Browsing by Author "Chen, YC"

Now showing 1 - 20 of 142

A 6 similar to 10-GHz ultra-WideBand tunable LNA
(2005)
Chen, YC
;
Kuo, CN
;
電子工程學系及電子研究所
;
Department of Electronics Engineering and Institute of Electronics
In this paper a CMOS low noise amplifier (LNA) is designed with tunable output over an ultra-wideband. The cascode configuration is employed in this circuit, with the inductive source degeneration (ISD) and a three-section band-pass Chebyshev filter to achieve broadband input impedance matching. A source follower acts as the buffer stage for broadband output impedance matching. Signal output is band-tunable over the frequency range from 6-GHz to MGM. The circuit is fabricated in a standard 0.18um CMOS process. Circuit performance achieves maximum power gain, S21, of 11.6 dB, the input return loss, S11, better than 9 dB, and the best noise figure of 4.2dB. The circuit consumes power of 11.6mW.
A cross-layer cost-function based rate adaptation mechanism for the WCDMA system with multi-class services by transport format selection
(2005-06-01)
Wang, LC
;
Chen, MC
;
Chen, YC
;
電信工程研究所
;
Institute of Communications Engineering
The growing demand of high speed multi-class data transmissions poses new challenges on wireless networks. The major objectives of the next generation wireless networks include: (1) achieving high data throughput in the fast varying wireless channel; (2) transmitting multi-class data by service multiplexing; and (3) controlling the delay for delay sensitive service. To achieve these goals, in the context of wideband code division multiple access (WCDMA) system, we propose a cost-function based rate adaptation mechanism by taking account of both physical layer channel impacts and higher layer performance parameters, such as buffer occupancy and service priority. We implement this cross-layer rate mechanism by exploiting the transport format (TF) selection procedure in the medium access control (MAC) layer of the WCDMA system. Through the proposed cross-layer cost function, the TF selection procedure can dynamically adapt suitable spreading factors every transmission time interval (TTI), usually 10-80 ms. Through simulations in a flat Rayleigh fading channel, we show that the proposed cross-layer cost-function based rate adaptation mechanism can effectively improve throughput and reduce the buffer occupancy for multi-class services for the WCDMA system at the cost of slightly higher power efficiency. Copyright (c) 2005 John Wiley & Sons, Ltd.
A distributed buffer management approach supporting IPv6 mobility
(2004)
Liu, YH
;
Chen, YC
;
資訊工程學系
;
Department of Computer Science
In wireless local area networks (WLANs), mobility support is essential for providing seamless services. The current Mobile IP standard suffers several problems, especially for accommodating real-time media applications. Most of the existing studies focus on improving the performance between the Home Agent (HA) and Foreign Agent (FA). In this work, we propose a buffer management approach to enhance the performance between the Mobility Agent (HA or FA) and the Mobile Node (MN). The proposed scheme deals with the packet delivery between MAs and MNs in Layer 2. Through the simulation, we show that our scheme improves TCP throughput as well as reduces the UDP packet loss rate. Moreover, it is implementation feasible in both IPv4 and IPv6, and suitable for supporting Quality of Service (QoS).
A distributed end-to-end rate control scheme for ABR service
(1998)
Chen, JR
;
Chen, YC
;
Chan, CT
;
資訊工程學系
;
Department of Computer Science
In ATM networks, the ABR service allows both the source and the destination to function simply, this means that we may need a certain complexity in the switch. To provide robust ABR service, policing and discarding functions are usually required. ABR rate control schemes such as UT [4] and OSU [5][7] can achieve high utilization, but they suffer the oscillation of transmission rate. We propose an End-to-End Rate Control Algorithm (EERCA), which performs the monitoring function in end systems, and achieves max-min fairness naturally. Our scheme relies on the round-robin discipline in combination with per-VC queuing for cell scheduling, it also covers the policing function. EERCA resolves the oscillation problem that is quite common in existing explicit rate schemes, as well as features very low cell loss ratio with much smaller buffer size.
