One of the important challenges in the design of ATM networks is how to provide quality-of-service (QoS) while maintaining high network resource utilization. In this paper, we discuss the role of real-time traffic characterization in QoS control for ATM networks and review several approaches to the problem of resource allocation. We then describe a particular framework for QoS control in which real-time measurements of a connection stream are used to determine appropriate parameters for usage parameter control (UPC). Connection admission control (CAC) is based on the characterization of the aggregate stream in terms of the individual stream UPC descriptors, together with real-time measurements.

In this paper an algorithm of Connection Admission Control in ATM is considered. It is shown that it works under many different kinds of dependence among arrivals, including long range dependence. This point is relevant, since recent papers show that ATM traffic is characterised by self-similarity, and hence by long range dependence. An upper bound for CLR is given, without assuming any specific cell arrival process. Applications to simulated and real data (obtained by segmenting and shaping Ethernet packets) are considered. They show the goodness and the tightness of the considered upper bound.

Bursts from a number of variable bit rate sources allocated to a virtual path with a given capacity can inundate the channel. Buffers used to take care of such bursts can fill up rapidly. The buffer size limits its burst handling capability. With large bursts or a number of consecutive bursts, the buffers fill up and this leads to high cell losses. Channel reconfiguration with dynamic allocation of spare capacities is one of the methods used to alleviate such cell losses. In reconfigurable networks, spare capacity allocation can increase the channel rates for short durations, to cope with the excess loads from the bursts. The dynamic capacity allocations are adaptable to the loads and have fast response times. We propose heuristic rules for spare capacity assignments in ATM networks. By monitoring buffer occupancy, triggers which anticipate excess traffic can be used to assign spare capacities to reduce the cell loss probabilities in the network.

Weighted Round Robin (WRR) scheduling is an extension of round robin scheduling. Because of its simplicity and bandwidth guarantee, WRR cell scheduling is commonly used in ATM switches. However, since cells in individual queues are sent cyclically, the delay bounds in WRR scheduling grow as the number of queues increases. Thus, static priority scheduling is often used with WRR to improve the delay bounds of real-time queues. In this paper, we show that the burstiness generated in the network is an even greater factor affecting the degradation of delay bounds. In ATM switches with per-class queueing, a number of connections are multiplexed into one class-queue. The multiplexed traffic will have a burstiness even if each connection has no burstiness, and when the multiplexed traffic is separated at the down stream switches, the separated traffic will have a burstiness even if the multiplexed traffic has been shaped in the upstream switches. In this paper, we propose a new WRR scheme, namely, WRR with Save and Borrow (WRR/SB), that helps improving the delay bound performance of WRR by taking into account the burstiness generated in the network. We analyze these cell scheduling methods to discuss their delay characteristics. Through some numerical examples, we show that delay bounds in WRR are mainly dominated by the burstiness of input traffic and, thus WRR/SP, which is a combination of WRR and static priority scheduling, is less effective in improving delay bounds. We show that WRR/SB can provide better delay bounds than WRR and that it can achieve the same target delay bound with a smaller extra bandwidth, while large extra bandwidth must be allocated for WRR.

The classical max-min policy has been suggested by the ATM Forum to support the available bit rate (ABR) service class. However, there are several drawbacks in adopting the max-min rate allocation policy. In particular, the max-min policy is not able to support the minimum cell rate (MCR) requirement and the peak cell rate (PCR) constraint for each ABR connection. Furthermore, the max-min policy does not offer flexible options for network providers wishing to establish a usage-based pricing criterion. In this paper, we present a generic weight-based rate allocation policy, which generalizes the classical max-min policy by supporting the MCR/PCR for each connection. Our rate allocation policy offers a flexible usage-based pricing strategy to network providers. A centralized algorithm is presented to compute network-wide bandwidth allocation to achieve this policy. Furthermore, a simple switch algorithm using ABR flow control protocol is developed with the aim of achieving our rate allocation policy in a distributed networking environment. The effectiveness of our distributed algorithm in a local area environment is substantiated by simulation results based on the benchmark network configurations suggested by the ATM Forum.

