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.

As an essential aerial platform in Internet of Things (IoT) applications, UAV swarms require high-precision attitude estimation in GPS-limited and dynamic environments, which supports higher-level IoT functions such as smart logistics, disaster response, and environmental monitoring. However, most odometry-based pose estimation methods in dynamic scenarios without GPS encounter issues with cumulative errors over time. In this paper, we propose a method to reduce these cumulative errors by constraining the absolute positioning of Visual-Inertial Odometry (VIO) using relative poses obtained from multi-view landmark and Resonant-Beam (RBeam) sensors between UAVs. For synchronous moments, we estimate the 6 Degree-of-Freedom (DoF) relative pose using the Angle of Arrival and Time of Flight data from the RBeam, combined with nonlinear optimization. For asynchronous moments, a two-stage visual estimation method is introduced, combining multi-camera epipolar geometry for rotation recovery and depth reconstruction optimization for translation recovery, enabling the estimation of asynchronous relative poses. Finally, we design a global objective function based on a sliding window and factor graph, integrating RBeam, multi-view landmark, and VIO for absolute 6-DoF pose optimization of the UAV swarm. Simulation results demonstrate that optimizing with the addition of RBeam synchronous relative poses improves overall positioning accuracy by 32.94% compared to pure VIO. Incorporating both RBeam synchronous and visual asynchronous relative poses further enhances overall positioning accuracy by 37.65%. Additionally, the UAV’s attitude benefits from the rotational constraints provided by the RBeam, achieving over 30% improvement in the pitch and yaw directions.

With the rapid development of the internet of things (IoT), location-based services are becoming increasingly prominent in various aspects of social life, and accurate location information is crucial. However, RF-based indoor positioning solutions are severely limited in positioning accuracy due to signal transmission losses and directional difficulties, and optical indoor positioning methods require high propagation conditions. To achieve higher accuracy in indoor positioning, we utilize the principle of resonance to design a triangulation-based resonant beam positioning system (TRBPS) in the RF band. The proposed system employs phase-conjugation antenna arrays and resonance mechanism to achieve energy concentration and beam self-alignment, without requiring active signals from the target for positioning and complex beam control algorithms. Numerical evaluations indicate that TRBPS can achieve millimeter-level accuracy within a range of 3.6m without the need for additional embedded systems.

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.

To meet the growing demand for data traffic, spectrum-rich optical wireless communication (OWC) has emerged as a key technological driver for the development of 6G. The resonant beam communication (RBC) system, which employs spatially separated laser cavities as the transmitter and receiver, is a high-speed OWC technology capable of self-alignment without tracking. However, its transmission through the air is susceptible to losses caused by obstructions. In this paper, we propose an intelligent reflecting surface (IRS) assisted RBC system with the optical frequency doubling method, where the resonant beam in frequency-fundamental and frequency-doubled is transmitted through both direct line-of-sight (LoS) and IRS-assisted channels to maintain steady-state oscillation and enable communication without echo-interference, respectively. Then, we establish the channel model based on Fresnel diffraction theory under the near-field optical propagation to analyze the transmission loss and frequency-doubled power analytically. Furthermore, communication power can be maximized in real-time by dynamically controlling the beam-splitting ratio between the two channels according to the varying loss levels encountered over air. Numerical results validate that the IRS-assisted channel can compensate for the losses in the obstructed LoS channel and misaligned receivers, ensuring that communication performance reaches an optimal value with dynamic ratio adjustments.

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.

Free space optical (FSO) transmission has emerged as a key candidate technology for 6G to expand new spectrum and improve network capacity due to its advantages of large bandwidth, low-electromagnetic interference, and high-energy efficiency. Resonant beam operating in the infrared band utilizes spatially separated laser cavities to enable safe and mobile high-power energy and high-rate information transmission but is limited by Line-of-Sight (LoS) channel. In this article, we propose a reconfigurable intelligent surface (RIS) assisted resonant beam simultaneous wireless information and power transfer (SWIPT) system and establish an optical field propagation model to analyze the channel state information (CSI), in which LoS obstruction can be detected sensitively and non line-of-sight (NLoS) transmission can be realized by changing the phased of resonant beam in RIS. Numerical results demonstrate that, apart from the transmission distance, the NLoS performance depends on both the horizontal and vertical positions of RIS. The maximum NLoS energy efficiency can achieve 55% within a transfer distance of 10 m, a translation distance of ±4 mm, and rotation angle of ±50°.

