With the increasing demand for internet of things (IoT) applications, especially for location-based services, how to locate passive mobile targets (MTs) with minimal beam adjustment has become a challenge. Resonant beam systems are considered promising IoT technologies with advantages such as beam self-alignment and energy concentration. However, resonant systems are difficult to apply to multi-user scenarios due to co-frequency interference. To establish a resonant system for multi-target localization, this paper designs an innovative resonant system architecture based on frequency division multiple access (FDMA), which enables a base station (BS) to establish connections with multiple mobile targets (MTs) with different carriers, and establishes a multi-channel cyclic model through a retro-directive array (RDA) to achieve one-to-many electromagnetic wave propagation and MTs direction of arrival (DOA) estimation through echo signals. Simulation results show that the proposed system supports resonant establishment between the BS and multiple MTs. This helps the BS maintain high DOA estimation accuracy when faced with multiple passive MTs, ensuring that the DOA error is less than 1° within a range of 5 m and 50° field of view, and the accuracy is higher than that of active beamforming localization systems under the same conditions.

The pronounced signal attenuation characteristic of mmWave frequencies necessitates enhanced beam alignment techniques. Existing systems require scanning and steering procedures before beams can be aligned. This study introduces a novel resonant beam system (RBS) optimized for mmWave bands, featuring self-alignment capability. Utilizing retro-directive antenna arrays, our system achieves adaptive resonance, obviating the need for dedicated beam alignment. To address the interference issue typically confronted by the resonant structure, we incorporate a dual-frequency design that enables frequency division duplex (FDD) communication, alleviating interference. Intuitive analysis reveals that our proposed system can establish stable resonance within a microsecond (μs) scale of time. Preliminary assessments of the communication channel indicate that the system achieves maximum spectral efficiency of 4.8 bps/Hz while maintaining a bit error rate below 3.8 × 10−3in indoor environments.

The Simultaneous Wireless Information and Power Transfer (SWIPT) technique heralds a new era for future Internet of Things (IoT) devices. Resonant Beam System (RBS) is emerging as a possible future for achieving long-range, high-power, and high-capacity SWIPT. However, ensuring human safety at higher power levels presents an unresolved issue. A novel approach to enhance safety utilizes self-mixing interference to minimize radiation exposure for invading objects. However, this design restricts the system to a predetermined position. Thus, the application of the system in mobile scenarios is still challenging. In this paper, we proposed an enhanced self-protection RBS with self-adaptive phase adjustment to support the mobility of the system. A phase adjuster is composed into the system which utilizes the linear Electro-optic effect (i.e. Pockels effect) to correct phase discrepancies. An Optical Phase-Locked Loop (OPLL) achieves self-adaptive functionality using its feedback loop. Based on the analytical model established in this paper, the proposed system does not compromise the safety of the original self-protection RBS but offers mobility. The SWIPT performance evaluations indicate a stable system output, with a spectral efficiency of approximately 13.77 bps/Hz and an electrical power output of 4.63 W over a distance of 6 m within a 5∘ field of view.

The relative localization (RL) of unmanned aerial vehicle (UAV) swarms has gained considerable traction within the realm of UAV formation control. However, most existing RL methods face the challenge of balancing accuracy and computational power in unknown environments. The Resonant Beam (RB) system, which features energy-concentrated and selfaligned transmission can be used for positioning with centimeterlevel accuracy. In this study, we improved the RB system through a double complementary metal-oxide-semiconductors (CMOS) design and proposed a corresponding calculation method to simultaneously obtain the relative position and relative attitude angle, making it adapt to RL problems of swarms. Building upon these advancements, we design a UAV system to solve the three-dimensional RL problems. For large-scale swarms and indirect RL situations, we propose an RB-featured direct-indirect link optimization algorithm considering dynamic correction to improve positioning accuracy and meet real-time requirements. The simulation results show that our root mean square error (RMSE) is within 4cm when the UAV reaches a maximum distance of 30m and is not adjacent to the baseline UAV. This represents a notable 24.2% improvement over the shortest path algorithm. Compared with using LiDAR only for RL, our method offers higher accuracy and achieves millisecond-level speed without requiring GPU computing power.

