Field Programmable Gate Arrays (FPGAs) are one of three fundamental types of digital architectures used for communications R&D.
The others are general purpose processors and graphical processing units (GPUs).
This fall, in San Diego, California, there will be an FPGA course sponsored by Open Research Institute. There are 10 spots with amateur communications as the focus of the work.
FPGAs are a primary technology in satellite communications. They’re used in R&D and in deployment. It is difficult to get started with FPGA design for several reasons. The tools have traditionally been proprietary. The companies that make the tools price them for large corporations to buy. Coursework for FPGA design is rare.
This is where iCEBreaker makes a difference.
An iCEBreaker Workshop 10 pack has been made available. They are described at this link https://www.crowdsupply.com/1bitsquared/icebreaker-fpga
I will use this hardware to put on a course for anyone interested in amateur radio satellite and terrestrial development. All course materials will be published.
The first course will be in San Diego. If you’re in the area, please get in touch! MakerPlace and CoLab are the likely sites.
Later workshops could be at places like Symposium, Xenia, or Hamcation. The full course cannot be accomplished in a day, but a workshop could get the basics across and provide a substantial boost to motivated amateur satellite engineering volunteers. Let me know what you think.
Badge report! Brag Tape, Radio Peripheral update, and our ESP32 development board. It’s from hacker boxes and has a TFT display, programmable RGB LEDs, an SD card for storage, up down left right select user interface input, and some circuitry for charging a lithium ion battery. It’s a good platform for building up the executive function code for Phase 4 Ground radios.
What do we have working?
A high resolution display, SD card access, and bluetooth advertising that sends commands to the trans ionospheric badge.
ESP32 development can be done with the Arduino IDE, but this is very limited and hogs memory. For Phase 4 Ground we use the ESP IDF. This means command line, but Visual Studio Code works with some setup. This gives you context colors and build and run functions.
We highly recommend the ESP32 check it out at the links below. Our next report will be about multicast IP SDR work. See you then!
Trans-Ionospheric is a successful fundraiser for our open source amateur radio satellite communications work.
Thank you so much for the support! Buy one here: https://www.ebay.com/itm/123328684692
Phase 4 Ground has had some good results with the RFNoC polyphase filterbank from Theseus Cores. Here’s our update on this week’s work!
Palomar Amateur Radio Club and Open Research Institute Donate $2,449.44 to Amateur Radio on the International Space Station
Palomar Amateur Radio Club (PARC) was founded in February of 1936 and serves the San Diego, CA, USA amateur radio community. PARC hosts monthly membership meetings and hosts several annual events. PARC repeater system serves individuals and groups and provides opportunities for recreation, emergency preparation, and technical experimentation.
Contact [email protected]
Open Research Institute (ORI) is a non-profit research and development organization which provides all of its work to the general public under the principles of Open Source and Open Access to Research.
Contact Michelle Thompson [email protected]
Amateur Radio on the International Space Station (ARISS) lets students worldwide experience the excitement of talking directly with crew members of the International Space Station, inspiring them to pursue interests in careers in science, technology, engineering and math, and engaging them with radio science technology through amateur radio.
Amateur Radio on the International Space Station (ARISS) is a cooperative venture of international amateur radio societies and the space agencies that support the International Space Station (ISS). In the United States, sponsors are the Radio Amateur Satellite Corporation (AMSAT), the American Radio Relay League (ARRL), the International Space Station (ISS) U.S. National Laboratory and National Aeronautics and Space Administration (NASA). The primary goal of ARISS is to promote exploration of science, technology, engineering, and mathematics (STEM) topics by organizing scheduled contacts via amateur radio between crew members aboard the ISS and students in classrooms or public forms. Before and during these radio contacts, students, educators, parents, and communities learn about space, space technologies, and amateur radio.
For more information, see www.ariss.org.
This donation is given to support the Multi-Voltage Power Supply (MVPS). ARISS needs to replace the current aging ISS amateur radio station power supply. ARISS has a fund-raising campaign throughout 2019 to help with the expensive space-rated parts required to finish building the MVPS units.
