MISO M-Ppm for Integrated-Receiver SWIPT with Pulse Shaping and PSO-Based Beamforming

Abstract

Integrated-receiver (IntRx) simultaneous wireless information and power transfer (SWIPT) enables low-power Internet of Things devices by eliminating energy-intensive radio frequency (RF) front-end components at the receiver. This paper investigates a multiple-input single-output (MISO) SWIPT system employing M-ary pulse position modulation (M-PPM), where high-amplitude time-localized pulses exploit rectifier nonlinearity via increased peak-to-average power ratio (PAPR). Transmit beamforming is employed to enhance harvested DC power, and the impact of pulse shaping is analyzed using rectangular and raised-cosine (RC) pulses with varying roll-off factors. Monte Carlo simulations under random channel realizations show that the proposed MISO M-PPM architecture achieves harvested energy gains of up to 37.8% compared to single-antenna transmission. Furthermore, RC pulse shaping consistently outperforms rectangular pulses, with harvested energy increasing with the roll-off factor. To enable beamforming without increasing receiver complexity, a particle swarm optimization (PSO)-based transmit beamforming method is proposed, using received power as the sole fitness metric and requiring no phase estimation at the receiver. Beamforming coherence is characterized by using the standard deviation of received signal phases. An analytical model is developed to estimate the expected number of PSO iterations required to satisfy a target coherence level as a function of swarm size, enabling efficient allocation of computational resources.