their findings.
> 1. Throughout the paper, they never identify the x86 processor that was
> present in their Dell Optiplex 745 computer. Several different Intel x86
> processors have been used in that machine, including Pentium D and Core 2
> Duo processors. I presume it was the latter.
> 2. Figures 8, 10, and 11 would have been much improved if they showed a
> fourth data series, namely the Cortex A9 CPU % Consumption (Figures 8, 10)
> and Success Rate (Figure 11) when assisted by moving critical code to the
> FPGA from the GPP.
> 3. I find Table VII mostly impossible to understand. In the first two
> columns, I don't understand what the percentage numbers are referring to.
> And the tabulated items under Post Implementation are not defined, and seem
> to be a mix of physical circuits in the FPGA (such as Flip Flops) and
> software subroutines (DSP48). It is poor practice to use descriptors such
> as "LUT", "MemoryLUT", "BRAM", "DSP48", "BUFG", and "MMCM" which are never
> defined in the paper. Without knowing what a "MMCM" is, I can barely
> appreciate that it stayed at 50% (half of what, I am uncertain) before and
> after FPGA implementation of critical software routines, giving an Overhead
> of 0% (no change). And the pictures of "Implementation on FPGA Fabric" are
> meaningless without any explanation of what they are and what they mean.
> The only thing I can offer as assistance in interpreting this table is to
> remind the reader that the dual Cortex A9 CPUs of the Zedboard are actually
> implemented using a portion of the FPGA. Therefore a pure GPP software
> implementation still uses some of the FPGA. What fraction of the FPGA
> capacity is consumed by the dual A9 implementation? What fraction of the
> FPGA capacity is consumed by the A9 implementation plus the software SDR
> implementation? What fraction of the FPGA capacity is consumed by the A9 +
> software SDR + FPGA implementation of the SDR? I can't figure this out from
> the paper.
> 4. The purpose of the paper, to show the improvement in functionality of
> an SDR by moving critical functions from GPP to FPGA, was accomplished in
> that it was shown that the FPGA implementation could receive more satellite
> signals concurrently at low data rates. But it appears that neither a
> dual-core A9, dual-core A9 + FPGA, nor a quad-core A15 + quad-core A7 could
> keep up with a lowly Intel Core 2 Duo processor. It seems that a ground
> station with a built-in SDR processor would do best with a modern x86
> processor rather than any of the ARM processors available at the present
> time. Given the higher power consumption of fast x86 processors than fast
> ARM processors, it may be best to handle the SDR functions in a desktop PC
> or at least in a high-end laptop PC, instead of embedding an ARM processor
> inside the ground terminal.
> Anyway, that's my take on the paper. I congratulate the authors and
> acknowledge their hard work. I sincerely hope that they continue their
> efforts in this field. Maybe we should personally invite them to join the
> team working on the AMSAT Ground Terminal for future digital satellites
> using the "5 and Dime" frequencies (5 GHz up and 10 GHz down).
> John Toscano, W0JT/5
> AMSAT LM
> On Thu, Jan 12, 2017 at 2:49 PM, M5AKA via AMSAT-BB <amsat-bb at amsat.org>
>> Mamatha R. Maheshwarappa 2E0CZO has released her paper "Improvements in
>> CPU & FPGA Performance for Small Satellite SDR Applications"
>> BY70-1 FM transponder contact video
>> Chertsey Radio Club article - Getting started with FM satellites http://
>> Video of Daniel Estévez EA4GPZ / M0HXM talk - Reverse Engineering the
>> Outernet - at Chaos Communication Congress #33c3
>> Blog update http://destevez.net/2017/01/updated-format-for-
>> ITF-2 CubeSat 437.525 MHz to deploy from ISS Monday
>> 73 Trevor M5AKA
>> AMSAT-UK http://amsat-uk.org/
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