MiniRetro: VLC Backscatter System for Miniaturized and Sustainable Internet of Things

Abstract

The proliferation of Internet of Things (IoT) devices demands communication technologies that are sustainable, low-power, and compact. While radio-frequency (RF) backscatter has enabled 𝜇��W-level operation, its miniaturization is constrained by the physical limits of RF antennas. Visible light communication (VLC) backscatter offers an alternative by reusing existing lighting infrastructure, yet current designs require a significant area and power consumption at the IoT device. In this paper we present MiniRetro, a miniaturized VLC backscatter module with an active retroreflective area of only 0.25 cm2, combining retroreflective sheetings with liquid crystal (LC) shutters. We model the VLC backscatter channel including the impact of retroreflector type, geometry, and photodiode (PD) placement, determining the configuration that maximizes the reflected signal strength. We also provide the first analytical and experimental framework characterizing the interaction between shutter and retroreflector, capturing polarization and transmittance losses and showing that the relative rotation angle can alter reflected power by up to 66%. We validate these features experimentally with a single-pixel VLC backscatter module, confirming a reliable meter-scale mobile communication while being the first VLC backscatter design to operate with a sub-cm2 active area. Finally, we show its implementation on a small-sized aquatic robot providing uplink connectivity for aquaponics monitoring. Our results demonstrate the feasibility of MiniRetro as a miniaturized and sustainable VLC backscatter system for next-generation IoT connectivity