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Derotation effects in multipath channel

Started by alberto.fuggetta June 15, 2010
Hi,

I'm simulating a DFE equalizer in Matlab for a MSK modulated signal.
The channel I'm testing is Ricean with max doppler shift of 50 Hz.
I noticed that the performance of the DFE deeply improves if I apply the
derotation before sending the samples to the equalizer.
Has anybody ever observed the same behavior?
Does any theoretical explanation for this phenomenon exist?
Thanks

Alberto

alberto.fuggetta wrote:

> Hi, > > I'm simulating a DFE equalizer in Matlab for a MSK modulated signal. > The channel I'm testing is Ricean with max doppler shift of 50 Hz. > I noticed that the performance of the DFE deeply improves if I apply the > derotation before sending the samples to the equalizer. > Has anybody ever observed the same behavior? > Does any theoretical explanation for this phenomenon exist?
Your model of the channel is wildly inadequate. Vladimir Vassilevsky DSP and Mixed Signal Design Consultant http://www.abvolt.com
On Jun 15, 4:27�pm, "alberto.fuggetta"
<alberto.fuggetta@n_o_s_p_a_m.gmail.com> wrote:
> Hi, > > I'm simulating a DFE equalizer in Matlab for a MSK modulated signal. > The channel I'm testing is Ricean with max doppler shift of 50 Hz. > I noticed that the performance of the DFE deeply improves if I apply the > derotation before sending the samples to the equalizer. > Has anybody ever observed the same behavior? > Does any theoretical explanation for this phenomenon exist? > Thanks > > Alberto
Rotation implies a frequency offset Freq offset implies the phase offset is always changing Your DFE is chasing a changing phase offset. So no suprise when you remove the rotation, your DFE works better. Clay