Kerry Banke N6IZW has been a core volunteer in the effort to design, build, and test the flight, training, and spare models of the MVPS. Inspired by his commitment, expertise, and mentoring throughout this project, individuals organized a fundraiser through the Amateur Radio Satellite Service Facebook group.
Palomar Amateur Radio Club agreed to be the 501(c)(3) of record. Open Research Institute handled logistics, publicity, and secured a corporate match from Qualcomm Incorporated.
The $2,449.44 donation was made to ARISS from PARC on 28 May 2019.
A substantial amount of additional funding is needed to replace the amateur radio power supplies on the ISS. This donation is a small part of a much larger effort to keep amateur radio in space, upgrade and update equipment on the space station, and promote peaceful international cooperation and the unparalleled educational opportunities enabled by ARISS.
Got two minutes? Then we have a Phase 4 Ground video report for you! :+)
Phase 4 Ground and GNU Radio
My daughter Geneva and I had a wonderful time at JAMSAT Symposium in March 2019! There was a wide variety of talks about so many different payloads, a very special banquet dinner, adventures in Kyoto and Osaka, visits to ham radio stores, getting to see a new ICOM radio up close, lots of Pokemon, a Fire Festival, and making so many new friends. We were welcomed and will never forget the hospitality. A big part of Symposium was the GNU Radio Workshop by Imamura-san. It was an honor to share how we on Phase 4 Ground use GNU Radio in our presentation on Sunday morning.
GNU Radio is a digital signal processing framework for software-defined radio. It’s the software that tells the hardware in your radio what to do. We need to be able to quickly and easily set up a software-defined radio to do whatever modulation and coding we want, and GNU Radio Companion can help us do this. GNU Radio Companion is a Graphical User Interface that allows us to drag and drop functions onto a canvas. We click block outputs to connect to block inputs. When we do this, it creates a directed graph that implements radio functions. The signals flow from beginning to end. Each block modifies the signal, as if it was part of a circuit. The flow graph looks something like a block diagram combined with a software flowchart. GNU Radio has software variables. It can adapt to signal conditions and user input.
The workshop was held after the last talk on Sunday. It was several hours of hands-on training. Participants brought their own computers, installed GNU Radio, and created useful radio flow graphs that worked with real hardware. Several experiments were done in order. Imamura-san kept everything organized through a set of projected slides that had clear instructions. Optimizations and customizations were made so that participants could see how they can use GNU Radio to achieve their goals. The hardware included RTL-SDRs and Plutos. Imamura-san also demonstrated a live video transmission from the podium.
GNU Radio comes with a very large number blocks included. When you install GNU Radio, these blocks come for free! The first type of block is a source block. This brings the digital samples, from the radio hardware attached to the computer, into the GNU Radio flow graph. The second type of block is a sink block, which consumes signals. Sink blocks include things like saving a signal to disk, an audio output, oscilloscopes, spectrum analyzers, time sequences, or video. In between the sources and the sinks are all the radio functions that we need to make our radios work. Filters, amplifiers, decoders, demodulators, counters, constellations, costas loops, synchronizers, and more! You can make your own custom blocks or modify an existing block.
If you install GNU Radio using PYBOMBs, then you can add additional blocks from outside GNU Radio very easily. PYBOMBS works on Linux.
One of the most useful GNU Radio Recipes for our community is gr-satellites, by Dr. Daniel Estévez. There are a lot of satellites supported in this module. For an introduction, please see the source code repository here: https://github.com/daniestevez/gr-satellites.
The introduction also covers how to submit telemetry to the projects that have requested this.
Other great open source satellite communications projects include Dan Cajacob’s base station network, Alexandru Csete’s gqrx and gpredict programs, Libre Space Foundation’s SatNOGs (satellite network on the ground) with RTL-SDR and GNU Radio, and PE4WJ Es’Hail2 (QO-100) uplink, beacon tracker and LNB drift correction flowgraphs.
Phase 4 Ground is a broadband digital microwave system for both terrestrial and space use. It complies with both ITAR and EAR open source and public domain carve-outs, so it’s open to participation worldwide. All engineering is published as it’s created. All are welcome to participate.
