Tagged: gnu radio

Solving a Frequency Hopping CTF Challenge with Aliasing

At this years BSides Ottawa security conference, Clayton Smith was tasked with setting up a wireless "Capture the Flag" (CTF) competition. CTF competitions generally consist of a mystery signal that participants need to figure out how to decode with an SDR such as an RTL-SDR. 

One CTF that Clayton set up was a frequency hopping challenge with several levels of difficulty. The signal consisted of a narrow band FM signal that constantly hopped between multiple fixed frequencies. The idea was to use whatever means possible to piece together that signal again so that the speech audio could be copied.

The first level had the audio signal hopping very slowly, so the speech could be pieced together manually by listening by ear to each channel it transmitted on. Subsequent levels had the signal hopping much faster, so they required some DSP work to piece everything back together.

In his post Clayton writes about three possible GNU Radio based DSP solutions to the problem. The first method he describes is an interesting method that abuses the effects of aliasing. Aliasing is a problem in SDRs when a signal can be folded on top of another, creating interference. However, this approach makes use of aliasing to purposely fold the hopping channels into one frequency, resulting in speech that can be copied.

The rest of his post explains two other methods that could be used as well. The second method involves treating the entire band consisting of the hopping signals as a single FM signal, then filtering it with a DC block. The third approach uses FFT to detect which channel is active with the highest power, then shifting that channel by it's offset.

Spectrum of the frequency hopping CTF challenge.
Spectrum of the frequency hopping CTF challenge.

Clayton also set up another CTF with gr-paint. The idea was to read text on a "painted" waterfall with ever decreasing text spacing that would eventually be too small to read on standard SDR programs like GQRX. Instead, the solution was to open the IQ data in a tool like Inspectrum or Baudline which has much higher FFT resolution. 

Gr-Painted spectrum with decreasing text.
Gr-Painted spectrum with decreasing text spacing.

Preview: GNU Radio 3.8 Running on an Un-Rooted Android Smartphone

Over on Twitter and YouTube Bastian Bloessl (@bastibl) have been posting teaser shots and videos of GNU Radio 3.8 running on an un-rooted Android device. Unfortunately there doesn't yet seem to be any word yet on how he's been able to do this, but we guess  that the details will all be released in due time, possibly on his blog.

GNU Radio is an open source digital signal processing (DSP) toolkit which is often used in cutting edge radio applications and research, and to implement decoders, demodulators and various other SDR algorithms.

GNU Radio 3.8 on un-rooted Android receiving FM w/ HackRF (take 2)

GNU Radio Conference 2019 Videos now up on YouTube

GNU Radio Conference 2019 (GRCon19) was a conference about GNU Radio and projects based on GNU Radio that was held back in September 2019. GNU Radio is an open source digital signal processing (DSP) toolkit which is often used in cutting edge radio applications and research, and to implement decoders, demodulators and various other SDR algorithms. 

Yesterday videos from all the GRCon19 talks were uploaded to YouTube. The talks consists of many high level and cutting edge SDR topics. All talks can be found on their GRCon19 YouTube playlist, and matching slides on the GRCon19 website presentations page.

A list of the talk titles is pasted below.

