Browsing by Author "Wu, SL"

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A multi-channel MAC protocol with power control for multi-hop mobile ad hoc networks
(2001)
Tseng, YC
;
Wu, SL
;
Lin, CY
;
Sheu, JP
;
資訊工程學系
In a mobile ad-hoc networks (MANET), one essential issue is Medium Access Control (MAC), which addresses how to utilize the radio spectrum efficiently and to resolve potential contention and collision among mobile hosts on rising the medium. Existing works have dedicated to using multiple channels [4, 6, 9. 10, 12, 18. 20] and power control [7, 13. 21] to improve the performance of MANET: III this paper.,ve investigate the possibility of bringing the concepts of power control a,ld multi-channel medium access together in the MAC design problem in a MANET: Existing protocols only address one of these issues independent): The proposed protocol is characterized by the following features: (i) it follows an "on-demand" style to assign, channels to mobile hosts. (ii) the number of channels required is independent of the network topology and degree, (iii) it flexibly adapts to host mobility: (iv) no form of clock synchronization is required, and(v) power control is used to exploit frequency reuse. Power control may also extend battery life and reduce signal interference. both of,which are important in wireless communication Through simulations, we demonstrate the advantage of our new protocol.
A multi-channel MAC protocol with power control for multi-hop mobile ad hoc networks
(2002)
Wu, SL
;
Tseng, YC
;
Lin, CY
;
Sheu, JP
;
資訊工程學系
In a mobile ad hoc network (MANET), one essential issue is Medium Access Control (MAC), which addresses how to utilize the radio spectrum efficiently and to resolve potential contention and collision among mobile hosts on using the medium. Existing works have been dedicated to using multiple channels and power control to improve the performance of MANET. In this paper, we investigate the possibility of bringing the concepts of power control and multi-channel medium access together in the MAC design problem in a MANET. Existing protocols only address one of these issues independently. The proposed protocol is characterized by the following features: (i) it follows an 'on-demand' style to assign channels to mobile hosts, (ii) the number of channels required is independent of the network topology and degree, (iii) it flexibly adapts to host mobility, (iv) no form of clock synchronization is required and (v) power control is used to exploit frequency reuse. Power control may also extend battery life and reduce signal interference, both of which are important in wireless communication. Through simulations, we demonstrate the advantage of our new protocol.
A priority MAC protocol to support real-time traffic in ad hoc networks
(2004-01-01)
Sheu, JP
;
Liu, CH
;
Wu, SL
;
Tseng, YC
;
資訊工程學系
Carrier sense multiple access and its variants have been widely used in mobile ad hoc networks. However, most existing access mechanisms cannot guarantee quality for real-time traffic. This paper presents a distributed medium access control protocol that provides multiple priority levels for stations to compete for the wireless channel. One common channel is assumed to be shared by all stations. Stations are assumed to be able to hear each other (i.e., the network is fully connected). The channel is accessed by stations according to their priorities, and for stations with the same priority, they send frames in a round robin manner. The channel access procedure is divided into three stages: priorities classification period, ID initialization period, and transmission period. Simulation results indicate that our protocol provides high channel utilization and bounded delays for real-time frames.
