LiteWiFi: Ultra-low Power Wi-Fi Radio for Ubiquitous IoT Connection

Ultra-low-power (ULP) Wi-Fi (consuming <100µW) is critical for creating battery-free IoT devices that operate via energy harvesting. While backscatter techniques effectively address the uplink, demodulating complex downlink Wi-Fi signals remains a major bottleneck due to the severe power constraints of ULP nodes. Existing downlink solutions are either slow (around 125 kbps) or require custom modifications to commercial off-the-shelf (COTS) Wi-Fi devices. In this paper, we present LiteWiFi, a system that achieves high-speed Wi-Fi demodulation at the microwatt level without requiring hardware modifications to COTS Wi-Fi infrastructure. LiteWiFi introduces a passive mixing model for OFDM signals and a lightweight passive alignment technique for eliminating phase errors. LiteWiFi achieves a data rate of up to 2.22 Mbps, representing a 17.8X improvement over prior symbol-level systems and a 1.97X improvement over state-of-the-art custom hardware solutions.