Re: [Discuss-gnuradio] RE: Discuss-gnuradio Digest, Vol 81, Issue 26

[Douglas Geiger]

 If you are using a USRP1 you need to be aware of the fact that you
cannot capture the full-bandwidth of the waveform through the USB
cable.  There has been work on getting around this fact by
implementing the despreading inside the FPGA (before the
filtering/downsampling required to pass the data through the usb
link), which works for the 1 and 2Mbps 802.11b data rates. Thus far I
believe the only code that's generally available is for the 802.11b
DSSS modes using the Barker sequence (i.e. 1Mbps and 2Mbps). There
have been various discussions about what is needed for the higher data
rates (CCK spreading for 802.11b, and OFDM for 802.11g and 802.11a),
but I'm not aware of any working code.
 The BBN code does not provide a fully-compliant MAC, although it does
both transmit and receive, I think one of the big issues is making the
timing requirements for things like ACK's, etc - as well as the
latency involved in the carrier-sensing to make sure the channel isn't
currently in use. Someone else may have more information on that - I
haven't worked much with the transmit side of things.
 I'm not sure what you mean by your third question: the bbn code uses
GNURadio already - I don't know what work would be involved to get it
to work with the Click router, although I believe other people have
gotten GNURadio applications to work with Click in the past.
 The end-all-be-all reference for 802.11 is the IEEE standard, which
you can download from their website. It's a dense read though, and is
mainly useful as a reference. There are plenty of books on WiFi in
general, although I think the main one for dealing with the PHY and
MAC layer is The 802.11 Handbook: A Designer's Companion by Bob
O'Hara. Although it looks like even the second edition may be hard to
find new (Amazon only lists used copies at least). Most other books
are really for networking folks, on setting them up, etc. But between
a decent digital comms book, the BBN code, and the IEEE standard you
can work most of it out.
 Good luck,
  Doug

2009/8/26 汤图杨 <address@hidden>:
> hello:
>      i am running bbn 802.11 on the usrp, and i have some problems during
> the process.
>  before i go on doing the running, i have some questions to be resolved:
>     1 which kind of protocol does the bbn 802.11 provide, 802.11a or
> 802.11b?
>     2 Does the bbn 802.11 provide the function of PHY  and MAC completely?
>     3 If we want to embed the bbn 802.11, should we embed it into the
> gnuradio or the
>       click  router?
>
>
>     I wish someone can give me the answer,it will be better if you can
> provide some reference book on bbn 802.11 to me , thanks a lot!
>
>
> xiaoming
>



-- 
Doug Geiger
address@hidden