Cepstrum to Abate Noise in OFDM Symbols

Reshma Rajendran, Ann Nita Netto

Abstract: The ability of cepstral analysis to reveal periodicites in a signal resulted in its widespread use in signal processing applications. The paper focus on the application of cepstrum on cancellation of noise in OFDM systems by using CRC. Cyclic prefix insertion induces periodicities in OFDM symbols. Cyclic Prefix mitigates completely the ISI and ICI in OFDM symbols. By cepstral analysis one could estimate the cyclic prefix length. Using this one could decide the length of redundancy bits for Cyclic Redundancy Check for error correction. To study the effect of frequency offset on subcarrier variance, the noise power is estimated using a 2D sliding window. The instantanoeus error in estimating the noise power determines the window size, thereby elaborating the importance of cyclic prefix in presrving sub-carrier orthogonality. The cepstral analysis of OFDM symbol is generic in nature and can be used for other applications, such as analysis the signals between the circuit components in larger circuits.

Keywords: OFDM, Cepstrum, Quefrency, Orthogonality, Carrier frequency Offset