Phase 4 Ground is best suited for GEO and HEO satellite missions. The uplink is frequency division multiple access. We use a 5GHz uplink. The regenerative repeater payload receives the uplink signals, digitizes them, multiplexes them, and processes them into DVB-S2 and DVB-S2X frames. The downlink is 10GHz. DVB-S2 is Digital Video Broadcasting Satellite 2nd edition. The X stands for extensions down in to Very Low SNR modulation and codings. Very Low SNR is of interest to hams, so we include the extension to the main standard DVB-S2.
We use both pilots and short frame lengths in order to make the receiver implementation as easy as possible. Pilot tones are optional, and there are medium and long frames available in the standard.
There is a recommended order to receive DVB-S2/X frames. The first stage of the demodulator is symbol timing recovery. We have to figure out the best possible time to measure the received signal. We don’t know what the transmitter clock is doing! We will not be coordinated with it. We may even be off a bit in terms of the period of the clocks, or we might have jitter, or we might have drift. We have to analyze the received waveform and synchronize our receiver clock to the transmitter clock that is “hidden” in the received signal. Then, once we are synchronized, we sample that symbol and report the results. Doing this gives us a reliable value for the received symbol. Now that we have a series of received symbols, we have to figure out the start of the frame. This is done in DVB-S2 (and many other protocols) by sending a fixed well-known pattern at the start of every frame. For DVB-S2, this is called a Physical Layer Start of Frame sequence. It’s 26 symbols long. This is what we look for. Once we see it, we know where the start of the frame is! Frame synchronization can be done in several ways. There are two different methods described in the implementation guidelines for DVB-S2/X. One is relatively simple, using shift registers. The other is bit more complex, using state machines. There are advantages to using the state machine method, but it’s more complicated and expensive. The shift registers is simple and cheap, but gives up a bit of performance. This is the constant balance in digital communications. Performance comes at a cost!
Right after frame synchronization, we correct for carrier frequency error. First we do a coarse correction. This can be done with a delay-and-multiply frequency error detector. Then we do a fine correction. This can be done with something like a feed-forward estimation algorithm. Coarse correction is in the MHz, and fine correction is the hundreds of kHz.
Next, we do phase recovery. This is to fix any residual frequency offset from the coarse and fine frequency offsets. Phase 4 Ground will support all the modulation and codings of DVB-S2/X, but we expect lower order modulations to be more heavily used. This means that a pilot-assisted maximum-likelihood (ML) feed-forward estimator will be the most useful. If you compute the average phase of each pilot field, then you can subtract this out and improve the signal. Higher-order modulations will need another feedback loop.
Automatic gain control is next. AGC can be done in many ways. One way to do it depends on the pilot symbols in DVB-S2/X standard. These symbols are sent at regular intervals to provide a known easy-to-receive signal. We use these known pilot symbols in order to determine the amplitude multiplication factor for the rest of the signal. Pilot symbols are optional in the DVB standard, but Phase 4 Ground requires them. When the pilot symbols are on, the AGC is listening. When the pilot symbols are off, the AGC turns off, and the information from the AGC is used.
After AGC, the constellation is decoded. DVB-S2 has a lot of them! There are many techniques to get the bits from the constellations. GNU Radio has a very versatile and powerful constellation block.
Instead of the usual MPEG transport stream (DVB-S2 is for satellite TV, so the content is usually broadcast television signals), we use the more flexible Generic Stream Encapsulation standard from DVB.org. This means we have less overhead and complexity, and can handle any digital traffic that the amateur operator wants to transmit. It’s just a digital pipe.
Phase 4 Ground uses GNU Radio extensively in research and development as well as for archiving and publishing our work. GNU Radio is not just a tool to figure things out, but is also a way to define a reference design for the radio.
Because Phase 4 Ground is not a bent pipe, the payload is more complex. This complexity needs to be fully tested on the ground before risking large digital circuits in space.
All the uplink channels are received with a polyphase filter bank. The current polyphase filter bank implementation in GNU Radio needs some updates in order to achieve the speeds and performance that we want. This is an active area of research and development. There have been three efforts over the past three years by various groups that have attempted to update and improve the existing working polyphase filter bank in GNU Radio.
