Low-Complexity Selected Mapping Scheme Using a Bank of Butterfly Circuits in Orthogonal Frequency Division Multiplexing Systems

Selected mapping schemes (SLMs) have gained popularity to improve the peak-to-average power ratio (PAPR) reduction performance. Even so, the computational load increases greatly owing to the many inverse fast Fourier transforms (IFFTs) in conventional SLM (CSLM) and to overcome this disadvantage, several low-complexity schemes are in vogue. This paper proposes two -point IFFTs, where N is the number of subcarriers in OFDM, and a bank of butterfly circuits (BFCs) to replace multiple IFFTs in the CSLM. The output sequence of the two -point IFFTs are simultaneously sent to a bank of M-BFCs to generate a set of M statistically independent candidate signals, including the original OFDM signal. The parameters of the first BFC, which generates the original OFDM signal, are derived. To simplify the complexity, constraints are imposed on the selection of parameters of the remaining M - 1 BFCs. The results indicate that the proposed SLM (PSLM), when compared with the CSLM, achieves an appreciable computational complexity reduction gain with the loss of a slight PAPR reduction performance.