Research On PAPR And ICI For OFDM System Based On Fractional Fourier Transform

When it comes to the4G era, the requirement of communication service is nolonger limited to voice and text transmission business, but the increasing videotransmission business. The fourth generation communication technology（4G）meets the need on it, which has a faster download speed compared to the3Gtechnology. It means that the OFDM system, the main technology of4G, shouldhave more subcarriers than before. More subcarriers of the OFDM system meanshigher peak to average power ratio（PAPR） and bigger inter carrier interference（ICI）, which restrict the development of OFDM technology. This article willperform a further research against these two problems of the OFDM system.This paper introduces the historical development of the fractional Fouriertransform theory with its definition, basic nature and application, especially therelationship between fractional Fourier transform and Fourier transform. The FRFT-OFDM system is also introduced with the provident of orthogonality amongsubcarriers and the definition of signal form is given after that.On one hand, this paper firstly introduces the definition and reasons of highPAPR of the OFDM system, which can be measured with CCDF curve from theangle of probability. What’s more, the technology of reducing the PAPR of thetraditional OFDM system is illustrated, including clipping, coding and probabilitytechnology with their merits and demerits. Finally, it explains the reason ofreducing PAPR of FRFT-OFDM system, presents the process of theoreticalderivation, illustrates the change of PAPR value with the change of transform angle,and applies the traditional methods to FRFT-OFDM system to have a furtherreduction of PAPR.On the other hand, this paper firstly analyses the ICI produced by the carrierfrequency offset（CFO）and derivates the expression of ICI. Secondly, the BERperformance is analyzed for BPSK modulated OFDM system. Lastly, we repeat theabove process in FRFT-OFDM system. After some theoretical analysis, the FRFT-OFDM system has smaller ICI and better BER performance than the traditionalOFDM system because of its order selection with the same CFO.