This paper presents a finite buffer M/G/1 queue with two classes of customers who are served by a combination of head-of-the-line priority and buffer reservation schemes. This combination gives each class of customers high or low priorities in terms of both delay and loss. The scheme is analyzed for the model in which one class of customers has high priorities over the other class of customers with respect to both delay and loss. First, steady-state joint probability distribution of the number of each class of customers in the buffer and remaining service time is derived by a supplementary variable method. Second, loss probability and mean waiting time for each class of customers are provided using this probability distribution. Finally, a combination of head-of-the-line priority and buffer reservation schemes is numerically compared with other buffer management schemes in terms of admissible offered load to show its effectiveness under differing QoS requirements.

In the future, more and more network providers will be established through the introduction of an open telecommunications market. At this time, it is necessary to guarantee the fair competition between these network providers. In this paper, a negotiation protocol for connection establishment is proposed. This negotiation protocol is based on the concept of open, competitive bidding and can guarantee fair competition between the network providers. In this negotiation protocol, each network providers objective is to maximize its profit. Conversely, each users objective is to select a network provider which will supply as much capacity as required. Employing this negotiation protocol, the users and the network providers can select each other based on their objectives. In this paper, adaptation strategies which network providers and users can adopt under the proposed negotiation protocol framework are also discussed. A network provider which adopts this strategy can obtain enough profit even when the number of connection requests is small relative to the idle bandwidth capacity. Moreover, a user who adopts this strategy can be sure to obtain bandwidth even when the idle bandwidth capacity is small relative to the number of connection requests.

This paper presents an efficient bandwidth allocation method for the two-layer video coding of different spatial resolution. We first find a model of distortion-bitrate relationship for the MPEG-2 spatial scalable coding in a fixed total bitrate system. Then we propose an adaptive bitrate allocation method for a constant distortion ratio between two layers with the given total bandwidth. In the proposed method, approximated model parameters are used for simple implementation. The validity of the approximation is proven in terms of the convergence to the desired distortion ratio. It is shown by simulation that the proposed bitrate allocation method can keep almost a constant distortion ratio between two layers in comparison to a fixed bitrate allocation method.

Huet and Levy showed that index reduction is a normalizing strategy for every orthogonal strongly sequential term rewriting system. Toyama extended this result to root balanced joinable strongly sequential systems. In this paper, we present a class including all root balanced joinable strongly sequential systems and show that index reduction is normalizing for this class. We also propose a class of left-linear (possibly overlapping) NV-sequential systems having a normalizing strategy.

By reserving transmission capacity on a series of links from one node to another, making a virtual path connection (VPC) between these nodes, several benefits are obtained. VPCs will simplify routing at transit nodes, connection admission control, and QoS management by traffic segregation. As telecommunications traffics experience variations in the number of calls per time unit due to office hours, inaccurate forecasting, quick changes in traffic loads, and changes in the types of traffic (as in introduction of new services), there is a need to cope for this by adaptive capacity reallocation between different VPCs. We have developed a type of local VPC capacity management policy that uses an allocation function to determine the needed capacity for the coming updating interval, based on the current number of active connections. We suggest an allocation function that is independent of the actual traffic, and determine its optimal parameters and the optimal updating interval for different overhead costs. The local approach is shown to be able to combine benefits from both VP and VC routing by fast capacity reallocations. The method of signaling is easy to implement and evaluations indicate that the method is robust.

This paper describes the design concept and characteristics of a power supply for optical network units in Fiber To The Home (FTTH) systems. Powering architectures of local powering, network powering and power hub powering are compared in terms of cost and maintainability. A local powering architecture is selected for an ONU power supply because it is the most cost-effective overall compared with the others. The local power supply is mainly composed of a rectifier, DC-DC converters, a ringer, and batteries. A battery deterioration test function is important for the local power supply because battery lifetime varies depending on ambient temperature, discharge history, and charging conditions, and it is shorter than other electrical components used in ONU. Supplying power using alternative batteries is also necessary because the capacity of batteries installed in the power supply is limited. These functions and electrical characteristics are checked using an experimental power supply with Ni-Cd batteries.

