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For example, in a PSK modulation. I saw that to plot the BER curves as a function of the noise, we never took into account the pulse shaping filter. More precisely, the signal is not filtered by the pulse shaping filter. In practice, it is necessary to filter the signal to have a limited bandwidth.

Why then is the pulse shaping filter not used to filter the sent signal in order to draw the BER curve?

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Why then is the pulse shaping filter not used to filter the sent signal in order to draw the BER curve?

When drawing a BER curve, we're considering the bit or symbol energy.

That energy is the convolution of transmit pulse shape with receive filter evaluated at the symbol instance.

So, that filter is taken into account. We just usually define it such that the pulse energy is 1, and then you don't see it in your equations.

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    $\begingroup$ To put it in other words: the pulse shape has no effect on the BER whatsoever. The BER depends only the bit energy and noise PSD. $\endgroup$
    – MBaz
    Dec 2, 2020 at 1:03
  • $\begingroup$ exactly! in any reasonable BER measurement, we're talking about symbol decisions, not about the whole transceiver chain, otherwise we'd also have to add info on "did someone scale the transmit filter by 100? What's the conversion gain of the mixer?" and so on. So, all these effects have already been considered, and what the decider (which makes the errors!) sees is simply a Eb/N0 or SNR. What the pulse shaping contributed to that doesn't matter at all. $\endgroup$
    – Marcus Müller
    Dec 2, 2020 at 8:45

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