In recent years, there has been a rapid growth in applications such as World Wide Web browsing, which are characterized by fairly short sessions that transfer substantial amounts of data. Conventional connection-oriented and datagram services are not ideally engineered to handle this kind of traffic. We present a new ATM service, called Dynaflow service, in which virtual circuits are created on a burst-by-burst basis and we evaluate key aspects of its performance. We compare Dynaflow to the Fast reservation protocol (FRP) and show that Dynaflow can achieve higher overall throughput due to the elimination of reservation delays, and through the use of shared "burst-stores. " We study the queueing performance of the dynaflow switch and quantify the relationship between the loss ratio and the buffer size.

Antidiffusion is a process running the diffusion equation reversely in the time domain. Though extremely important for image restoration of the Gaussian blur, it is a horribly ill-posed problem, since minor noise leads to very erroneous results. To solve this ill-posed problem stably, in this paper we first apply a multiscale method to decompose images into various scale components using the Gaussian and Laplacian of Gaussian (LOG) filters. We then show that the restored images can be reconstructed from the components using shrunk Gaussian and LOG filters. Our algorithm has a closed form solution, and is robust to noise because it is performed by the integration computation (convolution), contrasting with the differential computation required by direct discretization of the antidiffusion equation. The antidiffusion algorithm is also computationally efficient since the convolution is row and column separable. Finally, a comparison between the algorithm and the well-known Wiener filter is conducted. Experiments show that our algorithm is really stable and images can be restored satisfactorily.

Media processors have emerged so that a single LSI can realize multiple multimedia functions, such as graphics, video, audio and telecommunication with effectively shared hardware and flexible software. First, the difference between media processors and general-purpose microprocessors with multimedia extensions is clarified. Features for processes and data in the multimedia applications are summarized and are followed by the multimedia enhancements that the recent general-purpose microprocessors use. The architecture for media processors reflects the further optimized utilization of these features and realizes better price-performance ratio than the general-purpose microprocessors. Finally, the future directions of media processors are estimated, based on the performance, the power dissipation and the die size of the present microprocessors with multimedia extensions and the present media processors. The demand to improve the price-performance ratio for the whole system and to reduce the power consumption makes the media processor evolve into a system processor, which integrates not only the media processor but also the function of a general-purpose microprocessor, various interfaces and DRAMs.

In this paper, we propose a descriptor as a shape signature and the projective refinement as a verification method for recognizing 2D curved objects with occlusions from their partial views. For an extracted curve segment, we compute a series of the geometric invariance of equally spaced five co-planar points on the curve. Thus the resulting descriptor is invariant only under rotation, translation, and scale, but sufficient similarity is preserved even under large distortions. It is more stable and robust since it does not need derivatives. We use this transformation-invariant descriptor to index a hash table. We show the efficiency of the method through experiments using seriously distorted images of 2-D curved objects with occlusions.

A novel channel assignment scheme in DS-CDMA cellular systems is proposed, which overcomes the handoff interruptions of delay sensitive services by increasing the probability that soft handoff occurs in handoff for them. For that purpose, the priority of using the frequency channels served by all of cells is given to delay sensitive services over delay insensitive ones.

This paper describes a chip set architecture and its implementation for programmable MPEG2 MP@ML (main profile at main level) video encoder. The chip set features a functional partitioning architecture based on the MPEG2 layer structure. Using this partitioning scheme, an optimized system configuration with double bus structure is proposed. In addition, a hybrid architecture with dual video-oriented on-chip RISC processors and dedicated hardware and a hierarchical pipeline scheme covering all layers are newly introduced to realize flexibility. Also, effective motion estimation is achieved by a scalable solution for high picture quality. Adopting these features, three kinds of VLSI have been developed using 0. 5 micron double metal CMOS technology. The chip set consists of a controller-LSI (C-LSI), a macroblock level pixel processor-LSI (P-LSI) and a motion estimation-LSI (ME-LSI). The chip set combined with synchronous DRAMs (SDRAM) supports all the layer processing including rate-control and realizes real-time encoding for ITU-R-601 resolution video (720480 pixels at 30 frames/s) with glue less logic. The exhaustive motion estimation capability is scalable up to 63. 5 and 15. 5 in the horizontal and vertical directions respectively. This chip set solution realizes a low cost MPEG2 video encoder system with excellent video quality on a single PC extension board. The evaluation system and application development environment is also introduced.