Application and robustness design of fuzzy controller for resonant and chaotic systems with external disturbance
(2005-06-01)
Hsiao, FH
;
Chiang, WL
;
Chen, CW
;
Xu, SD
;
Wu, SL
A robustness design of fuzzy control via model-based approach is proposed in this paper to overcome the effect of approximation error between nonlinear system and Takagi-Sugcno (T-S) fuzzy model. T-S fuzz model is used to model the resonant and chaotic systems and the parallel distributed compensation (PDC) is employed to determine structures of fuzzy controllers. Linear matrix inequality (LMI) based design problems are utilized to find common definite matrices P and feedback gains K satisfying stability conditions derived in terms of Lyapunov direct method. Finally, the effectiveness and the feasibility of the proposed controller design method is demonstrated through numerical simulations on the chaotic and resonant systems
Characterization of thin textured tunnel oxide prepared by thermal oxidation of thin polysilicon film on silicon
(1996-02-01)
Wu, SL
;
Chiao, DM
;
Lee, CL
;
Lei, TF
;
電子工程學系及電子研究所
In this paper, the characteristics of thin textured tunnel oxide prepared by thermal oxidation of thin polysilicon film on Si substrate (TOPS) are studied, Because of the rapid diffusion of oxygen through the grain boundaries of the thin polysilicon film into the Si substrate and the enhanced oxidation rate at the grain boundaries, the oxidation rate of the TOPS sample is close to that of a normal oxide grown on a (111) Si substrate, Also, a textured Si/SiO2 interface is obtained, The textured Si/SiO2 interface results in localized high fields and causes a much higher electron injection rate, The optimum TOPS sample can be obtained by properly oxidizing the stacked alpha-Si film, independent of the substrate doping level, Also, the optimum TOPS sample exhibits a smaller electron trapping rate and a lower interface state generation rate when compared to the sample from a standard tunnel oxide process, These differences are attributed to a lower bulk electric field and a smaller injection area in the TOPS samples.
Code placement and replacement strategies for wideband CDMA OVSF code the management
(2001)
Tseng, YC
;
Chao, CM
;
Wu, SL
;
資訊工程學系
;
Department of Computer Science
The use of OVSF codes in WCDMA systems has offered opportunities to provide variable data rates to flexibly support applications with different bandwidth requirements. Two rarely addressed issues on such environment are the code placement problem and code replacement problem. The former may have significant impact on code utilization and thus code blocking probability, while the latter may affect the code reassignment cost if dynamic code. assignment is to be conducted. The general objective is to make the OVSF code tree as compact as possible in order to support new calls, either with less blocking or with less reassignment cost. This paper is perhaps the first one which addresses these issues on WCDMA. Three simple strategies, which can be adopted by both code placement and code replacement, are proposed: random, leftmost, and crowded-first. Among them the crowded-first strategy looks most promising, which is shown to be able to reduce, for example, the code blocking probability by 77 % and the number of reassignments by 81 % as opposed the random strategy when the system is 80% fully loaded and the max SF=256.
Cyclic m-cycle systems with m <= 32 or m=2(q) with q a prime power
(2006-01-01)
Wu, SL
;
Fu, HL
;
應用數學系
;
Department of Applied Mathematics
In this paper, the necessary and sufficient conditions for the existence of cyclic 2q-cycle and m-cycle systems of the complete graph with q a prime power and 3 <= m <= 32 are given. (c) 2005 Wiley Periodicals, Inc.
Cyclic m-cycle systems with m <= 32 or m=2q with q a prime power (vol 14, pg 66, 2005)
(2006-03-01)
Wu, SL
;
Fu, HL
;
應用數學系
;
Department of Applied Mathematics
Cyclically decomposing the complete graph into cycles
(2004-05-06)
Fu, HL
;
Wu, SL
;
應用數學系
;
Department of Applied Mathematics
Let m(1), m(2),..., m(k) be positive integers not less than 3 and let n = Sigma(i=1)(k) m(i). Then, it is proved that the complete graph of order 2n + 1 can be cyclically decomposed into k(2n + 1) cycles such that, for each i = 1, 2,...,k, the cycle of length mi occurs exactly 2n + 1 times. (C) 2003 Elsevier B.V. All rights reserved.
