PAPR Analysis for SOFDM and NC-SOFDM Systems in Cognitive Radio

Abstract

Noncontiguous OFDM (NC-OFDM) and Noncontiguous Spread OFDM (NC-SOFDM) have been proposed as two candidates for cognitive radio and dynamic spectrum access network. Since the available spectrum in cognitive radio system usually spreads through multiple non-contiguous spectrum holes, multi-carrier based transceivers need to deactivate some of their subcarriers to avoid interference to primary users. However, like OFDM and SOFDM, NC-OFDM and NC-SOFDM also suffer from large peak to average power ratio (PAPR). Hence, it is desired to analyze the PAPR performance of NC-OFDM and NC-SOFDM schemes with different spreading code sets. In this paper, we analyze the PAPR performance of NC-OFDM, NCSOFDM with binary Hadamard-Walsh spreading codes, and NCSOFDM with polyphase Carrier Interferometry (CI) spreading codes. Both analysis and simulation results show that the NCSOFDM with polyphase CI code set provides the lowest PAPR, while the NC-OFDM provides the highest PAPR and NC-SOFDM with Hadamard-Walsh code set in the middle.