Peak to Average Power Ratio Reduction in Orthogonal Frequency Division Multiplexed Systems

Abstract

High data rate transmission over wireless channel is a tedious task due to various channel impairments such as fading, inter symbol interference ISI especially when single carrier newlinemodulation is used Orthogonal frequency division multiplexing OFDM is a multi carrier newlinetransmission scheme where high data rate is split in narrowband low rate streams and newlinetransmitted in a parallel fashion using orthogonal subcarriers Due to its immunity towards newlinefading and ISI, OFDM is widely used in high data rate application such as digital audio newlinebroadcast DAV, Digital video broadcast DVB, wireless local area network WLAN, newlinewireless metropolitan area network WMAN, high speed digital subscriber line HDSL, newlineasymmetric digital subscriber line ADSL and 4G mobile technologies such as long term newlineevolution LTE and worldwide interoperability of microwave access WiMAX newlineApart from its advantages, OFDM too suffers from few drawbacks such as peak to newlineaverage power ratio PAPR and poor bit error rate BER performance in severe fading newlinechannels, which are of major concern OFDM is a multicarrier scheme, where subcarriers are newlineindependently modulated and the resultant signal has large envelope fluctuations or dynamic newlinerange When such signal passes through high power amplifier HPA circuits, nonlinearity of newlineHPA generates harmonics leading to in band and out of band signal distortion Large newlinedynamic range signal requires more complex and costly HPA circuits To avoid this problem, newlineback off is generally used but reducing the input power to make HPA work in linear region newlinereduces the efficiency of HPA There are various techniques available for PAPR reduction, newlinesome of them reduce PAPR at the cost of creating distortion and other techniques which are distortionless have some issues such as high complexity, side information etc newline