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- 摘要
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- 实验方案
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Hybrid TDOA/RSS based localization for visible light systems
摘要： In a visible light positioning (VLP) system, a receiver can estimate its location based on signals transmitted by light emitting diodes (LEDs). In this manuscript, we investigate a quasi-synchronous VLP system, in which the LED transmitters are synchronous among themselves but are not synchronized with the receiver. In quasi-synchronous VLP systems, position estimation can be performed by utilizing time difference of arrival (TDOA) information together with channel attenuation information, leading to a hybrid localization system. To specify accuracy limits for quasi-synchronous VLP systems, the Cramér–Rao lower bound (CRLB) on position estimation is derived in a generic three-dimensional scenario. Then, a direct positioning approach is adopted to obtain the maximum likelihood (ML) position estimator based directly on received signals from LED transmitters. In addition, a two-step position estimator is proposed, where TDOA and received signal strength (RSS) estimates are obtained in the first step and the position estimation is performed, based on the TDOA and RSS estimates, in the second step. The performance of the two-step positioning technique is shown to converge to that of direct positioning at high signal-to-noise ratios based on asymptotic properties of ML estimation. Finally, CRLBs and performance of the proposed positioning techniques are investigated through simulations.
关键词： Received signal strength (RSS),Estimation,Visible light,Localization,Time difference of arrival (TDOA)
更新于2025-09-23 15:22:29
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A Comprehensive Model for Correcting RNFL Readings of Varying Signal Strengths in Cirrus Optical Coherence Tomography
摘要： PURPOSE. To develop a model for the Cirrus HD-OCT that allows for the comparison of retinal nerve fiber layer (RNFL) thickness measurements with dissimilar signal strengths (SS) and accounts for test–retest variability. METHODS. Retinal nerve fiber layers were obtained in normals using the Cirrus optic disc cube 200 3 200 protocol during a single encounter. Five RNFL scans were obtained with a SS of 9 or 10. Diffusion lens filters were used to degrade SS to obtain five scans at each SS group of 7 or 8, 5 or 6, and 3 or 4. The relationship between average RNFL thickness and SS was established, and an equation was developed to allow for adjustment of an RNFL measurement had it been a SS of 7. Intravisit interclass correlation coefficient (ICC) and coefficient of variation (CV) parameter estimates for each SS group were calculated. Repeatability and upper tolerance limit were calculated as 1.96 3 =2 3 within-subject standard deviation (Sw) and 1.645 3 =2 3 Sw, respectively. RESULTS. There was a linear relationship between average RNFL and SS. RNFLadj ? RNFL (cid:2) 1.03*SS t 7.21 allows for the adjustment of RNFL readings to the same SS. Interclass correlation coefficients and CVs were good for all measurements down to SS of 3 or 4. Repeatability and upper tolerance limit were 5.24 and 4.40 lm, respectively. CONCLUSIONS. Our model adjusts RNFL readings based on SS and includes an upper tolerance limit of 5 lm. If validated, this model could improve the detection of real RNFL changes. Further study to validate this model should be performed before widespread use is adopted.
关键词： glaucoma anterior segment,Cirrus OCT,signal strength,optical coherence tomography
更新于2025-09-23 15:22:29
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[IEEE 2019 IEEE 46th Photovoltaic Specialists Conference (PVSC) - Chicago, IL, USA (2019.6.16-2019.6.21)] 2019 IEEE 46th Photovoltaic Specialists Conference (PVSC) - Post-Deposition Recrystallization of Co-Evaporated CuIn <sub/>x</sub> Ga <sub/>(1-x)</sub> Se <sub/>2</sub> Films by Bromide Vapor Treatments
摘要： In recent years, smart devices have become ubiquitous. Many of these devices are equipped with global positioning system (GPS), Wi-Fi, and other sensors. With their high mobility, the idea of mobile devices as probes has been attracting more and more attention. Mobility and flexibility offered by smart mobile devices are what traditional fixed sensors lack. However, mobile devices’ power supplies are quite limited. Although GPS is accurate, its high power consumption somewhat limits its accessibility and sustainability. In contrast, Wi-Fi is less power hungry, but at the same time, less accurate. For the sake of sustainability, by adopting Wi-Fi as an alternative to GPS, longer operation is attainable at the cost of losing some degree of accuracy. In this paper, a Wi-Fi-based algorithm based on log-normal probability distribution of distances with respect to received signal strength is proposed. It is suitable for an outdoor environment, where Wi-Fi access points (APs) are abundant. Simulations are conducted over known AP locations, and results show that the proposed algorithm can save, on average, as much as 35% more battery power than GPS does. The average localization error is ～18 m, and the average velocity estimation error is ～25%.
