This paper presents a robust and nonblocking group membership protocol for large-scale distributed systems. This protocol uses the causal relation between membership-updating messages (i. e. , those specifying the adding and deleting of members) and allows the messages to be executed in a nonblocking manner. It differs from conventional group membership protocols in the following points: (1) neither global locking nor global synchronization is required; (2) membership-updating messages can be issued without being synchronized with each other, and they can be executed immediately after their arrival. The proposed protocol therefore is highly scalable, and is more tolerant to node and network failures and to network partitions than are the conventional protocols. This paper proves that the proposed protocol works properly as long as messages can eventually be received by their destinations. This paper also discusses some design issues, such as multicast communication of the regular messages, fault tolerance and application to reliable communication protocols (e. g. , TCP/IP).

A large number of techniques have been proposed for acceleration of the Hough Transform, because the transformation is computationally very expensive in general. It is known that the sampling interval in parameter space is strongly related to the computation cost. The precision of the transformation and the processing speed are in a trade-off relationship. No fair comparison of the processing speed between various methods was performed in all previous works, because no criterion had been given for the sampling interval of parameter, and because the precision of parameter was not equal between methods. At the beginning of our research, we derive the relationship between the sampling interval and the precision of parameter. Then we derive a framework for comparing computation cost under equal condition for precision of parameter, regarding the total number of sampling points of a parameter as the computation cost. We define the transformation error in the Hough Transform, and the error is regarded as transformation noise. In this paper we also propose a design method called "Noise-level Shaping," by which we can set the transformation noise to an arbitrarily level. The level of the noise is varied according to the value of a parameter. Noise-level Shaping makes it possible for us to find the efficient parameterization and to find the efficient sampling interval in a specific application of the Hough Transform.

Broadband subscriber loop system and ATM switching system are the key equipment for construction of Broadband networks. In this paper, we describe the architecture of access network and the implementation of ATM switching system with multi-service interface for construction of broadband access network. We also represent the design of MAIN-AN (Multi-service Access Integrated Network--Access Node) system as integrated access network platform which enables to accommodate ATM/SDH-based and ATM/PON-based FTTx (Fiber-To-The-x) access architecture simultaneously. The system has a Cross-point ATM Switch Fabric with 10 Gbits/sec throughput and it has been implemented using 0.5 µm CMOS technology. For performance evaluation of it, we simulate it under burst traffic conditions. In addition, we show the implementation of prototype of ASIC (Application Specific Integrated Circuit), MAIN system and its core PBA (Printed circuit Board Assembly) and so on.

The Communications Research Laboratory (CRL), the National Astronomical Observatory (NAO), the Institute of Space and Astronoutical Science (ISAS), and the Telecommunication Network Laboratory Group of Nippon Telegraph and Telephone Corporation (NTT) have developed a very-long-baseline-connected-interferometry array, maximum baseline-length was 208 km, using a high-speed asynchronous transfer mode (ATM) network with an AAL1 that corresponds to the constant bit-rate protocol. The very long baseline interferometry (VLBI) observed data is transmitted through a 2.488-Gbps [STM-16/OC-48] ATM network instead of being recorded onto magnetic tape. By combining antennas via a high-speed ATM network, a highly-sensitive virtual (radio) telescope system was realized. The system was composed of two real-time VLBI networks: the Key-Stone-Project (KSP) network of CRL (which is used for measuring crustal deformation in the Tokyo metropolitan area), and the OLIVE (optically linked VLBI experiment) network of NAO and ISAS which is used for astronomy (space-VLBI). These networks operated in cooperation with NTT. In order to realize a virtual telescope, the acquired VLBI data were corrected via the ATM networks and were synthesized using the VLBI technique. The cross-correlation processing and data observation were done simultaneously in this system and radio flares on the weak radio source (HR1099) were detected.

