Open Source Low Density Parity Check Decoder for DVB-S2, DVB-S2X, DVB-T2 Working in GNU Radio

An open source Low Density Parity Check decode from Phase 4 Ground is working for DVB-S2, DVB-S2X, and DVB-T2 in GNU Radio, thanks to the efforts of Ahmet Inan, Ron Economos, and Charles Brain.

This is a big step forward for open source satellite communications.

Video report here:
https://youtu.be/fOYVOgybFKY

Out of Tree (OOT) GNU Radio module by Dr. MPEG here:
https://github.com/drmpeg/gr-dvbldpc

Decoder by Ahmet here:
https://github.com/xdsopl/LDPC

3D Printed Cassegrain Antenna Structures at 122GHz Demonstrated at Microwave Update 2018

Here’s a demonstration of a 3D printed Cassegrain antenna system for 122GHz amateur radio. It was presented in the demonstration room at Microwave Update 2018.

https://youtu.be/NbTWWNvtvOU

122 GHz is an amateur radio band. There’s activity and distance records and some contesting. 122GHz has significant attenuation due to atmospheric absorption. Specifically, oxygen gets in the way.

I’ve been working on a 3D printed rig for 122GHz. This was sparked by a request from Alan Devlin VK3XPD for a 3D printed subreflector for a Cassegrain dish. People generally get by with a flat subreflector, but you can get better performance if it’s a hyperbolic curve matched to the feed and parabolic dish.

So what is 122GHz good for? Well, car radar for one thing. That’s what Silicon Radar does. They’re a company in Germany, and they have a radar development board and Millimeter Wave Integrated Circuits (MMICs) for 122GHz. The patch antennas are actually on the chip. The dev boards were used in this experiment. They send out a wide chirped radar signal and measure the return. There is software provided by Silicon Radar that runs the dev board.

The goal for Microwave Update 2018 was to verify a 3D printed Cassegrain antenna design for 122GHz amateur use. This design was adapted from the Customizable Cassegrain dish by drxenocide on Thingiverse. Link is in the show notes.https://www.thingiverse.com/thing:1935824

This thing creates a customizable Cassegrain Reflector dish. It was created using the equations from the paper by Peter Hannan, “Microwave antennas derived from the Cassegrain telescope,” in IRE Transactions on Antennas and Propagation, vol. 9, no. 2, pp. 140-153, March 1961.

The antenna parts were designed, the 3d model specified, the parts were printed, the resulting pieces were metallized (with MG Chemicals conductive paint), and then the parts combined into their final form.

Design files and papers can be found here: https://github.com/Abraxas3d/122GHz

The assemblies were taken to Microwave Update 2018 and set up in the demonstration room. Here’s what happened next.

So what were the results? Here’s some screenshots from the Silicon Radar software with and without the Cassegrain antenna installed over the stock lens in the development board.

And, there’s more. Please read Mike Levelle’s wonderful report on his efforts with the Silicon Radar chip in building a simple 122GHz transceiver. Link is in the show notes.

Mike has a tremendous amount of expertise and enthusiasm for the higher microwave bands and is a fantastic mentor.

http://www.bay-net.org/docs/k6ml-122GHzradio-baycon2018.pdf

What’s next? Building a radio! Stay tuned and stay on the air!

http://microwaveupdate.org/

Open Research Institute – Open Source CubeSat Workshop 2018 Madrid, Spain

Bruce Perens was the keynote speaker at the Open Source CubeSat Workshop 2018 in Madrid, Spain.

Michelle Thompson presented a technical update on Phase 4 Ground activities and described recent progress with DVB-S2X receivers in GNU Radio.

Held at the European Space Astronomy Center in late September 2018, the conference drew 122 diverse and enthusiastic participants from 22 countries. Two days of presentations and workgroups resulted in a remarkable amount of progress and sharing in support of open source spacecraft and ground stations.

Below are links to notes from the four working groups in which Phase 4 Ground volunteers participated.

Open Source Satellites – Improving the Starting Point
SatNOGS Report and Discussion
Libre Cube Standard, Community Development
Hugh’s Blog Post

Links to video recordings of presentations will be released soon.

