title: Equation-Method for correcting clipping errors in OFDM signals.
abstract: Orthogonal frequency division multiplexing (OFDM) is the digital modulation technique used by 4G and many other wireless communication systems. OFDM signals have significant amplitude fluctuations resulting in high peak to average power ratios which can make an OFDM transmitter susceptible to non-linear distortion produced by its high power amplifiers (HPA). A simple and popular solution to this problem is to clip the peaks before an OFDM signal is applied to the HPA but this causes in-band distortion and introduces bit-errors at the receiver. In this paper we discuss a novel technique, which we call the Equation-Method, for correcting these errors. The Equation-Method uses the Fast Fourier Transform to create a set of simultaneous equations which, when solved, return the amplitudes of the peaks before they were clipped. We show analytically and through simulations that this method can, correct all clipping errors over a wide range of clipping thresholds. We show that numerical instability can be avoided and new techniques are needed to enable the receiver to differentiate between correctly and incorrectly received frequency-domain constellation symbols.
authors.affiliation: Department of Computer Science, Fatima Jinnah Women University, The Mall, Rawalpindi, Pakistan.
authors.forename: Nargis
authors.initials: N
authors.lastname: Bibi
authors.affiliation: School of Computing, Mathematics and Digital Technologies, Manchester Metropolitan University, Manchester, UK.
authors.forename: Anthony
authors.initials: A
authors.lastname: Kleerekoper
authors.affiliation: Department of Mathematics, Comsats Institute of Information technology, Wah Cantt, Pakistan.
authors.forename: Nazeer
authors.initials: N
authors.lastname: Muhammad
authors.affiliation: Department of Computer Science, The University of Manchester, Manchester, UK.
authors.forename: Barry
authors.initials: B
authors.lastname: Cheetham
keywords: Clipping; Equation-Method; FFT; Orthogonal frequency division multiplexing (OFDM); Square matrix; Symbol error probability