This paper describes two attacks against blind decryption (decode) based on the commutative random-self reducibility and RSA systems utilizing the transformability of digital signatures proposed in [2]. The transformable digital signature was introduced in [2],[8] for defeating an oracle attack, where the decrypter could be abused as an oracle to release useful information for an attacker acting as a requester of blind decryption. It was believed in [2],[8] that the correctness of a query to an oracle was ensured by the transformable signature derived from an original signature issued by the decrypter in advance, and a malicious query to an oracle could be detected before the blind decryption by the decrypter or would lead to release no useful information to an attacker. The first attack can decrypt all encrypted data with one access to an oracle. The second one generates a valid signature for an arbitrary message selected by an attacker abusing the validation check procedure.

This paper studies the ambiguity reduction ability of a probabilistic context-free grammar. We theoretically analyze a common behavior of any probabilistic context-free grammar. Moreover, we confirm by experiments that a probabilistic context-free grammar learnt from Japanese corpus has the ambiguity reduction ability as expected by the theoretical analysis.

A new type of fiber Fabry-Perot interferometer buried in a fiber connector housing was proposed. The transmission spectra revealed double peaks due to birefringence in the fiber and the peak separation showed a temperature dependence as large as -7. 7 MHz/deg, which was 2 orders of magnitude larger than that estimated from the thermal characteristics of its component materials.

Two types of hetero-epitaxial PbZr0. 48Ti0. 52O3 (PZT) capacitors were fabricated by pulsed laser deposition (PLD). One has an Au/PZT/SrRuO3(SRO)/SrTiO3(STO) structure with remanent polarization (Pr) of 32. 1 µC/cm2. The other has an Au/PZT/La-doped STO (La: STO) structure with Pr of 9. 6 to 13. 5 µC/cm2. X-ray diffraction patterns show that only the (00l) planes of the PZT and SRO are parallel to the substrate surface for the PZT/SRO/STO structure, however, a (111) plane of the PZT is observed, in addition to the (00l) planes, for the PZT/La: STO structure. High resolution-transmission electron microscope (HR-TEM) images show that the PZT/SRO interface is clean and coherent. However, spherical shape contrast with radius about 5 nm is observed at the PZT/La: STO interface. Diffusion of La and/or the contaminated surface of the La: STO substrate is thought to cause the differences in the PZT orientations and the interfaces, affecting the electrical characteristics of the capacitors.

We prepared alkoxide solutions to fabricate SrBi2Ta2O9 (SBT) ferroelectric capacitors with IrO2 electrodes. In this process, to minimize excess bismuth, the Sr : Bi : Ta mole ratio was kept at 0. 9 : 2. 1 : 2. 0, i. e. , nearly stoichiometric. Three types of solution - mixed-only (MIX), complexed (COMP), and hydrolyzed (HYD) - were used. The HYD capacitor had low absolute leakage current, 10-7 A/cm2 order, and good saturation properties to 6 V. When voltage was applied to each capacitor at 2 to 6 V, MIX and COMP capacitors showed only partial hysteresis loops due to a high leakage current, reflecting the I-V characteristics. These results are probably due to film density caused by metaloxane network bonding. A fatigue endurance test was conducted using cycling of polarization switching at 6 V using the HYD capacitor with IrO2 electrodes. Slight changes were, however, observed in hysteresis loop configuration, but good hysteresis properties were kept up to 1. 04 1012 cycles. We compared SBT ferroelectric thin films fabricated with Pt electrodes and with IrO2 electrodes. Scarcely any difference due to SBT in the XRD pattern was seen, depending on the substrate material. We found that the use of IrO2 electrodes had the effect of decreasing the crystallization temperature. On Pt and IrO2 electrodes, the two films have surface morphology quite different from that of the rod-like structure wellknown for SBT films prepared using a metal 2-ethylhexanate solution. Their surfaces show a similar morphology with relatively large, closely packed grains. A comparison of the I-V characteristics after reannealing showed that the capacitor with IrO2 electrodes had a higher leakage current than that with Pt electrodes. The leakage current was probably due to the density of the film and interface between the SBT film and electrodes.

