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.

Direction of arrival (DOA) estimation technology offers a promising solution to address the sensing and positioning demands of Internet of Things (IoT) devices. Optical resonant beam systems (RBS), owing to their inherent characteristics of self-alignment, self-established energy focusing, and passive target sensing, make them naturally suited for DOA estimation in IoT scenarios. However, RBS suffer from limited angular resolution and a narrow field of view (FoV) in multi-target environments. To overcome these limitations, this paper proposes a high-resolution wide-field-of-view resonant beam DOA estimation system (RB-HWDOA). The RB-HWDOA integrates an optical spectrum-based DOA estimation algorithm (OSB-DOA), which leverages amplitude information in the two-dimensional Fourier spectrum of the resonant beam, overcoming the resolution limit imposed by the beam size in spatial-domain methods. Furthermore, we designed a telescope modulation (TM) structure to correct phase and direction mismatches, enabling a multi-Tx framework that focuses beams onto a common sensing module, thereby extending the effective FoV. Combined with the OSB-DOA algorithm, this design supports high-resolution DOA estimation for multiple targets simultaneously over a wide FoV. Simulation results show that OSB-DOA resolves angular separations down to 0.1◦ across multiple resonant beams, remains robust under noise, and the TM architecture enables multi-Tx integration for wide-FoV coverage, making RB-HWDOA a scalable and efficient solution for passive multi-target DOA estimation in complex IoT environments.

Terahertz (THz) simultaneous wireless information and power transfer (SWIPT) is a promising technology for enabling ultra-high-rate and low-latency communications in massive battery-free Internet of Things (IoT) deployments for 6G networks. However, conventional THz systems rely on narrow directional beams that necessitate precise alignment, typically achieved through high-overhead beam scanning procedures, which fundamentally at odds with the energy constraints of battery-free IoT devices. In this paper, we propose a novel self-alignment architecture for THz SWIPT leveraging a reconfigurable intelligent surface (RIS) to eliminate complex beam scanning. By integrating phase conjugate circuits at both the base station and user equipment, the RIS facilitates a resonance-based bidirectional retroreflection mechanism, enabling the system to autonomously converge to an aligned state without manual intervention. We develop an analytical channel transfer model and a power cycle model to characterize the resonance-assisted beam alignment process and power transfer efficiency. Simulation results demonstrate that the RIS-enabled system achieves effective spatial power concentration with significant sidelobe suppression, leading to a communication capacity of 127.84 Gbit/s and a received power of 13.62 mW over a 2.2-meter link.

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.

Due to control limitations in the denoising process and the lack of training, zero-shot video editing methods often struggle to meet user instructions, resulting in generated videos that are visually unappealing and fail to fully satisfy expectations. To address this problem, we propose Align-A-Video, a video editing pipeline that incorporates human feedback through reward fine-tuning. Our approach consists of two key steps: 1) Deterministic Reward Fine-tuning. To reduce optimization costs for expected noise distributions, we propose a deterministic reward tuning strategy. This method improves tuning stability by increasing sample determinism, allowing the tuning process to be completed in minutes; 2) Feature Propagation Across Frames. We optimize a selected anchor frame and propagate its features to the remaining frames, improving both visual quality and semantic fidelity. This approach avoids temporal consistency degradation from reward optimization. Extensive qualitative and quantitative experiments confirm the effectiveness of using reward fine-tuning in Align-A-Video, significantly improving the overall quality of generated videos.

Resonant beam systems (RBS) have gained attention in optical wireless applications due to their unique self-alignment capability, enabling robust connections in mobile environments. However, RBS lacks physical layer encryption mechanisms, which poses security risks during identity authentication. This paper proposes a passive secure identity recognition (PSIR) system that directly embeds authentication features into the resonant beam’s physical characteristics. The proposed system utilizes a semi-reflective amplitude mask (SAM) to generate semi-reflective dark stripes (SDS) that induce nonlinear changes in the resonant beam modes at the Tx, facilitating secure transmission of identity information without explicit cryptographic protocols. Then, the convolutional neural networks (CNN) are employed for the classification of the resonant beam field, ensuring secure and accurate identity recognition. Simulation results demonstrate a nonlinear relationship between SDS and resonant beam modes, which cannot be distinctly displayed, thereby proving the security of the proposed PSIR system. Additionally, we trained an example model using a three-layer CNN. In a four-class classification task, the area under curve (AUC) value for each category was no less than 0.6, confirming the accuracy of the identity recognition.

