Browsing by Author "Chen, CJ"

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A fast lane and vehicle detection approach for autonomous vehicles
(2005)
Wu, BF
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Lin, CT
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Chen, CJ
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Lai, TC
;
Liao, HL
This paper proposes a lane detection algorithm, a fuzzy-based vehicle detection approach and a distance measurement method for intelligent autonomous vehicles. The lane detection algorithm reduces computational load and has proven successful on highway and in urban settings at different velocities (110km/h and 50km/h, respectively). The proposed fuzzy-based vehicle detection approach named Contour Size Similarity (CSS), compares the contour size of objects by fuzzy rules. CSS efficiently distinguishes target obstacles, namely vehicles, from other objects detected and differentiates between obstacles and pattern on the road surface. After the nearest vehicle in the lane is found, we estimate its distance to the intelligent autonomous vehicle according to its position in the image. Then the information obtained would sever as aids for automatic driving of the intelligent autonomous vehicles.
A real-time robust lane detection approach for autonomous vehicle environment
(2004)
Wu, BF
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Chen, CJ
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Chiu, CC
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Lai, TC
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電控工程研究所
This paper proposes a real-time lane detection algorithm which provides adaptive region of interesting to reduce computational load and is robust for real road environment, e.g., road inclination, road width calibration. Compared to previous approaches, the flat road assumption is released in our approach so that the result is more close to real road environment. This work has been successfully verified on highway and urban with different velocities 110 km/h and 50 km/h, respectively, in the real vehicle, TAIWAN iTS-1, which is an experimental car of Taiwan ITS project. The algorithm is also demonstrated on the lanes which are with shadows, texts, crooks, or sheltered by other vehicles for sunny and night environment.(1)
A unified capacity analysis for wireless systems with joint antenna and multiuser diversity in Nakagami fading channels
(2004)
Chen, CJ
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Wang, LC
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交大名義發表
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National Chiao Tung University
In this paper, we present a cross-layer analytical framework to jointly investigate antenna diversity and multiuser scheduling under the generalized Nakagami fading channels. We derive a unified capacity formula for the multiuser scheduling system with different multiple-input multiple-output (MIMO) antenna schemes, including the selective combining (SC), maximum ratio combining (MRC) and space-time block codes (STBC). Our analytical results indicate that, in the presence of multiuser diversity, the multiple antennas with the SC method can be viewed as virtual users to amplify multiuser diversity order, while the MRC scheme can even yield greater capacity than the SC scheme due to the increased array gain. However, applying the STBC method on top of the multiuser scheduling system may lead to capacity loss due to the reduced amount of fading.
An analytical framework for capacity and fairness evaluation in high speed wireless data networks
(2003)
Chen, CJ
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Wang, LC
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交大名義發表
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National Chiao Tung University
This paper presents an analytical framework to evaluate the downlink capacity and fairness performance for high speed wireless data networks from both the physical layer and the network layer perspectives. Prom the physical layer standpoint, we take into account of propagation loss, log-normal shadowing and Nakagami fading. From the network layer perspective, we model different scheduling policies and the impact of nonuniform traffic intensity of mobile users into our framework. We analyze the joint effects of radio channel impairments, nonuniform traffic intensity and scheduling algorithms on the downlink capacity and fairness performance of wireless data networks based on the developed framework. Our results indicate that it is crucial for wireless scheduling algorithms to consider not only the radio channel impairments, but also the traffic intensity distribution in the whole network.
An efficient hierarchical motion estimation on algorithm and its VLSI architecture
(2005)
Wu, BF
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Peng, HY
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Chen, CJ
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Yu, TL
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電控工程研究所
This manuscript addresses the design and implementation of an efficient hierarchical motion estimation algorithm, HMEA, using multiple motion vector candidates to increase the estimation quality. HMEA satisfies the high estimation performance and efficient VLSI implementation. The algorithm adopts multi-resolution frames to reduce the computation complexity, and the original frame is down sampled into one-fourth and one-sixteenth respectively. At the smallest resolution, the least two motion vector candidates are selected using full-search block matching algorithm with search range equals to 4. At the middle level, these two motion vector candidates are used as center points for local searches, and the search range is reduce to 2. Then, at the original resolution level, the final motion vector is obtained from local search around the single candidate from the middle level. This paper also describes an efficient VLSI architecture based on the HMEA. We implement this architecture with about 59K gates and 798 bytes of RAM for a search range of [-16.0, +15.5] by using a synthesizable VHDL.
An encrypted mobile embedded surveillance system
(2005)
Wu, BF
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Peng, HY
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Chen, CJ
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Chan, YH
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電控工程研究所
This manuscript addresses the design and implementation of an encrypted mobile embedded surveillance system, EMESS, including a wireless server and mobile devices. Not only the mobility of the hand-held devices, but also the surveillance system can work in a moving body, then, a real mobile surveillance system is provided. In the security applications of vehicles, EMESS also can provide the images of thieves and robbers to the vehicle owner. We complete the related works of EMESS and the corresponding application programs for wireless communication of hand-held devices.
An intelligent vision-based real-time integration system on autonomous vehicles
(2004)
Wu, BF
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Chiu, CC
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Chen, CJ
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Wu, WC
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Perng, JW
In this paper, an intelligent real-time system on autonomous vehicles is presented. A wireless-based remote control scheme is developed. A vision-based obstacle detection system and a radar sensor are integrated into the on-vehicle controller to automatically brake the vehicle under emergency. Finally, a successfully on-road demonstration is also completed with our experimental car. TAIWAN iTS-1.(1)
Coverage and capacity enhancement in multiuser MIMO systems with scheduling
(2004)
Chen, CJ
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Wang, LC
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交大名義發表
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National Chiao Tung University
Recent studies have revealed that the capacity improvement resulting from an open-loop multiple-input-multiple-output (MIMO) spatial multiplexing system may come at the sacrifice of reducing link reliability. The tradeoff of antenna multiplexing gain against antenna diversity gain may lead to smaller cell coverage sizes. In this paper, we propose a scheduling scheme, called the strongest-weakest-normalized-subchannel-first (SWNSF) scheduling, to replenish the diversity-deficient MIMO system with multiuser diversity. Our analysis and results indicate that the SWNSF scheduling can significantly increase both cell coverage and system capacity requiring only limited amount of feedback.
