Browsing by Author "Pan, Chien-Hung"

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A hybrid multiuser detection technique based on interference cancellation knowledge in MIMO communications
(2007)
Pan, Chien-Hung
;
Lee, Ta-Sung
;
Li, Yiming
;
電信工程研究所
;
Institute of Communications Engineering
In this paper, we propose a hybrid multiuser detection (MUD) technique, which is similar to the maximum likelihood detector (MLD) but with reduced complexity, for the application of multiple-input multiple-output (MIMO) communications. The proposed MUD technique avoids the exhaustive search required for the elimination of inter-antenna interference (IAI). Instead, the proposed method incorporates an efficient hybrid multiuser detection technique and consists of a two-stage procedure to achieve the performance of the ML detector with an acceptable level of computational complexity. The first stage performs interference cancellation by using the sorted QR decomposition (SQRD), and the second stage performs the genetic algorithm (GA). This two-stage procedure is thus called SQRD GA-MUD. The main advantage of the SQRD scheme is that it provides a "good initial setting knowledge" by eliminating IAI to improve the fitness of the population for GA. Simulation results obtained in this study demonstrate that SQRD GA-MUD achieves a gain of 6 dB to 15 dB compared to other well known detectors, with an acceptable number of iterations.
A Robustness and Low-Complexity Selection Criterion for Switching between Multiplexing and Diversity in MIMO Transmission
(2011-09-01)
Pan, Chien-Hung
;
電信工程研究所
;
Institute of Communications Engineering
In this paper, we propose a new QR-based selection criterion with reduced complexity for the development of switching between spatial multiplexing (SM) and spatial diversity (SD) transmission. Then, we investigate an effect of the QR-decomposition processes by exploiting orthogonal structure of channel matrix. Additionally, to solve the problem of the error transmission mode in transmitter, we claim that the proposed QR-based detection at receiver can be used to form the successive interference cancellation (SIC) detection and orthogonal space-time block code (O-STBC) decoding for the SM transmission and the SD transmission, respectively. Simulation results show that the proposed scheme is capable of achieving optimum performance, but at a low-complexity level.
An efficient near-ML algorithm with SQRD for wireless MIMO communications in metro transportation systems
(2007)
Pan, Chien-Hung
;
Lee, Ta-Sung
;
Li, Yiming
;
電信工程研究所
;
Institute of Communications Engineering
A high-speed multiple input multiple output (NEMO) wireless communication system is proposed for metro transportation. In order to better mitigate the inter-antenna interference (LAI) which degrades the quality of the MIMO receiver, we propose an efficient hybrid multiuser detection (MUD) technique. This approach consists of a two-stage procedure to achieve the optimum multiuser detector (OMD) by an acceptable computational complexity. The first stage performs interference cancellation by using sorted QR decomposition (SQRD), and the second stage performs the genetic algorithm (GA). It has two significant advantages: 1) The SQRD scheme provides "good initial setting knowledge" to improve the fitness of the population for GA. 2) The effect of fitness calculation is obtained from the QR decomposition (QRD) of a MIMO channel. Simulation results demonstrate that the two-stage procedure obtains a gain of 3 dB to 25 dB than other well-known MUD schemes. The computational complexity of the two-stage procedure can be reduced by 30% with QRD than other fitness calculation scheme in GA-MUD.
Complexity Reduction by Using QR-Based Scheme in Computing Capacity for Optimal Transmission
(2011-05-01)
Pan, Chien-Hung
;
電信工程研究所
;
Institute of Communications Engineering
Multiple-input-multiple-output (MIMO) technique is often employed to increase capacity in comparing to systems with single antenna. However, the computational complexity in evaluating channel capacity or transmission rate (data rate) grows proportionally to the number of employed antennas at both ends of the wireless link. Recently, the QR decomposition (QRD) based detection schemes have emerged as a low-complexity solution. After conducting QRD on a full channel matrix that results in a triangular matrix, we claim that computational complexity can be simplified by the following ways. First, to simplify channel capacity calculation, we prove that eigenvalues of the full channel matrix multiplication equals eigenvalues of the triangular channel matrix multiplication. Second, to simplify the calculation of the optimal transmission rate constrained constellation, we propose a simplistic multiplication of the resulted simple triangular matrix and a transmitted signal vector. Then, we also propose a modified mutual information calculation (MMIC) to achieve a quite low-complexity via the divided calculation. By using computer simulation and field- programmable gate array (FPGA) implementation, simulation results show that the proposed QRD-based schemes are capable of achieving conventional performance, but at a low-complexity level.
