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Re: [Discuss-gnuradio] Physical layer for packet-based communication
From: |
David Young |
Subject: |
Re: [Discuss-gnuradio] Physical layer for packet-based communication |
Date: |
Mon, 7 Feb 2005 20:53:39 -0600 |
User-agent: |
Mutt/1.4.1i |
On Fri, Feb 04, 2005 at 10:21:06AM -0500, Rahul Dhar wrote:
> Ideally, I'd like to see a physical layer API so I can write my own MAC
> layer. Can GNU Radio handle 802.11 a/b/g? What I'd like to do is have
> a MAC layer smart enough to detect when the MAC protocol it's using
> isn't optimal given network conditions, and then switch to a protocol
> better suited to the traffic characteristics. For examle, 802.11 has
> DCF and PCF modes. For smaller networks, DCF (based on CSMA/CA) is
> normally fine, but when you reach a certain number of nodes, or start
> having nodes that are sending large amounts of data, PCF can be better
> suited because of its contention-free period.
>
> I'm not sure how feasible that would be, but I'd like to start by
> implementing simple DCF and PCF schemes and eventually work towards an
> 802.11 implementation. A fake network device would be nice, though. If
> nothing more, it lets applications take advantage of the radio in a
> standard way.
Rahul,
I have been thinking a little about how to produce a novel MAC, without
spending gobs of time & money. Here are some ideas:
1 Use an off-the-shelf 802.11 card. Change its mode from
PCF/DCF using software that runs on the host.
2 Use an off-the-shelf 802.11 card. Tweak its MAC/PHY parameters
until the default carrier-sensing and such are effectively
disabled---this could get hairy! Use the host CPU or a
coprocessor to schedule packet transmissions.
3 Use an existing 802.11 PHY, but replace the MAC
with a microcontroller [*]. Design a PHY abstraction.
Implement, in C (say), the PHY abstraction for the PHY of your
choice [**]. Program your MAC in C.
4 Use an existing 802.11 PHY. Replace the MAC with
an FPGA. Program your MAC in VHDL. (I don't see much advantage
to this over #2.)
All those ideas need a lot of development, but I hope the general ideas
are clear.
Dave
[*] Lots of MACs are ARM u-controllers---TI's and Atmel's, for
instance---but docs are not freely available.
[**] Docs for PHYs by Intersil/Conexant, RF Microdevices, and others
are available, if you ask nicely.
--
David Young OJC Technologies
address@hidden Urbana, IL * (217) 278-3933
Message not available
Re: [Discuss-gnuradio] Physical layer for packet-based communication, Rahul Dhar, 2005/02/07
Re: [Discuss-gnuradio] Physical layer for packet-based communication, Bob Poortinga, 2005/02/07
Re: [Discuss-gnuradio] Physical layer for packet-based communication, Eric Blossom, 2005/02/07
[Discuss-gnuradio] A suggestion to the list manager, Ulf Soderberg, 2005/02/07