Design of Low PAPR Fundamental Modulation Waveform for Transform Domain Communication System

Abstract

To utilize white space spectrum in radio environment, transform domain communication system (TDCS) has been proposed to realize an overlay cognitive radio communication system by using spectrum bin nulling and frequency domain spreading. Being similar to OFDM systems, TDCSs still suffer from the problem of high peak to average power ratio (PAPR) in present of high power amplifier. In this paper, a distortionless PAPR reduction method is proposed for TDCS, namely clipping and phase replacement (CPR). Following this method, the clipping noise-dirty phase vector is replaced by an appropriate replacement, which is selected from the identical phase mapping space to avoid systematic performance degradation. Owing to the high computational complexity from exhaust search, an efficient implementation of CPR method is proposed through the iterative PAPR reduction and phase replacement. Moreover, some considerations for practical applications, such as imperfect spectrum sensing and the number of phase taps, are considered. Analytic and simulation results demonstrate that the distortionless CPR PAPR reduction method is a preferable candidate for TDCSs in both the single-user and multi-user scenarios.