Why does OFDM need cyclic prefix?

Cyclic prefix is inserted to avoid intersymbol interference due to the multipath channel. In practice, CP-OFDM modulator is implemented via the computationally efficient fast Fourier transform (FFT).

1. What will happen if we append zeros instead of a cyclic prefix?
2. What do you mean by cyclic prefix?
3. Why the first OFDM symbol has longer CP?
4. What do you mean by cyclic prefix in OFDM system and explain the advantages of using cyclic prefix in OFDM signals?

What will happen if we append zeros instead of a cyclic prefix?

The main idea of using Cyclic prefix in OFDM systems is because of 2 reasons, 1) To eliminate ISI from previous symbol. If an OFDM symbol is Zero padded instead of cyclic prefix, ISI due to adjacent symbol still gets eliminated, but it cannot be modeled using circular convolution.

What do you mean by cyclic prefix?

In telecommunications, the term cyclic prefix refers to the prefixing of a symbol, with a repetition of the end.

Why the first OFDM symbol has longer CP?

These longer symbols are generated by increasing the duration of the normal cyclic prefix, to ensure that each numerology has an integer number of symbols within each 0.5 ms time window, while also ensuring that as many symbol boundaries as possible coincide, e.g. every symbol boundary belonging to the 15 kHz ...

What do you mean by cyclic prefix in OFDM system and explain the advantages of using cyclic prefix in OFDM signals?

Use of cyclic prefix is a key element of enabling the OFDM signal to operate reliably. The cyclic prefix acts as a buffer region or guard interval to protect the OFDM signals from intersymbol interference.