Browsing by Author "Liu, Yen-Chun"

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100-m Long Distance RGB Visible Light Camera Communication
(2018-01-01)
Liu, Yen-Chun
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Shiu, Ruei-Jie
;
Wei, Liang-Yu
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Hsu, Chin-Wei
;
Chow, Chi-Wai
We demonstrate and analyze using different ISO values to achieve a 100-m long distance visible light camera communication using red/green/blue (RGB) light-emitting-diodes (LEDs).
Adaptive Thresholding Scheme for Demodulation of Rolling-Shutter Images Obtained in CMOS Image Sensor Based Visible Light Communications
(2018-12-01)
Chow, Chi-Wai
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Liu, Yen-Chun
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Shiu, Ruei-Jie
;
Yeh, Chien-Hung
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光電工程學系
Light-emitting-diode transmitter and complementary-metal-oxide-semiconductor (CMOS) image sensor receiver based visible light communication is a promising scheme for an optical wireless communication. During the demodulation of the rolling shutter pattern obtained from the CMOS image sensor Rx, due to the high signal fluctuation introduced by the uneven light exposure, special thresholding schemes are needed to correctly identify the data logic. In this work, we propose and demonstrate a modified adaptive scheme (MQA) for the demodulation of the rolling shutter pattern. Experimental bit-errorratio (BER) measurements using different thresholding schemes at different illuminance are analyzed. The results show that the proposed MQA scheme can provide much lower BER, with similar process latencies when compared with other schemes.
An efficient and accurate lattice for pricing derivatives under a jump-diffusion process
(2010-12-01)
Dai, Tian-Shyr
;
Wang, Chuan-Ju
;
Lyuu, Yuh-Dauh
;
Liu, Yen-Chun
;
資訊管理與財務金融系註：原資管所+財金所
Derivatives are popular financial instruments whose values depend on other more fundamental financial assets (called the underlying assets). As they play essential roles in financial markets, evaluating them efficiently and accurately is critical. Most derivatives have no simple valuation formulas; as a result, they must be priced by numerical methods such as lattice methods. In a lattice, the prices of the derivatives converge to theoretical values when the number of time steps increases. Unfortunately, the nonlinearity error introduced by the nonlinearity of the option value function may cause the pricing results to converge slowly or even oscillate significantly. The lognormal diffusion process, which has been widely used to model the underlying asset's price dynamics, does not capture the empirical findings satisfactorily. Therefore, many alternative processes have been proposed, and a very popular one is the jump-diffusion process. This paper proposes an accurate and efficient lattice for the jump-diffusion process. Our lattice is accurate because its structure can suit the derivatives' specifications so that the pricing results converge smoothly. To our knowledge, no other lattices for the jump-diffusion process have successfully solved the oscillation problem. In addition, the time complexity of our lattice is lower than those of existing lattice methods by at least half an order. Numerous numerical calculations confirm the superior performance of our lattice to existing methods in terms of accuracy, speed, and generality. (C) 2010 Elsevier Inc. All rights reserved.
An efficient and accurate lattice for pricing derivatives under a jump-diffusion process
(2010-12-01)
Dai, Tian-Shyr
;
Wang, Chuan-Ju
;
Lyuu, Yuh-Dauh
;
Liu, Yen-Chun
;
資訊管理與財務金融系註：原資管所+財金所
Derivatives are popular financial instruments whose values depend on other more fundamental financial assets (called the underlying assets). As they play essential roles in financial markets, evaluating them efficiently and accurately is critical. Most derivatives have no simple valuation formulas; as a result, they must be priced by numerical methods such as lattice methods. In a lattice, the prices of the derivatives converge to theoretical values when the number of time steps increases. Unfortunately, the nonlinearity error introduced by the nonlinearity of the option value function may cause the pricing results to converge slowly or even oscillate significantly. The lognormal diffusion process, which has been widely used to model the underlying asset's price dynamics, does not capture the empirical findings satisfactorily. Therefore, many alternative processes have been proposed, and a very popular one is the jump-diffusion process. This paper proposes an accurate and efficient lattice for the jump-diffusion process. Our lattice is accurate because its structure can suit the derivatives' specifications so that the pricing results converge smoothly. To our knowledge, no other lattices for the jump-diffusion process have successfully solved the oscillation problem. In addition, the time complexity of our lattice is lower than those of existing lattice methods by at least half an order. Numerous numerical calculations confirm the superior performance of our lattice to existing methods in terms of accuracy, speed, and generality. (C) 2010 Elsevier Inc. All rights reserved.