Open Research Institute at DEFCON 26

Amateur Radio and open source Amateur Satellite activities at this past week’s DEFCON were very successful.

Multiple talks across the somewhat daunting schedule provided plenty of opportunities to hear about amateur radio, open source satellites, modulation and coding, and ground station work. Phase 4 Ground had an opportunity to present at Cyberspectrum, and then helped host a Q&A the following day.

Open Research Institute had a booth in the WiFi Village Friday-Sunday. Services provided were the DEFCON ham radio license exam information/encouragement, SatNOGS information/handouts/stickers, Libre Space Foundation information/handouts/stickers, GNU Radio demonstrations and quick tutorials, FaradayRF information/handouts, SDR demonstrations, Trans-Ionospheric badges, Phase 4 Ground updates/recruitment/promotion, and more.

The landscape of amateur radio in space is diverse, interesting, and active. The audience at DEFCON is enthusiastic, positive, technical, and generally unafraid to build things and try stuff.

The Amateur Radio Relay League (ARRL) was there this year, and they are thinking about coming to GNU Radio Conference as well.

We met several university researchers and put them in touch with the right support networks to get their cubesats “off the ground”.

It’s hard work to be part of a event as large, loud, and busy as DEFCON. The attendance was estimated at 27,500 by Sunday. However, it’s very much worth it! It was great to meet so many people in person for the first time that we’ve gotten to know through electronic means.

We are solidly in the black on Trans-Ionospheric badge sales and are well on our way to funding the development board for Phase 4 Ground radios. Support and information here: http://openresearch.institute/badge/

We’ll be selling them online shortly. All proceeds go directly to support the non-profit ORI, and specifically for Phase 4 Ground project.

Next up: finding out how to improve representation for amateur radio on interplanetary missions from NASA. We’ll be at the Interplanetary Cubesat Workshop this week at Goddard Space Flight Center. We’ll have a poster session on open source satellite and ground station work, specifically allowed under ITAR 120.11.

Thank you to everyone that helped make this trip rewarding and fun with the encouragement, support, and materials.

DVB-S2/X Block Party at GNU Radio Conference

Hello everyone,
GNU Radio Conference is coming up in September. If you haven’t registered and want to go, please do at https://www.gnuradio.org/grcon-2018/
There’s a special event this year called Block Party.
It’s an effort to get DVB-S2 and DVB-S2X receivers in GNU Radio.
We will have our own room and tables and swag. We will have docents enthusiasm and test equipment. We’re looking for more! We’ll have documentation and refreshments.
We need blocks!
Most blocks needed for DVB-S2/X receive do, in some form, already exist. Some do not. Some just need additional modulation and codings added to them.
Receiver design is hard, but breaking it up into small blocks makes it tractable.
The DVB protocol documents are all open. There are implementation guidelines. See https://www.dvb.org/
There are several community members that are experts in this area. There is a team (Phase 4 Ground – find out more at https://phase4ground.github.io/) that needs DVB-S2/X to work in GNU Radio. There is a lot of interest from a variety of other groups including Libre Space, ARRL, AMSAT, and TAPR.
If you are able to contribute to this effort, I want to know about it! I am here to support it. I’d like nothing better than to complete the Block Party at GNU Radio Conference with working, tested, documented blocks for a DVB-S2/X receiver. This contribution makes our open source terrestrial and space radio designs for Phase 4 Ground possible, and also opens up a lot of other work.
The thing that is considered the hardest part is the LDPC FEC decode. We have an open source implementation that targets GPUs. We want to take this and get it into RFNoC. If you are working on this as well, we want to collaborate and support and combine and promote.
The GPU implementation (by Charles Brain G4GUO) of LDPC decode can be found at our repository folder here: https://github.com/phase4ground/DVB-receiver/tree/master/G4GUO-LDPC-on-GPU/DVB-S2XTxRx
Phase 4 Ground is devoted to an open source implementation of DVB-S2 and DVB-S2X for amateur radio terrestrial and space use. We are part of Open Research Institute. Learn more about this non-profit here: https://openresearch.institute/

ORI Fulfills ITAR Requirement

ORI has made its public technical data – all software, schematics, designs, and other information contained at http://openresearch.institute/public/ available for unlimited distribution at the 2018 Cal Poly Cubesat Developers Conference, in compliance with ITAR 121.11(a)(6).

