A Supplemental Zero-Energy Downlink Air-Interface Enabling 40-Year Battery Life in IoT Devices

A zero-energy downlink air-interface (ZE-DL) that does not draw power from the device's battery is introduced. Information packets sent on the ZE-DL are preceded by a power-optimized preamble (POP) where the energy harvested from the POP is used by an ultra-low power receiver (ULP-RX) to decode the information packets. An approach for estimating the POP duration as a function of free-space path loss, the energy harvester efficiency and the ULP-RX power consumption is outlined. An IoT device architecture is proposed where the ZE-DL functions as a supplement to the 3GPP Uu air-interface. On-demand features are introduced into the 3GPP system using a broad class of wake-up signal (WUS) transmissions on the ZE-DL. An analytical framework for estimating the network resource overhead associated with POP transmissions is developed. An energy model for the IoT device is developed and a pathway to 20, 40-year battery life for Uu uplink (UL) transaction cycles of 1, 5 days is demonstrated where the POP transmission related network overhead is limited to less than 6%.