I searched for length of cyclic suffix but all I can find information about is the cyclic prefix, I want to know also if there is short guard interval and long guard interval does it affect the length of the suffix

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    $\begingroup$ That's a design parameter, so it would depend on the implementation. In LTE e.g., there is a normal and extended mode. $\endgroup$ – vaz Feb 4 '19 at 10:39

You, as the designer of an OFDM system, define the length of the CP based on your requirements.

The main requirements are:

  1. Long enough to "swallow" the duration of the longest expected channel impulse response to inhibit ISI / make the linear convolution channel effect look like a circular convolution
  2. Not longer than necessary, since it "wastes" transmit time, and thus reduces data rate
  3. (optional, depending) in a length that allows for efficient synchronization (e.g. via Schmidl&Cox)

So, there's no single answer to this. The answer is:

It depends, and when you've fully understood the reason why we use CP in OFDM systems, this will become very much more intuitive.

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  • $\begingroup$ thank you for the answer but another question please, does the cyclic suffix length have to be equal to the cyclic prefix length? $\endgroup$ – Shorouk Raafat Feb 28 '19 at 6:48
  • $\begingroup$ You only ever use either, and it's extremely rare that you use a cyclic suffix. That really doesn't make much sense in OFDM; it's not harder to do a cyclic prefix than a suffix, and you get nicer timing properties. Anyway, mathematically, you can't tell the two apart unless you start looking at the symbols that you get under either decoding assumption, so your question makes no sense. $\endgroup$ – Marcus Müller Feb 28 '19 at 8:12
  • $\begingroup$ seriously, where did you find an OFDM system with a cyclic suffix? Coming to think of it, I don't know a single one! And no matter whether you're doing cyclic suffix or prefix, you'd always "cut away" the start of the symbol at the receiver since it contains ISI; in the cyclic suffix case, you then have to do a cyclic shifting of the whole symbol. $\endgroup$ – Marcus Müller Feb 28 '19 at 8:16

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