Browsing by Author "Huang, CC"

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A 9 kb/s CAPDM speech coder based on pitch synchronous substitution for wireless PCN applications
(2000)
Liu, CH
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Huang, CC
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電信工程研究所
;
Institute of Communications Engineering
This paper describes a low data rate speech coder, which is based on CAPDM (Controlled Adaptive Prediction Delta Modulation) algorithm [2] and operates at about 9 kb/s. It combines the features of one-step looking forward decision, syllabic companding, instantaneous companding, pitch detection, and adaptive prediction. A packet-based CAPDM speech coder for PCN applications, which operates at 16 kb/s, was presented previously and showed near toll quality performance [3]. In this paper, the data rate of CAPDM is further reduced by exploiting the quasi-periodic property of speech vowel waveform and by dropping speech samples every other pitch period. The dropped speech samples are recovered at receiver by duplicating the decoded speech samples according to the pitch periods. The MOS listening test results of the 9 kb/s CAPDM coder are compared with those of the 16 kb/s continuous variable slope delta modulation (CVSD), 16 kb/s CAPDM, and 32 kb/s ADPCM.
A background comparator calibration technique for flash analog-to-digital converters
(2005-01-01)
Huang, CC
;
Wu, JT
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電子工程學系及電子研究所
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Department of Electronics Engineering and Institute of Electronics
A background comparator calibration technique for flash analog-to-digital converters
(2005-09-01)
Huang, CC
;
Wu, JT
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電子工程學系及電子研究所
;
Department of Electronics Engineering and Institute of Electronics
This paper presents a background calibration technique for trimming the input-referred offsets of the comparators in a flash analog-to-digital converter (ADC) without interrupting the ADC's normal operation. For a random-chopping comparator, the polarity of its offset is detected by observing the code density of its comparison results. Binary feedback is then used to digitally adjust the comparator's offset so that the offset is minimized. All calibration procedures are performed in the digital domain. The calibration performance is characterized by the converging speed of the feedback loop and the offset fluctuation due to the disturbance of the ADC's input. These two performance indexes of a background-calibrated comparator (BCC) are determined by three parameters: the probabilistic distribution of the ADC's input, the BCC's offset quantized step size, and the threshold of an internal bilateral peak detector. The offset fluctuation of a BCC can be drastically reduced by employing a windowing mechanism. The use of windowed BCCs in a flash ADC can introduce nonmonotonic-threshold (NMT) effects which include an increase in calibration settling time and an increase in sigma(V-OS). The use of uncorrelated random chopping for neighboring BCCs can ensure the validity of offset detection and mitigate the NMT effects.
A complementary codes pilot-based transmitter diversity technique for OFDM systems
(2006-03-01)
Ku, ML
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Huang, CC
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電信工程研究所
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Institute of Communications Engineering
This letter presents a complementary codes pilot-based space-time block code/orthogonal frequency division multiplex (STBC/OFDM) system. In this system, a pair of complementary codes transmitted in a pre-defined order with the OFDM data signals is used as the pilot signals in a two-antenna transmitter diversity system, and used to estimate the channels for optimal data detection at the receiver side. A complete receiver architecture has been designed and Monte Carlo simulations have been used to verify the performance of the system in mobile radio fading channels.
A fully digital noncoherent and coherent GMSK receiver architecture with joint symbol timing error and frequency offset estimation
(2000-05-01)
Huang, YL
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Fan, KD
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Huang, CC
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電信工程研究所
;
Institute of Communications Engineering
We propose a fully digital noncoherent and coherent Gaussian minimum shift keying (GMSK) receiver architecture with joint frequency offset compensation and symbol timing recovery in this paper. Carrier phase offset ran be estimated if the coherent demodulation mode is adopted. The converted base-band complex signal is first frequency discriminated and then passed through a digital filter which performs a fast Fourier transform (FFT), The frequency offset can be estimated from the de component of the FPT, and the symbol timing error can be estimated from the phase angle of the FFT at a specified frequency which is equal to an integral multiple of half the bit rate. These two estimated parameters are then used for frequency offset compensation and symbol timing recovery during a preamble period. Coarse carrier phase can be estimated by averaging sampled in-phase and quadrature-phase signals and finding its phase angle within the preamble period after carrier frequency offset is estimated and compensated. The bit error rate (BER) performance of this GMSK receiver architecture is assessed for an additive white Gaussian noise (AWGN) channel by computer simulation.