Vision Transformers (ViTs) leverage the attention mechanism for feature extraction but often suffer from high computational costs. To address this issue, prior works have introduced token reduction methods involving fixed-window local merging and global Bipartite Matching. However, these methods face significant challenges, such as insufficient merging due to fixed-size local windows and incorrect merging of informative tokens in global merging. To overcome these limitations, we propose Efficient Semantic Segmentation via Token Joint Merging (ESTJ) for ViT-based semantic segmentation networks. Specifically, ESTJ merges tokens using two strategies: Hierarchical Condition Pooling (HCP), which employs hierarchical local windows to effectively select sufficient tokens, and Protected Bipartite Matching (PBM), designed to preserve informative tokens using average similarity between a token and all other tokens. Experimental results demonstrate that ESTJ improves throughput by 75%, reduces GFLOPs by 40%, and enhances mIoU by up to 1.1%. Moreover, ESTJ can adjust the merging threshold during inference to adapt to scenarios that prioritize efficiency or accuracy. Compared to existing methods, ESTJ achieves a better balance between computational efficiency and segmentation accuracy.

Due to power attenuation, improving transmission efficiency in the radio-frequency (RF) band remains a significant challenge, which hinders advancements in various fields of the Internet of Things (IoT), such as wireless power transfer (WPT) and wireless communication. Array design and retro-directive beamforming (RD-BF) techniques offer simple and effective ways to enhance transmission efficiency. However, when the target is an array or in the near field, the RD-BF system (RD-BFS) cannot radiate more energy to the target due to phase irregularities in the target region, resulting in challenges in achieving higher efficiency. To address this issue, we propose the RF-based resonant beam system (RF-RBS), which adaptively optimizes phase and power distribution between transmitting and receiving arrays by leveraging the resonance mechanism to achieve higher transmission efficiency. We analyze the system structure and develop an analytical model to evaluate power flow and resonance establishment. Numerical analysis demonstrates that the proposed RF-RBS achieves self-alignment without beam control and provides higher transmission efficiency compared to RD-BFS, with improvements of up to 16%. This self-alignment capability allows the system to effectively transfer power and information across varying distances and offsets. The numerical results indicate the capability to transmit watt-level power and achieve 21 bps/Hz of downlink spectral efficiency in indoor settings, highlighting the advantages of RF-RBS in information and power transfer for mobile applications.

Simultaneous wireless information and power transfer (SWIPT) is considered a promising technology for the future of the internet of things (IoT), with significant potential to enable advancements in both smart living and smart production. As IoT devices often operate wirelessly using various types of radiation, such as radio frequency (RF), microwave, laser, etc, the topic of human-safe irradiance is getting increasingly important. The resonant beam system (RBS) exploits the self-aligning characteristics of spatially distributed laser resonators to simultaneously achieve high-power and high-capacity SWIPT. The self-protection RBS, equipped with an adaptive phase adjuster, further mitigates safety concerns by reducing the irradiance on the invasion object. However, the power optimization under safety restrictions of this system remains underexplored, leaving significant potential for further enhancement of its performance. In this paper, we establish a theoretical model of RBS with an adaptive phase adjuster, including the irradiance on the invading object. Furthermore, based on the proposed model, we construct an optimization framework using alternating optimization to refine the system parameters, which are equivalent reflectance of the output reflector, radius of the beam on the gain medium, and split ratio of the protective beam. Finally, the numerical results demonstrate that the system’s optical power output is enhanced by 19.91% while adhering to safety limits for the human skin of 1 W/cm2 in the standard “safety of laser products IEC 60825-1.”. As a SWIPT system, it can deliver an average of 5 W of electric power and achieve a spectral efficiency of 14.7 bps/Hz with 300 W input power over a distance of 9 m.

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.

In the era of the Internet of everything (IoE) and the metaverse, there is a growing demand for high-accuracy indoor positioning for applications such as autonomous robots, virtual reality, and smartphones. This paper proposed a resonant beam phase-based passive localization (RBPPL) system optimized for high-precision indoor positioning in multi-access scenarios. By leveraging the self-alignment characteristic and integrating the analysis of resonant beam phase, angle of arrival (AoA) matching and binocular disparity method for 3D point coordinate acquisition, the RBPPL system achieves binocular passive multi-access 3D positioning with an error within 4 cm at a distance of 8 m. We present a novel multi-access AoA estimation method that overcomes the challenges of spot overlap in traditional CMOS-based angle analysis. We propose a telescope system to correct the phase and focus the propagation direction of optical resonant beam systems. Simulations demonstrate the system’s robustness and high accuracy. The proposed RBPPL system, optimized for multi-access scenarios, offers a promising solution for high-accuracy indoor positioning, supporting various IoE and metaverse applications. Future work will focus on real-world deployment and its potential in complex multi-access scenarios.

