GNU Radio

GNU Radio provides signal processing blocks to implement software radios, usable with external RF hardware like USRP devices or in simulation without hardware. It supports wireless communications research and real-world radio systems in hobbyist, academic, and commercial settings. Applications are primarily written in Python, with performance-critical signal processing in C++ utilizing processor floating-point extensions for real-time, high-throughput systems.

The toolkit includes gnuradio-companion, a graphical tool for creating signal flow graphs and generating source code, plus various utilities. While not primarily a simulation tool, it supports algorithm development using pre-recorded or generated data. GNU Radio enables rapid application development in a simple environment, with libraries for analog, digital, audio, channels, FEC, FFT, filters, network, and more specialized functions like DTV, trellis, vocoder, and wavelet processing.

Key components include support for UHD (USRP Hardware Driver), SoapySDR, IIO devices, and ZeroMQ messaging. It offers visualization tools like QT-based GUI sinks and plotting utilities for time series, FFT, PSD, and constellation plots.

GNU Radio operates as a flowgraph-based signal processing framework where blocks (implemented in C++ for performance) are connected via Python or gnuradio-companion GUI to form data flow pipelines. Signals flow between blocks asynchronously using a scheduler, with Python handling high-level orchestration and C++ managing real-time processing paths with SIMD optimizations via VOLK library. Hardware interfaces like UHD connect to USRP devices for TX/RX, while simulation uses generated sources/sinks. Polymorphic Types (PMT) enable generic data containers for message passing between blocks and threads.