A new ZCT precoded OFDM system with pulse shaping: PAPR analysis

Abstract

This paper studies the Peak to Average Power Ratio (PAPR) improvements in various precoding based Orthogonal Frequency Division Multiplexing (OFDM) systems. In particular, the Zadoff-Chu matrix Transform (ZCT) precoder based PAPR reduction technique is analyzed. The ZCTs are obtained from Zadoff-Chu (ZC) sequences by filling ZCT kernel row-wise or alternatively column wise. Row wise filling gives rise to Constant Envelope OFDM (CE-OFDM) system with 0 dB PAPR, while column wise filling give rise 7.8 dB, at clip rate of 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-3</sup> with system subcarriers N = 64 for QPSK modulation. However, since even CE-OFDM systems are required to operate with pulse shaping that helps in keeping out-of-band radiation low and meeting the transmission spectrum mask requirement, the PAPRs are no longer 0 dB. Therefore, in this paper, we present PAPR analysis of various precoding based OFDM systems with the popular Root Raised Cosine (RRC) pulse shaping. Simulation results show that, the ZCT Row-wise precoder based OFDM (ZCT-R-OFDM) system has lower PAPR than the ZCT Column-wise precoder based OFDM (ZCT-C-OFDM) system, the Hadamard Transform precoder based OFDM (WHT-OFDM) systems and the conventional OFDM systems.