Dynamic channel allocation with location awareness for multi-hop mobile ad hoc networks
(2002-05-01)
Tseng, YC
;
Chao, CM
;
Wu, SL
;
Sheu, JP
;
資訊工程學系
The wireless mobile ad hoc network (MANET) has received a lot of attention recently. This paper considers the channel assignment problem in a MANET which has access to multiple channels. Although a MANET does not have the infrastructure of base stations, interestingly its channel assignment can be conducted efficiently in a way very similar to that in cellular systems (such as GSM). In this paper, we propose a new location-aware channel assignment protocol called GRID-B (read as GRID with Channel Borrowing), which is a sequel of our earlier GRID protocol [Location-aware channel assignment for a multi-channel mobile ad hoc network, Technical Report NCU-HSCCL-2000-02, 2000]. The protocol assigns channels to mobile hosts based on the location information of mobile hosts that might be available from the positioning device (such as GPS) attached to each host. According to our knowledge, no location-aware channel assignment protocol has been proposed before for MANETs. Several channel borrowing strategies are proposed to dynamically assign channels to mobile hosts so as to exploit channel reuse and resolve the unbalance of traffic loads among different areas (such as hot and cold spots). We then propose a multi-channel MAC protocol, which integrates GRID-B. Extensive simulation results are presented to show the advantage of the new GRID-B protocol. (C) 2002 Elsevier Science B.V. All rights reserved.
Hybrid-damped resolved-acceleration control for manipulators
(1997-08-01)
Wu, SL
;
Lin, SK
;
交大名義發表
;
電控工程研究所
;
National Chiao Tung University
The singularity problem of the resolved-acceleration control scheme can be solved by the damped least-squares method. This approach, however, does suffer from one serious drawback: oscillations of the end-effector when the target is outside the workspace and self-motion of the manipulator when it is at the orientation degeneracy. In this paper, we present a hybrid-damped resolved-acceleration control scheme (HDRAC), which is capable of damping both the accelerations and the velocities to overcome this drawback. The main advantage of the present approach is that the control system need not plan the path to avoid the infeasible region of the manipulator, since the controller will automatically command the end-effector to move along the boundary of the workspace with a minimum trajectory error. Thus this approach renders the resolved-acceleration control scheme a much more practical control for the industry. The stability of the proposed control scheme is also proved in this paper. Incorporated with the concept of the degenerated-direction damped least-squares method (DDDLSM), this new control scheme can also apply only to the degenerated directions, which scheme is simulated on the PUMA 560 manipulator to verify its usefulness. (C) 1997 John Wiley & Sons, Inc.
Hybrid-damped resolved-acceleration control for manipulators
(1997-08-01)
Wu, SL
;
Lin, SK
;
電控工程研究所
;
Institute of Electrical and Control Engineering
The singularity problem of the resolved-acceleration control scheme can be solved by the damped least-squares method. This approach, however, does suffer from one serious drawback: oscillations of the end-effector when the target is outside the workspace and self-motion of the manipulator when it is at the orientation degeneracy. In this paper, we present a hybrid-damped resolved-acceleration control scheme (HDRAC), which is capable of damping both the accelerations and the velocities to overcome this drawback. The main advantage of the present approach is that the control system need not plan the path to avoid the infeasible region of the manipulator, since the controller will automatically command the end-effector to move along the boundary of the workspace with a minimum trajectory error. Thus this approach renders the resolved-acceleration control scheme a much more practical control for the industry. The stability of the proposed control scheme is also proved in this paper. Incorporated with the concept of the degenerated-direction damped least-squares method (DDDLSM), this new control scheme can also apply only to the degenerated directions, which scheme is simulated on the PUMA 560 manipulator to verify its usefulness. (C) 1997 John Wiley & Sons, Inc.
Implementation of damped-rate resolved-acceleration robot control
(1997-06-01)
Wu, SL
;
Lin, SK
;
交大名義發表
;
電控工程研究所
;
National Chiao Tung University
The damped least-squares method has frequently been used to solve the singularity problem of resolved-acceleration control schemes. It works by damping only the joint accelerations, so that the joint accelerations in the degenerated directions (the end-effector cannot move along these directions) are zero at a singular point. However, the joint velocities in the degenerated directions may be nonzero in some situations, in which case they will create fluctuations around the singular point. In this paper, a damped-rate resolved-acceleration control scheme (DRRAC) is proposed to overcome this drawback. The paper also shows that the DRRAC is asymptotically stable, and its convergent property is discussed. Experiments were undertaken to verify the proposed control scheme. Copyright (C) 1997 Elsevier Science Ltd.
