  Simultaneous wireless information and power transfer (SWIPT) has emerged as a
viable technique to energize and connect low-power autonomous devices and
enable future Internet of Things (IoT). A major challenge of SWIPT is the
energy consumption of the receiver of such low-power devices. An attractive
low-power solution consists in an integrated information decoder (ID) and
energy harvester (EH) architecture for SWIPT receiver (IntRx) where the
received RF signal is first rectified before being used for information
decoding. Such architecture eliminates the need for energy-consuming RF
components such as local oscillators and mixers. This paper proposes a novel
modulation and demodulation method for the IntRx SWIPT architecture based on
pulse position modulation (PPM) where information is encoded in the position of
the pulse. The new method transmits high amplitude pulses to increase the
Peak-to-Average Power Ratio (PAPR) of the transmit signal and exploits the EH's
nonlinearity so as to boost the harvested DC power. Simultaneously, the
information can be decoded from the rectifier signal by simply finding the
position of the pulse in a certain symbol duration. We have analyzed both the
information and the power transfer performance of the newly proposed PPM for
IntRx SWIPT theoretically, numerically, and experimentally. To that end, we
have established a SWIPT system testbed in an indoor environment by prototyping
a base station to transfer information-power signal and the IntRx SWIPT
receiver including ID and EH blocks. The performance evaluation of the PPM was
carried out in various conditions, and the results have been compared and
contrasted to conventional signals. Theoretical, numerical, and experimental
results highlight the significant benefits of the proposed PPM scheme to
enhance the power transfer performance and operate information decoding with
low-power consumption.
