Efficient radio resource utilization and fairness are important goals that must be achieved since wireless ATM systems support various services with different traffic characteristics such as CBR and UBR. This paper proposes a novel delay-and-queuing data size-based MAC protocol for broadband wireless ATM. The proposed MAC protocol relies on a new resource scheduling algorithm that decides the priority of channel assignment based on both the queuing delay and the queuing data size in the transmission buffer. Simulation results confirm that the proposed MAC protocol is able to provide throughput fairness and to achieve excellent throughput performance for ATM services that experience dynamic traffic fluctuations.

In this paper, a new set of difference equations is derived for transient analysis of the convergence of adaptive FIR filters using the Sign-Sign Algorithm with Gaussian reference input and additive Gaussian noise. The analysis is based on the assumption that the tap weights are jointly Gaussian distributed. Residual mean squared error after convergence and simpler approximate difference equations are further developed. Results of experiment exhibit good agreement between theoretically calculated convergence and that of simulation for a wide range of parameter values of adaptive filters.

The classical algebraic modelling approach for integer programming (IP) is not suitable for some real world IP problems, since the algebraic formulations allow only for the description of mathematical relations, not logical relations. In this paper, we present a language + for IP, in which we write logical specification of an IP problem. + is a language based on the predicate logic, but is extended with meta predicates such as at_least(m,S), where m is a non-negative integer, meaning that at least m predicates in the set S of formulas hold. The meta predicates facilitate reasoning about a model of an IP problem rigorously and logically. + is executable in the sense that formulas in + are mechanically translated into a set of mathematical formulas, called IP formulas, which most of existing IP solvers accept. We give a systematic method for translating formulas in + to IP formulas. The translation is rigorously defined, verified and implemented in Mathematica 3.0. Our work follows the approach of McKinnon and Williams, and elaborated the language in that (1) it is rigorously defined, (2) transformation to IP formulas is more optimised and verified, and (3) the transformation is completely given in Mathematica 3.0 and is integrated into IP solving environment as a tool for IP.

In this paper, we present our work on the design of a new FPGA architecture targeted for high-performance bit-serial pipeline datapath. Bit-parallel systems require large amount of routing resource which is especially critical in using FPGAs. Their device utilization and operation frequency become low because of large routing penalty. Whereas bit-serial circuits are very efficient in routing, therefore are able to achieve a very high logic utilization. Our proposed FPGA architecture is designed taking into account the structure of bit-serial circuits to optimize the logic and routing architecture. Our FPGA guarantees near 100% logic utilization with a straightforward place and route tool due to high routability of bit-serial circuits and simple routing interconnect architecture. The FPGA chip core which we designed consists of around 200k transistors on 3.5 mm square substrate using 0.5 µm 2-metal CMOS process technology.

We present calculations of the linear-response conductance of a SiGe based single-electron transistor (SET). The conductance and the discrete charging of the quantum dot are calculated by free-energy minimization. The free-energy calculation takes the discrete level-spectrum as well as complex many-body interactions into account. The tunneling rates for tunneling through the source and lead barrier are calculated using Bardeen's transfer Hamiltonian formalism. The tunneling matrix elements are calculated for transitions between the zero-dimensional states in the quantum dot and the lowest subband in the one-dimensional constriction. We compare the results for the conductance peaks with those from calculations with a constant tunneling rate where the shape of the peaks is only due to energetic arguments.

We gave in [1] the software and hardware algorithms for reconfiguring 1 1/2-track switch 2-D mesh arrays with faults of processing elements, avoiding them. This paper shows an implementation of the hardware algorithm using an FPGA device, and by the logical simulation confirms the correctness of the behavior and evaluates reconfiguration time. From the result it is found that a self-repairable system is realizable and the system is useful for the run-time as well as fabrication-time reconfiguration because it requires no host computer to execute the reconfiguration algorithm and the reconfiguration time is very short.

Patterns exist in many contexts and can be considered the useful information for decision making. However, many patterns are not directly visible without careful presentation. Here, we describe an interactive visualization approach for browsing patterns in a history of interacting with a computer system. While a user is carrying out his/her business using computers, activities with respect to time and location are captured to determine the situational interactions. We first integrate the timeline and geographical map to create a structure to visualize spatiotemporal events in the interaction history. The spiral-based interactive visualization technique, presented in this paper, is then used to derive patterns according to the user-specified different spatial viewpoints on the map. In this study, we demonstrate how patterns can be used as visual statements for the analysis of a spatiotemporal data set in the information visualization.