关键词： Mobile phone sensing,log-normal distribution,positioning algorithm,Wi-Fi-based localization,received signal strength indicator
更新于2025-09-23 15:19:57
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Relationship between macular thickness measurement and signal strength using Stratus optical coherence tomography
摘要： Purpose: To examine the relationship between signal strength and macular thickness as measured by Stratus optical coherence tomography (OCT)'s fast macular thickness protocol in healthy subjects. Methods: In this prospective cross-sectional study 79 eyes of 42 healthy subjects were enrolled. The age, gender, and eye (right vs left) of each subject were recorded. The Stratus OCT fast macular thickness scan protocol was used and the macular thickness was measured with retinal thickness map analysis. Each eye was imaged at least six times to acquire images with signal strengths of 4, 5, 6, 7, 8, and 9 out of 10 via adjustment of the focusing knob. The OCT parameters included in the analysis were thickness in the central 1 mm and in the different quadrants in the 3-mm area. Results: Overall 79 eyes of 42 patients with a mean age of 38.4±12.4 were included. There was no significant difference between the signal strength measurements obtained with different signal strengths in the central thickness (P=0.20). In the superior, nasal, inferior, and temporal quadrants, a signal strength of 8 demonstrated up to 3 μm thicker measurements than a signal strength of 5 (P<0.05). In general linear regression analysis, after accounting for age and gender, signal strength did not remain a significant predictor of thickness in any quadrant. Conclusions: When using fast map macular measurements, a signal strength of 5 is clinically as efficient as a signal strength of 8 in measuring macular thickness in all quadrants. Insisting on higher signal strength may not be necessary.
关键词： retinal thickness,macular thickness,Stratus OCT,fast map macular measurement,signal strength
更新于2025-09-19 17:15:36
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[IEEE 2019 IEEE 8th International Conference on Advanced Optoelectronics and Lasers (CAOL) - Sozopol, Bulgaria (2019.9.6-2019.9.8)] 2019 IEEE 8th International Conference on Advanced Optoelectronics and Lasers (CAOL) - Photoluminescence of SnO <sub/>2</sub> nanoparticle ensemble in porous glass with column structure
摘要： In recent years, smart devices have become ubiquitous. Many of these devices are equipped with global positioning system (GPS), Wi-Fi, and other sensors. With their high mobility, the idea of mobile devices as probes has been attracting more and more attention. Mobility and ?exibility offered by smart mobile devices are what traditional ?xed sensors lack. However, mobile devices’ power supplies are quite limited. Although GPS is accurate, its high power consumption somewhat limits its accessibility and sustainability. In contrast, Wi-Fi is less power hungry, but at the same time, less accurate. For the sake of sustainability, by adopting Wi-Fi as an alternative to GPS, longer operation is attainable at the cost of losing some degree of accuracy. In this paper, a Wi-Fi-based algorithm based on log-normal probability distribution of distances with respect to received signal strength is proposed. It is suitable for an outdoor environment, where Wi-Fi access points (APs) are abundant. Simulations are conducted over known AP locations, and results show that the proposed algorithm can save, on average, as much as 35% more battery power than GPS does. The average localization error is ～18 m, and the average velocity estimation error is ～25%.
关键词： Mobile phone sensing,log-normal distribution,positioning algorithm,Wi-Fi-based localization,received signal strength indicator
更新于2025-09-19 17:13:59
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Dependable Visual Light-Based Indoor Localization with Automatic Anomaly Detection for Location-Based Service of Mobile Cyber-Physical Systems
摘要： Indoor localization has become popular in recent years due to the increasing need of location-based services in mobile cyber-physical systems (CPS). The massive deployment of light emitting diodes (LEDs) further promotes the indoor localization using visual light. As a key enabling technique for mobile CPS, accurate indoor localization based on visual light communication remains nontrivial due to various non-idealities such as attenuation induced by unexpected obstacles. The anomalies of localization can potentially reduce the dependability of location-based services. In this article, we develop a novel indoor localization framework based on relative received signal strength. Most importantly, an efficient method is derived from the triangle inequality to automatically detect the abnormal LED lamps that are blocked by obstacles. These LED lamps are then ignored by our localization algorithm so that they do not bias the localization results, which improves the dependability of our localization framework. As demonstrated by the simulation results, the proposed techniques can achieve superior accuracy over the conventional approaches, especially when there exist abnormal LED lamps.
