Manolis Surligas

Equinox: A C++11 platform for realtime SDR applications

Equinox is a block programming platform suitable for SDR applications. It is written in C++11 and targets mainly realtime applications. To accomplish that, it exploits the flowgraph topology trying to optimize the scheduling of the different components and the data exchange between them. Using graph analysis algorithms and based on the available CPU cores, overheads like threading synchronization, as well as data dependencies or memory copies can be reduced.

At the same time, the platform tries to provide such an abstraction so it can easily adapt on the application requirements. To do so, it provides an abstracted scheduling mechanism, that can be easily extended. Currently there are two available schedulers. A simplified one, trying to equally distribute the number of blocks into the available CPU cores and a more sophisticated one, using the spectral graph partitioning algorithm which targets the minimum data dependencies between different CPU cores. Both of them can be used based on a user defined configuration parameter, without altering the flowgraph. For the DSP, Equinox will utilize the liquid-dsp library, abstracted in a visual block programming way.

As block programming platform, it provides a QT5 based GUI (equinox-ui) in order users to be able to develop their application with ease. The UI is responsible for generating the C++ source file and build system, so it can be then compiled and executed.

The code is licensed under the GPLv3 license and is available at the https://gitlab.com/equinox-sdr repository.

So many things happened from the FOSDEM 2017 in the SatNOGS project. The successful deployment and data reception of the UPSat satellite, high power amateur rocket launches and realtime telemetry decoding, automatic decoding of LEO satellite signals from our crowd-sourced network of ground stations are some of the milestones achieved. And all these with the help of Software Defined Radios!

In this talk, we present briefly the UPSat and the High Power Rocketry project and then the version 3 of the SatNOGS project. In the new version we have developed several decoders that operate in realtime during a LEO satellite pass. Combined with the SatNOGS rotator that tries to point as accurate as possible to the satellite trajectory, the decoder searches for transmitted frames. The successfully decoded frames are then uploaded automatically on the SatNOGS database for visualization and further analysis.

Currently, SatNOGS project incorporates decoders for many popular in LEO satellite missions transmission schemes such as AFSK1200, APRS1200, (G)FSK9600, APRS9600, APT, DUV, CW, LRPT using the GNU-Radio toolkit. In addition, decoders for APT and LRPT are producing on the fly the weather images transmitted by the corresponding meteorological satellites. For the most interesting of the available decoders, we present the design and the implementation details among with a live decoding demo from a IQ captured observation.

All of the available decoders are running in realtime on the RPi3 platform. To achieve this, several design decisions were made (RF performance vs realtime operation) and we discuss some of them.

This talk was moved backward one hour from its original timeslot (15:45).

SatNOGS: An SDR-based Satellite Networked Open Ground Station