Modeling and performance analysis have played an important role in the economical design and efficient operation of switching systems, and is currently becoming more important because the switching systems should handle a wide range of traffic characteristics, meeting the grade of service requirements of each traffic type. Without these techniques we could no longer achieve economy and efficiency of the switching systems in complex traffic characteristic environments. From the beginning of research on electronic switching systems offering circuit-switched applications, Stored Program Control (SPC) technology has posed challenges in the area of modeling and performance analysis as well as queueing structure, efficient scheduling, and overload control strategy design. Not only teletraffic engineers and performance analysts, but also queueing theorists have been attracted to this new field, and intensive research activities, both in theory and in practice, have continued over the past two decades, now evolving to even a broader technical field including traditional performance analysis. This article reviews a number of important issues that have been raised and solved, and whose solutions have been reflected in the design of SPC switching systems. It first discusses traffic problems for centralized control systems. It next discusses traffic problems inherent in distributed switching systems.

In this work we propose a recursive electric circuit which has a fractal structure composed of resistances and capacitors. It is first confirmed in practice that such a device, which is referred as fractance, possesses a novel characteristics between the constituent elements, or the resistance and the capacitance. That is, the absolute value of the impedance shows such a characteristics as |Z|ω-1/2, whereas the phase angle does such a constant phase property as θ=-π/4 independent of the frequency. As an application of the presently proposed fractance device, we constructed a fractional integral circuit as well as a fractional differential circuit, and confirmed that the observed output wave forms agree well with those derived from a computer simulation.

In this paper, scattering waves by a strip grating with an anisotropic substrate for the incidence of inclined polarization are analyzed, and polarization characteristics of scatterd waves are calculated. For simplicity, the analysis is limitted to the case of normal incidence and a perfectly conducting strip grating is assumed.

Chaotic behavior in a series resonance circuit with a ferroelectric triglycine sulfate (TGS) crystal was observed just below the ferroelectric phase transition temperature. We have analyzed the nonlinear responses by applying external electric fields to the crystal. The computer simulation was made for the modified forroelectric hysteresis loops to realize the experimental results. The fractal correlation dimension was determined to be ν=1.8 in the chaotic phase.

This paper surveys the developments and achievements of teletraffic studies in Japan. It briefly covers the period preceding 1970, then focuses on the period after 1970. Rather than attempting to cover the entire field of teletraffic engineering, it places its emphasis on basic models.

In this paper, we propose a new network organizing method for packet radio networks, a layered self-organizing method. In the layered self-organizing network, whole service area is divided into multiple sub-areas and one base station is settled in each sub-area. Communication links are settled in shorter time than the conventional self-organizing method. We evaluate the network organizing performance of the method by using simulations.

Video service is slated to be a major application of emerging high-speed communications networks of the future. In particular, full-motion video is designed to take advantage of the high bandwidths that will become affordably available with the advent of B-ISDN. A salient feature of compressed video sources is that they give rise to autocorrelated traffic streams, which are difficult to model with traditional modeling techniques. In this paper, we describe a new methodology, called TES (Transform-Expand-Sample) , for modeling general autocorrelated time series, and we apply it to traffic modeling of compressed video. The main characteristic of this methodology is that it can model an arbitrary marginal distribution and approximate the autocorrelation structure of an empirical sample such as traffic measurements. Furthermore, the empirical marginal (histogram) and leading autocorrelations are captured simultaneously. Practical TES modeling is computationally intensive and is effectively carried out with software support. A computerized modeling environment, called TEStool, is briefly reviewed. TEStool supports a heuristic search approach for fitting a TES model to empirical time series. Finally, we exemplify our approach by two examples of TES video source models, constructed from empirical codec bitrate measurements: one at the frame level and the other at the group-of-block level. The examples demonstrate the efficacy of the TES modeling methodology and the TEStool modeling environment.

We analyzed vergence change by moving both the target and the subject toward depth direction simultaneously. It has been suggested that the command for vergence movement caused by depth-direction-head-movement and that caused by target movement are generated separately, then combined in the oculomotor system.

This letter proposes a new UPC (Usage Parameter Control) method suitable for monitoring/controlling the ATM cell streams of VCs (Virtual Channels) and VPs (Virtual Paths) specified with a wide-range of traffic parameter values. The method, named the 2-phase T-X method, combines two credit window type monitoring circuits that are shifted in phase by T/2. The proposed method achieves the best of both the DB and T-X methods. Its cell mis-policing rate is very low (equivalent to that of the DB-method) while its minimal hardware requirements are equal to those of the T-X method. The proposed method ensures more effective network resource (link) utilization. As a result, the proposed method is shown to be a credible UPC technique for handling broadband VBR (Variable Bit Rate) traffic in ATM based multimedia networks.

This is a partly expository paper discussing how point processes with certain "bursty" features can be qualitatively modelled by the Markovian arrival process, a generalization of the Poisson or Bernoulli processes which can be used to obtain algorithmically tractable matrix solutions to a variety of problems in probability models.

This paper is a study on the behavioral aspects of the input buffer limiting scheme whose basic feature is to award priority to the transit messages over the input messages so that congestion does not develop in the network. The numerical method employed in the analysis is that proposed in Ref.(7). The performance aspects are studied for different buffer capacities, different message handling capacities and different levels of reservation for transit traffic. The numerical method indicates that thrashing occurs at low levels of reservation for the transit messages, irrespective of the buffer size or the processor capacities of the node. This observation is supported by simulation results. With reference to the state-space of the model of our study, the congestion aspects are related to two Liapunov functions. Under the domain of one of the Liapunov functions, the evolution of the perturbed system is towards a congested state whereas, under the domain of the other Liapunov function, the evolution is towards a congestion-free state. Regardless of the configuration, it is found that the fundamental characteristic of the congestion under the input buffer limiting scheme is the characteristic of a fold catastrophe. In the systems with insufficient level of reservation for the transit traffic, the performance degradation appears to be inevitable, irrespective of the capacities of the nodal processor and output channel processor, and the size of the buffer pool. Given such an inevitability, the active life of a node under a typical node configuration is studied by simulation. A suitable performance index is suggested to assess the performance of deadlock-prone nodes.