Positioning and power transfer are crucial demands in the existing Internet of Things networks, where intracavity laser-based systems are proposed as a potential alternative for providing sufficient wireless power and high-accuracy positioning simultaneously. However, existing intracavity laser-based systems still face challenges in improving power transfer efficiency and system Field of View (FoV). This article proposes a joint sensing and power transfer (JSPT) system based on distributed coupled-cavity laser (DCCL) design. Power efficiency and FoV are enhanced owing to the external-cavity feedback in DCCL. The angle of arrival estimation based on the intrinsic self-alignment feature and polarization self-modulation ranging based on the self-mixing feature are achieved in the DCCL-based JSPT system. Moreover, we build analytical models for revealing the principle of DCCL and verifying the system performance relying on diffraction propagation-based beam field simulation and rate equation-based gain simulation. Numerical results demonstrate that DCCL-based JSPT achieves 4-W charging power and mm-level 3-D positioning within an FoV of ±40° and 2-m vertical distances, showing its capability for Internet of Things applications.

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.

To address challenges in outdoor multi-robot collaborative localization (MRCL) due to low GPS accuracy, we propose a system using three UGVs, each equipped with a shared camera and a laser rangefinder. Our trilateral localization algorithm combines least-squares matrix and gradient descent methods, resulting in an 80.4% improvement in accuracy compared to traditional methods. The system mitigates the limitations of GPS accuracy by utilizing accurate baseline measurements and optimizing the localization process. These advancements have potential applications in transportation, production, and logistics, enhancing MRCL performance in outdoor environments.

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.

Coupled with identification, 3D positioning can significantly enrich location-based services. Resonant beam (RB) is emerging as a promising solution to indoor positioning due to its self-aligning and energy-focused transmission. We propose a system for simultaneous localization and identification using RB as the individual medium. The base station (BS) employs a single-source RB, and each mobile target (MT) is equipped with a signal reflection module. For 3D localization, the BS estimates direction by analyzing RB’s spatial distribution and determines the distance from its frequency components. For identification, the passive MT captures the RB for power and reflects its identity (ID) to BS as spot flicker signals. To demonstrate the working principles, we have developed models for location estimation and ID recognition, as well as the power flow within the RB channel. In implementation, we incorporate a threshold regulation scheme for accurate image signal retrieval, along with an input power distribution model tailored for multi-access scenarios. Through simulating the entire process, we verify the system’s feasibility, including confirming the viability of ID recognition. We also evaluate localization performance, averaging ~ 1 cm at heights of 1.5 m ~ 2.5 m, showing promise for a wide range of potential applications.

Both high-accuracy localization and power supply for mobile and Internet of Things (IoT) devices are demanding in the next-generation wireless networks. Recently, research on complete localization has been proposed, i.e., capturing the target’s location and identification (ID). However, the existing schemes face challenges, including: 1) improving positioning accuracy without the active emission of signals from the targets and 2) providing sufficient power for the targets to enable features such as ID. In this article, we present a simultaneous localization and power transfer (SLAPT) system relying on the resonant beam system (RBS), which can realize complete, passive, and high-accuracy positioning along with the capability of sufficient power supply. We first establish analytical models to illustrate the principles of power transfer to the target with an open-cavity laser, positioning the target, including Time-of-Flight (ToF) ranging and Angle-of-Arrival (AoA) estimation with the self-reproducing mode theory, wireless charging power conversion, and identifying the target using shutter modulation. Numerical results demonstrate that the proposed SLAPT system can achieve less than 1-cm positioning accuracy over 2-m distance in 16° Fields of View (FoVs) with 3-W wireless power supply. The proposed system allows passive and complete localization for the target without battery or power line in various IoT applications.

