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Re: [Discuss-gnuradio] OFDM update

From: Eric Blossom
Subject: Re: [Discuss-gnuradio] OFDM update
Date: Sun, 5 Aug 2007 03:11:03 -0700
User-agent: Mutt/1.5.9i

On Sat, Aug 04, 2007 at 01:01:21PM -0400, Robert McGwier wrote:
> All resolvable with in-band signaling and RSSI with feedback to agc 
> hardware and software.
> I know, I know, I am a broken record.
> Bob

Hi Bob!

Good to hear that you're still out there ;)


> Tom Rondeau wrote:
> >Matt and I have had a bit of a chance to work out some kinks in the OFDM
> >world. My latest merge should allow people to operate over the air ok.
> >The problem turns out to be false correlations when using the BasicRX
> >boards because with the low gain, the noise only toggles the last 1 or 2
> >LSBs, which correlate nicely and caused the assertions down the chain.
> >The new version avoids that issue as well as provides better default
> >parameters to run over the air.
> >
> >I recommend testing this on an RFX board and not a BasicRX/TX. Also,
> >adjust the --tx-amplitude option on the command line for performance.
> >It's set low still (200) as opposed to 1. This should be fine for a
> >couple of feet. Watch going too high with the amplitude because of
> >clipping. I think 4000 was about the max we saw with an RFX400, but
> >between 1000 and 2000 should work nicely for in-house tests.
> >
> >I also set the default packet size to 400, down from 1450 bytes. We have
> >not implemented frequency/phase tracking throughout the packet, just on
> >the preambles, so rotation throughout the packet can cause high packet
> >loss with long packets.
> >
> >I think this current version provides a usable base for people to play
> >with, though it's by no means perfect. However, I've got to bury myself
> >in my dissertation, so I won't doing any more work on it for a couple of
> >months.
> >
> >Tom

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