Passive IoT technology, valued for its self-sustaining and low-cost attributes, faces notable limitations in data rate, range, and power efficiency. While significant progress has been made in enhancing uplink performance through backscattering techniques, the primary performance bottleneck has now shifted to the downlink. In this paper, we propose 3in1, a novel multi-tone system that jointly optimizes wireless power delivery, high-precision clocking, and robust communication for long-range passive IoT devices. By carefully controlling the phase and frequency spacing of the multi-tone signals, 3in1 significantly improves energy harvesting efficiency, seamlessly provides wireless clocking, and enables reliable downlink communication without interrupting power transfer. Our design addresses critical challenges, including signal optimization, data encoding, and strict FCC compliance.

There has been a trend in passive IoT systems to move complexity from tag to reader for delivery of power, clock, and data [1, 2]. However, current designs either cannot deliver all these three simultaneously, or fail to do so in a co-optimized way, which leads to poor operating range and long charging time of passive IoT systems. To address this key bottleneck, we present 3in1, the first system co-design that optimizes Wireless Power Transfer (WPT) efficiency, accurate wireless clocking, and downlink communication simultaneously. We propose several novel designs: (i) an optimized multi-tone WPT waveform compliant with ISM band and FCC regulations; (ii) a robust and accurate wireless clocking mechanism integrated within the optimized waveform; (iii) a multi-tone Binary Phase Shift Keying (BPSK) downlink modulation scheme that maintains wireless clocking accuracy and WPT efficiency; and (iv) an ultra-low power receiver capable of simultaneously extracting power, clock, and data from the optimized waveform. Preliminary results demonstrate that higher WPT efficiency, precise wireless clocking, and downlink communication can be achieved simultaneously within a co-optimized waveform. We believe this paves the way for the next generation of passive IoT system design.

Passive IoT localization technology offers significant advantages across various applications due to its self-sustaining, maintenance-free, and low-cost nature. However, existing systems cannot effectively address the multipath problem in real-world deployments, leading to unreliable localization results in the severe multipath scenario. We propose to fill the gap with UWB2, the first ultra-wideband backscatter passive IoT system that can achieve centimeter-level 99th percentile accuracy even under severe multipath environments. The demo will illustrate UWB2's performance in localization accuracy, latency, operating range, and power consumption in severe multipath scenarios.