关键词： relative received signal strength,dependability,Visual light based indoor localization,mobile cyber-physical systems,triangle inequality
更新于2025-09-10 09:29:36
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[IEEE 2018 IEEE International Conference on RFID Technology & Application (RFID-TA) - Macau, Macao (2018.9.26-2018.9.28)] 2018 IEEE International Conference on RFID Technology & Application (RFID-TA) - A Flooding Warning System based on RFID Tag Array for Energy Facility
摘要： Passive radio-frequency identification (RFID) tags are widely used due to its economic cost and satisfactory performance. So far, passive RFID tags are mostly applied to such as underground pipe identify identification under buried conditions. However, there is lack of study on the application of buried tags for further application. In this paper, the performances of buried RFID tags are studied to develop a flooding warning system based on RFID tag array for energy facility such as power stations. In this study, the corresponding signal strength received by the RFID reader is evaluated when the RFID tags are buried by seven materials respectively. The results show that flood warning detector can be constructed using passive RFID tag array and reader.
关键词： RFID,buried,Passive RFID tags,RSSI,signal strength
更新于2025-09-09 09:28:46
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[IEEE 2018 IEEE International Conference on RFID Technology & Application (RFID-TA) - Macau, Macao (2018.9.26-2018.9.28)] 2018 IEEE International Conference on RFID Technology & Application (RFID-TA) - New Empirical Indoor Path Loss Model using Active UHF-RFID Tags for Localization Purposes
摘要： Indoor is one of the most complicated propagation environments depending on the specific type of buildings structure. In this paper, we present a combination of 2 models using active UHF-RFID tags at 433 MHz: The Dual One Slope Model (DOSM) and the Dual One Slope with Second Order Polynomial Model (DOSSOM). Further, a comparison with different propagation models have been proposed. Our work aims to study, analyze and improve the accuracy of the two new path loss models. Distance errors are determined based on all different propagation models. According to experimental validations, the mean distance error had a value 56 cm using the DOSM, whereas, it had a value of 51 cm using the DOSSOM. In short, distance errors derived from the two new empirical path loss models (DOSM and DOSSOM) closely match real measurements. Thus, referring to the mean distance errors already reached, the stability of our new indoor propagation models will be affirmed.
关键词： Distance estimation,UHF-RFID,Second Order Polynomial Model (SOPM),One Slope Model (OSM),Indoor Localization,Received Signal Strength Indicator (RSSI)
更新于2025-09-09 09:28:46
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[Institution of Engineering and Technology 12th European Conference on Antennas and Propagation (EuCAP 2018) - London, UK (9-13 April 2018)] 12th European Conference on Antennas and Propagation (EuCAP 2018) - RSS-Based Direction-of-Arrival Estimation with Increased Accuracy for Arbitrary Elevation Angles Using ESPAR Antennas
摘要： In this paper, we have proposed an improved direction-of-arrival (DoA) estimation algorithm, which uses the power pattern cross-correlation (PPCC) estimator and received signal strength (RSS) values recorded at electronically steerable parasitic array radiator (ESPAR) antenna’s output port, providing more accurate DoA results for unknown signals impinging the antenna. The PPCC estimator in its original form provides accurate DoA estimation results for directions lying within the horizontal plane. However, the estimation accuracy drops for other elevation angles as the estimator relies on ESPAR antenna’s radiation patterns measurements in the horizontal plane only. Our proposed modification allows one to measure ESPAR antenna’s radiation patterns in two different elevation planes during the calibration phase, which improves PPCC-based DoA estimation algorithm’s overall accuracy for signals impinging the antenna from arbitrary elevation angles. The proposed algorithm has been verified during anechoic chamber measurements using our ESPAR antenna prototype.
关键词： electronically steerable parasitic array radiator (ESPAR) antenna,direction-of-arrival (DoA),received signal strength (RSS),Switched-beam antenna
更新于2025-09-04 15:30:14