Interference suppression in TDD/CDMA cellular systems with asymmetric traffic using MVDR beamforming
(2002)
Chen, CJ
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Wang, LC
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交大名義發表
;
National Chiao Tung University
The primary advantage of the TDD syetem is to accommodate asymmetric traffic by allocating different numbers of uplink and downlink time slots. However, in the TDD/CDMA cellular system, uplink signals may suffer strong interference from the downlink transmission of neighboring base stations. This kind of opposite direction interference has adverse impact on the TDD/CDMA system performance. In this paper, we propose to apply the MVDR beamforming technique to suppress the opposite direction interference. We evaluate the uplink performance of the proposed technique by simulation. Moreover, by jointly employing transmit beamforming in all asynchronous cells, the TDD/CDMA cellular system can allow different rates of asymmetry in different cells. Thus, each cell can design its own pattern of slot allocation.
On the performance of the zero-forcing receiver operating in the multiuser MIMO system with reduced noise enhancement effect
(2005)
Chen, CJ
;
Wang, LC
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交大名義發表
;
National Chiao Tung University
Despite its simplicity, the zero-forcing receiver is known to suffer from noise enhancement to restore the spatially multiplexed data in a point-to-point MIMO system. Nevertheless, in the point-to-multipoint multiuser system, the poor channel avoidance property of the scheduling technique provides a natural way to overcome the drawback of noise enhancement. In this paper, we present an analytical framework to evaluate the performance of the zero-forcing receiver operating in the multiuser MIMO system with scalar feedback scheduling. Using the order statistics technique, we derive closed-form expressions for the achievable throughput of the zero-forcing receiver operating in the multiuser MIMO environment. Our analytical results indicate that the cross-layer cooperation of the simple zero-forcing receiver and scheduling technique can achieve the full capacity of the point-to-point MIMO system.
Real-time image segmentation and rule-based reasoning for vehicle head light detection on a moving vehicle
(2005)
Wu, BF
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Chen, YL
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Chen, YH
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Chen, CJ
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Lin, CT
This study proposes a vehicle detection system for identifying the vehicles by locating their headlights and rear-lights in the nighttime road environment. The proposed system comprises of two stages for detecting the vehicles in front of the camera-assisted car. The first stage is a fast automatic multilevel thresholding, which separates the bright objects from the grabbed nighttime road scene images. This proposed automatic multilevel thresholding approach provide the robustness and adaptability for the system to operate on various illuminated conditions at night. Then the extracted bright objects are processed by the second stage - the proposed knowledge-based connected-component analysis procedure, to identify the vehicles by locating their vehicle lights, and estimate the distance between the camera-assisted car and the detected vehicles. Experimental results demonstrate the feasibility and effectiveness of the proposed approach on vehicle detection at night.
Short-diode like diffusion capacitance of organic light emission devices
(2006-03-01)
Tsai, MN
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Chang, TC
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Liu, PT
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Ko, CW
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Chen, CJ
A prototypical organic light-emitting diode (OLED), anode/organic layers/cathode, is investigated via bias-dependent capacitance measurement of two-layer (HTL/ETL) and four-layer (HIL/HTL/EML/ETL) structure at low frequency. As applied voltage was larger than the built-in voltage, the capacitance is augmented by diffusion capacitance with increasing the forward bias voltage. In contrast, the capacitance dropped quickly. It is possibly due to the voltage drop in the bulk and conductivity modulation occurred by high carrier concentration for much higher forward biases, eventually showing negative for two-layer OLEDs. We infer that the phenomena were resulted from the extremely thin OLED structure, just like short p-n semiconductor diodes. This diffusion capacitance exhibiting like short-diode behavior also can be measured in C-V curves of single-layer structure OLED. (c) 2005 Elsevier B.V. All rights reserved.
Suppressing opposite-direction interference in TDD/CDMA systems with asymmetric traffic by antenna beamforming
(2004-07-01)
Chen, CJ
;
Wang, LC
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交大名義發表
;
National Chiao Tung University
One of the key advantages for the time-division duplex (TDD) system is the capability to deliver asymmetric traffic services by allocating different numbers of uplink and downlink time slots. However, in a TDD/code-division multiple-access (CDMA) system, asymmetric traffic may result in severe opposite-direction interference because downlink transmitted signals from neighboring base stations may interfere with the uplink received signals of the home cell. In this paper, we investigate the effect of four-antenna beamforming schemes from the perspective of suppressing the opposite-direction interference. We compare the uplink bit energy-to-interference density ratio of a traditional beam-steering technique (Scheme 1) with that of the minimum-variance distortionless-response (MVDR) beamformer (Scheme 11). Furthermore, Scheme III applies the conventional beam-steering technique for both downlink transmissions and the uplink reception. In Scheme IV, we implement beam-steering for downlink transmissions, while adopting the MVDR beamformer to process the uplink signals received at base stations. Our numerical results indicate that Scheme IV outperforms all the other three schemes, which can effectively suppress the strong opposite-direction interference in TDD/CDMA systems. While keeping low implementation costs in mind, employing the simpler Scheme HI in a sectorized cellular system can also allow every cell to provide different rates of asymmetric traffic services.