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A Proposed Constant Amplitude Modulator in OFDM Systems

W .Saad, N. El-Fishawy, S. El-Rabaie, M. Shokair

Abstract


The Orthogonal Frequency Division Multiplexing(OFDM) technique has recently recieved considerable attention for wireless networks.Despite its advantages,it has a major drawback of its high Peak-To-Average Power Ratio(PAPR)value which affects the system efficiency and the cost.In this paper, a proposed system is discussed to achieve 0 db PAPR  value.it depends on a proposed block,called Constant Amplitude(CA)modulation.It consists of three sub-blocks(inserting zero,inserting samples,and comparing samples).The whole mathematical analysis is presented for the proposal system.Additionaly the complexity evolution is explained.Only four simple adders,two simple subtractors,and two simple comparators are needed for the proposed CA modulator.Therefore,it is simple and applicable block.Afterwards,many MATLAB simulation programs are executed.Time and frequency domain behaviors are presented.Furthermore, in-band distortion introduced by the Proposed CA modulation is calculated in terms of Error Vector Magnitude(EVM).Moreover,the proposed system outperforms  the conventional one when compared in terms of PAPR,equalization,and BER under Additive White Gaussion Noise(AWGN)channel and multipath fading channels.In addition,the impact of the proposed scheme design parameter(the number of inserted samples) is studied.The more inserted samples are added,the more accurates results  are obtained,the less EVM values are achieved,the less transmission throughput values are occured.

Keywords


OFDM,Multipath Fading Channels,PAPR,BER,Equalizer and EVM.

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