VLBI is an important application of ATM technology because it can transmit huge amounts of data. A single VLBI experiment typically generates data (which must be recorded and transported until they are cross-correlated) of tera-bit order at each separated observing site. Conventional VLBI not only requires manpower but also limits the maximum observation data rate. Therefore, a realtime VLBI using a private ATM network was developed recently, but it could not be utilized for regular VLBI experiment. Since utilization of public ATM is most realistic solution for realtime VLBI between ordinary observing sites, we have developed an interface equipment that connects VLBI observation and processing equipment to a public ATM network and demonstrated a successful experiment. This equipment supports VLBI's standard bit rates as 128 Mbps and 256 Mbps, though data rate for user's payload in 155.52 Mbps (STM-1/OC-3) ATM network is actually only 119.5 Mbps. It can easily step to higher networks as 622 Mbps.

This paper presents a 7th-order channel-select filter for a spread-spectrum wireless receiver operating with a minimum power supply of 2.5 V. The channel-select filter implements a sharp transition from 2 MHz to 4 MHz and a stopband attenuation of 50 dB. The 7th-order filter is realized by a cascade of a passive RC integrator, a 3rd-order leapfrog filter, an operational amplifier based differentiator, a 2nd-order notch filter, and a 1st-order allpass filter. It is designed in a 0.35 µm single-poly BiCMOS process. Simulation results show feasibility of the proposed filter.

A 10-bit 3-Msample/s multibit cyclic A/D converter for mixed-signal LSIs with a small chip-area of 1.5 mm2 and low power consumption of 10.8 mW with a 2.7-V power supply was realized using a 0.8-µm CMOS process. This ADC module is designed for high-speed servo-controller LSIs used in hard-disk-drive systems. We found that three-cycle cyclic conversion (four bit, three bit+(one redundant bit), and three bit+(one redundant bit)) was optimal for achieving 10-bit resolution with a small chip-area and low power consumption given a required conversion time of 0.33 µs. Our multipath architecture cut power consumption by 30% compared to conventional cyclic A/D converters. By adding one signal path between the residue amplifier and the four bit subADC, the settling timing requirement can be relaxed, and the amplifier's power consumption thus reduced.

This paper presents a new data hiding scheme via steganographic image transformation, which is different from conventional data hiding techniques. The transformation is achieved in the frequency domain and the concept of Fourier filtering method is used. An input image is transformed into a fractal image, which can be used in Computer Graphic (CG) applications. One of the main advantages of this scheme is the amount of data to be hidden (embedded) is equal to that of the host signal (generated fractal image) while it is in general limited in the conventional data hiding schemes. Also both the opened fractal image and the hidden original one can be properly used depending on the situation. Unauthorized users will not notice the "secret" original image behind the fractal image, but even if they know that there is a hidden image it will be difficult for them to estimate the original image from the transformed image. Only authorized users who know the proper keys can regenerate the original image. The proposed method is applicable not only as a security tool for multimedia contents on web pages but also as a steganographic secret communication method through fractal images.

To provide QoS guarantees for each connection, efficient scheduling algorithms, such as WFQ, have been proposed. These algorithms assume a certain amount of buffer is allocated for each connection to provide loss free transmission of packets. This buffer allocation policy, however, requires much buffer space especially when many connections are sharing a link. In this paper we propose the use of partial buffer sharing (PBS) policy combined with usage parameter control (UPC) for efficient buffer management and flexible QoS control in ATM switches. We evaluate the feasibility of the proposed method by solving a Markov model. We also show that using the proposed method, we can control the cell loss ratio (CLR) independently of the delay. Numerical evaluations are presented, which indicates the PBS combined with UPC significantly reduces the buffer size required to satisfy given cell loss ratios.

As the nonlinear adaptive filter, the neural filter is utilized to process the nonlinear signal and/or system. However, the neural filter requires large number of iterations for convergence. This letter presents a new structure of the multi-layer neural filter where the orthonormal transform is introduced into all inter-layers to accelerate the convergence speed. The proposed structure is called the transform domain neural filter (TDNF) for convenience. The weights are basically updated by the Back-Propagation (BP) algorithm but it must be modified since the error back-propagates through the orthogonal transform. Moreover, the variable step size which is normalized by the transformed signal power is introduced into the BP algorithm to realize the orthonormal transform. Through the computer simulation, it is confirmed that the introduction of the orthonormal transform is effective for speedup of convergence in the neural filter.

