A packet-based leaky-bucket algorithm functions like the early packet discard (EPD), and accepts a newly arriving packet if the probability that all the cells of the packet are accepted is high. We derive some performance characteristics of the cell and packet arrival processes that are accepted by the leaky-bucket algorithm. From these analyses, a method to determine the values of the parameters of the leaky-bucket algorithm and certain relations between this leaky-bucket algorithm and the generic cell rate algorithm (GCRA) are obtained.

This paper proposes a new framework of managing virtual spaces based on spatial databases as an extension of VRML-based systems. The framework is suitable for treating continuous virtual spaces and for managing the quality of service (QoS) of the virtual spaces depending on user's operations and situations of computer resources. Levels of detail (LoD) of 3D objects is the most important rule for rendering scenes dynamically while managing the QoS. This paper describes a method of managing the QoS depending on the LoD in the form of spatial queries. An advantage of the framework is that spatial databases can incrementally construct virtual spaces in clients using differential descriptions based on VRML, that is, DVRML, proposed in this paper. Dynamic spatial data such as avatar's movement and real-time multimedia data such as videos should be shared by all participants in a virtual space in real time. Our framework can also handle dynamic spatial data by means of real-time updating of some spatial objects in spatial databases as well as static spatial data. We developed some experimental applications based on the framework in order to prove that it is feasible for networked virtual spaces with video components.

The static fatigue parameters of plastic sleeves are determined by dynamic fatigue and destructive tests. The failure probability and lifetime of the plastic sleeve are estimated by using these parameters. No failure is expected for 20 years if the plastic sleeve is used in a normal atmosphere (23, 60%RH) and hot water (50).

In this paper, we investigate a call admission control (CAC) problem in a multimedia wireless ATM network that supports various multimedia applications based on micro/pico cellular architectures. Due to reduced wireless cell size (compared to conventional cellular networks), forced termination of calls in progress becomes a more serious problem in the wireless ATM network. Another problem specific to the multimedia wireless network is how to avoid an excessive delay of non-realtime applications under the presence of various realtime applications with priority over non-realtime applications. We consider two service classes; CBR for realtime applications and UBR for non-realtime applications, and then propose a new CAC scheme that addresses above two problems while minimizing a blocking probability of newly arriving calls of CBR. Through the analytical methods, we derive the blocking probabilities and forced termination probabilities of CBR calls and the average packet delay of UBR connections. We also present a method that decides the optimal CAC threshold values in our CAC scheme.

Three multiplicative algorithms for the floating-point divide operation are compared: the Newton-Raphson method, Goldschmidt's algorithm, and a naive method that simply calculates a form of the Taylor series expansion of a reciprocal. The series also provides a theoretical basis for Goldschmidt's algorithm. It is well known that, of the Newton-Raphson method and Goldschmidt's algorithm, the former is the more accurate while the latter is the faster on a pipelined unit. However, little is reported about the naive method. In this report, we analyze the speed and accuracy of each method and present the results of numerical tests, which we conducted to confirm the validity of the accuracy analysis. Basically, the comparison are made in the context of software implementation (e. g. , a macro library) and compliance with the IEEE Standard 754 rounding is not considered. It is shown that the naive method is useful in a realistic setting where the number of iterations is small and the method is implemented on a pipelined floating-point unit with a multiply-accumulate configuration. In such a situation, the naive method gives a more accurate result with a slightly lower latency, as compared with Goldschmidt's algorithm, and is much faster than but slightly inferior in accuracy to the Newton-Raphson method.

This letter addresses how to set SIR targets higher than normally required, in order to mitigate the effect of signal-to-interference ratio (SIR) measurement error included in power control steps. We find that scaling up the SIR targets by 1 dB is conformable to resisting SIR measurement error for code division multiple access (CDMA) mobile systems.

Extremely small aperture radial line slot antennas (RLSAs) are analyzed by method of moments. At first, the analysis model of cylindrical waveguide in terms of rectangular cavity modes is confirmed for a RLSA with a spiral slot arrangement. The overall VSWR as well as rotational symmetry of the actual structure of RLSAs is predicted for the first time and is confirmed experimentally. Secondly, the minimum diameter of the concentric array RLSA is estimated for which the conventional analysis model of a rectangular waveguide is valid for the design of matching slot pairs at the shorted periphery of the radial waveguide. It is found that the curvature and cylindrical short wall at aperture periphery must be considered in the design and analysis of small RLSAs with the gain lower than about 25 dBi.