ITAR 121.11 does not explicitly state that making data available on the Internet places that data in the “public domain” (their wording) – although we believe any court would consider this to be so.  Instead, it gives a number of methods including unlimited distribution at a conference, and making the data available at a public library (most of which do provide web access, and thus we believe this requirement is satisfied by internet data).

Notices of the availability of our online data were posted in several locations at the conference and on the conference’s online discussion system. WiFi and cellular data were available at the conference for the attendees to explore or download our information.

“Public domain” information, in the context of ITAR, is information available to the public, rather than the copyright sense of “public domain” which means information for which copyrights have been abandoned. ORI and its volunteers generally retain copyright on their information, but it is placed under an Open Source license which grants a set of rights including use, modification, and redistribution to the general public.

Correlator Troubleshooting

https://youtu.be/T6TwN2FvfAo

 

Here’s an update from the lab on correlator troubleshooting. We are trying to get correlation understood and under control over the air.

We have two flowgraphs that we believe aren’t working due to the Correlation Estimation Issue here https://github.com/gnuradio/gnuradio/issues/1207

We don’t think it’s operator error, but we’re relatively new to GNU Radio, and would welcome any comment or critique that helps to solve this!

FM_ARAP_to_downlink.grc is the flowgraph we are using for transmit side.

What does it do?

It collects up four analog FM channels, digitizes, and transmits a time division multiplexed signal out. This is, in general, a simple model of our uplink for a Groundsat or payload.

We see the expected transmitted signal on a spectrum analyzer and on a HackRF portapack and on the receiving system across the lab.

The receiving flowgraph is called TDM_downlink_rx.grc

What does it do?

It takes the time division multiplex signal and is supposed to break the channels back out.

This demo has worked in the past, but not anymore, and definitely not over the air now.

The problem seems to be the correlator, and it seems to be the same trouble reported in the issue.

We want to write a DVB-S2/X correlator. I think we can also help fix this correlation estimation block. In all cases, we want to comply with the tag scheme produced, so that downstream blocks already in GNU Radio get what they’re expecting, if they are expecting these types of tags.

Plenty more at https://github.com/phase4ground

Paid Ground-Station Control Operators and Amateur Satellites

Paid personnel are not allowed to be control operator or license grantee of Amateur Satellites. In the United States, this means that a paid employee of the sponsoring organization of the satellite, for example a professor at the university that has built the satellite, can not be a control operator or the license grantee.

I recently corresponded with our IARU Divison 2 representatives regarding this issue. Thanks to Edson W. R. Pereira PY2SDR and Ray Soifer W2RS for this information:

The issue regarding paid operators is due to the definition of the amateur radio service as defined by the ITU.

ARTICLE 1 Terms and definitions

  • No. 1.56 amateur service: A radiocommunication service for the purpose of self-training, intercommunication and technical investigations carried out by amateurs, that is, by duly authorized persons interested in radio technique solely with a personal aim and without pecuniary interest.
  • No. 1.57 amateur-satellite service: A radiocommunication service using space stations on earth satellites for the same purposes as those of the amateur service.
  • No. 1.96 amateur station: A station in the amateur service.

The same definition is used by the FCC: https://www.fcc.gov/wireless/bureau-divisions/mobility-division/amateur-radio-service

The key point here is the term “pecuniary interest” — in otther words, “without financial compensation”. The definition is related to the *operation* of an amateur radio station, as you have stated in your message. Persons, including amateur radio operators, could be financially compensated to design and build amateur satellites, but according to the regulations, as they are presently written, the person cannot be compensated to operate the station.

 If the station will operate under a US FCC amateur license, the control operator may not be an employee of the sponsoring organization, whether or not he is being directly compensated for operating the station.  The license grantee is also deemed to be the operator of the space station operating under his license.
For those reasons, FCC licenses most Cubesats as experimental, not amateur.  Experimental licenses do permit operators to be compensated.  However, experimental stations may not communicate with amateur stations.