  • Huntsville's Connection to Space
  • GNU Radio Project Update
  • Mega Hertz, Mega Samples, Mega bits, Mega Confusing
  • Man or Machine?: Developing a Turing Test for Radio Intelligence
  • UHD Four-O
  • Striving for SDR Performance Portability in the Era of Heterogeneous SoCs
  • Fixing the E310 Bottleneck: Implementing a High-Rate Heterogeneous FPGA DMA 
  • Determining Optimized Radio settings for specific waveforms
  • Software Defined Everything
  • GNU Radio Beyond 3.8 - A Technical Outlook
  • GNU Radio Enhancements for Space-Based Research
  • A decade of gr-specest -- Free Spectral Estimation!
  • Open Source Licensing
  • Spectrum Monitoring Network: Tradeoffs, Results, and Future Directions
  • The Future of Digital RFICs
  • Phase Synchronization Techniques
  • Synchronization: Core Concepts and Applications
  • AI and SDR: Software Meets Hardware Again...
  • Building a radio with M2K and spare parts
  • How we talked from the Moon: the Apollo communication system
  • gr-satellites: a collection of decoders for Amateur satellites
  • gr-iio: Nuances, Hidden Features, and New Stuff
  • Open Sourcing the Search for Extraterrestrial Intelligence
  • Multi-Vehicle Map Fusion Using GNU Radio
  • SigMF.
  • GPUDirect + SDR: How to Move One Billion Samples per Second over PCIe
  • Multichannel phase coherent transceiver system with GNU Radio interface
  • Exponent: Arbitrary Bandwidth Receiver Architecture
  • UHD Streaming with DPDK: Raising the Throughput Ceiling with Drivers in User Space
  • USRP based X-band Digital Beam Forming Synthetic Aperture Imaging Radar
  • The GNU Radio PDU Utilities
  • MetaSat: Metadata for Good
  • Enabling Precise Timing Control in SDRs
  • Managing Latency in Continuous GNU Radio Flowgraphs
  • VLBI with GNU Radio and White Rabbit
  • Performance Evaluation of MIMO Techniques With an SDR-Based Prototype
  • UAS Community Testbed Architecture for Advanced Wireless Research with Open-Source SDRs
  • Demonstration of GNU Radio Compatibility with a NASA Space Communications
  • Network Modem (GRCON2019)
  • Prototyping LTE-WiFi Interworking on a Single SDR Platform
GNU Radio Conference 2019
GNU Radio Conference 2019

An Easy Windows GNU Radio Setup Guide and Video for the SDRplay

SDRplay have recently posted a new workflow document and video that shows how to easily set up GNU Radio on Windows with an SDRplay software defined radio. They write:

GNU radio is a popular environment for teachers and developers involved in Digital Signal Processing and exploring new radio architectures. For receiver applications, the low cost dongle is a popular hardware choice, but if you need reliable, clean, continuous radio signal reception from 1kHz to 2 GHz (without the need for block converters or external filters) then an SDRplay RSP is a useful alternative.

With help from the GNU radio foundation, SDRplay has now made available a workflow for windows for all its RSP radios: www.sdrplay.com/docs/gr-sdrplay-workflow.pdf

Special thanks goes to Frank Werner-Krippendorf (HB9FXQ) who did the original SDRplay source block development, and to Geof Nieboer who has developed the Powershell scripts which enable operation on Windows.

GNU Radio workflow for SDRplay and Windows

Podcasts: GNU Radio with Ben Hilburn + New Signals and Bits Episodes

The Scanner School Podcast has recently released a new episode featuring an interview with Ben Hilburn, President of the GNU Radio project. If you want to understand what GNU Radio is, and what role it plays in the SDR/radio world, then this is a good listen.

Ben Hilburn is the project lead for GNU Radio, the free and open software radio ecosystem.

GNU Radio works best in an Linux environment and can also run on the ever popular Raspberry PI.

Ben and I discuss what GNU Radio is, how people are using GNU Radio, and how easy it is to get started with this amazing piece of free software.

If you are looking to learn how the hardware inside of a radio makes it work, or maybe you already do…. GNU radio is a great resource for you

Ben himself has a new podcast of his own titled "Signals & Bits" and there are a number of episodes already out, including an interview with SignalsEverywhere YouTube channel host Harold Giddings, Manuel Uhm Director of Marketing at Xilinx who talks about SDR designs on FPGA chips, and most recently Daina Bouquin who talks about her project called "The Space Library" that is in collaboration with the LibreSpace Foundation.

Talks from GNU Radio Days 2019

GNU Radio Days 2019 was a workshop held back in June. Within the last week recordings of the talks have been uploaded to YouTube by the Software Defined Radio Academy channel. The talks cover a wide range of cutting edge SDR research topics and projects. Many of the presenters have also made use of RTL-SDR dongles, as well as other higher end SDRs in their research.