A fast IP routing lookup scheme
(2000)
Wang, PC
;
Chan, CT
;
Chen, YC
;
資訊工程學系
;
Department of Computer Science
A major design issue for the next generation routers is the 1P lookup mechanism. The router needs to perform a longest prefix matching on the address lookup for each incoming packet to determine the next hop. Currently, the process is done in software and has become a major performance bottleneck of the router. In this paper, we propose a fast IP lookup mechanism in which the forwarding table is small enough to fit in SRAM with very low cost. It also can be implemented in hardware using the pipeline technique. A large routing table with 45,000 routing prefixes can be compressed to a forwarding table with about 430 Kbytes in size by using our proposed method. In the worst case, the number of memory accesses for a lookup is three. When implemented in pipeline technique, the proposed mechanism can achieve one routing lookup per memory access. With current ions SRAM, this mechanism provides approximately 100 million routing lookups per second. Futhermore, the lookup speed can be improved linearly through the speedup of the memory access.
A fast IP routing lookup scheme
(2001-03-01)
Wang, PC
;
Chan, CT
;
Chen, YC
;
資訊工程學系
;
Department of Computer Science
A major issue in router design for the next generation Internet is the fast IP address lookup mechanism. The existing scheme by Huang et al. performs the IP address lookup in hardware in which the forwarding table can be compressed to fit into reasonable-size SRAM, and a lookup can be accomplished in three memory accesses. In this letter, we claim that with a little extra memory, it is able to further reduce the lookup time to two memory accesses.
A fast packet classification by using enhanced tuple pruning
(2002)
Wang, PC
;
Chan, CT
;
Tseng, WC
;
Chen, YC
;
資訊工程學系
In the packet classification, the route and resources allocated to a packet are determined by the destination address as well as other header fields of the packet such as source/destination address, TCP and UDP port numbers. It has been demonstrated that performing packet classification on a potentially large number of fields is difficult and has poor worst-case performance. In this work, we proposed an enhanced tuple pruning search algorithm called "Tuple Pruning +" that provides fast two-dimension packet classification. With reasonable extra filters added for Information Marker, only one hash access to the tuples is required. Through experiments, about 8 MB memory is required for 100K-filter database and 20 million packet per second (MPPS) is achievable. The results demonstrate that the proposed algorithm is suitable for high-speed packet classification.
A fast table update scheme for high-performance IP forwarding
(2002-01-01)
Wang, PC
;
Chan, CT
;
Chen, YC
;
資訊工程學系
;
Department of Computer Science
In the previous work, Lampson et al. proposed an IP lookup algorithm which performs binary search on prefixes (BSP) [1]. The algorithm is attractive, even for IPv6, because of its bounded worst-case memory requirement. To achieve fast forwarding, it may need to slow down the insertion speed. Although this can be justified, the routing-table reconstruction in BSP is too time-consuming to handle the frequent route updates. In this work, we propose a fast forwarding-table construction algorithm which can accomplish more than 4,000 route updates per second. Moreover, it is simple enough to fulfill the need of fast packet forwarding. With the enhanced multiway search tree, we further reduced the depth of the tree and eliminated the pointer storage; this reduces the forwarding table size and shortens the lookup time.
A fast table update scheme for high-performance IP forwarding
(2001)
Wang, PC
;
Chan, CT
;
Chen, YC
;
資訊工程學系
;
Department of Computer Science
There has been an extensive study in constructing the routing tables during the past few years. Although the existing works have certain advantages, ho,vel er, those approaches either use complicated data structures which result in large storage requirement and high complexity updating/building the forwarding table, or they are not scalable refit in IPv6. Lampson et al. proposed an IP lookup algorithm which performs binary search on prefixes (BSP) [11] The algorithm is attractive, even for IPv6, because of its bounded worst-case memory requirement. For achieving fast forwarding the cost paid is the slowing down insertion. Although this can be justified, the performance of routing-table reconstruction in BGP is too time-consuming,ring to handle the frequent route updates. In this work, we propose a fast forwarding-table construction algorithm which can handle more than 4,000 route updates per second. Moreover; it is simple enough to fufil the need of fast packet forwarding. With the modified multiway search tree, we can further reduce the depth of the tree and eliminate the storage for pointers, this reduces the fowarding table size and shorten the lookup time.