Increasing the throughput of multihop Packet Radio Networks with power adjustment
(2001)
Huang, CF
;
Tseng, YC
;
Wu, SL
;
Sheu, JP
;
資訊工程學系
The Packet Radio Network (PRN) is an attractive architecture to support mobile and wireless communication. Although the code assignment problem has been studied extensively on PRN, we observe in this paper that the power control problem has been ignored by most works, but may have significant impact on performance. By power control, we mean that the transmission ranges of stations are tunable. We show given a PRN in which each host already received a code, how to adjust the powers of stations to control/improve the topology of the PRN without violating the original code assignment. Several schemes are proposed. Through simulations, we demonstrate that although the code assignment problem is NP-complete and thus computationally very expensive, using our power adjustment schemes can easily improve the network performance by about 20% with polynomial costs.
Intelligent medium access for mobile ad hoc networks with busy tones and power control
(2000-09-01)
Wu, SL
;
Tseng, YC
;
Sheu, JP
;
資訊工程學系
;
Department of Computer Science
In mobile ad hoc networks (MANETs), one essential issue is how to increase channel utilization while avoiding the hidden-terminal and the exposed-terminal problems. Several MAC protocols, such as RTS/CTS-based and busy-tone-based schemes, have been proposed to alleviate these problems. In this paper, we explore the possibility of combining the concept of power control with the RTS/CTS-based and busy-tone-based protocols to further increase channel utilization. A sender will use an appropriate power level to transmit its packets so as to increase the possibility of channel reuse. The possibility of using discrete, instead of continuous, power levels is also discussed. Through analyses and simulations, we demonstrate the advantage of our new MAC protocol. This, together with the extra benefits such as saving battery energy and reducing cochannel interference, does show a promising direction to enhance the performance of MANET's.
Investigation of the polarity asymmetry on the electrical characteristics of thin polyoxides grown on N+ polysilicon
(1997-01-01)
Wu, SL
;
Chen, CY
;
Lin, TY
;
Lee, CL
;
Lei, TF
The polarity asymmetry on the electrical characteristics of the oxides grown on n(+) polysilicon (polyoxides) was investigated in terms of the oxidation process, the doping level of the lower polysilicon layer, the oxidation temperature and the oxide thickness, It was found that the thin polyoxide prepared by using a low-temperature wafer loading and N-2 preannealing process, has a smoother polyoxide/polysilicon interface and exhibits a lower oxide tunneling current, a higher dielectric breakdown field when the top electrode is positively biased, a lower electron trapping rate and a larger charge-to-breakdown than does the normal polyoxide. The polarity asymmetry is also strongly dependent on the doping level of the lower polysilicon layer, the oxidation temperature and the oxide thickness. It was found that only the thinner polyoxides (less than or equal to 240 Angstrom) grown on the heavily-doped polysilicon film (30 Ohm/sq) by using the higher-temperature oxidation process (greater than or equal to 950 degrees C) conduct a less oxide tunneling current when the top electrode is positively biased.
Location awareness in ad hoc wireless mobile networks
(2001-06-01)
Tseng, YC
;
Wu, SL
;
Liao, WH
;
Chao, CM
;
交大名義發表
Networks composed of dynamically repositioning mobile hosts require location awareness to provide new geographic services and to maximize routing efficiency and quality of service.
