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From: | Florian Schlembach |
Subject: | Re: [Discuss-gnuradio] OFDM Benchmark Tx Issue? |
Date: | Tue, 21 Feb 2012 19:06:26 +0100 |
User-agent: | Mozilla/5.0 (Windows NT 6.1; WOW64; rv:10.0) Gecko/20120129 Thunderbird/10.0 |
There is a coarse and a fine frequency offset correction. The fine correct makes sure that the subcarrier is centered in the bin; the coarse adjusts for an integer number of subcarriers off from the center frequency. By default, the OFDM receiver will correct for some number of subcarrier bins (it's either +/-5 or +/-10; I can't remember). If your radios have a frequency offset that is greater than the maximum number of subcarriers specified here, the receiver cannot receive the symbols correctly.
How about the fine frequency offset correction? How can I turn it on? For instance, how do I have to modify the benchmark/tunnel scripts in order to do that?
Yes, you can transmit a tone using uhd_siggen.py to fine out a rough estimate of the frequency offset and adjust either the transmitter or receiver based on this number.
Thanks, I will try that next days.
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