Peak-to-average power ratio suppression schemes in DFT based OFDM

Abstract

One of the most serious problems of orthogonal frequency division multiplexing (OFDM) is its high peak-to-average power ratio (PAPR) which substantially degrades the efficiency of a linear power amplifier. PAPR suppression schemes for OFDM are investigated in this paper. Coding schemes suppress the PAPR of an OFDM signal to a low level, but they cause considerable spectral loss and do not work efficiently when the number of subcarriers is large. Phase rotation schemes cause very small spectral loss but their suppression performance is not so good. Clipping schemes suppress the PAPR effectively but they increase the sidelobes of the signal spectrum substantially. Amplitude limiting schemes suppress the PAPR very well without any spectral loss before pulse shaping but will have an additional PAPR after pulse shaping. However, the additional PAPR can be suppressed by using an adaptive peak suppression (APS) algorithm. Thus, a new limiter plus APS scheme is introduced for bandwidth efficient PAPR suppression in OFDM. It suppresses the PAPR of 128-QPSK-OFDM from 12.7 dB to 5.2 dB with 1 dB power loss at 10/sup -3/ symbol error rate (SER) in an additive white Gaussian noise (AWGN) channel or 0.31 dB power loss at 10/sup -3/ SER in a Rayleigh fading channel. The limiter plus APS scheme shows better performance than any other schemes for DFT based BPSK or QPSK-OFDM when the number of sub-carriers is not too small (D/spl ges/32).