Locating mobile devices precisely in indoor scenarios is a challenging task because of the signal diffraction and reflection in complicated environments. One vital cause deteriorating the localization performance is the inevitable power dissipation along the propagation path of localization signals. In this paper, we propose a high-accuracy localization scheme based on the resonant beam system (RBS) and the binocular vision, i.e., binocular based resonant beam localization (BRBL). The BRBL system utilizes the energy-concentrated and self-aligned transmission of RBS to realize high-efficiency signal propagation and self-positioning for the mobile target (MT). The binocular method is combined with RBS to obtain the three-dimensional (3-D) coordinates of the MT for the first time. To exhibit the localization mechanism, we first elaborate on the binocular localization model, including the resonant beam transmission analysis and the geometric derivation of the binocular method with RBS. Then, we establish the power model of RBS, and the signal and noise models of beam spot imaging, respectively, to analyse the performance of the BRBL system. Finally, the results of numerical analysis and comparison show that BRBL balances system complexity and localization precision effectively, i.e., providing cm-level localization accuracy with its simplicity and ease of implementation.

The self-protection resonant beam system (RBS) is a promising long-range and high-power simultaneous wireless information and power transfer (SWIPT) scheme for energy-constrained Internet of Things (IoT) devices, which can achieve safe power and information transfer without mechanical control measures. In the system, a portion of the emitted resonant beam (RB) is reflected and refracted to form protective beams encircling the RB in 360° degrees. In this article, we propose an external object invasion model to evaluate the safety performance of self-protection RBS. With the invading of external object, the field propagation mode of the protective beam shifts, leading to the change of the pumping power threshold of the system, which controls the presence or absence of RB. The numerical results show that the maximal irradiance on invading object is around$0.5 \rm {W/cm^{2}}$at 2-$\rm {m}$transmission distance, with approximately 3-$\rm {W}$output electric power and 12-$\rm {bps/Hz}$spectral efficiency, which is less than the maximum permissible exposure (MPE) requirement for the human skin of$1 \rm {W/cm^{2}}$in the standard “safety of laser products IEC 60825-1.” As a result, the self-protection RBS can achieve high-range, high-power, and human-safe SWIPT.

The resonant beam system (RBS) with double spherical retroreflectors presents a potential mobile simultaneous wireless information and power transfer (SWIPT) technology without any tracking control. However, the movement distance and performance are limited due to the effect of spherical aberration. To improve mobility performance in RBS, including movement distance and output power, we adopt an aspherical lens as the focusing mirror in a retroreflector. By shifting the beam phase distribution, the aspherical lens focuses all passing beams, particularly edge beams, on the focal mirror, enhancing energy concentration in the resonant cavity. The beam field propagation through cat’s-eye retroreflectors, gain medium, and air is studied for analyzing the transfer efficiency and output power, and we demonstrate that the axial movement distance in the aspherical resonator is about 7 m, which is more than twice as far away as the spherical resonator. Within a field of view of 3° at a distance of$1~\rm {m}$, the output power of the aspherical resonator is greater than that of the spherical resonator with the same movement angle, up to two times. The maximum output electric power and spectral efficiency are approximately$4~\rm {W}$and$12~\rm {bps/Hz}$, respectively.

Wireless charging for mobile Internet of Things (IoT) devices such as smartphones is extremely difficult. To reduce energy dissipation during wireless transmission in mobile scenarios, laser or narrow radio beams with sophisticated tracking control are typically required. However, reaching the necessary tracking accuracy and reliability is really difficult. In this article, inspired by the features of optical resonators and retroreflectors, we develop an experiment on a self-aligned resonant beam charging system for long-distance mobile power transfer. It exploits light resonances inside a double-retroreflector-based spatially separated laser resonator (SSLR), which eliminates the requirement for any kind of tracking control. Focal telecentric cat’s eye retroreflectors are employed here. The SSLR was investigated by both theoretical calculation and experiment. We also well assembled the transmitter and the receiver and demonstrated its application in mobile smartphone charging. The results show that above 5-W optical power (also obtained more than 0.6-W electrical power) transferring with negligible diffraction loss to a few-centimeter-size receiver is realized while the receiver moves arbitrarily within 2-m vertical distance and 6° field of view from the transmitter. The maximum horizontal moving range is up to ±18 cm. This wireless charging system empowers a smartphone in mobile operation with unlimited battery life without the need for a cable.

High communication speed and sufficient energy supply are the directions of technological development. Energy and information available anywhere and anytime have always been people’s good wishes. On this basis, the resonant beam system (RBS) has demonstrated its unique superiority in meeting the needs for energy and communication. The previous work has mostly focused on the analysis of charging performance of RBS and its steady-state characteristics. In order to analyze the communication performance of RBS more thoroughly, we propose a resonant beam charging and communication (RBCC) system and use the equivalent circuit analysis method to conduct transient analysis on it. The equivalent circuit reveals the dynamic establishment process of the resonant beam from scratch, which facilitates the analysis of the relaxation oscillation process and a deeper understanding of the energy transmission and communication performance. In addition, we explore the energy transmission and communication performance of the RBCC under different energy allocation strategies.