Simultaneous lightwave information and power transfer (SLIPT) is increasingly vital in the burgeoning field of mobile Internet of Things (IoT) technologies. It offers a dual advantage: high-power wireless charging and high-rate data communication, essential for IoT devices. Resonant beam system, utilizing spatially separated laser resonators (SSLR), presents a promising solution. These systems enable the creation of resonant beams without necessitating beam steering devices or alignment/tracking processes, even when the receiver’s location changes. However, a critical challenge in deploying these systems within IoT scenario lies in their limited field of view (FoV) and coverage angle. In this paper, we present a design strategy for integrating concave mirrors with lenses in a cat’s-eye retroreflector configuration. This adjustment significantly enhances the FoV of the resonant beam SLIPT system, resulting in more efficient and broader system coverage. Through an analysis grounded in optical field propagation, we evaluate the FoV performance of the resonant beam SLIPT system. The numerical results show that with a retro-reflector dimension of 2.5 mm, our proposed system demonstrates the capability of conducting watt-level electrical power transfer, coupled with a communication capacity of approximately 10-bit/s/Hz under a 6.87° FoV. This substantial improvement in FoV not only addresses the current limitations but also provides new avenues for resonant beam SLIPT systems in a wide range of IoT applications.

In industrial environments where pedestrians and vehicles closely interact, existing point positioning systems often yield inaccurate results by disregarding crucial vehicle information, such as shape and angles, thereby compromising effective early warning mechanisms. Moreover, existing positioning systems relying on visual or radar methodologies also have limitations due to environmental factors. To address these challenges, this article introduces a novel pedestrian and vehicle area positioning and warning system base on multiple ultrawideband (UWB) signals, offering detailed information about vehicle positioning, orientation, and shape. Employing multiple UWB tags alongside the two-way ranging (TWR) algorithm, this system models the vehicle’s positioning area and triggers alerts when the pedestrian-to-vehicle distance falls below a specified threshold derived from the shape and orientation data of the positioning area. Additionally, this work proposes a priori data for coordinate calibration, integrating extended Kalman filtering (EKF) and a dynamic threshold algorithm to seamlessly recalibrate the vehicle’s positioning in both stationary and mobile scenarios. Experimental results demonstrate that, compared with using original area data for positioning, the modified algorithm can reduce the positioning coordinate STD by 18.43%, and the vehicle body shake variance by 50.56%, while also achieving a 4.30% increase in success warning rate and a notable 33.35% decline in false warning rate.

The rapid expansion of the Internet of Things (IoT) necessitates robust solutions for charging and communicating with a multitude of devices, making simultaneous wireless information and power transfer (SWIPT) technology increasingly vital. However, existing methods can hardly provide high charging power, great channel capacity, and flexible mobility at the same time. This manuscript introduces a millimeter-wave resonant beam system for SWIPT (mmRB-SWIPT), leveraging retro-directive antenna arrays to enable automatic beam alignment and enhanced transmission efficiency without additional controls. A dual-frequency design allows the system to operate in a frequency-division duplex mode, thereby resolving the echo interference issues encountered in prior resonant beam systems. Analytical models are developed to evaluate the system’s viability and performance, with numerical analysis indicating the capability to transmit watt-level power and achieve 4.8 bps/Hz of spectral efficiency in indoor settings.