A FIFO-based buffer management approach for the ATM GFR services
(2000-06-01)
Chan, CT
;
Hu, SC
;
Wang, PC
;
Chen, YC
;
資訊工程學系
We investigate the TCP packet transmission over the ATM Guaranteed Frame Rate (GFR) service using a selective packet-discard with buffer vacancy tracking strategy and a packet-based push-out buffering scheme. Our approach is based on FIFO queueing discipline, it features fair sharing of available resources as well as feasibility in hardware implementation.
A fully all-planar integrated Ka-band FSK transceiver module
(2001)
Lee, CJ
;
Hung, TP
;
Lin, SC
;
Wu, HS
;
Tsai, CY
An open RFIC (Radio Frequency Integrated Circuit) architecture employing ACSS (Advanced Coplanar Strips System) guiding technology is presented in this paper. This approach can integrate all the RF front-end components in one module using conventional PCB (printed circuit board) fabrication process. A 10 Mb/s FSK signal is upconverted to 30.18 GHz and 30.28 GHz and broadcasted through a cone-shaped antenna at power level of 10 dBm. The received signal is directly converted to baseband by even harmonic quadrature mixer, which shows a great isolation of 30 dB between RF and LO signal. The measured waveforms of the reported transceiver demonstrate the potential of constructing the wireless system with all-planar integrated circuits.
A joint physical layer multi-state rate adaptation and cost-function based MAC scheduling for the WCDMA system
(2003)
Wang, LC
;
Chen, MC
;
Chen, YC
;
交大名義發表
;
National Chiao Tung University
This paper presents a joint physical layer multi-state rate adaptation algorithm combined with MAC scheduling for the WCDMA system. According to the cumulative distribution function of the received signal to noise ratio (SNR), our proposed multi-state rate adaptation scheme determines a set of state transition thresholds to dynamically adjust spreading factors via the transport format (TF) selection procedures in the MAC layer. Moreover, we proposed a cost function based TF selection procedures to incorporate many important factors in both the MAC layer and physical layer, such as service priority, buffer occupancy, and radio link quality. Through a cross-layer design in both the two layers, the proposed cost function based transport format selection procedures can effectively enhance throughput, save power, and guarantee service fairness for the WCDMA system.
A novel approach of combining thin-layer chromatography with surface-assisted laser desorption/ionization (SALDI) time-of-flight mass spectrometry
(2002-01-01)
Wu, JY
;
Chen, YC
;
應用化學系
;
Department of Applied Chemistry
A novel means of combining thin-layer chromatography (TLC) with laser desorption/ionization mass spectrometry using a liquid matrix is proposed. Surface-assisted laser desorption/ionization (SALDI) mass spectrometry, which uses a mixture of a micrometer-sized carbon powder (graphite or activated carbon, the SALDI solid) and 13% sucrose/glycerol, dissolved in an equal volume of methanol (SALDI liquid) as a SALDI matrix, is used for laser desorption mass analysis. The ablation of carbon powder from a pencil drawing was used as an alternative to the SALDI solid. The liquid matrix resembled that used in a conventional SALDI matrix system. A line was drawn before separation with a pencil on the track of the sample developed on the TLC plate. After TLC separation, similar to0.1 mul of SALDI liquid was directly applied to the chromatographic spots on the TLC plate. Porphyrins were used to demonstrate this combination owing to the visible colors of this type of compound. The analyte signal can be easily detected by irradiating the laser along the pencil line on the TLC plate. An additive, p-toluenesulfonic acid, is added to the SALDI liquid to enhance the signal's intensity. This additive dramatically improves the signal-to-noise ratio. A detection limit of similar to500 pg is demonstrated for porphines, which is 50 times better than that corresponding to conventional TLC SALDI Copyright (C) 2001 John Wiley Sons, Ltd.
