Linear Precoding of OFDMA Signals to Minimize Their Instantaneous Power Variance

The large instantaneous power fluctuations of orthogonal frequency division multiple access (OFDMA) signals necessitate significant power backoff to minimize the effects of nonlinear power amplifier distortion. Is there an optimum linear block precoding that significantly reduces the instantaneous power variance of OFDMA signals? For contiguous and block-interleaved non-contiguous frequency mappings we find that there is a power variance-minimizing linear block precoding which requires a slightly lower power backoff than that for DFT precoding (which in the form of SC-FDMA, is used for the uplink signaling in the 3GPP-LTE standard). The optimum precoding is not unique, and in its simplest form it imposes only mild linear filtering and a moderate noise enhancement penalty if the receiver uses linear equalization.