GNU Radio release 3.7.0 is available for download:
This is a major new release of GNU Radio, culminating a year and a half
of side-by-side development with the new features added to the GNU Radio
3.6 API. With the significant restructuring that was occurring as part
of the 3.7 development, at times this seemed like rebuilding a race car
engine while still driving it.
All the appropriate bug fixes applied in the 3.6.0 - 22.214.171.124 series of
releases were incorporated into 3.7.0 and are not re-listed here.
Otherwise, this release has all the features added to 3.6 and the new
ones listed below that could only be done in the 3.7 API.
The GNU Radio SDR framework/runtime gained many new capabilities in 3.6,
and our project focus now during the 3.7 development series will be to
use these new capabilities to improve GNU Radio DSP block libraries and
The detailed release notes follow.
Code Structure Changes (Johnathan Corgan, Tom Rondeau)
The GNU Radio source code was restructured and flattened. All top-level
components now use the same structure for consistency and ease of use.
All blocks were moved out of gnuradio-core, which has been renamed to
gnuradio-runtime. The blocks are now in their appropriate top-level
components and reimplemented with the new 3.7 API style. The new API
makes use of C++ namespaces and the virtual private implementation class
pattern to better hide GNU Radio internals from user code.
Details about this can be found here:
A Google doc showing all items that were moved from one place to another
in the new style is here:
Blocks not listed were already in their own components. Many blocks were
removed. All columns marked with ‘-----’ means that column is not
applicable to that block or class. Any column (except those marked as
Remove) that are blank means that we might be able to improve upon it,
which normally indicates using VOLK or improving documentation.
A Google doc showing the new component and Doxygen categories for all
components is here:
Important new features:
ControlPort (Tom Rondeau, Tim O’Shea)
ControlPort is a new interface for standardizing remote procedure calls
in GNU Radio:
* Remote control and visualization.
* Use of ControlPort to debug without requiring extra debug streams.
* Abstracted interface, but currently using ICE (www.zeroc.com).
* No additional CPU usage while no monitoring is occurring.
* Can connect multiple remotes to same GNU Radio application.
* Can also have single ControlPort app control multiple GR apps.
Each block creates interfaces to control data members, by defining
and ‘set’ interface to query and update values of block variables.
Preference files control the state of ControlPort in section
[ControlPort] of gnuradio-runtime.conf.
ControlPort comes with a generic utility to allow you to see all
interfaces of a flowgraph:
* gr-ctrlport-monitor -p
Within a flowgraph, one can also use ControlPort probes to pass vectors
of data to a ControlPort client, including complex IQ data. One useful
probe calculates the power spectral density of a block output for remote
See the ControlPort page in the GNU Radio manual for more information:
Performance Measurement Tools
Performance Counters were first built into GNU Radio in 3.6.5, but could
only be accessed locally. Now, all Performance Counters can be exported
Performance Counters must be compiled into GNU Radio using
-DENABLE_PERFORMANCE_COUNTERS=True. They can be toggled on/off at
runtime using the [PerfCounters] section in gnuradio-runtime.conf. Use
option ‘export’ to export Performance Counters over ControlPort.
We now include a new tool to visualize the Performance Counters over
ControlPort. This is installed as gr-perf-monitorx and requires the
Python modules Scipy, NetworkX, and Matplotlib. Nodes of the flowgraph
are represented as blue squares. The size of the square is proportional
to the amount of time spent in the work function (either thread time or
monotonic (wall clock) time). The size and depth of the shade of red of
the edges is proportional to how full the block’s output buffer is.
QTGUI Enhancements (Tom Rondeau, Nick Foster, Ben Reynwar)
The QTGUI widgets defined in gr-qtgui have had a major overhaul in 3.7.
All plots are now split out into individual components, including:
* Time plots (amplitude versus time)
* FFT plots (or PSD) (log magnitude versus frequency)
* Waterfall plots (or spectrograms) (time versus frequency with
magnitude as the color intensity)
* Constellation plots (imaginary (quadrature) versus real (inphase))
* Time raster plots (time vs. time)
Each plot can accept multiple connections that will overlay the signals
on them. Zooming and unzooming are the same using the left and right
mouse buttons. The center mouse button will pull up a context menu to
allow manipulations of all kinds of properties of the display, such as
line and marker styles, the size of the FFT, averaging, line
transparency, etc. Significant work has gone into improving the
performance, including the use of VOLK and more intelligent ways of
handling the display to reduce the computational load.