Presently, mobile robots are navigated by means of a number of methods, using navigating systems such as the sonar-sensing system or the visual-sensing system. These systems each have their strengths and weaknesses. For example, although the visual system enables a rich input of data from the surrounding environment, allowing an accurate perception of the area, processing of the images invariably takes time. The sonar system, on the other hand, though quicker in response, is limited in terms of quality, accuracy and range of data. Therefore, any navigation methods that involves only any one system as the primary source for navigation, will result in the incompetency of the robot to navigate efficiently in a foreign, slightly-more-complicated-than-usual surrounding. Of course, this is not acceptable if robots are to work harmoniously with humans in a normal office/laboratory environment. Thus, to fully utilise the strengths of both the sonar and visual sensing systems, this paper proposes a fusion of navigating methods involving both the sonar and visual systems as primary sources to produce a fast, efficient and reliable obstacle-avoiding and navigating system. Furthermore, to further enhance a better perception of the surroundings and to improve the navigation capabilities of the mobile robot, active sensing modules are also included. The result is an active sensor fusion system for the collision avoiding behaviour of mobile robots. This behaviour can then be incorporated into other purposive behaviours (eg. Goal Seeking, Path Finding, etc. ). The validity of this system is also shown in real robot experiments.

We have developed and fabricated an LSI called the FMPP-VQ64. The LSI is a memory-based shared-bus SIMD parallel processor containing 64 PEs, intended for low bit-rate image compression using vector quantization. It accelerates the nearest neighbor search (NNS) during vector quantization. The computation time does not depend on the number of code vectors. The FMPP-VQ64 performs 53,000 NNSs per second, while its power dissipation is 20 mW. It can be applied to the mobile telecommunication system.

An algorithm for modular division which is suitable for VLSI implementation is proposed. It is based on the plus-minus algorithm which is a modification of the binary method for calculating the greatest common divisor (GCD). The plus-minus algorithm for calculating GCD is extended for performing modular division. A modular division is carried out through iteration of simple operations, such as shifts and addition/subtractions. A redundant binary representation is employed so that addition/subtractions are performed without carry propagation. A modular divider based on the algorithm has a linear array structure with a bit-slice feature and carries out an n-bit modular division in O(n) clock cycles, where the length of clock cycle is constant independent of n.

The asymptotic behavior of the recurrence time with fidelity criterion is discussed. Let X= be a source and Y= a database. For a Δ>0 and an integer l>0 define (Y,X,Δ) as the minimum integer N satisfying dl(,) Δ subject to a fidelity criterion dl. In this paper the following two i. i. d. cases are considered: (A) Xi P and Yi Q, where P and Q are probability distributions on a finite alphabet, and (B) Xi N(0,1) and Yi N(0,1). In case (A) it is proved that (1/l)log2(Y,X,Δ) almost surely converges to a certain constant determined by P, Q and Δ as l. The Kac's lemma plays an important role in the proof on the convergence. In case (B) it is shown that there is a quantity related to (1/l)log2 (Y,X,Δ) that converges to the rate-distortion bound in almost sure sense.

This paper presents experimental results obtained in indoor broad-band transmission experiments using a QPSK-100 Mbps modem in the 37 GHz band. Transmission performance is measured at many antenna locations in an office. The zone coverage, defined points where as the BER was less than 10-7, was derived in order to evaluate the possibility of high-speed transmission. It was found that adjusting the receiving antenna position a few centimeters greatly improves the zone coverage in utilizing millimeter waves. This result indicates the effectiveness in improving zone coverage of space diversity reception with an antenna spacing of several centimeters. Experimental results obtained show that zone coverage of up to 70% in the measured range is achieved by space diversity reception. Thus, the feasibility of 100 Mbps indoor wireless transmission, conventionally thought to be impossible, is experimentally confirmed.

Unfolding originally introduced by McMillan is gaining ground as a partial-order based method for the verification of concurrent systems without state space explosion. However, it can be exposed to redundancy which may increase its size exponentially. So far, there have been trials to reduce such redundancy resulting from conflicts by improving McMillan's cut-off criterion. In this paper, we show that concurrency is also another cause of redundancy in unfolding, and present an algorithm to reduce such redundancy in live, bounded and reversible Petri nets which is independent of any cut-off algorithm.

A system combining multicarrier modulation and adaptive modulation in which a suitable level of quadrature amplitude modulation (QAM) is selected for each subcarrier and time-slot, is proposed for high-bit-rate and high-quality digital land mobile communications. The advantages of the system are a mode in which information cannot be transmitted under adverse propagation conditions and a buffer memory to limit a transmission delay time. If the allowable delay time is small, such as in voice and video transmissions, the system tends to have a poor bit error rate (BER) because of the forcible QAM-level selection. Our new selection scheme improves the BER for small transmission delay time. Suitable distribution of the delay time among subcarriers is obtained by using the scheme where the QAM-level of each subcarrier is chosen collectively using the number of data bits stored in memory. Computer simulation of the systems BER performance showed that the system could provide a noticeable BER improvement over frequency-selective fading channels as well as flat Rayleigh fading channels. The QAM-level selection scheme was also effective for a low maximum Doppler frequency and a small memory size. The system could thus attain about 25-fold improvement in BER at Es/N030 dB compared to the multicarrier/16QAM system. It also attained about 60-fold and 3. 5-fold improvement in BER at fd=10Hz compared with the system with multicarrier/16QAM and without the QAM-level selection scheme, respectively.