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.

Reconfigurable intelligent surface (RIS)-assisted index modulation system schemes are considered to be a promising technology for sixth-generation (6G) wireless communication systems, which can enhance various system capabilities such as coverage and reliability. However, obtaining perfect channel state information (CSI) is challenging due to the lack of a radio frequency chain in RIS. In this paper, we investigate the RIS-assisted full-duplex (FD) two-way space shift keying (SSK) system under imperfect CSI, where the signal emissions are augmented by deploying RISs in the vicinity of two FD users. The maximum likelihood detector is utilized to recover the transmit antenna index. With this in mind, we derive closed-form average bit error probability (ABEP) expression based on the Gaussian-Chebyshev quadrature (GCQ) method, and provide the upper bound and asymptotic ABEP expressions in the presence of channel estimation errors. To gain more insights, we also derive the outage probability and provide the throughput of the proposed scheme with imperfect CSI. The correctness of the analytical derivation results is confirmed via Monte Carlo simulations. It is demonstrated that increasing the number of elements of RIS can significantly improve the ABEP performance of the FD system over the half-duplex (HD) system. Furthermore, in the high SNR region, the ABEP performance of the FD system is better than that of the HD system.

The rapid advancement of the next generation of communications and internet of things (IoT) technologies has made the provision of location-based services for diverse devices an increasingly pressing necessity. Localizing devices with/without intelligent computing abilities, including both active and passive devices is essential, especially in indoor scenarios. For traditional RF positioning systems, aligning transmission signals and dealing with signal interference in complex environments are inevitable challenges. Therefore, this paper proposed a new passive positioning system, the RF-band resonant beam positioning system (RF-RBPS), which achieves energy concentration and beam alignment by amplifying echoes between the base station (BS) and the passive target (PT), without the need for complex channel estimation and time-consuming beamforming and provides high-precision direction of arrival (DoA) estimation for battery-free targets using the resonant mechanism. The direction information of the PT is estimated using the multiple signal classification (MUSIC) algorithm at the end of BS. The feasibility of the proposed system is validated through theoretical analysis and simulations. Results indicate that the proposed RF-RBPS surpasses RF-band active positioning system (RF-APS) in precision, achieving millimeter-level precision at 2m within an elevation angle of 35°, and an error of less than 3cm at 2.5m within an elevation angle of 35°.

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.

Simultaneous wireless information and power transfer (SWIPT) is a prospective technology that can handle the energy consumption and communication requirements in the Internet of Things. Resonant beam SWIPT (RB-SWIPT) scheme utilizes narrow optical beam as carrier and with spatially separated resonator structure, which can support high power and high rate SWIPT for mobile devices. However, the performance of original RB-SWIPT systems is limited by returning beam interference and transmission loss. In this paper, we propose a RB-SWIPT scheme for transmission-enhanced and anti-interference. The telescope internal modulator (TIM) and second harmonic generator (SHG) are adopted in the proposed system. The TIM can compress beams to reduce the transmission loss. The SHG can generate frequency-doubled beams to avoid interference. To evaluate the proposed system, we establish mathematical models to depict the beam transmission, energy conversion, electric power output and data receiving. Numerical results illustrate that the proposed system can achieve 18 bit/s/Hz spectral efficiency and deliver 8 W power over 100 m distance.

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.

