Cyclic prefix in ofdm

The cyclic prefix used in Frequency Division Multiplexing schemes including OFDM to primarily act as a guard band between successive symbols to overcome intersymbol interference, ISI. Use of cyclic prefix is a key element of enabling the OFDM signal to operate reliably.

1. What do you mean by cyclic prefix?
2. How do you find the cyclic prefix?
3. How does the cyclic prefix remove ISI?
4. What is normal cyclic prefix?

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.

How do you find the cyclic prefix?

Therefore, the number of samples allocated for cyclic prefix can be calculated as Ncp=Tcp*N/T, where N is the FFT/IFFT length, T is the IFFT/FFT period and Tcp is the duration of cyclic prefix.

How does the cyclic prefix remove ISI?

ISI effect can be reduced by interesting a guard interval (cyclic prefix). The cyclic prefix or guard interval is a periodic extension of the final section of an OFDM symbol that is appended to the forepart of the symbol in the transmitter, and is removed at the receiver before demodulation.

What is normal cyclic prefix?

Δf, step between subcarriers; l, number of the symbol in the time slot. The normal cyclic prefix is used in case the delay between the different reflected signals is low, which is the case in cells of small diameter (microcell, pico-cell, femto-cell).