Simultaneous wireless information and power transfer (SWIPT) is regarded as the enabling technology for IoT, 5G and beyond, or even 6G. Resonant beam system (RBS) is a promising candidate to provide high-power, long-range, and intrinsically safe SWIPT. Yet ensuring human safety under high-power application scenarios is still challenging. In this paper, we propose a portable auto-protection (AP) scheme to enhance the safety of RBS. Leveraging self-mixing interference, the high-power resonant beam is automatically cut off as the low-power protective beam is obstructed by foreign objects, resulting in less radiation exposure to invading objects. The paper proposes a phase compensation scheme that resolves the contradiction between portability and interference-induced mode variation, allowing the receiver to be placed anywhere within the field of view. Moreover, by approximating the cavity to Fabry-Pérot interferometer, analytical models are established to reveal the safety-enhancement mechanism and evaluate the system performance. Numerical results demonstrate that the AP scheme will not significantly compromise the portability and SWIPT performance of RBS, as the average spectral efficiency and electric power are 13.55bps/Hz and 5.42W respectively, within 6m transmission distance.

In the rapidly evolving field of the Internet of Things (IoT), simplifying infrastructure and deployment is highly competitive. This study introduces a novel approach using an individual-source resonant beam (RB) for passive 3-D positioning in IoT scenarios, excelling in efficient system design and signal utilization. The proposed solution simultaneously exploits the frequency structure and spatial distribution of RB to estimate position parameters, facilitating a compact design for both the base station (BS) and the mobile target (MT). The BS incorporates an individual-source RB transmitter, while the MT is equipped with a passive (electricity-free) reflector. Specifically, for extracting the distance information from RB, we develop theoretical models to illustrate the frequency attributes and associated structural variations of RB due to MT’s movement. Regarding angle estimation, we deduce the relationship between the RB field distribution and incident angles. We also conduct simulations to validate the entire positioning process. The results indicate the positioning accuracy can reach approximately 2 cm over a distance from 1.7 to 2.5 m. This technique sets a new benchmark for precise and efficient 3-D positioning, making it suitable for various IoT scenarios, such as smart homes, industrial automation, and asset tracking.

Simultaneous lightwave information and power transfer (SLIPT) is a potential way to meet the demands of sustainable power supply and high-rate data transfer in next-generation networks. Although resonant beam-based SLIPT (RB-SLIPT) can realize high-power energy transfer, high-rate data transfer, human safety, and self-alignment simultaneously, mobile transmission channel (MTC) analysis under non-line-of-sight (NLOS) propagation has not been investigated. In this paper, we propose analytical models and simulation tools for reflector-assisted NLOS transmission of RB-SLIPT, where transmission loss and accurate beam field profile of NLOS MTC can be obtained with a receiver at arbitrary positions and attitude angles. We establish analytical models relying on full diffraction theory for beam propagation between tilted or off-axis planes. Then, we provide three numerical methods (i.e., NUFFT-based, cubic interpolation-based, and linear interpolation-based methods) in simulations. Moreover, to deal with the contradiction between limited computing memory and high sampling requirements for long-range transmission analysis, we propose a multi-hop sliding window approach, which can reduce the sampling number by a factor of thousands. Finally, numerical results demonstrate that RB-SLIPT can achieve 3W charging power and 10bit/s/Hz data rate over a 2m distance in NLOS scenarios.

The demands for integrated communication and positioning (ICP) have been put forward in Internet of Things. However, the existing ICP systems either face challenges in trade-off between data rates and positioning accuracy or have difficulties in guaranteeing human safety while maintaining excellent performance. In this paper, we propose a monocular resonant beam-based ICP (RB-ICP) design for simultaneously realizing high-rate data transfer and high-accuracy localization while keeping the features as intrinsic safety. Utilizing the high-efficiency transmission channel of resonant beam system and the frequency-doubled beam design, we introduce the communication model without the echo interference issue. Then, we propose a distance estimation model using the phase-shift method with frequency-quadrupled beam design. Next, the angle of arrival estimation can be conducted relying on the energy-concentrated and self-alignment features of resonant beam. The simulation methods including centroid algorithm and signal conversion simulation in a photosensor along with the noise analysis are presented. In numerical analysis, we demonstrate that the positioning error can be less than 1cm and the achievable spectral efficiency can reach 16bit/s/Hz over 2m distance in 15° field of view (FoV). This proposed system enables simultaneous high-rate data transfer and high-accuracy receiver positioning for the applications such as augmented reality/virtual reality (AR/VR).