A key agreement protocol using mutual authentication for ad-hoc networks
(2005)
Lo, CC
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Huang, CC
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Huang, YX
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資訊管理與財務金融系註：原資管所+財金所
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Department of Information Management and Finance
Security is the major concern on designing a communications network. As for ad-hoc networks, the security problem is much more complicate than that of conventional networks. In this paper, the problem of securely generating and distributing a group key to group members of an ad-hoc network is addressed. A key agreement protocol using mutual authentication is proposed. The idea of using the XOR operator suggested in a previous study is adopted. By using mutual authentication, the proposed protocol prevents both replay attack and password-guessing attack, which are two potential problems in the previous study. To further enhance security, a rekeying mechanism is introduced for updating the group key if there were no changes in group members. Both security and complexity analyses show that the proposed protocol is not only securer but also more efficient than other well-known key agreement protocols.
A low TF GMSK modem architecture with joint symbol timing recovery and frequency offset compensation
(1996)
Huang, YL
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Huang, CC
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交大名義發表
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電信工程研究所
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National Chiao Tung University
This paper records our work in developing a GMSK modem with joint symbol timing recovery and frequency offset compensation capability. The received RF signal is first down converted to a low IE and then converted to complex baseband by a digital complex sampler. This baseband signal is then frequency discriminated and passed through a digital filter which in fact performs a Fast Fourier Transform (FFT). In other words, we apply an FFT algorithm on the frequency discriminated baseband signal in order to estimate symbol timing error and frequency offset simultaneously. The frequency offset can be estimated from the DC component of the FFT and the symbol timing error can be estimated from the phase angle of the FFT at a specified frequency which is equal to an integral multiple of half the bit rate. These two estimated parameters are then used for symbol timing recovery and frequency offset compensation. The Bit Error Rate (BER) performance of our GMSK receiver architecture is assessed for an AWGN channel by computer simulation.
A new controlled adaptive prediction delta coder for wireless PCN applications
(1996)
Liu, CH
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Huang, CC
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交大名義發表
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電信工程研究所
;
National Chiao Tung University
A median-rate speech delta coder with low complexity is presented in this paper. It combines the features of one-step looking forward decision, syllabic companding, instantaneous companding, and adaptive prediction. This coder uses not only short-term prediction filter but also long-term prediction filter to estimate the current speech sample. The performance for this coder with and without pitch prediction is compared by computer simulation. Comparisons between the performance of this coder and the performance of CVSD are also included.
A novel two-stage channel estimation method for wireless communications
(2004-06-01)
Lin, WJ
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Lin, TT
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Huang, CC
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電信工程研究所
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Institute of Communications Engineering
In this paper, we proposed a novel two-stage channel estimation (2S-CE) method. In contrast to conventional channel estimation methods, this method makes the maximum use of the information contributed by the known data in every transmission burst. In the first stage, the least-squares (LS) algorithm was used to estimate the channel impulse response (CIR) based on the normal training sequence. Then the maximum channel memory was estimated and used to locate the uncorrupted data in the guard interval. In the second stage, the uncorrupted data together with the normal training sequence were sent to the LS algorithm again to obtain the fine-tuned CIR. To verify the efficiency of the proposed 2S-CE method, both a theoretical analysis and computer simulations have been done. Computer simulation results confirm the analysis results and demonstrate that the proposed 2S-CE method outperforms a conventional single-stage channel estimation method.
A packet-based CAPDM speech coder for PCN applications
(2000-05-01)
Liu, CH
;
Huang, CC
;
電信工程研究所
;
Institute of Communications Engineering
In this paper, we present a median-rate speech coder, the controlled adaptive prediction delta modulation coder (CAPDM), which operates at 16 kb/s with good speech quality and low algorithm complexity [15], The coder is dedicated to personal communication network (PCN) applications and transmits speech samples on the basis of packets. It combines the features of one-step looking forward decision, syllabic companding, instantaneous companding, and adaptive prediction. In addition to the use of a short-term prediction filter, CAPDM also exploits the pitch property to predict speech waveform explicitly. With the aid of a pitch prediction filter, the performance of a CAPDM codec improves about 3 dB in segmental signal-to-noise ratio (SEGSNR), The average SEGSNR of CAPDM.FF is about 21 dB, which is 7 dB over traditional CVSD at 16 kb/s, We also utilize an adaptive postfilter (APF) to enhance the perceptual quality of the decoded speech. The mean opinion score (MOS) listening test of CAPDM.FF with APF shows that its average score achieves 4.19, which is as good as G.728 16-kb/s LD-CELP and is comparable with CCITT G.721 32-kb/s ADPCM, The complexity of CAPDM.FF is evaluated to be 8 MIPS, which Is much lower than that of LD-CELP and could be further reduced by adopting a smaller correlation window for pitch detection. To solve the problem of packet loss, we developed a packet-based waveform substitution method by reinitializing the codec parameters at the beginning of each packet. The simulation results show that CAPDM.FF could tolerate 5% of packet loss and still keep an SEGSNR at 10 db and an MOS at about 3.0.
