Re: [Discuss-gnuradio] Enabling the cognitive radio with GNU Radio+USRP

[Eric Blossom]

On Thu, Mar 04, 2010 at 02:45:54PM -0500, Jakub Moskal wrote:
> Hi everyone,
> 
> I am trying to use the GNU-Radio+USRP to implement a cognitive radio
> use case in which radios exchange information (XML-based documents)
> between each other in order to achieve a defined goal (e.g. to improve
> connectivity), without disturbing the usual communication. I have
> several questions regarding this scenario..
> 
> In a packet-based communication (e.g. tunnel.py) I imagine that I
> could transmit my own packets which would include the "cognitive
> information" and then receive them on the other end. It would require
> some special marking of the packets (binary level?) to distinguish the
> cognitive information from the regular data, so that it could be
> filtered out on the receiver side. I looked into the tunnel.py, but it
> seems that it doesn't implement anything higher than the MAC layer -
> therefore I cannot use it to reliably transfer data, packets get lost
> or are too small and I would have to split/merge data manually. Would
> it be possible to combine the tunnel.py with the TCP source/sinks in
> order to achieve a reliable link?

In reality, you'd need some kind of FEC to get the packet error rate
down to something you can deal with.  Then you could run TCP across
the interface.  No need for TCP sources or sinks.  You've got a
(virtual) network interface with an IP address.  Just run something
that uses TCP on that IP address.

> It looks like some of the examples don't use the concept of a packet
> (eg. usrp_tv_rcv.py) -- how would I add my own data and filter it in
> such streams? Would it require writing a C++ block? If so, how would I
> ensure the reliability then?

Good question, see below for reading suggestions.

> I have a CS background and the digital communication is rather new to
> me, I would appreciate any help or links to resources.

To really grok s/w radio, folks need to have a decent clue about
software, dsp, digital comms and RF.  Sounds like you've got the
software part wired, so that's handled.  Other folks come with the
digital comms background but lacking experience in s/w.  There's always
something new to learn :-)

Take a look at this list of suggested reading, and spend some time
with a few things that capture your interest:

  http://gnuradio.org/redmine/wiki/gnuradio/SuggestedReading

For DSP, I'd suggest starting with Lyons.  For Digital Comms, try Sklar.

> Thanks,
> Jakub

You're welcome!
Eric