On the stability of the hybrid-damped resolved-acceleration control
(1998-09-01)
Lin, SK
;
Wu, SL
;
電控工程研究所
;
Institute of Electrical and Control Engineering
This paper points out that the stability analysis of the hybrid-damped resolved-acceleration control in our earlier work is incomplete, since the stability was concluded directly from the fact that the joint velocities come to rest as time approaches infinity. A similar incomplete technique was also used in the work of Wampler and Leifer to prove the stability of a damped least-squares resolved-acceleration control scheme. In this paper, we use LaSalle's invariance principle rigorously to show that the solution trajectory of the hybrid-damped resolved-acceleration control will eventually come to the target without steady-state error or will stay at a kinematic singular point with some steady-state error. Discussions on the case of staying at a singular point are also given. (C) 1998 John Wiley & Sons, Inc.
Photochemistry and photodissociation of benzosultine and naphthosultine: electronic relaxation of sultines and kinetics and theoretical studies of fragment o-quinodimethanes
(2005-02-28)
Tang, KC
;
Lee, SJ
;
Chi, SH
;
Lu, KL
;
Chen, WC
Fluorescence decays of benzosultine and naphthosultine excited at 263 nm are detected with time-correlated single-photon counting (TCSPC). Both molecules display biexponential decay with a rapid component (time constants 90 and 350 ps for benzosultine and naphthosultine, respectively) assigned to an electronically excited state S-n at high energy and the slow one (constants 7.5 and 9.0 ns for benzosultine and naphthosultine, respectively) to the S-1 state. Dissociation of both molecules was investigated with nanosecond laser flash photolysis combined with transient absorption to detect the intermediates and products. With excitation at 266 nm, benzosultine yields a transient with absorption maximum at lambda(max) = 370 nm; this transient has a short-lived component with lifetime around 1 mus and a long-lived component. Both components are insensitive to molecular oxygen. The short-lived component is tentatively assigned to the dissociation intermediate and the long-lived to be singlet o-benzoquinodimethane (o-BQDM). Photolysis of naphthosultine yields two transient species with absorption at; lambda(max) = 420 and 520 nm; we assign the former band to triplet-triplet absorption of naphthosultine and the latter to absorption by the product singlet o-naphthoquinodimethane. Optimal geometries, energetics, and vertical transitions of benzosultine, naphthosultine, o-benzoquinodimethane, and o-naphthoquinodimethane are calculated using methods based on density-functional theory (B3LYP/6-311++G**) and time-dependent density-functional theory (TD-DFT). The results of these calculations imply that the ground electronic state of these two o-quinodimethanes (o-QDM) is singlet with a structure of diene form. Their triplet states display a biradical structure. The energy separation between singlet and triplet states of o-benzoquinodimethane is calculated to be ca. 93.6 kJ/mol, but for o-naphthoquinodimethane, it is only ca. 27.8 kJ/mol. (C) 2004 Elsevier B.V. All rights reserved.
Suppression of the boron penetration induced dielectric degradation by using a stacked-amorphous-silicon film as the gate structure for pMOSFET
(1996-02-01)
Wu, SL
;
Lee, CL
;
Lei, TF
;
電控工程研究所
;
Institute of Electrical and Control Engineering
This work proposes a stacked-amorphous-silicon (SAS) film as the gate structure of the p(+) poly-Si gate pMOSFET to suppress boron penetration into the thin gate oxide, Due to the stacked structure, a large amount of boron and fluorine piled up at the stacked-Si layer boundaries and at the poly-Si/SiO2 interface during the annealing process, thus the penetration of boron and fluorine into the thin gate oxide is greatly reduced, Although the grain size of the SAS film is smaller than that of the as deposited polysilicon (ADP) film, the boron penetration can be suppressed even when the annealing temperature is higher than 950 degrees C, In addition, the mobile ion contamination can be significantly reduced by using this SAS gate structure, This results in the SAS gate capacitor having a smaller flat-band voltage shift, a less charge trapping and interface state generation rate, and a larger charge-to-breakdown than the ADP gate capacitor, Also the Si/SiO2 interface of the p(+) SAS gate capacitor is much smoother than that of the p(+) SAS gate capacitor.