Modelling and Simulation in Engineering 
Volume 2008 (2008), Article ID 345478, 9 pages
doi:10.1155/2008/345478
Research Article

A New-Trend Model-Based to Solve the Peak Power Problems in OFDM Systems

Ashraf A. Eltholth,1 Adel R. Mekhail,1 A. Elshirbini,1 M. I. Dessouki,2 and A. I. Abdelfattah3

 1National Telecommunication Institute, P.O. Box 7070, Cairo 11768, Egypt
2Department of Communication Engineering, Faculty of Electronic Engineering, Minufiya University, Minufiya, Egypt
3Department of Electrical Communication, Faculty of Engineering, Mansoura University, Mansoura, Egypt
Received 29 August 2007; Revised 30 April 2008; Accepted 6 July 2008

Recommended by Adel Alimi

Abstract

The high peak to average power ration (PAR) levels of orthogonal frequency division multiplexing (OFDM) signals attract the attention of many researchers during the past decade. Existing approaches that attack this PAR issue are abundant, but no systematic framework or comparison between them exists to date. They sometimes even differ in the problem definition itself and consequently in the basic approach to follow. In this paper, we propose a new trend in mitigating the peak power problem in OFDM system based on modeling the effects of clipping and amplifier nonlinearities in an OFDM system. We showed that the distortion due to these effects is highly related to the dynamic range itself rather than the clipping level or the saturation level of the nonlinear amplifier, and thus we propose two criteria to reduce the dynamic range of the OFDM, namely, the use of MSK modulation and the use of Hadamard transform. Computer simulations of the OFDM system using Matlab are completely matched with the deduced model in terms of OFDM signal quality metrics such as BER, ACPR, and EVM. Also simulation results show that even the reduction of PAR using the two proposed criteria is not significat, and the reduction in the amount of distortion due to HPA is truley delightful.