Browsing by Author "Chen, Chien-Hua"

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A Pitch-Aided Lane Tracking Algorithm for Driver Assistance System with Insufficient Observations
(2012)
Tang, Chi-Wai
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Feng, Kai-Ten
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Tseng, Po-Hsuan
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Chen, Chien-Hua
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Guo, Jing-Wei
The driver assistance system (DAS) is important to assist drivers with driving safety and efficiency. The lane departure warning system (LDWS), being an essential portion within the DAS, aims at providing warning messages under irregular driving behaviors due to distraction, drowsiness, or driver negligence. As the developments of mobile devices are boosted vigorously, it becomes more feasible to integrate sensing, photographing and displaying components within the LDWS. In this paper, the pitch-aided lane tracking (PALT) algorithm is proposed to detect and track the lanes on the roadways base on the particle filter. A pitch model is proposed to track the lane attributes associated with the pitch angle of a mobile device in order to conquer the effects from bumpy road and loosely-equipped of a mobile device. Moreover, the proposed PALT scheme can compensate the influences of insufficient observations from the display. Numerical results show that proposed PALT scheme can provide better lane-tracking performance compared to both original observations and the model without considering pitch angle.
A real-time and bandwidth guaranteed arbitration algorithm for SoC bus communication
(2006)
Chen, Chien-Hua
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Lee, Geeng-Wei
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Huang, Juinn-Dar
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Jou, Jing-Yang
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電子工程學系及電子研究所
In shared SoC bus systems, arbiters are usually adopted to solve bus contentions with various kinds of arbitration algorithms. We propose an arbitration algorithm, RT lottery, which is designed to meet both hard real-time and bandwidth requirements. For fast evaluation and exploration, we use high abstract-level models in our system simulation environment to generate parameters for our configurable arbiter. The experimental results show that RT-lottery can meet all hard real-time requirements and perform very well in bandwidth allocation. The results also show that RT-lottery outperforms several commonly-used arbitration algorithms today.
Enhanced Distance and Location Estimation for Broadband Wireless Networks
(2015-11-01)
Chen, Chien-Hua
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Feng, Kai-Ten
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電機資訊學士班
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Undergraduate Honors Program of Electrical Engineering and Computer Science
In recent years, wireless positioning technologies have been widely integrated into new developments of telecom systems and services. As path loss characteristics are comprehensively investigated and adopted by international telecommunication union (ITU), received signal strength (RSS) is utilized as a type of measurement and can be properly transformed to obtain distance information. With the models and parameters addressed in the technical reports of 3GPP, the RSS-based distance and location estimation (RDLE) algorithm is proposed for mixed line-of-sight (LOS)/non-line-of-sight (NLOS) in LTE cellular networks. The proposed RDLE algorithm consists of a distance estimation method and a location estimation scheme. The particle-based distance estimation (PDE) method is proposed to estimate distances with RSS measurements under various environments and mixed sight conditions. Moreover, the geometry-improved location estimation (GILE) algorithm is proposed to explore geometric relationships between base stations (BSs) and mobile station (MS). A geometric constraint based on range differences which is related to time-difference-of-arrival (TDOA) information is constructed to confine MS\'s location estimation within a specific closed region. Moreover, a geometric reformation derived from minimizing the geometric dilution of precision (GDOP) is utilized as an assistance to increase the degree of freedom in space domain against the errors in location estimations. The theoretic Cramer-Rao lower bound is also derived as a benchmark to evaluate the precisions of positioning algorithms with range differences. The proposed RDLE algorithm is perceived to outperform other existing localization methods, especially under poor network topologies and insufficient measurement inputs.
Femto-Assisted Location Estimation in Macro/Femto Heterogeneous Networks
(2013)
Lee, Ke-Ting
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Tseng, Po-Hsuan
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Chen, Chien-Hua
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Feng, Kai-Ten
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電機工程學系
Location estimation and tracking for mobile stations (MSs) have attracted a significant amount of attention in recent years. In indoor environment where the signals from global positioning system (GPS) are either weak or blocked, signal sources from long term evolution advanced (LTE-A) system can be adopted to provide location estimation for MS. Based on the range signals from both macro base station (mBS) and femto BS (fBS) in LTE-A heterogeneous networks (HetNet), we propose femto-assisted location estimation (FALE) schemes to estimate MS's position especially for indoor environments with insufficient signal inputs from mBSs. Since fBSs are usually deployed by users in their residential or business buildings, the locations of these fBSs generally cannot be known exactly. We depict the imprecise fBSs' positions as belief information to investigate a Bayesian estimation method based on the time difference of arrival (TDOA) measurement, and utilize particle filtering technique to develop the FALE algorithm. Moreover, a simplified FALE (FALE-S) scheme is proposed to reduce the computation cost resulting from the particle filter in original FALE method. Performance evaluation is conducted based on the LTE-A HetNet environments. Compared to conventional scheme, simulation results show that the proposed FALE algorithms can provide better location estimation of MS through the assistance of fBSs.
