Re: [Discuss-gnuradio] Latest Hackfest

[Tom Rondeau]

On Thu, Apr 3, 2014 at 3:05 PM, Miklos Maroti <address@hidden> wrote:

Dear Tom,

I have read about the FEC work done during the Hackfest, so this would
be an appropriate time to bring this up. We have participated in the
Darpa Spectrum Challenge, and developed some good and fast codes.
Specifically, we have a generic convolutional code encoder and decoder
(any R and K is supported, tailbiting can be enabled), with fast SSE
implementation. In the attached BER figure we have used R=1/8, K=9 and
length = 3 bytes = 24 bits for encoding headers. The speed is not much
worse than the spiral generated one. More importantly, we have a
specially crafted version of a repeat accumulate coder/decoder that
can be quickly decoded with SSE. On the figure we have used rates 1/3,
1/2, 1/3 and 4/5 with a payload size of 1440 bytes. On the orbit-lab
machines (core-i7) our SSE code can decode more than 1000 packets per
second on a single core.

I plan to release this code under the GPL (and maybe under an MIT
license as well) after I have a paper written up about it. So the
question would be:

Miklos,

This sounds like a fantastic result.

 

1) how to incorporate this into gnuradio (separate OOT or built in)

If it's to go into GNU Radio, it would only be license GPLv3, like the rest of the code base. Also, we require a copyright transfer from you. We can discuss and work on that on the side.

Also, with the use of SSE, we'd want to separate the code into a VOLK kernel with a generic and SSE implementation. That way, we're not restricting ourselves to certain platforms. And then, we can extend it to other SIMD architectures.

 

2) how to deal with puncturing (we have some good generic solution)

We let the FEC API encoder and decoder blocks handle the puncturing and depuncturing separate from the coders themselves. I think they are generic enough, but we'd probably want to update them if they don't fit every scenario.

 

3) how to deal with variable packet lengths and variable rates (have some ides)

The FEC API encoder/decoder blocks don't care about the packet lengths as long as the coders themselves can handle it. Right now, our working example uses fixed packet length, but (I don't think) that's a requirement. Might have to double-check this. Same should go for the rate.

In the FEC API world, there is an FEC encoder and decoder block that sets just a few parameters. One of them is the variable that actually defines the encoder and decoder code, and those variables are designed to work with the API. So most of this is on how these variable blocks are built.

 

4) how mature is the FEC API, can it be modified if needed?

It's mature in that we've tested it out-of-tree with a number of situations. But as we're moving it into GNU Radio, there's a window here to update it. Best done before we merge it into master, though, which will set the API until 3.8 of GNU Radio. It'd be great if you could take my current github repo branch "fecapi" and see about fitting your coder into it. That'll get us some feedback before we merge into master.

 

Best,
Miklos

Thanks!

Tom

 

On Thu, Apr 3, 2014 at 7:32 PM, Tom Rondeau <address@hidden> wrote:

> We had our latest GNU Radio Hackfest last week at Ettus Research. It was a
> fantastic week with a lot of good work getting done. If you're interested in
> what we are working on and to get a glimpse of some of the new things we'll
> be rolling out in the next few GNU Radio versions, find our working notes
> here:
>
> http://gnuradio.org/redmine/projects/gnuradio/wiki/Hackfest1403-2
>
> Thanks to everyone who came and hacked with us. Thanks, too, to Ettus
> Research for being great hosts for our motley band of developers!
>
> Tom
>
>

> _______________________________________________
> Discuss-gnuradio mailing list
> address@hidden
> https://lists.gnu.org/mailman/listinfo/discuss-gnuradio
>