Ron Economos and Paul Williamson successfully implemented GSE in GNU Radio and in Wireshark. This made it possible to do transport layer testing. Ron Economos is the lead author of the DVB blocks in GNU Radio. Improvements to GSE continue today. The current focus is improving internetworking functions so that large amounts of data can be more easily handled. We intend to use multicast IP as much as possible, and making sure GSE integrates well with multicast IP is important.
The error correction in DVB-S2/X is state of the art. There are not many other error correcting codes that are better than Low Density Parity Check + BCH. This is a concatenated digital code specified by the DVB standard for S2 and T2 transmissions. We have two open source implementations of LDPC decode for DVB-S2/X. The first one is for graphical processing units and was written by Charles Brain. It was demonstrated at 2017 AMSAT-NA Symposium and at several events following. The second open source implementation is in C by Ahmet Inan and can be found here: https://github.com/xdsopl/LDPC
This version has been incorporated into GNU Radio by Ron Economos. This can be found here: https://github.com/drmpeg/gr-dvbs2rx
The next step for LDPC is to implement and publish an open source version for FPGA.
GNU Radio is very important for our voice codec work, uplink modulation experiments, and trying out authentication and authorization schemes. GNU Radio allows us to use a wide variety of off the shelf hardware to achieve things that were not possible only a few short years ago. The GNU Radio community has been welcoming, helpful, supportive, friendly, and a source of continually amazing software-defined radio advancements.
GNU Radio has an annual conference. In 2018, we held a week-long “Block Party” for DVB-S2/X. We had fun, set up multiple demos, explained DVB-S2/X, made the case for open source LDPC, and made progress on DVB-S2 correlates and GSE. Phase 4 Ground made significant progress due to the generous support of the conference organizers and the community.
Learn more about the conference here: https://www.gnuradio.org/grcon/grcon19/
Registration for 2019 is open. The conference will be held September 16-20, 2019 in Huntsville, AL, USA. There is a poster session, proceedings, talks, workshops, contests, and social activities. The theme for 2019 is Space Communications! There are special gifts for space themed content. If you have a GNU Radio project that you want to share, consider making a presentation at or sending a poster to GNU Radio Conference 2019.
One of the proposals coming out of JAMSAT 2019 was localization of GNU Radio Companion for the Japanese language. Work has begun. The first step is to make sure that all Japanese characters can be displayed in GNU Radio Companion. This means going through the codebase and removing anything that prevents Japanese characters from being freely displayed. GNU Radio project leadership is very supportive of the project. We will do our best on this! We will need help reviewing and perfecting the language support in GNU Radio Companion.
The collaboration between Phase 4 Ground and JAMSAT has been absolutely stellar and we all look forward to continued enjoyment and success. Next generation payloads will be more complicated with multiplexing and advanced digital techniques. We all need to be able to work together, internationally. Open source and public domain is the best way. Phase 4 Ground and Open Research Institute are entirely dedicated to making this happen. We will be keeping the momentum and progress going. ORI is proud to be an affiliate member of Open Source Initiative https://opensource.org/
Join the Phase 4 Ground team! Our mailing list can be found at our website https://openresearch.institute/ Write Michelle Thompson [email protected] to join our Slack account. This is where daily engineering discussions take place.
Dear friends and fans of GNU Radio,
GNU Radio Conference celebrates and showcases the substantial and remarkable progress of the world’s best open source digital signal processing framework for software-defined radios. In addition to presenting GNU Radio’s vibrant theoretical and practical presence in academia, industry, the military, and among amateurs and hobbyists, GNU Radio Conference 2019 will have a very special focus.
Summer 2019 marks the 50th anniversary of NASA’s Apollo 11 mission, which landed the first humans on the Moon. GNU Radio Conference selected Huntsville, AL, USA as the site for GNU Radio Conference 2019 in order to highlight and celebrate space exploration, astronomical research, and communication.
Space communications are challenging and mission critical. Research and development from space exploration has had and continues to have far-reaching effect on our communications gear and protocols.
Please join us September 16-20, 2019 at the “Huntsville Marriott at the Space & Rocket Center” hotel for the best technical conference of the year.
Registration and an online and mobile-friendly schedule will be posted at the conference web site:
Call for All!
