Update and 3.7.4
Tuesday, June 24, 2014 at 7:08PM
Tom Rondeau in 3.7.4, FEC API, ISEE-3, development, gnuradio, gr-fec, release

It's been a while since I've provided an update. Lots of travel, both work and otherwise, has kept me from letting everyone know what's been going on in GNU Radio. So let me see if I can start to fix that.

I think that our most interesting and fun development was the success of the ISEE-3 reboot team, including our own Balint Seeber (ok, so he's technically with Ettus, but for all of his work with GNU Radio, I'll claim him; at least partially) and John Malsbury. This was an incredibly cool and successful project, and Balint, John, and the rest of the reboot team have done and continue to do an amazing job. I'm not going to try and poorly rehash the work here. But there's been plenty of articles written on the effort and the links provided above here will give you a much better review of what happened and how.

In other news, we're close to releasing GNU Radio 3.7.4. I was really happy with our 3.7.3 release a few months ago, and this next release continues to strengthen the project. We have a lot more support and have debugged a few issues with the message passing infrastructure. I see the use of the message passing system as a growing trend in GNU Radio, especially for control and updating parameters of blocks.

Another development is a massive update and improvement to gr-atsc. While the original work here was great, it was based on GNU Radio ideas and capabilities from probably 10 years ago or so. Andrew Davis and Johnathan Corgan have done a wonderful job bringing this up to date and improving its speed and stability. This is part of a trend that we're working on (hopefully in the next version release) for more support of other digital TV standards, both transmitter and receiver code. Keep an eye out for gr-dtv in the near future.

A huge part of my work recently has been in the integration, development, documentation, and building examples for our new FEC API that is now a part of gr-fec. Historically, GNU Radio hasn't done a very good job with managing or allowing use of forward error correction (FEC) techniques. It's a difficult problem to solve to allow us to easily integrate different types of FECs in transmitters and receivers, either for streaming or packet-based communication links. Each FEC has different properties and conditions for use in the different types of comms links, and they can have different input/output data types that they are built to work with. The new FEC API that's been introduced allows us to handle these situations more seamlessly within a GNU Radio flowgraph.

The new gr-fec includes FEC encoders and decoders for a convolutional code (K=7, Rate=1/2, polynomials=[79, 109]) that has been highly optimized with SIMD (through VOLK), a repetition code that simply repeats each bit N times, and a dummy code that actually does no coding but provides a simple mechanism to use and study the API. We are also providing different blocks, called “deployments” in the FEC API, that allow us to make use of these encoders/decoders in streaming, tagged stream, and PDU message-passing flowgraphs. I was able to use the convolutional code FEC encoder and decoder in the gr-mac project for full network communications between multiple computers. This work can be found in the “fec_gmsk” branch of my fork of gr-mac.

The GNU Radio manual covers the API and deployments in a fair amount of depth. Obviously, you can always build the docs yourself with GNU Radio, but the main manual page on gnuradio.org will be updated to include this when 3.7.4 is released. Likewise, there are examples for the use of the codes and deployments that are distributed and installed with GNU Radio.

So that's just a brief review of what we've been up to the past few months. There are plenty of little fixes, tweaks, and additions that we've been making to the code base in this time that I've left out. But I'm really pleased with the progress and rate of progress we've been making lately. Lots of new, good stuff to help us fill a few gaps in capabilities we've had.

Article originally appeared on GNU Radio (http://gnuradio.squarespace.com/).
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