Abstract
Abstract
High peak-to-average power ratio (PAPR) remains a central obstacle for power-limited uplink terminals in sixth-generation (6G) networks. This paper proposes a transmitter that combines a hybrid OFDM/SC-FDMA waveform, a cascaded selected-mapping and partial-transmit-sequence (SLM-PTS) stage, a joint spatial-temporal phase optimizer (JST-PO) that minimizes the worst-antenna PAPR over several transmit chains, and a final relaxed projection-onto-convex-sets (POCS) refinement. We derive the side-information cost, a statistical model of the cascade, a convergence argument for both the coordinate-descent optimizer and the relaxed projection, and a Bussgang model of the residual distortion. Monte Carlo results for a $2\times2$ Rayleigh MIMO uplink show that the 99.9th-percentile PAPR falls from about 10.2~dB for plain OFDM to about 5.4~dB, a gain of roughly 4.8~dB, and is 1.5~dB lower than clipping-and-filtering and 1.1~dB lower than $\mu$-law companding. In AWGN the proposed scheme matches the BER and EVM of OFDM and SC-FDMA, whereas clipping-and-filtering exhibits an error floor. In MIMO fading the BER and BLER are marginally better than those of the PAPR-reduction baselines. The price is a considerably higher transmit-side processing time, which is quantified and discussed.