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Re: [Discuss-gnuradio] Re: USRP2 802.11 BBN code on the TX side

From: Doug Geiger
Subject: Re: [Discuss-gnuradio] Re: USRP2 802.11 BBN code on the TX side
Date: Fri, 11 Dec 2009 08:37:33 -0500
User-agent: Thunderbird (Windows/20090812)

George Nychis wrote:

Hi Doug,

I can guarantee you that the scrambler is not working ;) The 802.11 spec states that at the beginning of every transmission, the scrambler needs to reset its seed, however the BBN code does not do this.

That's interesting on the clocks.  What daughterboard are you using?

- George
I'm using the RFX2400. Looking at the spectrum in a spectrum analyzer suggests we aren't making the correct spectrum on transmit - not sure if that's simply because we aren't doing any filtering (i.e. RRC or other pulse shaping), or if it's something more fundamental. I think as long as the scrambler isn't set to all ones at the start of a transmitted frame, we're all good. It's self-synchronizing, so it doesn't need to be at any known state at the start of a frame.

Douglas Geiger
Code 5545
U.S. Naval Research Laboratory
Washington, DC 20375
(202) 767-9048

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