A scalable architecture for differentiated services
(2002)
Lee, CL
;
Chen, JR
;
Chen, YC
;
交大名義發表
;
National Chiao Tung University
Differentiated services (DiffServ) model is a potential solution for providing quality of services (QoS) on the Internet. In this paper, we propose a scalable architecture that fulfills the design philosophy of the DiffServ model. Different from other existing architectures, our proposed architecture puts complexity on edge routers so that core routers do not need to support any specific function for service differentiation. Further, the proposed architecture only needs few additional functions in edge routers. Thus its deployment is simpler than most existing architectures. We also address how to achieve weighted proportional fairness solely by edge routers.
A simplified approach based on source control for ATM ABR service
(2001-08-15)
Lee, CL
;
Chen, YC
;
Chen, JR
;
資訊工程學系
;
Department of Computer Science
The available bit rate (ABR) service is designed to provide efficient support of data traffic in ATM networks. A variety of rate-based flow control approaches have been proposed to support ABR service. Most of these approaches improve both the fairness among active connections and the link utilization by putting more and more complexity into a switch. In this article, we propose a flow control approach in which part of rate-calculation work is moved from switches to end-systems. As a result, the proposed approach reduces the rate-calculation effort in the switch. This may reduce the switch complexity and thus the implementation cost. Furthermore, it mitigates the difficulty for setting the measurement interval in switches. as well as features lower and more stable queue occupancy in the network. Simulation results are presented to demonstrate that the proposed approach achieves better performance than ERICA +, a well-known switch algorithm. (C) 2001 Elsevier Science B.V. All rights reserved.
A study of typenumber in book-embedding
(2002-01-01)
Chen, YC
;
Fu, HL
;
Sun, IF
;
應用數學系
;
Department of Applied Mathematics
The type of a vertex v in a p-page book-embedding is the p x 2 matrix of nonnegative integers [GRAPHICS] where l(v,i) (respectively, r(v,i)) is the number of edges incident to v that connect on page i to vertices lying to the left (respectively, to the right) of v. The typenumber of a graph G, T(G), is the minimum number of different types among all the book-embeddings of G. In this paper, we disprove the conjecture by J. Buss et. al. which says for n greater than or equal to 4, T(L-n) is not less than 5 and prove that T(L-n) = 4 for n greater than or equal to 3.
A TCP-friendly stateless AQM scheme for fair bandwidth allocation
(2005)
Ho, CY
;
Chan, YC
;
Chen, YC
;
資訊工程學系
;
Department of Computer Science
Queue management, bandwidth share, and congestion control are very important to both robustness and fairness of the Internet. In this article, we investigate the problem of providing a fair bandwidth allocation to those flows that share congested link in a router A new TCP-friendly router-based AQM (active queue management) scheme, termed WARD, is proposed to approximate the fair queueing policy. WARD is a simple packet dropping algorithm with a random mechanism, and discriminates against the flows which transmit more packets than allowed. By doing this, it not only protects TCP connections from UDP flows, but also solves the problem of competing bandwidth among different TCP versions such as TCP Vegas and Reno. In addition, WARD works quite well for TCP flow isolation even with different round trip times. In other words, WARD improves the unfair bandwidth allocation properties. Furthermore, it is stateless and easy to implement, so WARD controls unresponsive or misbehaving flows with a minimum overhead.
