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Re: [Discuss-gnuradio] Channel Response in OFDM with MIMO USRP
From: |
Marcus D. Leech |
Subject: |
Re: [Discuss-gnuradio] Channel Response in OFDM with MIMO USRP |
Date: |
Sun, 13 Jan 2013 16:14:35 -0500 |
User-agent: |
Mozilla/5.0 (X11; U; Linux x86_64; en-US; rv:1.9.2.24) Gecko/20111108 Fedora/3.1.16-1.fc14 Thunderbird/3.1.16 |
I see.
Well, I'm running the regular OFDM rx-chain which includes preamble
detection->sampler->fft->so on. On the transmitter, each frame
(preamble[1 OFDM symbol] + data[multiple OFDM symbols]) acts as a
burst which includes the required timestamps and the burst tags.
I was just somehow hoping to get a flat channel for some analysis
which otherwise is a pain, since I have to do it without channel
equalization. This phase change results in symbols rotating in the I/Q
domain. :)
-jack
I've only been half paying attention to this thread.
But two frac-N synthesizers, even when fed with a phase-coherent
reference clock, will have some random phase-offset between them every
time they're tuned. With newer UHD versions on the N2XX series
machines and the SBX daughtercard, you can get around this with
the special phase-alignment mode using timed commands for tuning.
But that isn't a particularly realistic scenario for real-world
communications
apps.
In the real world, the TX and RX will not be phase coherent in any way.
--
Marcus Leech
Principal Investigator
Shirleys Bay Radio Astronomy Consortium
http://www.sbrac.org