Mitigation of performance degradation due to dynamic display contents in visible light communication using TV backlight and CMOS image sensor
(2018-08-20)
Chow, Chi-Wai
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Shiu, Ruei-Jie
;
Liu, Yen-Chun
;
Wang, Wei-Chung
;
Liao, Xin-Lan
Here, we propose and demonstrate a performance degradation mitigation scheme in TV backlight and smart-phone-based visible light communication (VLC) system when the display content in the light-panel is dynamically changing. In order to evaluate the influence of the dynamic display contents to the VLC performance, we use a noise-ratio (NR) and noise-ratio standard deviation (NRSD) as the figure-of-merits for the bright-and-dark contrast of the display content; and the dispersal of the changing display content regarding the brightand-dark contrast respectively. Performances of 4 dynamic display contents with different combinations of NR and NRSD are analyzed. They are: low NR and low NRSD (NR 36.69%; NRSD = 0.0226); low NR and high NRSD (MR = 30.09%; NRSD = 0.2698); high NR and low NRSD (NR = 81.66%; NRSD = 0.0052); high NR and high NRSD (NR = 73.91%; and NRSD = 0.2717). The proposed scheme can work well; that is, even the transmission distance is up to 200 cm in both smart-phones. If the proposed scheme is not used, then high success rate can be observed only at the low NR and low NRSD display content when the transmission distance is < 100 cm. (C) 2018 Optical Society of America under the terms of the OSA Open Access Publishing Agreement
Non-flickering 100 m RGB visible light communication transmission based on a CMOS image sensor
(2018-03-19)
Chow, Chi-Wai
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Shiu, Ruei-Jie
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Liu, Yen-Chun
;
Liu, Yang
;
Yeh, Chien-Hung
We demonstrate a non-flickering 100 m long-distance RGB visible light communication (VLC) transmission based on a complementary-metal-oxide-semiconductor (CMOS) camera. Experimental bit-error rate (BER) measurements under different camera ISO values and different transmission distances are evaluated. Here, we also experimentally reveal that the rolling shutter effect- (RSE) based VLC system cannot work at long distance transmission, and the under-sampled modulation- (USM) based VLC system is a good choice. (C) 2018 Optical Society of America under the terms of the OSA Open Access Publishing Agreement
Novel Zinc Porphyrin Sensitizers for Dye-Sensitized Solar Cells: Synthesis and Spectral, Electrochemical, and Photovoltaic Properties
(2009)
Lee, Cheng-Wei
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Lu, Hsueh-Pei
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Lan, Chi-Ming
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Huang, Yi-Lin
;
Liang, You-Ren
Novel meso- or beta-derivatized porphyrins with a carboxyl group have been designed and synthesized for use as sensitizers in dye-sensitized solar cells (DSSCs). The position and nature of a bridge connecting the porphyrin ring and carboxylic acid group show significant influences on the spectral, electrochemical, and photovoltaic properties of these sensitizers. Absorption spectra of porphyrins with a phenylethynyl bridge show that both Soret and Q bands are red-shifted with respect to those of porphyrin 6. This phenomenon is more pronounced for porphyrins 3 and 4, which have a pi-conjugated electron-donating group at the meso position opposite the anchoring group. Upon introduction of an ethynylene group at the meso position, the potential at the first oxidation alters only slightly whereas that for the first reduction is significantly shifted to the positive, thus indicating a decreased HOMO-LUMO gap. Quantum-chemical (DFT) results support the spectroelectrochemical data for a delocalization of charge between the porphyrin ring and the amino group in the first oxidative state of diarylamino-substituted porphyrin 5, which exhibits the best photovoltaic performance among all the porphyrins under investigation. From a comparison of the cell performance based on the same TiO(2) films, the devices made of porphyrin 5 coadsorbed with chenodeoxycholic acid (CDCA) on TiO(2) in ratios [5]/[CD-CA]=1:1 and 1:2 have efficiencies of power conversion similar to that of an N3-based DSSC, which makes this green dye a promising candidate for colorful DSSC applications.