The increasing demands of power supply and data rate for mobile devices promote the research of simultaneous wireless information and power transfer (SWIPT). Optical SWIPT, as known as simultaneous light information and power transfer (SLIPT), has the potential for providing high-capacity communication and high-power wireless charging. However, SLIPT technologies based on light-emitting diodes have low efficiency due to energy dissipation over the air. Laser-based SLIPT technologies need strict positioning accuracy and scanning resolution, which may lead to the increase of costs and complexity. In this paper, we propose a mobile SLIPT scheme based on spatially separated laser resonator (SSLR) and intra-cavity second harmonic generation. The power and data are transferred via separated frequencies, while they share the same self-aligned resonant beam path, without the needs of receiver positioning and beam steering. We establish the analysis model of the resonant beam power and its second harmonic power. Numerical results show that the proposed system can achieve watt-level battery charging power and above 10-bit/s/Hz achievable rate at 6-m distance, which satisfies the requirements of most indoor mobile devices.

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).

Simultaneous lightwave information and power transfer (SLIPT) has been regarded as a promising technology to deal with the ever-growing energy consumption and data-rate demands in the Internet of Things. We propose a resonant beam based SLIPT (RB-SLIPT) system, which deals with the conflict of high deliverable power and mobile receiver positioning with the existing SLIPT schemes. At first, we establish a mobile transmission channel model and depict the energy distribution in the channel. Then, we present a practical design and evaluate the energy/data transfer performance within the moving range of the RB-SLIPT. Numerical evaluation demonstrates that the RB-SLIPT can deliver more than 4W charging power and enable 3Gb/s achievable data rate with the moving range of 20° field of view (FOV) over 3m distance. Thus, RB-SLIPT can enable simultaneous high deliverable power and high data rate in mobile scenarios without tracking control.

Optical wireless communications (OWC) utilizing infrared or visible light as the carrier attracts great attention in 6G research. Resonant beam communications (RBCom) is an OWC technology which simultaneously satisfies the needs of non-mechanical mobility and high signal-to-noise ratio (SNR). It has the self-alignment feature and therefore avoids positioning and pointing operations. However, RBCom undergoes echo interference. Here we propose an echo-interference-free RBCom system design based on second harmonic generation. The transmitter and the receiver constitute a spatially separated laser resonator, in which the retro-reflective resonant beam is formed and tracks the receiver automatically. This structure provides the channel with adaptive capability in beamforming and alignment, which is similar to the concept of intelligent reflecting surface (IRS) enhanced communications, but without hardware and software controllers. Besides, we establish an analytical model to evaluate the beam radius, the beam power, and the channel capacity. The results show that our system achieves longer distance and smaller beam diameter for the transmission beyond 10 Gbit/s, compared with the existing OWC technologies.

Wireless energy transfer (WET) has recently emerged as an appealing solution for power supplying mobile/Internet of Things (IoT) devices. As an enabling WET technology, resonant beam charging (RBC) is well documented for its long-range, high-power, and safe “WiFi-like” mobile power supply. To provide high-quality wireless charging services for multiple users in a given region, we formulate a deployment problem of multiple RBC transmitters for balancing the charging fairness and quality of charging service. Based on the RBC transmitter's coverage model and receiver's charging/discharging model, a genetic algorithm (GA)-based scheme and a particle swarm optimization (PSO)-based scheme are put forth to resolve the above issue. Moreover, we present a scheduling method to evaluate the performance of the proposed algorithms. The numerical results corroborate that the optimized deployment schemes outperform uniform and random deployment in 10%-20% charging efficiency improvement.

The vision and requirements of the sixth generation (6G) mobile communication systems are expected to adopt freespace optical communication (FSO) and wireless power transfer (WPT). The laser-based WPT or wireless information transfer (WIT) usually faces the challenges of mobility and safety. We present a mobile and safe resonant beam communication (RBCom) system, which can realize high-rate simultaneous wireless information and power transfer (SWIPT). We propose an analytical model to depict its carrier beam and information transfer procedures. The numerical results show that RBCom can achieve more than 40 mW charging power and 1.6 Gbit/s channel capacity with orthogonal frequency division multiplexing (OFDM) scheme, which can be applied in future scenario where power and high-rate data are simultaneously desired.