The OMG have made the trading service one of the basic CORBA services. A specification has been drawn up (OMG RPF5) but seems to have some problems in terms of scalability and complexity. This paper introduces an architecture called Contextual Clustering Using Service Properties (CCUSP) that deals with issues of scalability. It uses a contextual approach to clustering object service offers based on property commonalities. It also handles issues of scalability of trader federation. An ontological approach is to be used, however not covered in this paper. An implementation of the specialisation graph context model is detailed.

The advent of high-speed networks with quality of service guarantees, will enable the deployment of data-server distributed systems over wide-area networks. Most implementations of data-server systems have been over local area networks. Thus it is important, in this context, to study the performance of existing distributed data management protocols in the new networking environment, identify the performance bottlenecks and develop protocols that are capable of taking advantage of the high speed networking technology. In this paper, we examine and compare the scalability of the server-based two-phase locking protocol (s-2PL), and the group two-phase locking protocol (g-2PL). The s-2PL protocol is the most widely used concurrency control protocol, while the g-2PL protocol is an optimized version of the s-2PL protocol, tailored for high-speed wide-area network environments. The g-2PL protocol reduces the effect of the network latency by message grouping, client-end caching and data migration. Detailed simulation results indicate that g-2PL indeed scales better than s-2PL. For example, upto 28% improvement in response time is reported.

Adaptive infinite impulse response (IIR) digital filter implemented using a cascade of second order direct form allpass filters and a finite impulse response (FIR) filter, has the property of its poles converging to those of the unknown system. In this paper we implement the adaptive allpass-FIR digital filter using a lattice allpass filter with minimum number of multipliers. We then derive a simple adaptive algorithm, which does not increase the overall number of multipliers of the proposed adaptive digital filter (ADF) in comparison to the ADF that uses the direct form allpass filter. The proposed structure and algorithm exhibit a kind of orthogonality, which ensures convergence of the poles of the ADF to those of the unknown system. Simulation results confirm this convergence.

This paper introduces a material management system for newspapers that was developed for The Yomiuri Shimbun. Material transferred to the system is stored in a material database and sent to terminals located in the related sections. The material can be processed effectively just by checking information on the terminals. Special requirements for this system will be discussed first in the paper, then problem-solving will be explored.

In this paper, we represent a class structure using directed graph in which each node corresponds to each member of the class. To quantify the dependence relationship among members, we define weighted closure. Using this quantified relationship and effort equation proposed by M. H. Halstead, we propose a metric for class structural complexity.

In this work, we propose an End-to-End Rate Control Approach (EERCA) for congestion avoidance in Available Bit Rate (ABR) service on Asynchronous Transmit Mode (ATM) networks. In our approach, the network estimates the number of cells stored in the switch for each VC. The source generates a specific traffic pattern, then a proper explicit rate can be derived based on the received traffic pattern at the destination. This approach is designed to reduce the rate calculation effort in the switch as well as to avoid the complexity in setting the monitoring-interval. EERCA features higher efficiency, higher utilization, more stable queue occupancy, shorter transient response time, and better fairness compared with existed schemes.

This paper proposes two types of acceleration parameters for the Durand-Kerner method and its variant, where the values of parameters are determined at each iteration step. Numerical examples are also shown.

A double-layer Associative Memory System (AMS) based on the Cerebella Model Articulation Controller (CMAC) (CMAC-AMS), owing to its advantages of simple structures, fast searching procedures and strong mapping capability between multidimensional input/output vectors, has been successfully used in such applications as real-time intelligent control, signal processing and pattern recognition. However, it is still suffering from its requirement for a large memory size and relatively low precision. Furthermore, the hash code used in its addressing mechanism for memory size reduction can cause a data-collision problem. In this paper, a new high-order Associative Memory System based on the Newton's forward interpolation formula (NFI-AMS) is proposed. The NFI-AMS is capable of implementing high-precision approximation to multivariable functions with arbitrarily given sampling data. A learning algorithm and a convergence theorem of the NFI-AMS are proposed. The network structure and the scheme of its learning algorithm reveal that the NFI-AMS has advantages over the conventional CMAC-type AMS in terms of high precision of learning, much less required memory size without the data-collision problem, and also has advantages over the multilayer Back Propagation (BP) neural networks in terms of much less computational effort for learning and fast convergence rate. Numerical simulations verify these advantages. The proposed NFI-AMS, therefore, has potential in many application areas as a new kind of associative memory system.