Optimal Power Allocation and Signal Phase Selection in NOMA Wireless Relay Networks
(2020-01-01)
Liu, Yen-Chun
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Gau, Rung-Hung
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電信工程研究所
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Institute of Communications Engineering
In this paper, we propose a novel approach of optimal power allocation and signal phase selection for NOMA wireless relay networks. Specifically, to optimize the network throughput, the base station and the stronger relay optimally allocate their transmission power, while the weaker relay selects an optimal signal phase. To maximize the end-to-end sum rate, we formulate a non-convex optimization problem and derive novel analytical results. In addition, we propose the four-candidate greedy algorithm for optimal power allocation and signal phase selection in NOMA wireless relay networks. Simulation results show that the proposed greedy algorithm could significantly improve the system performance.
Polarization-Multiplexed Rolling Shutter Demodulation in Mobile-Phone Based Visible Light Communication
(2018-01-01)
Chang, Yuan-Chia
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Chen, Chia-Wei
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Liu, Yen-Chun
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Shiu, Ruei-Jie
;
Chow, Chi-Wai
We propose and demonstrate using polarization-multiplexing of rolling-shutter-effect (RSE) based visible-light-communication (VLC) to increase the transmission capacity. Experimental net data rate of 11.52 kbit/s was achieved at typical room illuminance of 500 lux.
Secure Mobile-Phone Based Visible Light Communications With Different Noise-Ratio Light-Panel
(2018-04-01)
Chow, Chi-Wai
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Shiu, Ruei-Jie
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Liu, Yen-Chun
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Yeh, Chien-Hung
;
Liao, Xin-Lan
We propose and demonstrate a visible light communication (VLC) system using a light-panel and a mobile-phone camera. We also propose the rolling-shutter-effect (RSE) pattern synchronization and demodulation algorithms. By using our developed mobile-phone application program, the RSE pattern can be demodulated even at very low illuminance. As the light-panel will have different advertisements on it, we also define a noise-ratio (NR) as the figure-of-merit; hence, different VLC data rates can be adjusted according to different advertisement NR values. Experimental bit error rate measurements at different free-space transmission distances and different NRs are performed.
Using advertisement light-panel and CMOS image sensor with frequency-shift-keying for visible light communication
(2018-05-14)
Chow, Chi-Wai
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Shiu, Ruei-Jie
;
Liu, Yen-Chun
;
Liao, Xin-Lan
;
Lin, Kun-Hsien
A frequency-shift-keying (FSK) visible light communication (VLC) system is proposed and demonstrated using advertisement light-panel as transmitter and mobile-phone image sensor as receiver. The developed application program (APP) in mobile-phone can retrieve the rolling shutter effect (RSE) pattern produced by the FSK VLC signal effectively. Here, we also define noise-ratio value (NRV) to evaluate the contrast of different advertisements displayed on the light-panel. Both mobile-phones under test can achieve success rate > 96% even when the transmission distance is up to 200 cm and the NRVs are low. (C) 2018 Optical Society of America under the terms of the OSA Open Access Publishing Agreement
Visible Light Communication Using Advertisement-Light-Board and Rolling-Shutter-Effect based CMOS Mobile-Phone Camera
(2018-01-01)
Shiu, Ruei-Jie
;
Liu, Yen-Chun
;
Chow, Chi-Wai
;
Wei, Liang-Yu
;
Hsu, Yung
We demonstrate a visible-light-communication (VLC) system using advertisement-light-board and CMOS-camera. Experiments at wireless transmission distances of 50cm, 100cm and 150cm are performed, and at data-rate of 720bit s, satisfying the forward-error-correction (FEC) threshold.