Silicon self-interstitial atom diffusion and implantation induced damage were studied by using molecular dynamics methods. The diffusion coefficient of interstitial silicon was calculated using molecular dynamics method based on the Stillinger-Weber potential. A comparison was made between the calculation method based on the Einstein relationship and the method based on a hopping analysis. For interstitial silicon diffusion, atomic site exchanges to the lattice atoms occur, and thus the total displacement-based calculation underestimates the ideal value of the diffusivity of the interstitial silicon. In addition with calculating the diffusion constant, we also identified its migration pathway and barrier energy in the case of Stillinger-Weber potential. Through a study of molecular dynamics calculation for the arsenic ion implantation process, it was found that the damage self-recovering process depends on the extent of damage. That is, damage caused by a single large impact easily disappears. In contrast, the damage leaves significant defects when two large impacts in succession cause an overlapped damage region.

The use of intelligent agents is on the rise, fueled by the unprecedented growth in the Internet and web based applications. Consequently, agent-oriented software is becoming large and complex. To support a systematic development of such software, an agent-oriented software development methodology is necessary. This paper focuses on the modeling phase of agent-oriented software life cycle and, presents an approach for agent modeling consisting of Agent Elicitation, Intra, and Inter Agent modeling methods. Agent Elicitation deals with identifying and extracting agents from "classes" in the real world. Intra Agent Modeling involves expressing agent characteristics - Goal, Belief, Plan and Capability - whereas, Inter Agent modeling incorporates agent mobility and communication in a multi-agent system.

To evaluate or compare the convergence speed of adaptive digital filters (ADF) with least mean squared (LMS) algorithm, the condition numbers of correlation matrices of tap-input vectors are often used. In this paper, however, the comparison of the conventional fullband ADF and the subband ADF based on their condition numbers is shown to be invalid. In some cases, the over-sampled subband ADF converges faster than the fullband ADF, although the former has larger condition numbers. To explain the above phenomenon, an expression for the convergence behavior of the subband ADF and simulation results are provided.

In order to serve traffic hot spots, the hierarchical cellular systems or the hybrid TDMA/CDMA have been proposed, recently. In order to depress the multi-user interference and increase capacity, the forward link power control strategy is adopted in the macrocell/microcell hierarchical cellular system using code division multiple access (CDMA). Its effects are estimated in this paper. Especially, the impact of -th distance power control laws on the forward link outage probability and capacity plane for the hierarchical cellular system are investigated. The coverage area user capacity of the overlaid macrocell/microcell cellular system is obtained. The numerical results and discussions with previous published results are presented in detail.

A repeating watermarking technique based on visual secret sharing (VSS) scheme provides the watermark repeated throughout the image for avoiding the image cropping. In this paper, the watermark is divided into public watermark and secret watermark by using the VSS scheme to improve the security of the proposed watermarking technique. Unlike the traditional methods, the original watermark does not have to be embedded into the host image directly and, thus, it is hard to be detected or removed by the pirates or hackers. The retrieved watermark extracted from the watermarked image does not require the complete original image, but requires a secret watermark. Furthermore, the watermarking technique suits the watermark with an adaptive size of binary image for designing the watermarking system. The experimental results show that the proposed method can withstand the common image processing operations, such as filtering, lossy compression and the cropping attacking etc. The embedded watermark is imperceptible, and that the extracted watermark identifies clearly the owner's copyright.

We present a simulation system which meets the requirements for practical application of inverse modeling in a professional environment. A tool interface for the integration of arbitrary simulation tools at the user level is introduced and a methodology for the formation of simulation networks is described. A Levenberg-Marquardt optimizer automates the inverse modeling procedure. Strategies for the efficient execution of simulation tools are discussed. An example demonstrates the extraction of doping profile information on the basis of electrical measurements.

Since mobile communication systems using optical rays (optical mobile communication systems) do not radiate radio waves from the mobile terminals, they are expected to be used in environments containing sensitive electronic equipment. However, the placement and direction of the optical receivers must be suitably determined for mobile communication because light has high directivity. In optical mobile communication systems, the communication quality varies with the direction of the mobile terminal. Therefore, we examined the angle over which communication is possible at various measurement points and defined it as the communication angle. The mean opinion score (MOS) was obtained to assess the communication quality using the communication angle as a parameter. In this paper, the two situations, walking and sitting down, was considered the way optical mobile communication systems actually used. We found that for walking, when the communication angle was over 180 degrees, the MOS was over 3 and over 50% of users could communicate usefully. When used sitting down, the communication quality did not depend on the communication angle, but only on whether or not the user could communicate in the direction he/she was facing. Thus, if the communication angle in the service area is over 180 degrees, it is possible to communicate in practical situations, even while walking.