A simulation study of a distributed antenna-based CDMA system
(1996)
Chen, GH
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Yu, CM
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Huang, CC
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交大名義發表
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電信工程研究所
In this paper, a computer simulation study on both coverage and capacity performance of a distributed antenna based CDMA system is presented. Wideband direct sequence spread spectrum signalling with a perfect RAKE receiver is assumed. Computer simulations are used to evaluate the distribution of received signal strength in a single cell architecture, and the distribution of received signal's SIR in a cellular architecture, for both a central antenna based system and a distributed antenna based system. It is found from our simulation that a distributed antenna based system has the potential to provide larger coverage area and higher capacity as compared with a central antenna based system.
A statistical background calibration technique for flash analog-to-digital converters
(2004)
Huang, CC
;
Wu, JT
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電子工程學系及電子研究所
;
Department of Electronics Engineering and Institute of Electronics
A new background calibration technique is described to digitally trim the input-referred offset voltage of comparators in a high-speed flash analog-to-digital converters. The polarity of comparator's offset is detected by observing the output code density of a random chopping comparator. Binary feedback is used to adjust the comparator's offset. All calibration processing is performed in the digital domain. thus minimizing the overhead for analog circuitry. Two key design parameters are the comparator's trimming step and the thresholds of a peak detector, which determine the offset's standard deviation and the time constant of the calibration loop.
A two-dimensional RAKE receiver architecture, with an FFT based matched filtering
(2005-01-01)
Wang, SY
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Huang, CC
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Quek, CC
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交大名義發表
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National Chiao Tung University
This paper proposes a two-dimensional (2-D) RAKE receiver, which is a spatial-temporal matched filter implemented in the-frequency domain. To form a beam pattern, we calculate the spatial frequency spectra of received signals on the antenna array using fast Fourier transform (FFT). After FFT beamforming, a bank of FFT-based matched filters is used to perform code matching. Afterward, the code-matched signals are summed up with maximal-ratio combining through a spatial-temporal channel-matched filter implemented in the frequency domain. This 2D-DRAKE receiver includes a channel sounder-that is used to estimate the spatial and temporal channel impulse response parameters, such as delays, directions. of arrivals, and complex gains of multipath components. Monte Carlo simulations have been used to evaluate the receiver bit-error rate performance in both static channel and mobile radio channel environments. Simulation results show that the RAKE receiver performs well in both kinds of channels.
Adhesion, permeability, and mechanical properties of multilayered blown films using maleated low-density polyethylene blends as adhesion-promoting layers
(2003)
Huang, CH
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Wu, JS
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Huang, CC
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Lin, LS
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應用化學系
We have fabricated three-layer films, comprising a varying content of ethylene-vinyl alcohol copolymer (EVOH) as the internal layer and blends of low-density polyethylene (LDPE) and low-density ethylene grafted with maleic anhydride (LDPE-g-MAH) as the external layers, by a coextrusion blown-film process. We chose to use blends to promote the adhesion between EVOH and LDPE and to reduce the number of layers in the coextrusion system. The peel strength increased sharply when the amount of LDPE-g-MAH was greater than 12.5 wt% and we associate it with the promotion of adhesion between layers brought about by specific interactions between EVOH and LDPE-g-MAH. FT-IR spectroscopic analysis showed an increase in the intensity of the absorbance of the ester band upon increasing the content of LDPE-g-MAH, which indicates that a chemical reaction occurs that promotes adhesion at the interface. The tensile strength did not change significantly with increasing LDPE-g-MAH content, which had a small effect on elongation and modulus in both the machine direction (MD) and transverse direction (TD). Tear strength decreased continuously with increasing LDPE-g-MAH content, in both the MD and TD, as a result of the greater ease of crack propagation in the EVOH layer. The oxygen permeability of the three-layer films remained almost constant upon varying the amount of LDPE-g-MAH. These three-layer films all followed the theoretical prediction made by the inverse additivity rule. The water vapor permeabilities of the three-layer films, however, were affected by the degree of hydrogen bonding, which was analyzed by FT-IR spectroscopy. The effects of this hydrogen bonding resulted in a discrepancy between the experimental findings and the theoretical predictions, especially when the EVOH content was increased.
