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LF: Re: Slow mode comparisons

To: [email protected]
Subject: LF: Re: Slow mode comparisons
From: Alberto di Bene <[email protected]>
Date: Sun, 06 Mar 2005 01:12:33 +0100
In-reply-to: <[email protected]>
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[email protected] wrote:

My half-penny's worth is that the transmitted energy per symbol is 3.3 times larger, giving exactly 5.23 dB improvement ;-) That's assuming that the FFT bandwidth is somewhere near the optimum (0.3 Hz and 0.1 Hz respectively).
Markus,

you are correct, but in an ideal situation. Given that for performance reasons the FFT works at its best when done on a sample length which is a power of two, in Argo, when going from QRSS3 to QRSS10 I multiply the sample length by four, which causes a reduction of four times of the bin size. This has the consequence that the noise energy that falls
into a single bin is 6 dB lower, hence the 6 dB gain in SNR.
There are algorithms to perform FFTs on arbitrary sizes, but they are slower than when working with powers of two.
73  Alberto  I2PHD




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