We propose Direct Sequence CDMA with Optical Multicarriers and Parallel Forward Error Correcting (PFEC) coding technique. Proposed DS-CDMA with OPTICAL MULTICARRIERS, is new in lightwave systems and its alliance with PARALLEL FEC codes, makes it further unique. Optical multicarriers approach is effective to increase throughput by combating dispersion and ISI (Intersymbol Interference), whereas FEC is effective to increase reliability by diluting interactions among optical multicarriers. Till now, both the techniques in lightwave systems have been discouraged. The former because of the wandering effect of optical multicarriers owing to unstability of laser diodes and later because it involves insertion of parity bits that changes data rate and results in insertion distortion that is not desirable in optical systems. To avoid change due to spreading code we also propose to take spreading code equal to serial to parallel converted streams. It bounds initial data (before S/P conversion) to data per carrier (after S/P conversion and spreading) on one hand and relaxes the requirement of high speed electronics on the other. The alliance of optical multicarriers with suitably applied FEC that we refer as Parallel FEC (PFEC) is effective as the beneficial aspects of each mitigate the shortcomings of the other and make the system practicable. Theoretical treatment confirms that the proposed approach is fundamentally sound and holds the potential for promising network performance.

RZ signal transmission in an anomalous region with periodic dispersion compensation is examined by a straight-line experiment in terms of the compensation ratio, the signal power, and the pulse width. The optimum condition enables single-channel 20-Gbit/s RZ signal and two-WDM-channel 20-Gbit/s signals (40-Gbit/s in total) to be transmitted over 5,520 km and 2,160 km, respectively. Numerical simulations with the assistance of a basic theory enables analysis of the experimental results. It is shown that the balance between the waveform distortion and the remaining Gordon-Haus jitter determines the optimum conditions to achieve the longest transmission distance. Excess dispersion compensation results in waveform distortion, while insufficient compensation causes a greater amount of remaining jitter. Moreover, spectrum deformation during propagation is experimentally and numerically clarified to have a large effect on the transmission performance, especially for WDM transmission.

In this paper, we give a new approach to the computation of primary decomposition and associated prime components of a zero-dimensional polynomial ideal (f1,f2,. . . ,fn), where fi are multivariate polynomials on Z (the ring of integer). Over the past several years, a considerable number of studies have been made on the computation of primary decomposition of a zero-dimensional polynomial ideal. Many algorithms to compute primary decomposition are proposed. Most of the algorithms recently proposed are based on Groebner basis. However, the computation of Groebner basis can be very expensive to perform. Some computations are even impossible because of the physical limitation of memory in a computer. On the other hand, recent advance in numerical methods such as homotopy method made access to the zeros of a polynomial system relatively easy. Hence, instead of Groebner basis, we use the zeros of a given ideal to compute primary decomposition and associated prime components. More specifically, given a zero-dimensional ideal, we use LLL reduction algorithm by Lenstra et al. to determine the integer coefficients of irreducible polynomials in the ideal. It is shown that primary decomposition and associated prime components of the ideal can be computed, provided the zeros of the ideal are computed with enough accuracy. A numerical experiment is given to show effectiveness of our algorithm.

In indoor optical channels, intersymbol interference (ISI) due to multipath propagation prevents high data rate transmission. In this paper, a new Optical Multi-Wavelength Modulation technique has been investigated for improving the quality of transmission. In this technique, parallel transmission is used, which lowers the data rate per channel and thus reduces the effects of ISI. Furthermore, parallel coding is used in predetermined parallel branches, so that coding can correct errors without changing the system data rate. Simulation results show that a combination of these methods can achieve high quality transmission without reduction of the total data rate.

Many Ziv-Lempel algorithms have a similar property, that is, slow encoding and fast decoding. This paper proposes a simple improved Ziv-Lempel algorithm to encode a large amount of data quickly as well as compactly by using multiple-processor system.

A simple circuit structure implementing digital-to-analog data conversion function is presented. The proposed digital-to-analog converter utilizes the inherent characters of single-electron tunneling which consist of the periodic voltage oscillation and the ability of counting the number of trapped charges. It produces an analog output voltage for a given digital input. We proposed the device structure performing the weighted summation of inputs, which is converted into an analog voltage by the proposed sensing circuit. Monte Carlo simulation results give us the clear performance of the 3-bit digital-to-analog conversion function and the effect of temperature, capacitance variations, and background charge fluctuations. Moreover, we examined the possibility of extending a N-bit digital-to-analog converter with the proposed scheme.

In this paper, Wavelength Division Multiple access (WDM) ring is proposed for interconnection in workstation clusters or parallel machines. This network consists of ring connected routers each of which selectively passes signals addressed in some particular wavelengths. Other wavelengths are once converted to electric signals, and re-transmitted being addressed in different wavelengths. Wavelengths are assigned to divisors of the number of nodes in the system. Using the regular WDM ring with imaginary nodes, the diameter and average distance are reduced even if the number of nodes has few divisors. It provides better diameter and average distance than that of the uni-directional torus. Although the diameter and average distance is worse than that of ShuffleNet, the physical structure of the WDM ring is simple and the available number of nodes is flexible.