Amplitude Shift Keying Constellation Space for Simultaneous Wireless Information and Power Transfer

Simultaneous wireless information and power transfer (SWIPT) has the potential to realize the envisioned ubiquity of the internet of things (IoT) by energizing them wirelessly whilst exchanging information. Recently, low-complexity receiver architectures for SWIPT are being considered for decoding information from amplitude modulated signals after rectification. However, less attention is paid towards improving the non-linear rectifier model prevalent in these architectures which is often truncated till fourth-order term in diode characteristic. In this paper, a novel, tractable analytical model for the rectenna non-linearity is presented which provides a theoretical upper bound to harvested DC power over the amplitude shift keying (ASK) constellation space corresponding to the entire diode non-linear region. Besides, the work also exposes the convexity of harvested DC power vis-à-vis incoming signal power thereby verifying the rate-energy (R-E) tradeoff in SWIPT for different choices of transmitted symbol amplitude distributions. Finally, the theoretical results presented using the adopted model are substantiated with the Monte Carlo circuit simulations allowing to conveniently evaluate and draw compromise in SWIPT performance against a choice of modulation scheme out of the ASK constellation space.