QT defined QT Style Sheets (QSS) that allow us to specify looks, colors,
and other properties of a display. Support for the use of QSS has been
added to gr-qtgui to make establishing your preferences easier.
gr-qtgui/examples contains a number of examples showing how to use each
type of plot and the QSS definition and interface.
Uninstalled imports (Ben Reynwar)
The GNU Radio source tree was updated to allow us to directly import all
GNU Radio components in-tree before install but using the same syntax.
This change greatly reduces problems and complexity of writing Python
code for use in both normal installations and QA code. This change will
also allow us to automatically build the Sphinx Python manual during
Updated gr_filter_design (Sreeraj Rajendran)
Overhauled the current gr_filter_design to add better visualization and
interactive tools. Installed as part of the gr-filter component now, the
gr_filter_design tool adds many new features for visualizing filters as
well as support for IIR filter tap design. The new tool also includes a
programmatic API that allows a user to launch the filter design tool
inline in a program, design the new filter, and pass back an object
containing the filter taps and parameters. Passing a callback function
allows the designer to run in a separate thread and every time a new
filter is designed, the callback function can be triggered to update a
Examples of using the programmatic access to gr_filter_design can be
found in gr-filter/examples/gr_filtdes_*.
Other New Components and Features
New blocks added:
* gr::analog::fast_noise_source - pre-generates a table of random
samples from the selected PDF and randomly samples from them. This has
somewhat less entropy than the normal noise_source block but is
* gr::analog::agc3_*: Performs an initial linear gain ramp to quickly
converge on a signal during startup and then falls back to an iterative
loop similar to agc2.
* The agc, agc2, and agc3 blocks have been made to use a unified
interface that now includes a default maximum gain value (set to 2^16 so
that it can scale up even the LSB of a USRP’s device).
New gr-fec component
This new top-level component mainly functions as a placeholder for new
FEC block implementations. Currently contains only a couple of
purpose-built FEC blocks.
New gr-channels component (Tim O'Shea)
This new top-level component holds current and future channel model
blocks. The standard AWGN channel_model has moved here. In addition,
there are two new channel models:
* fading_model - Uses configurable max Doppler shift, Rician power
factor, and lists of the delays (in samples) and magnitudes of a power
* selective_fading model - Basic fading model that can have a number of
sinusoids, max Doppler shift, and Rician power factor defined for it.
volk_modtool (Nick McCarthy)
This new tool allows the creation of out-of-tree VOLK libraries. These
allow developers or organizations to develop a set of VOLK kernels for
internal use apart from the main libvolk provided by GNU Radio.
GnuradioConfig.cmake (Tom Rondeau, Tim O’Shea)
New GnuradioConfig.cmake and GnuradioConfigVersion.cmake cmake files are
installed into the system under $prefix/lib/cmake/gnuradio. These files
can be used by any other project to easily test if any GNU Radio
components are installed and the minimum API-compatible version required.
Set GR_REQUIRED_MODULES to any of the top-level components in GNU Radio
in all caps. Then use find_package(Gnuradio) to search for them. The
second optional argument is the API compatible version is was built
against. For example, to test if gnuradio-runtime, gnuradio-blocks, and
gnuradio-filter are installed, we would use:
set(GR_REQUIRED_MODULES RUNTIME BLOCKS FILTER)
Additional Fixes (Ben Reynwar, Tom Rondeau, Josh Blum, Nicholas Corgan)
* Added symbol output stream from constellation_receiver so we can see
the locked constellation as well as the output bits.
* Introduced a new pfb_arb_resampler kernel class that can be used by
other blocks. We have used this to significantly simplify the
* All PFB code has new QA and fixed a few minor bugs in the calculation
of some of the filters.
* Added more QAM support with Gray coding.
* Reworked VOLK. All kernels are now in volk/kernels/volk, made all
kernels consistent in use of num_points, and redid any kernels that used
* Removed assumptions that were Linux-only to continue to support native
Obsoleted and/or removed functionality
The following components have been removed or redone:
* gr-shd (removed)
* gruel (removed; all functionality now in gnuradio-runtime)
* gr-howto-write-a-block (functionality replaced by gr_modtool)
For more removed items, see:
These are items that are currently part of GNU Radio, but are planned to
be removed in the next API release (3.8).
* gr-noaa - will be reimplemented as a stand-alone, out-of-tree project
and supported with PyBOMBS
* gr-pager - will be reimplemented as a stand-alone, out-of-tree project
and supported with PyBOMBS
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