Design of Robust Transceiver for Precoded Uplink MU-MIMO Transmission in Limited Feedback System
(2014-07-01)
Pan, Chien-Hung
;
電子工程學系及電子研究所
;
Department of Electronics Engineering and Institute of Electronics
This paper proposes a robust transceiver design against the effect of channel state information (CSI) estimation error to optimize precoded uplink (UL) multi-user multiple-input multiple-output (MU-MIMO) transmission in limited feedback system under the consideration of the least-square technique on CSI estimation. To improve this limited feedback precoding, the constrained minimum variance (MV) approach with quadratic form to realize the computationally-efficient optimization problem, advantageously invoking the characteristics of the CSI estimation error, is proposed to suppress the effect of CSI estimation error, multiple user interference and noise. According to the Lagrange multiplier method on this MV approach, the deterministic function to resist uncertain CSI can be obtained to optimize design of the precoder and adaptive matrices jointly. With these optimum adaptive and precoder matrices, an optimum robust weighting matrix can be obtained to facilitate the user-wise detection in precoded UL MU-MIMO system. Performance analysis shows that the proposed robust weighting matrix is an unbiased design and it also can regularize the diagonal loading factor technique, and the detection performance of the proposed robust transceiver design can be predicted simplistically by applying our derived signal-to-interference-plus-noise ratio formulation. Computer simulations are conducted to confirm the efficacy of the proposed design in both perfect and imperfect CSI estimation.
Design of Robust Transceiver for Precoded Uplink MU-MIMO Transmission in Limited Feedback System
(2014-07-01)
Pan, Chien-Hung
;
電機工程學系
;
Department of Electrical and Computer Engineering
This paper proposes a robust transceiver design against the effect of channel state information (CSI) estimation error to optimize precoded uplink (UL) multi-user multiple-input multiple-output (MU-MIMO) transmission in limited feedback system under the consideration of the least-square technique on CSI estimation. To improve this limited feedback precoding, the constrained minimum variance (MV) approach with quadratic form to realize the computationally-efficient optimization problem, advantageously invoking the characteristics of the CSI estimation error, is proposed to suppress the effect of CSI estimation error, multiple user interference and noise. According to the Lagrange multiplier method on this MV approach, the deterministic function to resist uncertain CSI can be obtained to optimize design of the precoder and adaptive matrices jointly. With these optimum adaptive and precoder matrices, an optimum robust weighting matrix can be obtained to facilitate the user-wise detection in precoded UL MU-MIMO system. Performance analysis shows that the proposed robust weighting matrix is an unbiased design and it also can regularize the diagonal loading factor technique, and the detection performance of the proposed robust transceiver design can be predicted simplistically by applying our derived signal-to-interference-plus-noise ratio formulation. Computer simulations are conducted to confirm the efficacy of the proposed design in both perfect and imperfect CSI estimation.
Efficient QR-Based Multi-Mode Precoding for Limited Feedback Multi-User MIMO Systems
(2014-01-01)
Pan, Chien-Hung
;
Lee, Ta-Sung
;
電子工程學系及電子研究所
;
Department of Electronics Engineering and Institute of Electronics
This paper proposes QR-based criteria for efficient selection of multi-mode precoders in multi-user multiple-input multiple-output (MU-MIMO) precoded systems with a limited feedback. In particular, a MU-MIMO QR based precoding scheme is developed which takes advantage of the overall precoder design among users in conjunction with QR detection. A selection criterion is developed to identify the precoder that yields the maximum free distance. Efficient mode selection and tree search strategies are adopted to reduce the complexity associated with the identification of the optimum precoder. To further improve the detection performance in correlated channels, an efficient QR-based MMSE V-BLAST detector is proposed. Computer simulations confirm that the proposed QR-based precoding scheme attains the performance of existing schemes with a significantly lower complexity level.
Electrically injected 1.3-mu m quantum-dot photonic-crystal surface-emitting lasers
(2017-12-25)
Hsu, Ming-Yang
;
Lin, Gray
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Pan, Chien-Hung
;
電子工程學系及電子研究所
;
Department of Electronics Engineering and Institute of Electronics
We have fabricated electrically injected InAs/InGaAs/GaAs quantum-dot (QD) photonic-crystal (PC) surface-emitting lasers (SELs) and successfully demonstrated roomtemperature lasing emissions at 1.3-mu m wavelength for the first time. The PCSEL device fabrication was greatly simplified by deposition of transparent conducting layer of indiumtin- oxide over "PC slab-on-substrate" structure. The threshold current density per QD layer was as low as 50 A/cm(2)/layer; however, the optical output was limited to 2 mW. The bandedge lasing mode was identified and near-circular beam with narrow divergence angle less than 2 degrees was achieved. (C) 2017 Optical Society of America under the terms of the OSA Open Access Publishing Agreement
Electrically pumped quantum dot surface emitting lasers with Bragg grating capped by ITO cladding layers
(2016)
Hong, Kuo-Bin
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Chang, Ting-Yuan
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Pan, Chien-Hung
;
Lin, Chien-Hung
;
Lin, Gray
QD based Bragg gratings surface emitting lasers using ITO as transparent cladding layers were demonstrated. Measured lasing peak locates at 1298nm and threshold current density of 210 A/cm(2). The laser shows extremely small divergence surface-emitted beam and thermal redshift of 0.08 nm/K in peak wavelength.
