With the dramatic rise in the number of Internet users, the expansion of international corporate activity and the arrival of multimedia services, highly-competitive information and communication services are entering a period of severe global change. There is widespread recognition that as these changes take place, it is important to establish operation and management (O&M) that will enable "seamless" end-to-end communication services between any points on the earth. With worldwide trends moving toward automation, the study of automation of O&M is being energetically pursued. This paper describes the requirements for service O&M and gives an overview of the technology believed to be essential to achieve them. The progress of developments is also reported.

This paper presents a character recognition method based on a dynamic model, which can be applied to character patterns from both on-line and off-line input. Other similar attempts simply treat on-line patterns as off-line input, while this method makes use of the on-line input's characteristics by representing the time information of handwriting in the character pattern representations. Experiments were carried out on the Hiragana character set. Without non-linear normalization, this method achieved recognition rates of 92.3% for on-line input and 89.1% for off-line input. When non-linear normalization is used, there is an increase in performance for both types of input with on-line input achieving 94.5% and off-line input achieving 94.1%. The reason for the difference in the effectiveness of non-linear normalization on off-line and on-line patterns could be that while the method used for off-line input was an established and proved one, we used our own initial attempt at non-linear normalization for the on-line patterns. If the same level of effectiveness of non-linear normalization as off-line input is achieved on the on-line input, however, the recognition rate for on-line input again improves becoming 96.3%. Since only one standard pattern was used per category for the dictionary patterns, the above results show the promise of this method. This result shows the compatibility of this method to both on-line and off-line input, as well as its effective use of on-line input's characteristics. The effectiveness of this use of the time information is shown by using an actual example. The data also shows the need for a method of non-linear normalization which is more suitable for on-line input.

The use of selective oxidation to fabricate vertical-cavity surface-emitting lasers is described. The nativeoxide impacts the device design in two ways, the first being in the introduction of an intracavity dielectric aperture that laterally confines the mode, and the second in the formation of high contrast dielectric Bragg reflectors to shorten the effective cavity length. To date the more important has been the indexconfinement, with record low threshold currents, threshold voltages, and power conversion efficiencies being reported from several groups. However, future designs will likely also benefit from the reduced diffraction loss for a small mode size that is possible with high contrast native oxide/semiconductor mirrors. We describe some of the most important design issues in obtaining ultralow threshold operation.

In the measurement of actual random phenomenon, the observed data often contain the fuzziness due to the existence of confidence limitation in measuring instruments, permissible error in experimental data, some practical simplification of evaluation procedure and a quantized error in digitized observation. In this study, by introducing the well-known fuzzy theory, a state estimation method based on the above fuzzy observations is theoretically proposed through an establishment of wide sense digital filter under the actual situation of existence of the background noise in close connection of the inverse problem. The validity and effectiveness of the proposed method are experimentally confirmed by applying it to the actual fuzzy data observed in an acoustic environment.

A Time-Division Multiplexed (TDM) Hierarchical Switching System (HSS), proposed by Eng and Acampora [5], provides any size of bandwidth for a number of subscribers by allocating proper number of time-slots in a frame. In this paper, we present a binary time-slot assignment (TSA) algorithm by which a proper size of time-slots in the frame are allocated to each subscriber so as to meet its bandwidth requests. The time complexity of the proposed algorithm is O(NLlog2 L) in which N is the number of input/output links of the central switch and L is the number of time-slots allotted to each link in the frame. As the authors know, the most efficient algorithm proposed in the literature has time complexity of O(min(L, M2)min(N, M)M2), in which M is the number of subscribers that is larger than N in TDM/HSS system. To give a clear idea of relative efficiency between two algorithms, let us give a typical situation of M = L = O(N2). In this configuration our algorithm makes a significant improvement in time complexity by the order of O(M2/log2M).

We study state feedback control of discrete event systems described by the Golaszewski-Ramadge model. We derive a necessary and sufficient condition for the existence of a balanced state feedback controller under partial observations.

We frequently use a polynomial to approximate a complex function. This study shows a method which determines the optimum coefficients and the number of terms of the polynomial, and the error of the polynomial is estimated.

Topological sorting is, given with a directed acyclic graph G = (V, E), to find a total ordering of the vertices such that if (u, v) E then u is ordered before v. Instead of finding total orderings, we wish to find out how many total orderings exist in a given directed acyclic graph G = (V, E). Here we call a total ordering as legal sequence and the problem as legal sequence number problem. In this paper, we first propose theorems on equivalent transformation of graphs with respect to legal sequence number. Then we give a formula to calculate legal sequence number of basic series-parallel digraphs and a way of the calculation for general series-parallel digraphs. Finally we apply our results to show how to obtain legal sequence number for a class of extended series-parallel digraphs.