GALE: An enhanced geometry-assisted location estimation algorithm for NLOS environments
(2008-02-01)
Feng, Kai-Ten
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Chen, Chao-Lin
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Chen, Chien-Hua
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電信工程研究所
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Institute of Communications Engineering
Mobile location estimation has attracted a significant amount of attention in recent years. The network-based location estimation schemes have been widely adopted based on the radio signals between the mobile device and the base stations. The two-step Least- Squares (LS) method has been studied in related research to provide efficient location estimation of the mobile devices. However, the algorithm results in insufficient accuracy for location estimation with the existence of Non-Line-Of-Sight (NLOS) errors. A Geometry-Assisted Location Estimation (GALE) algorithm is proposed in this paper with the consideration of different geometric layouts between the mobile device and its associated base stations. In order to enhance the precision of the location estimate, the GALE scheme is designed to incorporate the geometric constraints within the formulation of the two-step LS method. The algorithm can be utilized to estimate both the two-dimensional and the three-dimensional positions of a mobile device. The proposed GALE scheme can both preserve the computational efficiency from the two-step LS algorithm and obtain a precise location estimation under NLOS environments. Moreover, the Cramer-Rao Lower Bound (CRLB) for various types of measurement signals is derived to facilitate the performance comparison between different location estimation schemes. Numerical results illustrate that the proposed GALE algorithm can achieve better accuracy compared with other existing network-based location estimation schemes.
Geometry-Improved Location Estimation Algorithm for LTE-A Wireless Networks
(2014)
Chen, Chien-Hua
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Feng, Kai-Ten
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電機工程學系
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Department of Electrical and Computer Engineering
In recent years, wireless positioning technologies have been widely considered in the developments of new telecom systems and services. The increasing requirements of location-based services (LBS) in many practical applications have promoted the investigations of location estimation methods. With the system models and network structures addressed in the technical reports of 3GPP, the geometry-improved location estimation (GILE) algorithm is proposed to explore geometric relationships between base stations (BSs) and mobile station (MS) in order to improve the accuracy and precision of location estimations. A geometric constraint based on the network topology and time-difference-of-arrival (TDOA) measurements is constructed to confine MS\'s location estimation within a specific closed region. Moreover, a geometric reformation derived from minimizing the geometric dilution of precision (GDOP) is utilized as an assistance to increase the degree of freedom in space domain against the errors from TDOA measurements to location estimations. According to the performance evaluations, proposed GILE algorithm is perceived to outperform other existing localization methods, especially under poor network topologies and insufficient measurement inputs.
Investigating effect of water level variation and surface tension crack on riverbank stability
(2017-06-01)
Chen, Chien-Hua
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Hsieh, Te-Yung
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Yang, Jinn-Chuang
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土木工程學系
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防災與水環境研究中心
During high flow season, the rise and fall of river water level could induce riverbank instability and threaten structural safety of flood-protection facilities on floodplains. Through a flume experiment, this paper investigates the influences of three factors (namely, drawdown rate of river stage, initial water elevation, and riverbank slope angle) on riverbank stability due to the fall of river water level. From the laboratory experiments it was observed that tension crack appeared in all riverbank failure cases and all failure patterns were of planar type. Moreover, this paper presents a riverbank stability analysis model that explicitly incorporates the integral effect of all forces acting upon the failure plane and tension crack. The prediction accuracy of the proposed model is examined by using experimental data obtained in this study and field data of the Hotophia Creek in the USA and the Sieve River in Italy. A comparison of model simulation results with and without considering tension crack clearly indicates the importance and necessity of including tension crack for achieving good accuracy in riverbank stability simulations. For practical application of the improved riverbank stability model, two empirical formulas for estimating tension crack location and failure plane angle were examined and modified to enhance their appropriateness in riverbank stability simulation. Finally, the improved model with the modified empirical formulas was verified to show its good prediction in riverbank stability analysis. (C) 2017 International Association for Hydro-environment Engineering and Research, Asia Pacific Division. Published by Elsevier B.V. All rights reserved.
Modelling of hyperconcentrated flow in steep-sloped channels
(2018-01-01)
Chen, Chien-Hua
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Lin, Ying-Tien
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Chung, Hau-Rong
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Hsieh, Te-Yung
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Yang, Jinn-Chuang
An unsteady two-dimensional depth-averaged numerical model for hyperconcentrated flows in steep-sloped alluvial channels is developed and applied to the Zhuoshui River in Central Taiwan. In this model, the suspended load and bed load are both included to reproduce actual sediment transport characteristics of steep-sloped channels in the chosen study river reaches. A rheological relationship for Bingham fluid and the formula for the sediment carrying capacity, established through laboratory experiments, are used to describe the hyperconcentrated flow behaviour in the model. At peak discharge during Typhoon Morakot, bed shear stress from the hyperconcentrated flow model can be 150% larger than that from the clear water model. According to the simulation for Tung-Pu-Rey Creek, an upstream tributary of Zhuoshui River, the temporal evolution of bed changes obtained from the model can be used to provide plausible explanations for the reasons behind levee failure during Typhoon Toraji.