Age differences in remote pointing performance
(1997-10-01)
Hsu, SH
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Huang, CC
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Tsuang, YH
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Sun, JS
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工業工程與管理學系
The purpose of this study was to investigate age differences in remote pointing movements. The subjects were recruited from three age groups (ages 18-22 yr., 40-50 yr., and 60-70 yr., with 9 men and 9 women in each group). They were required to perform cursor-positioning tasks using a remote pointing device, in which the dependent measures were the time taken to reposition the cursor and the accuracy of subjects' movement trajectories. The movement time was further separated into two components, First Submovement duration and Adjustment Submovement duration. Analysis indicated that age groups showed reduced performance on remote pointing. Moreover, remote positioning movement for the young-adult group was mostly completed in their First Submovement phase, while the elderly subjects spent most of their movement time on the Adjustment Submovement phase. These results support the proposition that different age groups exhibit different kinds of movement patterns.
Age-related differences in remote pointing performance
(1997)
Hsu, SH
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Huang, CC
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Tsuang, YH
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Sun, JS
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交大名義發表
The present study investigated age-related differences in remote pointing performance. Three age groups (i.e., the Young adult, Middle-aged, and Elderly) performed cursor positioning tasks by using a remote pointing device. The time taken to reposition the cursor was collected. The result showed that age groups had differences in movement time. Further analysis on the submovement duration times showed that movement time for the Young-adult group was mostly travel time, while the Elderly subjects spent most of their movement time on fine adjustment. This study supports the proposition that different age groups exhibit different kinds of movement patterns.
Alkaline hydrolysis of the sludge generated from a high-strength, nitrogenous-wastewater biological-treatment process
(1998-07-01)
Lin, JG
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Ma, YS
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Huang, CC
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環境工程研究所
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Institute of Environmental Engineering
The production of acrylonitrile butadiene styrene (ABS, a petrochemical product) in Taiwan is one of the biggest manufactoring processes in the world. The large amount of ABS sludge generated in the wastewater treatment plant from the highly nitrogenous-wastewater contains significant amount of complex and biorefractory organic substances. Resource recovery is the optimal conception of the traditional sludge treatment for the purpose of organic matters removal. An alkaline pretreatment method is used to enhance the efficiency of biological hydrolysis of industrial wastewater sludge in the present study. The operating conditions for the alkaline pretreatment of the ABS sludge were maintained at room temperature (25+/-3 degrees C), reaction time of 24h, total solids in the feed of 0.5-2%, and NaOH dosages of 10-50 mg l(-1). Considering the increasing concentrations of soluble chemical oxygen demand and biochemical oxygen demand, the experimental results indicated that the alkaline pretreatment method was useful in biodegradability enhancement. (C) 1998 Elsevier Science I;tn. All rights reserved.
An unified vehicle supervising and traffic information system
(1996)
Wang, SI
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Huang, CC
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交大名義發表
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電信工程研究所
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National Chiao Tung University
An unified vehicle supervising and traffic information system architecture is proposed in this paper. This new architecture integrates different system functions such as digital mobile radio communication, vehicle monitoring, traffic information collection, dynamic route guidance, and automatic toll collection into a single system architecture. A vehicle communication and ranging system is the radio interface of the architecture. Packetized data transmission through this radio interface can be used to measure received signal delay by pulse ranging. An uplink message from a vehicle containing vehicle speed information and the measured delay are both sent to a traffic control and information center for vehicle monitoring. The center estimates vehicle location, calculates average traveling time and average congestion level for each road link accordingly. Vehicle monitoring information and the estimated traffic condition can be offered to either the public or dispatching centers. A toll collection center will be able to automatically charge a vehicle through the monitoring process. Furthermore, a vehicle will be able to access the traffic control and information center to obtain its own dynamic route guidance information, and each vehicle can be guided in such a way to optimize the overall road traffic. Finally, we suggest two methods which use the infrastructure of existing digital cellular systems (GSM and IS-95) to implement the proposed system architecture.
Color-tunable multilayer light-emitting diodes based on conjugated polymers
(2004-02-16)
Huang, CC
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Meng, HF
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Ho, GK
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Chen, CH
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Hsu, CS
Wide-range low-voltage continuous color tuning is achieved in multilayer light-emitting diodes based exclusively on the commonly used high-efficiency electroluminescent conjugated polymers. There are three layers for red, green, and blue emission, and one extra layer for electron blocking. The color of the emitted photon depends on the position of the electron-hole recombination. Due to the stronger field dependence of the electron mobility relative to the hole mobility, the recombination zone is pushed away from the cathode and concentrated in different emissive layers as the voltage increases. (C) 2004 American Institute of Physics.
Comment on "Triplet-to-singlet exciton formation in poly(p-phenylene-vinylene) light-emitting diodes" - Reply
(2004-02-06)
Lin, LC
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Meng, HF
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Shy, JT
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Horng, SF
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Yu, LS