The wall admittance of an arbitrarily shaped microstrip antenna is generally formulated. As examples, elliptical microstrip antennas with and without a circular slot are calculated. The wall admittance is determined by the spectral domain analysis in order to consider the effect of the dielectric substrate. The electromagnetic fields within the cavity are expanded in terms of the eigenfunctions in the cylindrical coordinate system and their expansion coefficients are determined by applying the impedance boundary condition at the aperture in the sense of the least squares. The calculated input impedance and axial ratio agree fairly well with the experimental data. The proposed method is valid for the microstrip antennas with a patch whose geometry deviates from the particular coordinate system, such as single-feed circularly polarized microstrip antennas.

The design of effective traffic and resource management policies is a key issue in the deployment of ATM-satellite systems. This paper proposes a technique of call admission control and dynamic resource management to support ATM traffic classes in satellite environments. The effectiveness of the strategy is assessed by referring to the EuroSkyWay multimedia satellite platform, based on Ka-band payload and on-board processing. The main advantage is the effective exploitation of the satellite bandwidth by means of the statistical multiplexing of traffic sources and the guarantee of QoS provisioning to both real-time and non real-time, constant and variable bit rate sources.

This paper presents an architecture for a single-chip MPEG-2 video encoder and demonstrates its flexibility and usefulness. The architecture based on three-layer cooperation provides flexible data-transfer that improves the encoder from the standpoints of versatility, scalability, and video quality. The LSI was successfully fabricated in the 0.25-µm four-metal CMOS process. Its small size and its low power consumption make it ideal for a wide range of applications, such as DVD recorders, PC-card encoders and HDTV encoders.

The VSOP terminal is a new data-acquisition system for the Very-Long-Baseline Interferometry (VLBI). This terminal was primarily designed for ground telescopes in the VLBI Space Observatory Programme (VSOP). New technologies; higher-order sampling and digital filtering techniques, were introduced in the development. A cassette cart was also introduced, which supports 24-hour unattended operations at the maximum data rate of 256 Mbps. The higher-order sampling and digital filtering techniques achieve flat and constant phase response over bandwidth of 32 MHz without using expensive wide base-band converters. The digital filtering technique also enables a variety of observing modes defined on the VSOP terminal, even with a fixed sampling frequency in an A/D converter. The new terminals are installed at Nobeyama, Kashima, Usuda, Mizusawa, and Kagoshima radio observatories in Japan, and are being used in VSOP and other domestic VLBI observations. In this paper the key features of the VSOP terminal focusing on these advanced technologies are presented, and the results of performance tests are shown.

Speech can be modeled as short bursts of vocal energy separated by silence gaps. During typical conversation, talkspurts comprise only 40% of each party's speech and remaining 60% is silence. Communication systems can achieve spectral gain by disconnecting the users from the spectral resource during silence periods. This letter develops a simple and efficient Voice Activity Detection (VAD) algorithm to work in a mobile environment exhibiting dynamically varying background noise. The VAD uses a classification method involving the full-band energy, ratio of low-band energy to full-band energy, zero-crossing rate, and peakiness measure.

This paper analyzes the effective radiation efficiency of a ground-penetrating radar (GPR) consisting of two resistor-loaded bow-tie antennas covered with a ferrite-coated conducting cavity by using finite-difference time-domain (FDTD) method. The GPR is located above a lossless or lossy ground surface. The relation between the radiation powers into the ground and air, dissipated powers at the loaded resistors and ferrite absorber, and the reflected power due to impedance mismatching, is clarified numerically.