A brief overview is done to the development of the fiber-optic technology. These recent topics, not the commonly established techniques, are described connecting with the developments of the basic concepts and the expected applications. Some of these newly introduced ideas will become the seeds for the future development of the fiber-optic technology. These seeds include the very deep understanding of the fiber material, new concepts for the fiber characteristics, the brandnew fiber-optic devices and the fiber-optic systems and the applications.

In this paper, we propose a handoff scheme with two-level priority for the reservation of handoff request calls in mobile cellular radio systems. We assume two types of mobile subscribers with different distributions of moving speed, that is, users with low average moving speed (e.g., pedestrians) and high average moving speed (e.g., people in moving cars). A fixed number of channels in each cell are reserved exclusively for handoff request calls. Out of these number of channels, some are reserved exclusively for the high speed handoff request calls. The remaining channels are shared by both the originating and handoff request calls. In the proposed scheme, both kinds of handoff request calls make their own queues. The system is modeled by a three-dimensional Markov chain. We apply the Successive Over-Relaxation (SOR) method to obtain the equilibrium state probabilities. Blocking probabilities of calls, forced termination probabilities and average queue length of handoff calls of each type are evaluated. We can make the forced termination probabilities of handoff request calls smaller than the blocking probability of originating calls. Moreover, we can make the forced termination probability of high speed handoff request calls smaller than that of the low speed ones. Necessary queue size for the two kinds of handoff request calls are also estimated.

Petrify is a tool for (1) manipulating concurrent specifications and (2) synthesis and optimization of asynchronous control circuits. Given a Petri Net (PN), a Signal Transition Graph (STG), or a Transition System (TS) it (1) generates another PN or STG which is simpler than the original description and (2) produces an optimized net-list of an asynchronous controller in the target gate library while preserving the specified input-output behavior. An ability of back-annotating to the specification level helps the designer to control the design process. For transforming a specification petrify performs a token flow analysis of the initial PN and produces a transition system (TS). In the initial TS, all transitions with the same label are considered as one event. The TS is then transformed and transitions relabeled to fulfill the conditions required to obtain a safe irredundant PN. For synthesis of an asynchronous circuit petrify performs state assignment by solving the Complete State Coding problem. State assignment is coupled with logic minimization and speed-independent technology mapping to a target library. The final net-list is guaranteed to be speed-independent, i.e., hazard-free under any distribution of gate delays and multiple input changes satisfying the initial specification. The tool has been used for synthesis of PNs and PNs composition, synthesis and re-synthesis of asynchronous controllers and can be also applied in areas related with the analysis of concurrent programs. This paper provides an overview of petrify and the theory behind its main functions.

We propose two multipriority reservation protocols for wavelength division multiplexing (WDM) networks. The network architecture is a single-hop with control channel-based passive star topology. Each station is equipped with two pairs of laser and filter. One pair of laser and filter is always tuned to wavelength λ0 for control and the other pair of laser and filter can be tuned to any of data wavelengths, λ1, λ2, ..., λN. According to the access methods of the control channel, one protocol is called slotted ALOHA-based protocol and the other protocol is called TDM-based protocol. The two protocols have the following properties. First, each of them has its own priority control scheme which easily accommodates multipriority traffics. Second, they can be employed in the network with limited channels, i.e. the number of stations in the system is not restricted by the number of data channels. Third, they are conflict-free protocols. By using a reservation scheme and a distributed arbitration algorithm, channel collision and destination conflict can be avoided. For the performance point of view, the TDM-based protocol gives an optimal solution for the priority control. However it is less scalable than the slotted ALOHA-based protocol. The slotted ALOHA-based protocol also performs good priority control even though it is not an optimal solution. We analyze their performances using a discrete time Markov model and verify the results by simulation.

This paper presents severl radio resource scheduling algorithms which aim to provide best-effort service for non-real-time unit-oriented, or message traffic. The objective of resource scheduling algorithm is to distribute radio resources between competing message traffic sources while attaining throughput as high and fair as possible for each source without any explicit quality-of-service (QoS) guarantee. Computer simulations are carried out to evaluate the performance in terms of the average of allocation plus transfer delay, the average of throughput, the variance of throughput, and the usage of resources. The message-size distributions of homepages in World-Wide-Web and e-mails obtained by actual measurement are used. Message size-based resource scheduling algorithms are found to provide high and fair throughput as well as efficient use of the resources.

A leaky-bucket-with-gate algorithm is proposed to control connection-setup congestion in telecommunication networks providing multimedia services, in place of the call-gapping algorithm used in telephone networks. Multimedia services may use more than one connection simultaneously, while standard telephone services use only one connection at a time. A set of connections used to construct a multimedia service is called a correlated connection group, and the setup requests of such a group form correlated request group. A correlated request group is assumed to be accepted into the network only when all the connection-setup requests for the group are accepted. In this paper, the proposed leaky-bucket-with-gate algorithm, a pure leaky-bucket algorithm, and a call-gapping algorithm are evaluated by simulating traffic with a mix of correlated and uncorrelated connection-setup requests, which models setup requests for video conferencing and telephone services. The simulation results show that the proposed algorithm accepts correlated request groups more efficiently than the pure leaky-bucket and call-gapping algorithms under the simulated traffic conditions, except when the interarrival time in a correlated request group is longer than the acceptance interval. We also present queueing analysis for determining the control parameters in the proposed algorithm. Implementation of this algorithm will facilitate the handling of both setup request traffic for correlated connection groups and for uncorrelated connections in multimedia networks.

