GNU Radio overview and evaluation

Notes and URLS

Jon Jacky, May 2005

To be evaluated

Shall we use GNU Radio as the framework for ---

These are two separate issues.

Neither application is in the intended domain, but will probably work anyway.

I'm leaning toward yes and yes, but there could still be show-stoppers.


Excellent pedigree: MIT EE/CS mid-late 1990's

  1. VuSystem multimedia
  2. SpectrumWare/PSpectra software radio

JSAC 96 and JSAC 98 papers from these projects provide nice description of motivation and architecture.

Two spinoffs, one commercial, one open source

  1. Vanu, Inc.
  2. GNU Radio

Both apparently thriving now.

This technology has been shown to work well in its intended domain.


Active, technically savvy user community --- dozens build hardware, write code

Hobbyists and individuals, also university research groups and government labs.

High traffic mailing list with high SNR

One developer (Eric Blossom) currently manages core system, project direction ---
but system appears sufficiently mature and robust to survive regardless.

Platform, software

Core software developed on PC with Linux, GNU tools

Much of the software has been ported to BSD, Windows, Mac OS X by other developers (all using GNU tools)

Complex, fragile development environment is a serious barrier to casual use. Must obtain, install, configure many prerequisites.

Many users write software which is not part of core, no systematic distribution (Sourceforge, email, author's web site, etc.)


A few commercial PCI ADC, DAC supported (most quite expensive)

A few users have supported custom hardware (one-of-a-kind)

USRP: Universal Software Radio Peripheral


Signal flow graph composed of signal processing blocks connected by wires

One-way flow from signal source (ADC) to sink (DAC, scope, ...)

No loops among blocks --- feedback must be modeled within a block
Any other restrictions? Not yet clear.

Wires can carry many data types, including vectors (spin simulation!)

Blocks can have multiple inputs, outputs

Blocks can run at different sample rates (decimation, interpolation)

Hierarchical blocks planned, not yet supported

Scheduling and buffering among blocks is complex and obscure.

Flow graph scheduling and buffering

Key issues for our evaluation.

No detailed explanation in GNU Radio documentation. Inferred from MIT papers, mailing list traffic, code reading, observation

Create schedule for blocks by working back from sink to sources

Calculate each block by working forward from sources to sink, guided by schedule

Traverse entire flow graph to calculate each sample at sink (possibly no propagation delay from source to sink)

Calculate with whole buffers (4095 samples typically), not one sample at a time

On wires within the network, time is not represented in any obvious way

Depend on hardware clock to "push" data from source (ADC) and "pull" from sink (DAC).

Much buffering within flow graph. Implies FIFO at input and output. Implies latency through network, but no fixed lower limit on buffer/FIFO size.

Scheduling within flow graph managed by GNU Radio code, not OS

Flow graph computation is all in one OS process/thread. Multithreading has been discussed.

Not clear how GUI scheduling fits in


Three levels:

  1. Signal flow processing (blocks) in C++
  2. Signal flow topology (wires) in Python
  3. GUI in wxPython

Documentation scant but usable

I can work with this. I've already debugged/modified in all three categories.

Status of Mac OS X port

We're doing it

  1. Signal flow processing (blocks) in C++: working well
  2. Signal flow topology (wires) in Python: working well
  3. GUI in wxPython: some is working

wxPython GUI seems fragile, lots of platform sensitivity, unlike the rest

Packaging issues

Pending issues

Short latency (cantilever control)

Concurrency, multiprocessing (spin simulation)

Neither issue is a problem in the intended domain --- we're on our own
(but EB willing to offer advice)

What's next?

Press on!

Finish and distribute port, gain experience, final decision later

Even major changes to scheduling etc. seem easier than starting from scratch


Revised June 2006

GNU Radio home

GNU Radio mailing list, discussion, searchable archive (very useful), also 2006-01/threads.html etc.

GNU Radio Wiki

USRP, GNU Radio hardware

GNU Radio GUI screenshots

GNU Radio installation instructions (Linux) (Mac OS X) (Mac OS X) (Mac OS X) (Windows)

GNU Radio tutorial articles by Eric Blossom, with code samples

GNU Radio tutorials by other users

GNU Radio users' web sites, with code and screenshots of experiments and applications

USRP hardware packaging and installation (scroll to bottom of this page for picture)

GNU Radio at government and university laboratories

VuSystem, multimedia, MIT ancestor of GNU Radio (mid 90s)

SpectrumWare/PSpectra, software radio, MIT immediate ancestor of GNU Radio (late 90s)

Vanu, Inc., commercial spin-off of MIT SpectrumWare project

Readings and other resources

Jon Jacky,