Low PAPR FBMC

Abstract

Unlike single carrier-frequency division multiple access (SC-FDMA), just combining discrete Fourier transform (DFT) spreading and filter bank multicarrier with offset quadrature amplitude modulation (FBMC-OQAM) results in only marginal peak to average power ratio (PAPR) reduction. To utilize the single carrier effect of DFT spreading, a special condition of the coefficients at each subcarrier’s in-phase and quadrature-phase (IQ) channels should be satisfied. As a starting point, we first derive this condition, which we call the identically-time-shifted-multicarrier (ITSM) condition. Then, based on this condition, we propose a new type of FBMC for low PAPR. The main features of the proposed scheme are summarized as follows. First, in order to further enhance the amount of PAPR reduction, we generate the four candidate versions of the DFT-spread and ITSM-conditioned FBMC waveform and select the one with minimum peak power. Even with multiple candidate generation, the major computation parts, such as DFT and IDFT are shared and need to be performed only once, unlike the conventional side information (SI)-based PAPR reduction schemes. Consequently, with a fractional complexity overhead compared with the previous DFT-spread FBMC, the proposed scheme achieves a PAPR reduction comparable to that of SC-FDMA. Second, the proposed scheme transmits only two bit SI per data block consisting of multiple FBMC-OQAM symbols. Hence, the SI overhead is significantly low compared with the usual SI-based schemes, such as selective mapping or partial transmit sequence.