Pb(ZrxTi1-x)O3 (PZT) thin films were prepared on various electrodes. When Ir system materials were used as electrodes, fatigue properties of PZT thin films were improved. Moreover, in the case of the PZT thin film on an Ir/IrO2 electrode, not only fatigue but imprint properties were clearly improved. We could find these improvements were caused by good barrier effect of IrO2 from secondary ion mass spectroscopy (SIMS) analysis. By applying these Ir system electrodes, we fabricated stacked capacitors on polycrystalline silicon (poly-Si) plugs. In spite of high temperature thermal processing, we found poly-Si plugs were ohmically connected with the bottom electrodes of the capacitors from hysteresis measurements and I-V characteristics, and could greatly expect them for practical use.

The crystallization process of Sr0. 7Bi2. 3Ta2O9 (SBT) ferroelectric thin films with different crystal orientations formed by chemical liquid deposition using an alkoxide precursor was investigated. One film showed strong c-axis orientation (a-type film), while another shows scarcely any c-axis orientation (b-type film). We report that the crystallization process was the same even when crystal orientation differed. Thin films first change from amorphous to fluorite fine grains; the fluorite grains then change to bismuth layer-structure grains. The different orientation of the SBT films is not caused by different crystallization process. Both SBT films with different crystal orientations consist of fine fluorite grains after 650 heat-treatment. Their leakage current density characteristics differ, however. The leakage current density of the a-type film was independent of the electric field, and showed a low value of 10-8 A/cm2. The leakage current density of the b-type film, however, was dependent on the electric field, and increased continuously with the increasing electric field. After 700 heat-treatment, both films consist of large grains with bismuth layer-structure and fine fluorite grains. The matrix of both films contains large grains with bismuth layer-structure that determines the leakage current density characteristics. Since the fluorite grain size after a 700 heat-treatment is the same as that after 650 heat-treatment, nucleation is predominant at the structural phase boundary from amorphous to fluorite. The bismuth layer-structure grains are large and single-crystal grains after both a 700 and 800 heat-treatment. Increased grain size predominates at the structural phase boundary from fluorite to bismuth layer-structure grains. Clearly, ferroelectric SBT films with bismuth layer-structure are crystallized in two steps, each having a different predominant crystal growth mechanism.

An improved numerical computation model is presented to calculate the metal-ferroelectric-semiconductor field effect transistor (MFSFET) characteristics with a sufficiently large gate area which can be applied for large drain voltages. In the presented model, the polarization of the ferroelectric gate insulator is inhomogeneous and treated as a variable along the channel. We have calculated electrical properties of SrBi2Ta2O9/Si MFSFETs and demonstrate that the conventional model, in which the polarization of the ferroelectric gate insulator (Pd) is treated as a constant, overestimate the drain current when the drain voltage is large. In addition, effects of the ratio of remanent polarization to spontaneous polarization (Pr/Ps ratio) of the ferroelectric film on the transistor characteristics are discussed.

We have applied hot-carrier circuit-level simulation to memory peripheral circuits of a few thousand to over 12K transistors using a simple but accurate degradation model for reliability verification of actual memory products. By applying simulation to entire circuits, it was found that the location of maximum degradation depended greatly upon circuit configuration and device technology. A design curve has been developed to quickly relate device-level DC lifetime to circuit-level performance lifetime. Using these results in conjunction with a methodology that has been developed to predict hot-carrier degradation early in the design cycle before TEG fabrication, accurate total-circuit simulation is applied early in the design process, making reliability simulation a crucial design tool rather than a verification tool as technology advances into the deep sub-micron high clock rate regime.