The demand for mobile communications is continuing to grow, but there is a limit on the radio frequency resources. Micro cellular systems are a strong solution to this problem. However, Forced Call Termination (FCT) and Channel Changing (CC) occur frequently in these systems because of their small cell size. This paper proposes a new Dynamic Channel Assignment (DCA) strategy which uses information of moving direction of Mobile Stations (MSs) to reduce FCT and CC. This strategy, the MD (Moving Direction) strategy, is compared with other major DCA strategies by simulating a one-dimensional service area covering a road, such as an expressway. The simulation shows that the MD strategy performs better than the other strategies with regard to FCT, CC, and carried load. FCT is an especially important factor in the quality of service. The MD strategy reduces FCT and has the largest carried load of the strategies, which means that it has the most efficient channel usage. This is an attractive characteristic of the MD strategy for micro cellular systems.

Two types of multicast error control protocols based on a product code structure with or without interleaving are considered. The performances of these protocols are analyzed on burst error channels modeled by Gilbert's two-state Markov chain. The numerical results reveal that the interleaving does not always succeed in improving the performance of the protocol proposed in Part .

A multicast error control protocol proposed by Metzner is generalized and the performance of the proposed protocol on random error channels (binary symmetric channels) is analyzed. The proposed protocol adopts an encoding procedure based on a product code structure, whith enables each destined user terminal to decode the received frames with the Reddy-Robinson algorithm. As a result, the performance degradation due to the re-broadcasting of the replicas of the previously transmitted frames can be circumvented. The numerical results for the analysis and the simulation indicate that the proposed protocol yields higher throughput and less degradation of throughput with an increase of the number of destined terminals.

The embedded Markov processes associated with Markovian queueing systems are closely related, and their relationships are important for establishing an analytical basis for performance evaluation techniques. As a first step, we analyze the embedded processes associated with a general M/M/1 queueing system. Linear transformations between the infinitesimal generators and the transition probability matrices of embedded processes at arrival and departure times are explicitly derived. Based upon these linear transformations, the equilibrium distributions of the system states at arrival and departure times are obtained and expressed in terms of the equilibrium distribution at arbitrary times. The approach presented here uncovers an underlying algebraic structure of M/M/1 queueing systems, and establishes an algebraic methodology for analyzing the equilibrium probabilities of the system states at arrival and departure times for more general Markovian queueing systems.

A 0.1-µm-gate CMOS/SIMOX has been successfully fabricated using high quality SIMOX substrates. The propagation delay time for the 0.1-µm-gate CMOS/SIMOX is not so noticeable due to the parasitic resistance of the source and drain regions. We anticipate 0.1-µm-gate CMOS/SIMOX devices with a delay time of less than 20 ps at a supply voltage of 1.5 V by reducing the remaining parasitic resistance and capacitances.

Separability is a valuable property of nonlinear mappings. By exploiting this property, computational complexity of many numerical algorithms can be substantially reduced. In this letter, a new algorithm is presented that detects the separability of nonlinear mappings using the concept of "computational graph". A hybrid algorithm using both the top-down search and the bottom-up search is proposed. It is shown that this hybrid algorithm is advantageous in detecting the separability of nonlinear simultaneous functions.

The design of N-dimensional (N-D) FIR filters requires in general an enormous computational effort. One of the most successful methods for design and implementation is the McClellan transformation. In this paper a numerically simple technique for determining the coefficients of the transformation is suggested. This appears to be the simplest available method for the design of N-D hyperspherically symmetric FIR filters with excellent symmetry.

With the use of a two-dimensional model, single laser beam trapping of particles is analyzed as the electromagnetic boundary-value problem. From the numerical results, it is found that the trapping mechanism for this system depends upon the surface field distribution of the object.

Hot carrier stressing is carried out on ultra-thin-film SOI/pMOSFET's under a front gate operation. Degradations of both front and back gate characteristics are estimated. Effects of trapped electron in the front and the back gate oxide on device characteristics are also estimated. In a triode region, it is found that degradation in front gate characteristics is correlated with that in back gate characteristics, although ΔVth(b) is twenty times as large as ΔVth(f), due to difference between the front gate and the buried oxide thickness. In a pentode region, Δβ/β0 in a forward-mode is larger than that in a reverse-mode. This is because of the non-uniformly distributed hot carrier damage along the channel. Based on the charge-coupling theory, damages in the front gate and buried oxide by hot carrier effects are estimated separately. Flat-band-voltage shift in the back gate due to trapped charges in the buried oxide, is obtained from Vth (f) dependence on back gate bias. For Leff=2.0 µm devices, the flat-band-voltage shift varies in the range of 1.00 to 1.50 V. This indicates that trapped electrons are created in the buried oxide. Trapped electrons in the buried oxide increase gm(f) through the effect equivalent to back gate bias. From gm(f) dependence on back gate bias, it is found that effective channel length is decreased by trapped electrons in the front gate oxide near the drain. Therefore, it is worth noticing that, in hot carrier effects in ultra-thin-film SOI/pMOSFET's, gm is increased not only by the reduction of effective channel length but also by the equivalent back gate bias effect.