Statistical Distance Estimation Algorithms With RSS Measurements for Indoor LTE-A Networks
(2017-02)
Chen, Chien-Hua
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Feng, Kai-Ten
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電機工程學系
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Department of Electrical and Computer Engineering
An indoor base station (BS), such as a remote radio head or home eNodeB, is a cost-effective solution to achieve ubiquitous access and positioning functions in indoor Long-Term Evolution Advanced (LTE-A) networks. In this paper, two distance estimation algorithms adopt received signal strength (RSS) to estimate the corresponding distance between a BS and a mobile station. The statistical inference distance estimation (SIDE) algorithm is proposed to provide a consistent distance estimator when the particle number is larger than an inferential theoretic lower bound given a confidence level and an error constraint. Moreover, the particle-based distance estimation (PDE) algorithm is proposed to estimate distance information with the technique of particle filtering under mixed line-of-sight (LOS) and non-line-of-sight (NLOS) conditions in indoor LTE-A networks. Furthermore, the theoretic Cramer-Rao lower bound (CRLB), considering the variations from fading effects and time-variant channels, is derived as a benchmark to evaluate the precision of distance estimators. The performance of the proposed SIDE algorithm is verified through simulations, and the results fulfill the requirements of different confidence levels and error constraints. Furthermore, the proposed PDE algorithm outperforms other distance estimation schemes and reveals robustness against mixed-sight and time-variant indoor LTE-A networks.
Two-Dimensional Numerical Investigation for Short- and Long-Term Effects of Spur Dikes on Weighted Usable Area of Rhinogobius candidianus (Goby)
(2013-12-01)
Chang, Yin-Lung
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Hsieh, Te-Yung
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Chen, Chien-Hua
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Yang, Jinn-Chuang
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土木工程學系
The weighted usable area (WUA) is one of the popular metrics to quantify the stream physical habitat and the effects of instream structures. However, most habitat studies only considered existing or proposed channel geometries in their WUA computations and not how the channel will evolve over time. This study reports a numerical investigation for the effects of spur dikes on WUA along the Juanchiao levee, Touchien River, Taiwan. Seven virtual dikes were placed along the outer bend in the study reach and the Rhinogobius candidianus was selected for target species. The horizontal two-dimensional (2D) flow fields at various flows and the corresponding WUAs for R. candidianus were computed under four channel bathymetry configurations, including: (1)existing; (2)immediately after dikes are implemented; (3)after 10-year channel migration without dikes; and (4)10years after dikes are implemented. The WUA obtained from the first two bathymetry configurations aimed to investigate the short-term spur dikes effect, whereas the last two examined the long-term effect. The channel geometry after 10years channel migration under the conditions of both with and without spur dikes were simulated through a 2D mobile bed model. The analyses of short-term effect showed the WUA of R. candidianus, shortly after the virtual dikes were placed, increases due to increased water depth near the dikes, especially in low-flow conditions. As for long-term effects, however, the WUA in the case with spur dikes are lower than the case without spur dikes, especially in relatively high-flow conditions. The adverse effects of spur dikes on WUA appeared in the long-term investigation and resulted from the ever-increasing water depth and flow velocity around the tip of spur dikes and the main channel. This study showed that the habitat quality and availability might be overestimated if the channel bed changes over time. When using the WUA approach to evaluate the effects of instream structure on physical habitat prior to actually placing them in the river, quantitative predictions of the long-term variation of channel geometry and the associated physical habitat conditions are important. (C) 2013 American Society of Civil Engineers.
Wireless Location Estimation With the Assistance of Virtual Base Stations
(2009-01-01)
Chen, Chien-Hua
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Feng, Kai-Ten
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Chen, Chao-Lin
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Tseng, Po-Hsuan
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電信工程研究所
In recent years, wireless location estimation has attracted a significant amount of attention in different areas. Various types of radio signals are applied for the development of location-estimation algorithms. In this paper, the range measurements acquired from the received time-based information are adopted, and the modified least square (LS) method is utilized to process the raw data and to finally locate the target object. Practical issues, such as the nonline-of-sight (NLOS) errors and the geometric dilution of precision (GDOP) effect, are of concern. The NLOS error will cause a large nonnegative bias while measuring the propagation delay, which will lead to an unreliable result for location estimation. On the other hand, a large GDOP value corresponds to a poor geometric topology, which will result in inferior performance by adopting most of the existing location algorithms. The proposed location-estimation algorithms with virtual base stations (VBSs) will both mitigate the influence from the NLOS errors by imposing the geometric constraints and reduce the GDOP effect by incorporating the assisted VBSs. Two iterative schemes are proposed, including the center-of-gravity-based VBS (VBS-CG) and the minimal GDOP-based VBS (VBS-MG) algorithms, to determine the required number and the locations of the assisted VBSs. The proposed VBS algorithms are compared with other existing location-estimation schemes via simulations. The performance of the VBS-MG algorithm is observed to outperform the other schemes, particularly under the environments with larger NLOS errors and poor geometric layouts.