Adaptive feature extractions in an EEG-based alertness estimation system
(2005)
Lin, CT
;
Chao, WH
;
Chen, YC
;
Liang, SF
;
腦科學研究中心
During the past years, the public security has become an important issue, especially, the safe manipulation and control of various vehicles. Maintaining high cognition is particularly important for the drivers behind the steering wheel. It requires an optimal estimation system to online continuously detect drivers' cognitive state related to abilities in perception, recognition, and vehicle control. In this paper, we proposed an EEG-based alertness estimation system with automatic feature selection mechanism. The independent component analysis (ICA) is used first to decompose the measured electroencephalogram (EEG). Then, a time-frequency analysis is performed to evaluate the time-frequency characteristic of each ICA component. We also proposed a new adaptive feature extracting mechanism for selections of frequency bands and ICA components. Different ranges of the alpha rhythm of subjects can be evaluated by the adaptive feature extracting mechanism according to the correlation coefficient between the ICA time-frequency response and the driving performance. The extracted features are then trained both by linear regression model and Self-cOnstructing Neuro-Fuzzy Inference Network (SONFIN) for the estimation of driving performance. The training and testing results of SONFIN are 96% and 91%, while the results of linear regression model are 90% and 85%, respectively. It demonstrates that the proposed adaptive feature extracting mechanism can achieve a great performance in alertness estimation with frequency band and component selection.
Affinity capture using vancomycin-bound magnetic nanoparticles for the MALDI-MS analysis of bacteria
(2005-03-15)
Lin, YS
;
Tsai, PJ
;
Weng, MF
;
Chen, YC
;
應用化學系
Matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS) provides a straightforward means to differentiate microorganism species based on mass spectral fingerprinting. The pathogen cell concentration in an infected sample, however, is generally lower than that capable of being detected directly by MALDI-MS. Furthermore, the presence of proteins or metabolites in biological fluids always causes unavoidable interference for the identification of microorganism species. Vancomycin, which binds to D-Ala-D-Ala moieties on the cell walls of Gram-positive bacteria and, therefore, inhibits peptidoglycan synthesis, is one of the most potent antibiotics. Thus, we have employed vancomycin-modified magnetic nanoparticles as affinity probes to selectively trap Gram-positive pathogens from sample solutions; i.e., these bacteria can be isolated from sample solutions by applying a magnetic field. The isolated cells could then be characterized by MALDI-MS. This approach effectively reduces the interference of protein and metabolite signals in the mass spectra of Gram-positive bacteria because vancomycin has such high specificity for the D-Ala-D-Ala units of the cell walls. The lowest cell concentration we detected for both Staphylococcus saprophyticus and Staphylococcus aureus in a urine sample (3 mL) was similar to 7 x 10(4) cfu/mL.
Aggregation of zinc protoporphyrin in anodized aluminum oxide (AAO) nanoporous environments
(2006-02-01)
Lin, JS
;
Chen, YC
;
Chen, CC
;
Diau, EWG
;
Liu, TF
The aggregation behavior of zinc protoporphyrin (ZnPP) inside nanoporous environments of anodized aluminum oxide (AAO) has been investigated through observation of the variation of UV/visible absorption and emission spectra of the system. The Soret band in the absorption spectrum of ZnPP/AAO thin-film samples becomes much broader than that observed for ZnPP/THF solutions, and the relative intensity of the Q band is distinctly enhanced for the former. The broad Soret band overlaps the enhanced Q band increasingly as the degree of aggregation increases with increasing duration of immersion, with initial concentration of ZnPP/THF solutions, or with decreasing pore size of AAO nanotubes. A strong excitonic coupling between the Soret and Q transition dipoles causes the absorption spectrum of the ZnPP/AAO system to cover the entire visible spectral region. Emission spectra of ZnPP/AAO samples in the steady state contain multiple resolvable components assigned to monomer, dimer and higher aggregates. The observed systematic variation of emission spectra of ZnPP/AAO samples is consistent with the observation in absorption spectra of the system and reflects the significance of aggregation of ZnPP in a specific nanoporous environment.