With the introduction of ATM technology, service providers around the world have actively engaged in offering high bandwidth services. Currently, services, such as T1/E1, T3/E3 circuit emulation, are made available to large-volume account users. However, more advanced services, such as multimedia applications, have demanded not just high bandwidth but also flexible rate adaptation with quality-of-service (QoS) guarantee. To support the above service requirements, sophisticated network planning and engineering procedures should be taken. In the past few years, we have conducted various researches on developing the engineering strategies for resource control and management to support multi-rate service offering. We have also looked into the design details of connection control and management for achieving the QoS requirement. We considered the service quality of the underlying transport in regard with the QoS management. In this paper, we will outline those results and give an overview description about the proposed framework.

This paper proposes an intelligent and autonomous radio resource management scheme for a multi-layered cellular system with different assigned bandwidths to achieve flexible and high capacity wireless communication systems under any traffic conditions, especially under nonuniform traffic conditions. In the proposed system, terminals with lower mobility are connected to the wideband microcell systems to achieve higher system capacity, and terminals with higher mobility are connected to the narrowband macrocell systems to reduce intercell hand-off frequency. To flexibly cope with variations of traffic conditions, radio spectrum is adaptively and autonomously shared by both systems, and its control is conducted by each microcell base station. Moreover, at the existence of nonuniform traffic conditions , the proposed system introduces downlink power control for the microcells and graceful degradation thereby achieving high system capacity even under such extraordinary traffic situations . Computer simulation confirms that the proposed scheme can achieve lower blocking probability than the centralized scheme especially under nonuniform traffic conditions.

Simple disjunctive decomposition is a special case of logic function decompositions, where variables are divided into two disjoint sets and there is only one newly introduced variable. It offers an optimal structure for a single-output function. This paper presents two techniques that enable us to apply simple disjunctive decompositions with little overhead. Firstly, we propose a method to find symple disjunctive decomposition forms efficiently by limiting decomposition types to be found to two: a decomposition where the bound set is a set of symmetric variables and a decomposition where the output function is a 2-input function. Secondly, we propose an algorithm that constructs a new logic representation for a simple disjunctive decomposition just by assigning constant values to variables in the original representation. The algorithm enables us to apply the decomposition with keeping good structures of the original representation. We performed experiments for decomposing functions and confirmed the efficiency of our method. We also performed experiments for restructuring fanout free cones of multi-level logic circuits, and obtained better results than when not restructuring them.

In this paper, a transceiver VLSI architecture is proposed for high speed digital CATV modems, which can perform both the QAM and the VSB transmissions. The proposed architecture of all-digital dual-mode QAM/VSB receiver consists of digital AGC, digital demodulator, fractionally spaced blind equalizer and DFE, digital carrier recovery, and symbol timing recovery. Finite word-length simulation results show that the proposed architecture can achieve an SNR 29 dB for both the 64-QAM mode and 8-VSB mode when the 10 bit ADC input signal SNR is 36 dB, and there are 6 kHz of carrier frequency offset, 110 ppm of symbol rate offset, and -82 dBc carrier phase-jitter at 10 kHz away from the nominal carrier frequency.

Call tracking data contains a calling address, called address, service type, and other useful attributes to predict a customer's calling activity. Call tracking data is becoming a target of data mining for telecommunication carriers. Conventional data-mining programs control the number of association rules found with two types of thresholds (minimum confidence and minimum support), however, often they generate too many association rules because of the wide variety of patterns found in call tracking data. This paper proposes a new method to reduce the number of generated rules. The method proposed tests each generated rule based on Akaike Information Criteria (AIC) without using conventional thresholds. Experiments with artificial call tracking data show the high performance of the proposed method.