The raised cosine pulse is essentially a windowed sinc function, designed with some roll-off in mind. Why do we use this particular window, as opposed to other windows such as Hann, Hamming, Kaiser, etc? All of these have zero ISI when applied to a sinc function, and have tunable frequency characteristics just like the raised cosine. Is the raised cosine optimal for digital comms in any sense?


There is no good reason, except that it's familiar and "good enough" for many applications. Many other better pulses have been proposed; see for instance "Nyquist filters in non-ISI transmission", by Ping-Kuen Lam, E.W. McCune and M.A. Soderstrand, DOI:10.1109/MWSCAS.1997.666198.

  • $\begingroup$ well, it does still prevent ISI sufficiently well when heavily truncated; that's a pretty good property for practical implementation in digital systems. $\endgroup$ – Marcus Müller Apr 25 '18 at 7:44
  • $\begingroup$ @MarcusMüller I believe that other pulses are equally good or better in that regard, too. I don't have a lot of experience with them, though. $\endgroup$ – MBaz Apr 25 '18 at 14:01
  • $\begingroup$ I think the "don't have much experience with anything but RRC" definitively applies to me, too. This might actually be an important reason: noone hears about anything but RRC in their education. $\endgroup$ – Marcus Müller Apr 25 '18 at 15:45
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    $\begingroup$ That's a good point, and something that I'll change in my own graduate wireless course next year. In fact, I was inspired to research this subject by McCune's recent textbook on wireless (he's one of the co-authors of the paper I linked to). $\endgroup$ – MBaz Apr 25 '18 at 17:02

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