Ruiyi Shen

Electromagnetic beams carrying orbital angular momentum (OAM) exhibit helical phase structures and doughnut-shaped intensity profiles, offering a promising basis for mode-division multiplexing and for fine-grained sensing in millimeter wave and sub-terahertz regimes. The simultaneous use of multiple OAM modes in joint communication and sensing systems has nevertheless remained unexplored due to conflicting requirements. While concurrent transmission of multiple orthogonal modes maximizes throughput in favor of communication, sensing relies on obtaining location-dependent scattering signatures by probing individual modes. In this work, we exploit the flexibility of OAM multiplexing to reconcile these requirements, based on the core insight that communication capacity depends primarily on the number of active modes, rather than the specific mode indices. Hence, by reconfiguring subsets of OAM modes, we generate diverse composite field distributions, whose reflections from sensing targets encode rich spatial information, while maintaining orthogonality for data multiplexing. We derive the theoretical limits of joint sensing performance and validate our approach through extensive over-the-air experiments at 120 GHz, demonstrating accurate target localization alongside high-speed data transmission. Our modeling and design are built on a deep understanding of the physics of OAM-carrying beams and the fundamentals of multiple-input multiple-output wireless propagation channels.

The real-time knowledge of mmWave device orientation offers dual benefits for wireless networks and Internet of Things (IoT) applications: it enhances communication and localization performance through link diagnosis, and it enables context inference with asset and wearable tracking. This article presents metasurface-assisted polarization sensing (MetaPol), a novel system architecture that augments commodity mmWave access points (APs) with a carefully designed ultralow-cost anisotropic metasurface to noninvasively extract the orientation of client devices, without hindering data reception or modifying hardware. MetaPol leverages the polarization of transmitted electromagnetic (EM) waves as an accurate indicator of the orientation of linearly polarized antenna arrays, prevalent in commercial mmWave mobile and IoT devices. Yet, polarization sensing is rarely supported by commodity APs due to the need for two orthogonally polarized antenna arrays to capture the incident electric field. Instead, MetaPol creates virtual polarization channels to characterize impinging electric fields, through the conversions of wave polarization on the fly as it interacts with the metasurface. To design MetaPol, we model and exploit the properties of a unique anisotropic metamaterial based on C-shaped split-ring resonators (SRRs). We discover that, when grouped in certain configurations, these meta-elements can convert the incident polarization in a deterministic way. We show that three polarization channels are sufficient for unambiguous orientation sensing, and we provide a corresponding three-shot noncoherent protocol that extracts user orientation by comparing the power received from distinct surface areas. Through extensive over-the-air experiments with more than 1000 measurements in the mmWave band, we demonstrate that MetaPol achieves a mean error of 2.6° across practical settings with negligible compromise to the underlying data communication link.

The integration of communication and sensing functions within mmWave systems has gained attention due to the potential for enhanced passive sensing and improved communication reliability. State-of-the-art techniques separate these two functions in frequency, use of hardware, or time, i.e., sending known preambles for channel sensing or unknown symbols for communications. In this paper, we introduce Panoptic, a novel system architecture for integrated communication and sensing sharing the same hardware, frequency, and time resources. Panoptic jointly detects unknown symbols and channel components from data-modulated signals. The core idea is a new beam manipulation technique, which we call compressive sidelobe forming, that maintains a directional mainlobe toward the intended communication nodes while acquiring unique spatial information through pseudorandom sidelobe perturbations. We implemented Panoptic on 60 GHz mmWave radios and conducted extensive over-the-air experiments. Our results show that Panoptic achieves reflector angular localization error of less than 2° while at the same time supporting mmWave data communication with a negligible BER penalty when compared with conventional communication-only mmWave systems.

Integrated sensing and communication (ISAC) is an emerging technology that can enable future wireless communication networks to also provide wireless sensing services, thus enabling smart cities, homes, and factories that will transform the businesses and societies of the future. In this article, an overview of ISAC is presented, considering the ongoing standardization and research activities while emphasizing the industrial outlook. First, we provide a brief introduction to ISAC fundamentals, including the sensing configurations used in classical radar-like sensing. This is complemented by a description of the major use cases of ISAC, appreciating the interplay between ISAC and emerging technologies such as digital twins and artificial intelligence. To facilitate a smooth integration of sensing into the cellular ecosystem, the key design considerations for the physical layer and spectrum aspects are outlined. Furthermore, the key technology gaps and challenges in integrating sensing functionalities into current wireless communication networks are identified. Finally, we dive deeper into some innovative research directions for ISAC—such as novel antenna design, sensing-aware beam manipulation, waveform design, reconfigurable intelligent surfaces, wavefront engineering, and near-field communications—while highlighting their relevance for future wireless networks.

Sensing the coefficient of friction (COF) is crucial for robotic and Cyber-Physical System applications, including grasping. We introduce RoboTera, a novel system for non-contact COF estimation using sub-Terahertz (sub-THz) perception in robotics. Unlike tactile sensors that require direct contact, our approach leverages sub-THz signals with sub-millimeter wavelength to capture surface roughness characteristics as an essential factor in non-contact COF inference, that conventional imaging modalities like cameras and LiDAR cannot detect. Our system enables precise COF inference by integrating sub-THz-estimated roughness with image-based material classification. Further, we exploit COF inferences to identify stable grasp configurations and improve grasping performance. Experiments show over 92% accuracy in COF estimation, with a 31.8% improvement in grasp success rates in real-world robotic tasks.

MmWave antenna array calibration is a necessary yet tedious and costly process in manufacturing to capture the non-idealities in phased arrays, in order to obtain codebooks for accurate and stable beam steering. Unfortunately, predefined codebooks provided by manufacturers to steer beams in a given set of directions do not support the arbitrary beam shapes required for various mmWave communication, sensing, and security applications. To create arbitrary beam patterns, one needs to first find the unknown calibration vector for the particular phased array in use. In this paper, we introduce EiCal, a novel zero-shot technique that leverages the beamforming codebook advertised by the manufacturer to extract the calibration vector at zero cost (i.e., with no additional measurements). The key idea is that the unknown desired calibration vector can be obtained via an appropriately designed eigen-decomposition of the given codebook. We experimentally demonstrate the efficacy of EiCal on a 60 GHz mmWave array for two scenarios: angle estimation using compressive pseudorandom beams, and simultaneous steering of beams and nulls. Our results also point to potential simplifications in the calibration process at the manufacturer.