A new GSM data protocol called high speed circuit switched data (HSCSD) have been developed by European Telecommunications Standards Institute (ETSI) for high speed file transfer and mobile video applications. HSCSD increases data rate by using multiple TDMA time slots (up to 8) instead of one time slot in the current GSM implementation. The problem of multiple time slot assignment is that blocking rate of the system will increase. This problem can be solved by flexible resource assignment where the service specifies the maximum and the minimum capacity. Based on the current available capacity of a base station, a user will be assigned any rate between the maximum and the minimum capacities. This article describes HSCSD protocol and presents four radio resource allocation strategies for HSCSD: always allocates maximum, always allocates minimum, allocates maximum unless available resources are not enough, and allocates resources according to the current blocking statistics of the base station. A simulation model is proposed to investigate the performance of these algorithms. The blocking probability, the call completion probability, and the quality of service are used to evaluate the effects of algorithms in different system behaviors.

Fiber physical contact (FPC) is proposed and demonstrated as a new method designed to enable fibers to be connected easily with a small structure while maintaining high optical performance. FPC is performed by mating two bare optical fibers in a micro sleeve and fixing them to a holder while they are buckled. Buckling is a phenomenon whereby a long column is bent by compression along its length. PC connection is realized by the buckling force of the fibers themselves and does not require any springs. Optical fiber buckling is studied both theoretically and experimentally. The buckling force, which is determined by an initial span between the optical fiber holding points, remains constant when the span is changed and is useful as the PC force. The buckling amplitude which is determined by the span reduction must be so small that it does not cause excess radiation loss. A suitable span is about 7 mm. This generates a 0.7 N. The allowed span reduction is 0.1 mm. This results in a buckling amplitude of 0.64 mm which prevents radiation losses of above 0.1 dB for 1.31 µm light. Based on a study of fiber buckling, we demonstrate the optical performance for FPC connection with a 0.126 mm diameter micro sleeve in which optical fibers are mated and with polished fiber end faces. The insertion loss is under 0.3 dB and the average return loss is 50 dB for 1.31 µm light. These values are stable in the 20 to 70 temperature range. We confirm that FPC connection realizes high optical performance with a small simple structure.

Photovoltaic devices capable of generating more than 200 volts with an area of 1 cm2 have been developed for directly driving microactuators such as piezoelectric or electrostatic actuators. The micro-devices interconnect 285 micro cells (unit cell size: about 0.5 mm 2.0 mm) in series, and have an open circuit voltage (Voc) of 207 volts, a short circuit current (Isc) of 36.6 µA, a maximum output power (Pmax) of 4.65 mW and a fill factor (F.F.) of 0.615 under AM (Air Mass) 1.5 and 100 mW/cm2 illumination. This voltage is the highest in the world for the area of 1 cm2. The series connection is precisely processed by a focused laser beam, thereby significantly reducing the area needed for device connections. It has been confirmed that a piezoelectric polymer can be directly driven by the electrical output in evaluating the potential of the devices to be used as a microactuator's power source.

Significant traffic variations occur in telecommunication networks. This paper focuses on hour-to-hour traffic variations during 24 hours and investigates the possibility of using idle periods effectively by introducing non-realtime service at a discount rate. In order to provide non-realtime service, memory is placed at each telecom center. When immediate service is not available, messages of non-realtime calls are stored in the memory and served later when network resources are available. Realtime calls are served with preference. A basic model and a method of dimensioning the memory capacity are presented. The basic model is extended to the network model, and methods of designing a minimum cost network and pricing and profit issues are presented. The results for a basic model are verified by traffic simulation. Numerical examples are given to show the effectiveness of non-realtime service.

In a conventional client-server system using the satellite communications, the responsibility of the system to the client user is considerably degraded by the long transmission time between the satellite and the ground terminal as well as the relatively low data transmission rate in comparison with the ground transmission line as the Ethernet. In this paper, a new client-server control, VEEC, is proposed to solve the problem. As a result of the experimental performance studies, it is clarified that the responsibility in the client is remarkably improved when the pre-fetching mechanism of VEEC works efficiently.

We have developed an easily-assembled optical coupling device which consists of two multifiber array connectors and a single-mode planar waveguide chip whose ends are passively positioned in novel plastic plug components compatible with the multifiber array connectors. The assembled 18 splitter device exhibits a low exess loss of 0.8 dB.