Long-range, high-power wireless power transfer (WPT) and high-capacity communication can be achieved simultaneously in the resonant beam system (RBS), characterized with spatially separated transmitter and receiver. However, human safety in space transmission cannot be guaranteed if the transmitted power is above a certain level (e.g., several Watts). Thus, in this article, we propose a self-protection RBS, in which the protective beams embrace the energy-transfer resonant beam and are formed by the refracting part of the resonant beam emitted from the output reflector. If an external object comes across the protective beam whose power is very low, the protective beam transmission is cut off. Meanwhile, the resonant beam is interrupted due to the limit of excitation threshold. Then, we reveal the self-protection mechanism based on electromagnetic field propagation, self-mixing interference effect, and output power model. Afterward, we demonstrate that safe energy transfer can be realized by pumping gain medium with a pumping power that is greater than the threshold of the self-protection RBS and less than that of the unprotected RBS. Finally, the numerical results show that about 4.6-W electric power and 12.8 bps/Hz spectral efficiency can be transmitted at 2-m transmission distance safely in the self-protection RBS. Hence, the self-protection RBS provides a new way for safe simultaneous wireless information and power transfer (SWIPT) without mechanical control.

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.

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).

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.

Resonant beam charging (RBC) is the wireless power transfer (WPT) technology, which can provide high-power, long-distance, mobile, and safe wireless charging for Internet of Things (IoT) devices. Supporting multiple IoT devices charging simultaneously is a significant feature of the RBC system. To optimize the multiuser charging performance, the transmitting power should be scheduled for charging all IoT devices simultaneously. In order to keep all IoT devices working as long as possible for fairness, we propose the first access first charge (FAFC) scheduling algorithm. Then, we formulate the scheduling parameters quantitatively for algorithm implementation. Finally, we analyze the performance of FAFC scheduling algorithm considering the impacts of the receiver number, the transmitting power, and the charging time. Based on the analysis, we summarize the methods of improving the WPT performance for multiple IoT devices, which include limiting the receiver number, increasing the transmitting power, prolonging the charging time, and improving the single-user's charging efficiency. The FAFC scheduling algorithm design and analysis provide a fair WPT solution for the multiuser RBC system.

As a long-range high-power wireless power transfer (WPT) technology, resonant beam charging (RBC) can transmit watt-level power over long distance for the devices in the Internet of Things (IoT). Due to its open-loop architecture, RBC faces the challenge of providing dynamic current and voltage to optimize battery charging performance. In RBC, battery overcharge may cause energy waste, thermal effects, and even safety issues. On the other hand, battery undercharge may lead to charging time extension and significant battery capacity reduction. In this paper, we present an adaptive RBC (ARBC) system for battery charging optimization. Based on RBC, ARBC uses a feedback system to control the supplied power dynamically according to the battery preferred charging values. Moreover, in order to transform the received current and voltage to match the battery preferred charging values, ARBC adopts a dc-dc conversion circuit. Relying on the analytical models for RBC power transmission, we obtain the end-to-end power transfer relationship in the approximate linear closed-form of ARBC. Thus, the battery preferred charging power at the receiver can be mapped to the supplied power at the transmitter for feedback control. Numerical evaluation demonstrates that ARBC can save 61% battery charging energy and 53%-60% supplied energy compared with RBC. Furthermore, ARBC has high energy-saving gain over RBC when the WPT is unefficient. ARBC in WPT is similar to link adaption in wireless communications. Both of them play the important roles in their respective areas.

Wireless power transfer (WPT) is a promising solution to provide convenient and perpetual energy supplies to electronics. Traditional WPT technologies face the challenge of providing Watt-level power over meter-level distance for Internet of Things (IoT) and mobile devices, such as sensors, controllers, smart-phones, laptops, etc. Distributed laser charging (DLC), a new WPT alternative, has the potential to solve these problems and enable WPT with the similar experience as WiFi communications. In this paper, we present a multimodule DLC system model, in order to illustrate its physical fundamentals and mathematical formula. This analytical modeling enables the evaluation of power conversion or transmission for each individual module, considering the impacts of laser wavelength, transmission attenuation, and photovoltaic-cell (PV-cell) temperature. Based on the linear approximation of electricity-to-laser and laser-to-electricity power conversion validated by measurement and simulation, we derive the maximum power transmission efficiency in closed-form. Thus, we demonstrate the variation of the maximum power transmission efficiency depending on the supply power at the transmitter, laser wavelength, transmission distance, and PVcell temperature. Similar to the maximization of information transmission capacity in wireless information transfer (WIT), the maximization of the power transmission efficiency is equally important in WPT. Therefore, this paper not only provides the insight of DLC in theory, but also offers the guideline of DLC system design in practice.