We invite developers and users from the GNU Radio Community to present your projects, presentations, papers, posters, and problems at GNU Radio Conference 2019. Submit your talks, demos, and code! Please share this Call for All with anyone you think needs to read it.
To submit your content for the conference, visit our dedicated conference submission site at:
If you have questions or need assistance with OpenConf, or have content that doesn’t quite fit and you want to talk it over, please write [email protected]
Topics may include but are not limited to:
Space (including ground stations)*
Digital Signal Processing
*special focus awards given to all accepted work with Space as a topic.
Please visit our booth in the expo area at HamCation in Orlando, Florida 8-10 February 2019.
Thank you to European Space Agency and MyriadRF for giving Open Research Institute the opportunity to get LimeSDR Minis into the hands of some very amazing people doing open source space communications research and development.
ORI and Phase 4 Ground are very proud to present the following international recipients. We commit to supporting, enabling, promoting, and publicizing their work.
Sahana Raghunandan, USA
As part of discussions at the 2018 GNU Radio Conference DVB-S2X Block Party, one of the functionalities of the demodulator that was identified as needing additional review and testing was the frame synchronization and symbol timing recovery loop. The goal of targeting LimeSDR is to modify and test existing GNNU Radio flowgraphs related to this subsystem of the demodulator. In order test this functionality independently, it is assumed that signal captures at the input to the baseband demodulator will be available.
Sahana Raghunandan is a researcher at Virginia Tech and an independent consultant focusing on satellite and terrestrial systems engineering including waveform design & implementation and interference analysis for spectrum management. Her experience includes design and FPGA-based implementation of waveforms for satellite broadband modems and satellite ground systems architecture with emphasis on modeling and simulation of cross layer optimization techniques. She has also worked on platforms and architectures for software and cognitive radio networks. Her research experience also includes design of modules for radar data acquisition, system integration of radar depth sounders and application of synthetic aperture radar techniques for ice sheet tomography.
Jeremy Reeve, New Zealand
Jeremy has been working on VHF and L-band LNA designs. He has been running qucs simulations to look at optimum noise matching and stability circles and the like. His goals are to contribute RF hardware and baseband/FPGA content. He expects to be able to work with his educational institution to create a project that will result in quality open source publications.
Edson W. R. Pereira, Brazil
Edson is an open source advocate and extremely active in amateur radio. He implemented a GUI (SDR-Shell) for Bob McGwier’s and Frank Brickle’s DttSP SDR, has contributed code for Joe Taylor’s WSJT-X, and has been a primary contributor on many other projects.
He is a lead maintainer for the Phase 4 Ground polyphase filter bank repository and is heavily involved with Phil Karn KA9Q’s development effort for multicast IP SDR innovations and implementations.
Matias LU9CBL, Argentina
Matias is active in many areas of open source space communications. He is part of a group working to build a ground station design that supports a wide variety of satellite missions.
He has a SatNOGS ground station that is making rapid progress through the development portal. He is working to build and test antennas to add to this station.
He is active in his club station (LU4AA), which plans to run a station with an azimuth and elevation rotor from Yaesu, 2 crossed Yagis for VHF, and 2 crossed Yagis for UHF. Multiple fixed station will be added for remote control, and the station will be added to the SatNOGS network after it is functional.
Matias is active on SatNOGS forums and has a blog at lu9cbl.blogspot.com.
It is critically important to increase the number of stations and people involved in satellite communications from the southern hemisphere. Matias is deeply committed to publishing, sharing, and supporting others that are working in open source space communications.
David Fannin, USA
David Fannin KK6DF works closely with Phase 4 Ground volunteer David Viera and wrote the code for David Viera’s LMX2594 oscillator and CW beacon project. David Viera demonstrated this system at GNU Radio Conference 2018 to great acclaim.
David Fannin has worked on a number of oscillator and SDR projects, his github account is https://github.com/dfannin, and he is committed to open source development in advanced digital communications.
Open Research Institute and Phase 4 Ground are honored to be given the chance to put advanced software defined radio hardware like the LimeSDR Mini into the hands of active developers across the world. We are ready to help make the most of this very generous donation to open source space communications work.