Re: Adaptive filtering

thom wrote:
(top posting fixed)

With adaptive equalization it is common to use the demodulated data to generate the prototype signal. If your SNR is good enough to get mostly


good data out of a demodulator then this should work for you -- and if it's not you may not be able to recover the signal with any kind of filtering.

My understanding of OFDM is that it is inherently resistant to the kinds


of effects that demand adaptive filtering or equalization -- what effects are you trying to mitigate, and do you really need to?

> Actually I have to work on signals that are good enough to be
> demodulated... Although I would like to reduce the noise part in the
> received signal to improve the transmission system. And I don't know
> what signal I can use as a reference, since I only have the received
> signal with white noise.
>
> Thom

* If the noise characteristics are known you don't need an adaptive filter.

* If your channel doesn't suffer from fading or dispersion then you don't need an equalizer, adaptive or not -- and OFDM is designed to eliminate the need for fancy equalization in any case.

* If the noise is white and the channel is purely attenuating then the classical demodulation technique of using a matched filter is optimal: any extra filtering, adaptive or otherwise, will only degrade your system performance.

--

Tim Wescott
Wescott Design Services
http://www.wescottdesign.com

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"Applied Control Theory for Embedded Systems" came out in April.
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