Joint sidelobe suppression and PAPR reduction in OFDM using partial transmit sequences

Orthogonal frequency-division multiplexing (OFDM) waveform is known for its drawbacks that affect application in practice: high out-of-band (OOB) radiation and high peak-to-average power ratio (PAPR). In this paper, we propose a three-stage technique for the joint reduction of OOB radiation and PAPR, therefore minimizing the spectral regrowth after the power amplifier as well as signal distortion. In the first and the second stages, the OFDM data vector is partitioned into contiguous blocks that are naturally suited for PAPR reduction using partial transmit sequences (PTS). Since edge blocks/subcarriers have more impact on the OOB radiation, each edge block is further divided into smaller interleaved sub-blocks, and optimized phase rotations are applied to each sub-block to suppress the spectral sidelobes. Following the frequency domain techniques, optimum phase rotation for the time domain OFDM symbol is calculated to achieve smoother transition with the previous symbol, which further reduces the OOB spectrum. The proposed method improves the joint containment in frequency and power dimensions, along which the OFDM signal suffers from high spreading.