Listening Alone, Understanding Together: Collaborative Context Recovery for Privacy-Aware AI

We introduce CONCORD, a privacy-aware asynchronous assistant-to-assistant (A2A) framework that leverages collaboration between proactive speech-based AI. As agents evolve from reactive to always-listening assistants, they face a core privacy risk (of capturing non-consenting speakers), which makes their social deployment a challenge. To overcome this, we implement CONCORD, which enforces owner-only speech capture via real-time speaker verification, producing a one-sided transcript that incurs missing context but preserves privacy. We demonstrate that CONCORD can safely recover necessary context through (1) spatio-temporal context resolution, (2) information gap detection, and (3) minimal A2A queries governed by a relationship-aware disclosure. Instead of hallucination-prone inferring, CONCORD treats context recovery as a negotiated safe exchange between assistants. Across a multi-domain dialogue dataset, CONCORD achieves 91.4% recall in gap detection, 96% relationship classification accuracy, and 97% true negative rate in privacy-sensitive disclosure decisions. By reframing always-listening AI as a coordination problem between privacy-preserving agents, CONCORD offers a practical path toward socially deployable proactive conversational agents.

MmBack: Clock-free Multi-Sensor Backscatter with Synchronous Acquisition and Multiplexing

Backscatter tags provide a low-power solution for sensor applications, yet many real-world scenarios require multiple sensors-often of different types-for complex sensing tasks. However, existing designs support only a single sensor per tag, increasing spatial overhead. State-of-the-art approaches to multiplexing multiple sensor streams on a single tag rely on onboard clocks or multiple modulation chains, which add cost, enlarge form factor, and remain prone to timing drift-disrupting synchronization across sensors. We present mmBack, a low-power, clock-free backscatter tag that enables synchronous multi-sensor data acquisition and multiplexing over a single modulation chain. mmBack synchronizes sensor inputs in parallel using a shared reference signal extracted from ambient RF excitation, eliminating the need for an onboard timing source. To efficiently multiplex sensor data, mmBack designs a voltage-division scheme to multiplex multiple sensor inputs as backscatter frequency shifts through a single oscillator and RF switch. At the receiver, mmBack develops a frequency tracking algorithm and a finite-state machine for accurate demultiplexing. mmBack's ASIC design consumes 25.56uW, while its prototype supports 5 concurrent sensor streams with bandwidths of up to 5kHz and 3 concurrent sensor streams with bandwidth of up to 18kHz. Evaluation shows that mmBack achieves an average SNR surpassing 15dB in signal reconstruction.

TerraTrace: Temporal Signature Land Use Mapping System

Understanding land use over time is critical to tracking events related to climate change, like deforestation. However, satellite-based remote sensing tools which are used for monitoring struggle to differentiate vegetation types in farms and orchards from forests. We observe that metrics such as the Normalized Difference Vegetation Index (NDVI), based on plant photosynthesis, have unique temporal signatures that reflect agricultural practices and seasonal cycles. We analyze yearly NDVI changes on 20 farms for 10 unique crops. Initial results show that NDVI curves are coherent with agricultural practices, are unique to each crop, consistent globally, and can differentiate farms from forests. We develop a novel longitudinal NDVI dataset for the state of California from 2020-2023 with 500~m resolution and over 70 million points. We use this to develop the TerraTrace platform, an end-to-end analytic tool that classifies land use using NDVI signatures and allows users to query the system through an LLM chatbot and graphical interface.