The individually normalized least mean square (INLMS) algorithm is proposed as an adaptive algorithm suitable for the fixed point processing. The convergence property of the INLMS algorithm, however, is not yet analyzed enough. This paper first derives an equation describing the convergence property by exploiting the technique of expressing the INLMS algorithm as a first order infinite impulse response (IIR) filter. According to the equation derived thus, the decreasing process of the estimation error is represented as the response of another IIR filter expression. By using the representation, this paper second derives the convergence condition of the INLMS algorithm as the range of the step size making a low path filter of the latter IIR filter. This paper also derives the step size maximizing the convergence speed as the maximum coefficient of the latter IIR filter and finally clarifies the range of the step size recommended in the practical system design.

An approach for analysis of the small signal response of the carriers in semiconductors is presented. The integro-differential equation, describing the phenomenon in the time domain is transformed into a Fredholm integral equation of the second kind. The response of the carrier system to a small signal of a general time dependence can be calculated by the knowledge of the response to an impulse signal, defined by a delta function in time. For an impulse signal, the obtained integral equation resembles the basic structure of the integral form of the time dependent (evolution) Boltzmann equation. Due to this similarity a physical model of the impulse response process is developed. The model explains the response to an impulse signal in terms of a relaxation process of two carrier ensembles, governed by a Boltzmann equation. A Monte-Carlo method is developed which consists of algorithms for modeling the initial distribution of the two ensembles. The numerical Monte-Carlo theory for evaluation of integrals is applied. The subsequent relaxation process can be simulated by the standard algorithms for solving the Boltzmann equation. The presented simulation results for Si and GaAs electrons serve as a test of the Monte-Carlo method and demonstrate that the physical model can be used for explanation of the small signal response process.

We investigate the intrinsic current fluctuations in small Si-MOSFETs via the Monte Carlo device simulation. It is demonstrated that the temporal fluctuation of the drain current in Si-MOSFETs attains a significant fraction of the averaged drain current when the device width is scaled down to the deep sub-µm regime. This is caused by the drastic decrease in the number of channel electrons. This finding holds true whenever the device width is reduced to deep sub-µm, regardless of the channel length. Most importantly, current fluctuation is associated with the quasi-equilibrium thermal noise in the heavily-doped source and drain regions, whereas its magnitude with respect to the averaged drain current is directly related to the number of channel electrons underneath the gate.

In this paper we report on the modeling and simulation of tunneling current in MOS devices including quantum mechanical effects. The simulation model features an original scheme for the self-consistent solution of Poisson and Schrodinger equations and it is used for the extraction of the oxide thickness, by fitting CV curves, and the calculation of the tunneling current. Simulations and experiments are compared for different device types and oxide thicknesses (1.5-6.5 nm) showing good agreement and pointing out the importance of quantum mechanical modeling and the presence of many tunneling mechanisms in ultra-thin oxide MOS devices.

The ATM Wireless Access (AWA) System allows portable terminals such as notebook PCs to provide up to 10Mbits/s to each user. AWA will be one of the last hops of the fiber system; it seamlessly provides wireless terminals with most of the services available in the fiber system. A prototype is developed to confirm system realization and the technical feasibility of the radio transmission rate of 80 Mbit/s, the highest yet reported in wireless access systems, by employing ATM technology to support multimedia communication with different communication quality requirements. The prototype uses TDMA as the multiple access method. This paper proposes the system concept and technical issues of the AWA system. The design and performance of the AWA prototype are clarified. It is confirmed that the target performance of the prototype can be achieved and technical issues are feasible.

A circuit-level electrothermal simulator, MICS (MItsubishi Circuit Simulator), is presented with parasitic bipolar transistor action and lattice heating taken into account. Diffusion capacitance in parasitic bipolar transistors is introduced to cover turn-on behavior under short rise-time current. Device temperatures are simulated from calculated electrical characteristics and the closed-form solution of the heat transfer equation. Simulation results show that this tool is valuable in evaluating electrostatic discharge (ESD) robustness in integrated circuits (ICs).