Low-Threshold Short-Wavelength Infrared InGaAs/GaAsSb \'W\'-Type QW Laser on InP Substrate
(2015-02-01)
Chang, Chia-Hao
;
Li, Zong-Lin
;
Lu, Hong-Ting
;
Pan, Chien-Hung
;
Lee, Chien-Ping
The electrically driven short-wavelength infrared semiconductor laser using InP-based InGaAs/GaAsSb W-type quantum wells (QWs) is investigated. Using Sb-free separate confined layer and engineered QWs, the laser lasing at 2.35 mu m exhibits a low-threshold current density at infinite cavity length of 83 A/cm(2) per QW under pulsed operation at room temperature. The internal loss alpha(i) and internal quantum efficiency eta(i) of the laser are 17.5 cm(-1) and 15%, respectively.
Observation of long-lived excitons in InAs quantum dots under thermal redistribution temperature
(2012-03-26)
Cheng, Chun
;
Lin, Sheng-Di
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Pan, Chien-Hung
;
Lin, Chien-Hung
;
Fu, Ying-Jhe
We study the temperature-dependent time-resolved photoluminescence (TRPL) of self-assembled InAs quantum dots (QDs). Under low excitation power, a surprisingly long PL decay time is observed at about 60 K, under the thermal redistribution temperature. The long decay time decreases with increasing excitation power but is nearly independent of the detection energy of TRPL measurements. A model considering the spin relaxation through the excited excitonic state is proposed to quantitatively explain the unusual phenomena. The rate equation analysis indicates that the observation of long-lived excitons is caused by the shortened spin-flip time. (c) 2012 Elsevier B.V. All rights reserved.
Quantum-Dot Surface Emitting Distributed Feedback Lasers Using Indium-Tin-Oxide as Top Claddings
(2016-08-01)
Chang, Ting-Yuan
;
Pan, Chien-Hung
;
Hong, Kuo-Bin
;
Lin, Chien-Hung
;
Lin, Gray
We demonstrate InAs/InGaAs quantum-dot surface emitting distributed feedback (SE-DFB) lasers, using an indium-tin-oxide layer as top cladding, which eliminates the regrowth process used in conventional DFB lasers to greatly simplify laser process. The lasing peak near 1.30 mu m realized using the grating period of 375 nm exhibited a 0.13-nm linewidth and a low-temperature red-shift rate of 0.1 nm/K. The laser had a threshold current density of 210 A/cm(2) and a characteristic temperature of 94.6 K. The surface emitting laser light had the divergence angles of less than 1 degrees and 8 degrees similar to 9 degrees along and perpendicular to the grating direction, respectively.
Room Temperature Optically Pumped 2.56-mu m Lasers With "W" Type InGaAs/GaAsSb Quantum Wells on InP Substrates
(2012-07-01)
Pan, Chien-Hung
;
Chang, Chia-Hao
;
Lee, Chien-Ping
;
電子工程學系及電子研究所
;
Department of Electronics Engineering and Institute of Electronics
The optically pumped laser using InGaAs/GaAsSb W-type quantum wells is demonstrated with a threshold power density similar to 40 kW/cm(2). The L-L curve and the dramatic line width shrinkage above threshold confirm, for the first time, mid-infrared lasing in this structure on InP substrates. The lasing wavelength at 2.56 mu m is the longest lasing wavelength at room temperature for the interband transition of InP-based material system.
Room-temperature mid-infrared "M"-type GaAsSb/InGaAs quantum well lasers on InP substrate
(2014-02-14)
Chang, Chia-Hao
;
Li, Zong-Lin
;
Pan, Chien-Hung
;
Lu, Hong-Ting
;
Lee, Chien-Ping
We have demonstrated experimentally the InP-based "M"-type GaAsSb/InGaAs quantum-well (QW) laser lasing at 2.41 mu m at room temperature by optical pumping. The threshold power density per QW and extracted internal loss were about 234 W/cm(2) and 20.5 cm(-1), respectively. The temperature-dependent photoluminescence (PL) and lasing spectra revealed interesting characteristics for this type of lasers. Two distinct regions in the temperature dependent threshold behavior were observed and the transition temperature was found to coincide with the cross over point of the PL and lasing emission peaks. The current-voltage characteristic of "M"-type QW laser was superior to the inverse "W"-type one due to its thinner barrier for holes. Further improvement of the "M"-type QW structure could lead to a cost-effective mid-infrared light source. (C) 2014 AIP Publishing LLC.
Temperature Dependence of Electrically Injected Quantum-Dot Photonic-Crystal Surface-Emitting Lasers
(2018-01-01)
Hsu, Ming-Yang
;
Lin, Gray
;
Chen, Yu-Chen
;
Pan, Chien-Hung
;
電子工程學系及電子研究所
We have simplified fabrication of electrically injected quantum-dot photonic-crystal surface-emitting lasers and demonstrated lasing emissions at 1313 nm. Excellent threshold temperature characteristics was exhibited in range of 20 similar to 45 degrees C with characteristics temperature of almost infinity.