The vision and requirements of the sixth generation (6G) mobile communication systems are expected to adopt free-space optical communication (FSO) and wireless power transfer (WPT). The laser-based WPT or wireless information transfer (WIT) usually faces the challenges of mobility and safety. We present here a mobile and safe resonant beam communication (RBCom) system, which can realize high-rate simultaneous wireless information and power transfer (SWIPT). We propose the analytical model to depict its SWIPT procedure. The numerical results show that RBCom can achieve 9 Gbit/s with 200 mW received optical power, which seems to connect the transmitter and the receiver with a mobile “wireless optical fiber”.

Resonant beam charging (RBC) is a promising wireless power transfer technology to provide long-range, high-power, mobile, and safe wireless power for the Internet of Things devices. The point-to-multipoint (PtMP) RBC system can charge multiple receivers simultaneously similar to WiFi communications. To guarantee the quality of charging service (QoCS) for each receiver and maximize the overall earning in the PtMP RBC service, we specify the charging pricing strategy and develop the high priority charge (HPC) scheduling algorithm to control the charging order and power allocation. Each receiver is assigned a priority, which is updated dynamically based on its state of charging (SOC) and specified charging power. The receivers with high priorities are scheduled to be charged in each time slot. We present the pseudo code of the HPC algorithm based on quantifying the receiver's SOC, discharging energy, and various relevant parameters. Relying on simulation analysis, we demonstrate that the HPC algorithm can achieve better QoCS and earning than the round-robin charge scheduling algorithm. Based on the performance evaluation, we illustrate that the methods to improve the PtMP RBC service are: 1) limiting the receiver number within a reasonable range and 2) prolonging the charging duration as long as possible. In summary, the HPC scheduling algorithm provides a practical strategy to maximize the earning of the PtMP RBC service with each receiver's QoCS guarantee.

Power supply for Internet of Things (IoT) devices is one of the bottlenecks in IoT development. To provide perpetual power supply for IoT devices, resonant beam charging (RBC) is a promising safe, long-range, and high-power wireless power transfer solution. How long distance RBC can reach and how much power RBC can transfer? In this paper, we analyze the consistent and steady operational conditions of the RBC system, which determine the maximum power transmission distance. Then, we study the power transmission efficiency within the operational distance, which determines the deliverable power through the RBC energy transmission channel. Based on the theoretical model of the wireless energy transmission channel, we establish a testbed. According to the experimental measurement, we validate our theoretical model. The experiments verify that the output electrical power at the RBC receiver can be up to 2 W. The maximum energy transmission distance is 2.6 m. Both the experimental and theoretical performance of the RBC system are evaluated in terms of the transmission distance, the transmission efficiency, and the output electrical power. Our theoretical model and experimental testbed lead to the guidelines for the RBC system design and implementation in practice.

Resonant beam charging (RBC) can realize wireless power transfer (WPT) from a transmitter to multiple Internet of Things devices via resonant beams. The adaptive RBC (ARBC) can effectively improve its energy utilization. In order to support multiuser WPT in the ARBC system, we propose the time-division multiple access (TDMA) method and design the TDMA-based WPT scheduling algorithm. Our TDMA WPT method has the features of concurrently charging, continuous charging current, individual user power control, constant driving power, and flexible driving power control. The simulation shows that the TDMA scheduling algorithm has high efficiency, as the total charging time is roughly half (46.9% when charging 50 receivers) of that of the alternative scheduling algorithm. Furthermore, the TDMA for WPT inspires the ideas of enhancing the ARBC system, such as flow control and quality of service.

To enable electric vehicles (EVs) to access to the Internet of Intelligent Vehicles (IoIV), charging EVs wirelessly anytime and anywhere becomes an urgent need. The resonant beam charging (RBC) technology can provide high-power and long-range wireless energy for EVs. However, the RBC system is unefficient. To improve the RBC power transmission efficiency, the adaptive RBC (ARBC) technology was introduced. In this paper, after analyzing the modular model of the ARBC system, we obtain the closed-form formula of the end-to-end power transmission efficiency. Then, we prove that the optimal power transmission efficiency uniquely exists. Moreover, we analyze the relationships among the optimal power transmission efficiency, the source power, the output power, and the beam transmission efficiency, which provide the guidelines for the optimal ARBC system design and implementation. Hence, perpetual energy can be supplied to EVs in IoIV virtually.