All the talks are combined into two 3 hour long videos from the morning and day sessions from day one. Day two also has two videos that consist of recordings from the tutorial sessions which make use of the PlutoSDR. Finally there is also the keynote speech from Marcus Müller where he dives into the internal workings of GNU Radio.

Below we list the talks with timestamps for the YouTube video. Short text abstracts for each of the talks can also be found in the conference book. We note that not all the abstracts appear to have been presented in the videos, so it may be worth checking out the book for missed talks about passive radar, a 60 GHz link, embedded GNU Radio on a PlutoSDR, an SDR 802.11 infrared transmission system, PHY-MAC layer prototyping in dense IoT networks and hacking the DSMx Drone RC protocol.

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GNU Radio Released – First Minor Release Version in Six Years

GNU Radio is an open source digital signal processing (DSP) toolkit which is often used to implement decoders, demodulators and various other SDR algorithms. Several SDR programs are based on GNU Radio code, and it is responsible for a lot of DSP development and knowledge within the SDR and radio community. It is compatible with almost all SDR devices, including the RTL-SDR.

Recently GNU Radio has been updated to version The release is classed as the first "minor" release version in six years, as they are going from version 3.7 to 3.8. That doesn't mean there have been no changes for six years, it just means that over the last six years all releases have remained within the 3.7 version and they have mostly been bug fixes rather than larger changes like added features. Behind the scenes over the last six years developers have been working on these larger changes, and now is the time that they have been officially released.

Marcus Müller from GNU Radio writes:

Witness me!

Tonight, we release GNU Radio

It’s the first minor release version since more than six years, not without pride this community stands to face the brightest future SDR on general purpose hardware ever had.

Since we’ve not been documenting changes in the shape of a Changelog for the whole of the development that happened since GNU Radio 3.7.0, I’m afraid that these release notes will be more of a GLTL;DR (git log too long; didn’t read) than a detailed account of what has changed.

What has not changed is the fact that GNU Radio is centered around a very simple truth:

Let the developers hack on DSP. Software interfaces are for humans, not the other way around.

And so, compared to the later 3.7 releases, nothing has fundamentally modified the way one develops signal processing systems with GNU Radio: You write blocks, and you combine blocks to be part of a larger signal processing flow graph.

With that as a success story, we of course have faced quite a bit of change in the systems we use to develop and in the people that develop GNU Radio. This has lead to several changes that weren’t compatible with 3.7.

The changelog is too long to quote here, but as a summary they have fixed bugs, updated dependencies to newer versions, enabled C++ code generation, changed XML to YAML, moved from QT4 to QT5 and removed a few stale projects. Some of these changes could break compatibility with older GNU Radio tutorials and programs. It also seems that unfortunately due to a lack of updates, support for the Funcube Dongle has been removed.

Signals and Bits A New SDR Podcast by the President of the GNU Radio Project

[Ben Hilburn] the president of the [GNU Radio Project] has recently started a new podcast called [Signals and Bits]. If you were unaware, GNU Radio is the defacto open source framework for implementing digital signal processing code. Without it, many SDR programs that we take for granted may have never been developed as it is responsible for a lot of community DSP knowledge and algorithm development.

This podcast is scheduled for a new release every Wednesday and will be composed in an interview style focusing on a multitude of topics from Software Defined Radio to Spectrum Enforcement, Radio Astronomy and so much more.

In the first episode Ben interviews Harold Giddings AKA Corrosive of [Signals Everywhere] where they discuss the state of Software-Defined radio and how he got started with radio communications having come from an IT/Computer Networking background.

Ben has already pre-recorded several episodes which will ensure great content is always just around the corner. Ben would love it if you could also send feedback his way over on the [Signals and Bits Twitter] page.

Ben Hilburn President of GNU Radio (Left), Harold Giddings AKA Corrosive of Signals Everywhere (Right)