The ATM Virtual Path(VP)-based transport network is a candidate for the future multi-reliability and broadband integrated service infrastructure. This paper compares the performance attributes of the VP transport network with those of the conventional SDH network and future optical path-based transport network. This paper shows that the VP-based network is superior in terms of path-grooming efficiency and connection capability, and will still play an important role when WDM technologies are introduced to carrier networks. This paper also describes the recently fabricated VP Cross Connect(VP-XC) system configuration and the VP Automatic Protection Switching(APS) performance of the XC.

This paper describes a 0.35µm SOI-CMOS gate array using partially-depleted transistors. The gate array adopts the field-shield isolation technique with body-tied structures to suppress floating-body problems such as: (1) kink characteristics in drain currents, (2) low break-down voltage, and (3) frequency-dependent delay time. By optimizing the basic-cell layout and power-line wiring, the SOI-CMOS gate array also allows the use of the cell libraries and the design methodologies compatible with bulk-CMOS gate arrays. An ATM (Asynchronous Transfer Mode) physical-layer processing LSI was fabricated using a 0.35µm SOI-CMOS gate array with 560k raw gates. The LSI operated at 156 Mbps at 2.0 V, while consuming 71% less power than using a typical 0.35µm 3.3 V bulk-CMOS gate array.

Recently, researchers in various fields have shown interest in the behavior of creatures from the viewpoint of adaptiveness and flexibility. Ants, known as social insects, exhibit collective behavior in performing tasks that can not be carried out by an individual ant. In ant colonies, chemical substances, called pheromones, are used as a way to communicate important information on global behavior. For example, ants looking for food lay the way back to their nest with a specific type of pheromone. Other ants can follow the pheromone trail and find their way to baits efficiently. In 1991, Colorni et al. proposed the ant algorithm for Traveling Salesman Problems (TSPs) by using the analogy of such foraging behavior and pheromone communication. In the ant algorithm, there is a colony consisting of many simple ant agents that continuously visit TSP cities with opinions to prefer subtours connecting near cities and they lay strong pheromones. The ants completing their tours lay pheromones of various intensities with passed subtours according to distances. Namely, subtours in TSP tourns that have the possibility of being better tend to have strong pheromones, so the ant agents specify good regions in the search space by using this positive feedback mechanism. In this paper, we propose a multiple ant colonies algorithm that has been extended from the ant algorithm. This algorithm has several ant colonies for solving a TSP, while the original has only a single ant colony. Moreover, two kinds of pheromone effects, positive and negative pheromone effects, are introduced as the colony-level interactions. As a result of colony-level interactions, the colonies can exchange good schemata for solving a problem and can maintain their own variation in the search process. The proposed algorithm shows better performance than the original algorithm with almost the same agent strategy used in both algorithms except for the introduction of colony-level interactions.

It is now known that a seemingly random irregular time series can be deterministic chaos (hereafter, chaos). However, there can be various kind of noise superimposed into signals from real systems. Other factors affecting a signal include sampling intervals and finite length of observation. Perhaps, there may be cases in which a chaotic time series is considered as noise. J. Theiler proposed a method of surrogating data to address these problems. The proposed method is one of a number of approaches for testing a statistical hypothesis. The method can identify the deterministic characteristics of a time series. In this approach, a surrogate data is formed to have stochastic characteristics with the statistic value associated with the original data. When the characteristics of the original data differs from that of a surrogate data, the null hypothesis is no longer valid. In other words, the original data is deterministic. In comparing the characteristics of an original time series data and that of a surrogate data, the maximum Lyapunov exponents, correlation dimensions and prediction accuracy are utilized. These techniques, however, can not calculate the structure in local subspaces on the attractor and the flow of trajectories. In deal with these issues, we propose the trajectory parallel measure (TPM) method to determine whether the null hypothesis should be rejected. In this paper, we apply the TPM method and the method of surrogate data to test a chaotic time series and a random time series. We also examine whether a practical time series has a deterministic property or not. The results demonstrate that the TPM method is useful for judging whether the original and the surrogate data sets are different. For illustration, the TPM method is applied to a practical time series, tap water demand data.