OFDM IFFT/FFT processing

1. What is FFT and IFFT in OFDM?
2. What does IFFT do in OFDM?
3. What is the relationship between FFT and IFFT?
4. What is the need for using FFT in OFDM?

What is FFT and IFFT in OFDM?

Implementation of OFDM deals with application of Fast Fourier Transform (FFT) to modulation and demodulation processes to generate carriers orthogonal to each other. In conventional system, IFFT (Inverse Fast Fourier Transform) is used at transmitter side and FFT is used in receiver side.

What does IFFT do in OFDM?

The IFFT output is the summation of all N sinusoids. Thus, the IFFT block provides a simple way to modulate data onto N orthogonal subcarriers. The block of N output samples from the IFFT make up a single OFDM symbol.

What is the relationship between FFT and IFFT?

FFT (Fast Fourier Transform) is able to convert a signal from the time domain to the frequency domain. IFFT (Inverse FFT) converts a signal from the frequency domain to the time domain. The FFT of a non-periodic signal will cause the resulting frequency spectrum to suffer from leakage.

What is the need for using FFT in OFDM?

Using FFT algorithms provides speed enhancements for data processing for OFDM systems. This technique is being used for Digital Audio Broadcasting (DAB), Digital Video Broadcasting (DVB), Wireless Local Area Network (WLAN), Wireless Metropolitan Area Network (WMAN), Multi Band-OFDM Ultra Wide Band (MB-OFDM-UWB) etc.