Figure 1: EchoSight leverages in-situ optical backscatter tethering to achieve a look-and-control bidirectional interaction on commercial AR glasses.This process mimics human's natural interaction with low mental burden.EchoSight requires no pre-registration or network connection, facilitating scenarios where interactions are opportunistic and impromptu.

As embodied AI gradually transitions into practical applications, enhancing the fidelity of how embodied agents perceive the physical world has become a critical challenge. Current perception methods typically rely on computer vision-based fiducial marker systems, which suffer from limitations such as insufficient reading distance, poor localization accuracy, and high susceptibility to environmental lighting conditions. Currently, SPAD sensor-based LiDAR technology is emerging in commercial mobile devices due to its compact size, high precision, and low power consumption. This paper presents the design of the RetroLiDAR system, which chimes with the concept of backscatter in wireless technology, to create a liquid-crystal fiducial marker system that can be directly read by LiDAR. On the marker side, we use retroreflective materials to reflect the LiDAR's emitted light back and employ a liquid crystal modulator to adjust the intensity of the light signal. On the LiDAR end, we design a signal processing pipeline to demodulate the marker's modulation message using the temporal received signal strength. Experimental results from our prototype demonstrate that compared to visual fiducial markers, RetroLiDAR extends the reading distance by 2.6x compared to QR codes and by 44% compared to AprilTags, while reducing the median ranging error by 85%. We also present a low-power marker circuit design, a link budget analysis, and two proof-of-concept applications to validate the system's efficacy and practicality.

We introduce Nada, the first framework to autonomously design network algorithms by leveraging the generative capabilities of large language models (LLMs). Starting with an existing algorithm implementation, Nada enables LLMs to create a wide variety of alternative designs in the form of code blocks. It then efficiently identifies the top-performing designs through a series of filtering techniques, minimizing the need for full-scale evaluations and significantly reducing computational costs. Using adaptive bitrate (ABR) streaming as a case study, we demonstrate that Nada produces novel ABR algorithms---previously unknown to human developers---that consistently outperform the original algorithm in diverse network environments, including broadband, satellite, 4G, and 5G.

Passive visible light communication (VLC) modulates light propagation or reflection to transmit data without directly modulating the light source. Thus, passive VLC provides an alternative to conventional VLC, enabling communication where the light source cannot be directly controlled. There have been ongoing efforts to explore new methods and devices for modulating light propagation or reflection. The state-of-the-art has broken the 100 kbps data rate barrier for passive VLC by using a digital micro-mirror device (DMD) as the light modulating platform, or transmitter, and a photo-diode as the receiver. We significantly extend this work by proposing a massive spatial data channel framework for DMDs, where individual channels can be decoded in parallel using an event camera at the receiver. For the event camera, we introduce event processing algorithms to detect numerous channels and decode bits from individual channels with high reliability. Our prototype, built with off-the-shelf event cameras and DMDs, can decode up to ~2,000 parallel channels, achieving a data transmission rate of 1.6 Mbps, markedly surpassing current benchmarks by 16x.

Visible light communications (VLC) have gained significant attention as a potential solution for the radio spectrum crunch. To achieve high data rates, emerging transmitter devices like 2D digital micro-mirror devices (DMD) have been proposed, offering significantly faster state flipping rates compared to conventional liquid crystalline shutters. However, previous approaches utilizing DMD suffered from a lack of spatial diversity, as they used all micro-mirrors in the same state. This paper introduces EV-DMD, a novel approach that utilizes DMD as a 2D transmitter, working in tandem with an event-based vision (EV) camera. In this method, multiple bit streams are transmitted in parallel through different mirror blocks of the DMD, while an EV camera simultaneously decodes multiple light blocks, enabling a truly 2D high-speed VLC system. To the best of our knowledge, this is the first implementation of a 2D VLC system that achieves an order-of-magnitude improvement in bit rate compared to state-of-the-art solutions.

Visible Light Backscatter Communication (VLBC) presents an emerging ultra-low-power IoT connectivity solution with high spatial-spectral efficiency and intrinsic human-perceivable privacy advantages. However, research progress on enhanced data rate and sophisticated device coordination of state-of-the-art VLBC systems still cannot meet the low-latency requirement (sub-second level for an IoT network) for massive connections.

Conventional road signs convey very concise and static visual information to human drivers, and bear retroreflective coating for better visibility at night. This paper introduces RetroI2V - a novel infrastructure-to-vehicle (I2V) communication and networking system that renovates conventional road signs to convey additional and dynamic information to vehicles while keeping intact their original functionality. In particular, RetroI2V exploits the retroreflective coating of road signs and establishes visible light backscattering communication (VLBC), and further coordinates multiple concurrent VLBC sessions among road signs and approaching vehicles. RetroI2V features a suite of novel VLBC designs including late-polarization, complementary optical signaling and polarization-based differential reception which are crucial to avoid flickering and achieve long VLBC range, as well as a decentralized MAC protocol that make practical multiple access in highly mobile and transient I2V settings. Experimental results from our prototyped system show that RetroI2V supports up to 101 m communication range and efficient multiple access at scale.

Visible light backscatter communication (VLBC) presents an emerging low power IoT connectivity solution with spatial reuse and interference immunity advantages over RF-based (backscatter) technologies. State-of-the-art VLBC systems employ COTS LCD shutter as optical modulator, whose slow response fundamentally throttles its data rate to sub-Kbps, and limits its deployment at scale for use cases where higher rate and/or low latency is a necessity.