Performance analysis of Multicarrier code division multiple Access system under clipping noise

Abstract

Multicarrier Code Division Multiple Access MC CDMA is a newlinetransmission technique which combines the advantages of both OFDM and newlineCode Division Multiplexing Access CDMA to allow high transmission rates newlineover severe time dispersive multi path channels without the need of a newlinecomplex receiver implementation MC CDMA exploits frequency diversity newlinevia the different subcarriers and therefore allows the high code rate systems newlineto achieve good Bit Error Rate BER performances newlineThe foremost limitation of MC CDMA system is the Multiple newlineAccess Interference MAI and high peak to average power ratio PAPR newlineHigh PAPR leads to nonlinear distortion of the amplifier and results in intercarrier newlineinterference and out of band radiation The simplest method for PAPR newlinereduction is clipping Clipping at the Nyquist sampling rate has been used for newlinelow complexity applications but suffers from peak regrowth after digital toanalog newline D A conversion Clipping of the oversampled MC CDMA signals newlinereduces the peak regrowth after D A conversion But it causes out of band newlineradiation which has to be filtered Also clipping of MC CDMA signals causes newlineclipping noise which has sparsity in time domain The performance of MCCDMA newlineunder such scenario is poor and optimal detection is one of the newlinesolutions with a high complexity is required In this thesis the Bit Error Rate newline BER performance is compared under clipping noise with sphere decoding newlineand Global search algorithm based Multiuser detectors The detector for the newlineMC CDMA can be of two types namely Single User detector and Multi User newlineDetector The Single User detector is usually a suboptimal detector having an newlineequalizer and quantizer combination The Multi User detection can be of newlineoptimal or suboptimal newline