Re: [Discuss-gnuradio] complex examples

[Eric Blossom]

On Thu, Sep 08, 2005 at 02:01:47PM -0500, Jim Lindstrom wrote:

> Can anyone point me at some very complex gnuradio examples? I'm curious to 
> see how the control and feedback side of things are managed, and how 
> unwieldly (or not) the building of the graph can be. For instance, when 
> looking through the HowtoHdTv, I realized that there isn't so much an "HDTV 
> Application" as there is a "HDTV Process" that one goes through to get 
> everything tweaked and serially run through a few tools. Does anyone have an 
> example of gnuradio being used in scenarios such as:

Hi Jim,

Sorry for the delay getting back to you.

The control and feedback side of things are still an area of
research.  The HDTV stuff was done in the earlier framework, the 
GNU Radio 0.x series, and hasn't (yet) been ported to the 2.x code
base. 

With the HDTV Tx or Rx there really was just a single process
running.  What you may have been looking at were some scripts that
were used to debug the whole mess.  The guts were called atsc_tx and
atsc_rx. 

> - a COTS network stack integrating with GNURadio as the L1 implementaiton? 
> I.e., has anyone tried making a real radio w/ GNURadio and managing all the 
> communication between some C++ App to do the network stack stuff and the 
> RF-level GNURadio graph?

I am aware of some grad students who are working in this area.  
Matt & I are also working on a simple PHY + MAC that uses the tun
interface to allow IP packets to be pushed through GNU Radio.

In the bigger picture, I know of other academic and industrial
researchers who are definitely planning on using GNU Radio as the L1
layer in a radio stack.  What this will take is other people (beside
me) diving in and figuring out how they think this should best be
structured, and then making it so.  I'd be delighted to advise on any
part of this undertaking.  

Besides the data flow abstraction, the gnuradio-core code base
supports a message passing / message queueing discipline.  [See
gr_message.h, gr_msg_queue.h]  This has not yet been heavily used, and
you could expect the "shape" to vary as we learn more about what is
the "right answer".  Most uses to date have been related to building MACs.

> - examples like in HDTV where the application manages the feedback of 
> tweaking AGC settings or monitoring the adc3_fftavg in realtime to warn if 
> the levels get too low, or watching ./point in real time to see if error 
> rates get too high.. Has this been attempted?

This kind of stuff isn't too difficult to do, even right now.  It
depends on how tight of a control loop you need to build.  The HDTV
code had built-in AGC.

Eric