This paper presents a heuristic floorplanning method that improves the method proposed by Vijayan and Tsay. It is based on tentative insertion of constraints, that intentionally produces redundant constraints to make it possible to search in a wide range of solution space. The proposed method can reduce the total area of blocks with the removal and insertion of constraints on the critical path in both horizontal and vertical constraint graphs. Experimental results for MCNC benchmarks showed that the quality of solutions of the proposed method is better than [7],[8] by about 15% on average, and even for the large number of blocks, the proposed method keeps the high quality of solutions.

The statistical properties of insertion losses and return losses for optical connectors are investigated theoretically using the probability theory and the Monte Carlo simulation. Our investigation is focused on an orientation method for reducing insertion loss by which a fiber-core center is adjusted in a region of within a certain angle to the positioning key direction. It is demonstrated that the method can significantly improve insertion losses, and that an adjusting operation angle of 90 degrees is sufficient to realize an insertion loss of less than 0.5 dB with 99% cumulative probability. Good agreement was obtained between the theoretical distribution and the experimental results for single-mode fiber connection. Consequently, it is indicated that the statistical distributions of insertion losses and return losses of optical connectors in the field can be predicted theoretically from the values measured in the factory by connection to a master connector.

When we design a human interface of a computer-mediated communication (CMC) system, it is important to take a socio-behavioral approach for understanding the nature of the human communication. From this point of view, we conducted experimental observations and post-experimental questionnaires to investigate communicative characteristics in a teleconference using Fujitsu Habitat" visual telecommunication software. We experimentally held the following three kinds of small-group conferences consisting of five geographically distributed participants: (a) teleconference using a visual telecommunication system (Fujitsu Habitat"), (b) teleconference using a real-time keyboard telecommunication system of NIFTY-Serve and (c) live face to face physical conference. Analyses were made on (1) effects of the media on utterance behaviors of conference members, and (2) satisfaction of conference members with communicative functions of the media. Satisfaction was measured by a seven-level rating scale. We found that participants in a telconference held by using Habitat showed significant differences in contents of utterances and the rating of satisfaction with nine communicative functions compared with those of conferences held by using a real-time keyboard telecommunication system and a live face-to-face conference. These results suggest some features that could facilitate multi-participant on-line electronic conferences and conversations.

A new rate-controlled queueing discipline, called virtual rate-based queueing (VRBQ), is proposed for packet-switching nodes in connection-oriented, high-speed, wide-area networks. The VRBQ discipline is based on the virtual rate which has a value between the average and peak transmission rates. By choosing appropriate virtual rates, various requirements can be met regarding the performance and quality of services in integrated-service networks. As the worst-case performance guarantee, we determine the upper bounds of queueing delay when VRBQ is combined with an admission control mechanism, i.e., Dynamic Time Windows or Leaky Bucket. Simulation results demonstrate the fairness policy of VRBQ in comparison with other queueing disciplines, and the performance of sources controlled under different virtual rates.

This paper compares three typical system-sharing configurations for FTTH networks that provide narrowband and video distribution services and proposes a remote node locating strategy for each configuration. Two new evaluation factors, required land space and service provisioning effort, are included in the calculation, in addition to facility cost and maintenance effort. By considering these factors together, the total network cost is calculated and the sensitivity to the number of remote nodes is evaluated. Finally, the most economical system-sharing configuration is identified on the basis of the evaluations for two typical service areas in Japan, for both present and future cost environments.

We discuss ISDB (Integrated Services Digital Broadcasting) which has a transport structure to meet the technical requirements such as the flexibility and the extensibility of broadcasting in the future. The basic configuration of the ISDB transmission signal for distribution into various transmission channels is shown. Hybrid multiplexing, which uses common fixed-length packets and structured transmission units called "slots," is introduced to construct a transmission signal for low-cost signal processing in ISDB receivers. We show that a fixed packet length of 40-240 bytes results in high transmission efficiency in a diverse range of service arrangements. Furthermore, we use transmission control methods, which show the relationship between programs and packet IDs, to select the desired program with certainty and ease.

This paper first proposes an object-oriented service network model, which is composed of application, server and resource object groups, from both viewpoints of rapid and smooth introduction and effective execution of the next generation IN services. The paper also, proposes a testbed system, which is referred to as "To-be-IN (Testbed on Object-oriented and B-ISDN Environment for IN)", for evaluating network architecture based on the proposed model. Using the testbed, several technical issues can be solved such as object-oriented realization of IN services, a provision of distribution transparent environment and a transition strategy from today's IN network. The testbed system is constructed on a currently available computing environment in which a distribution transparency mechanism is added. This system provides Service Creation Environment (SCE) for a purpose of achieving seamless software transfer from a development phase to an operation phase in the object-oriented service network model. The paper finally summarizes some results of an experimental implementation of the system.

Coupling optics for a monolithic array LD module has been developed. High efficient and small sized confocal optics with aspheric lenses based on hyperbolic surfaces has been designed to achieve the uniformity of coupling loss. A small sized (7.2 cc) 4 channel array LD module with this optics was fabricated. This module has low (4.2 dB) and uniform (0.5 dB) coupling loss.

The propagation characteristics of dielectric waveguides with slanted grating structure are analyzed by using the combination of the improved Fourier series expansion method and the approximated multilayer method. The slanted grating region is appoximated by a structure with stratified thin modulated index layers. This method is effective to the guiding problems of the planar slanted grating, because the electromagnetic fields in each layer can be expressed by shifting the phase of the solution in the first layer. In this paper, numerical results are given for the grating with the rectangular and the sinusoidal profile for arbitrary slant angle. The radiation efficiencies for the grating with negative and positive slant angle are also discussed.

We propose and demonstrate an excellent linearly frequency-swept laser diode (LD) for sensing system utilizing frequency-moduleted continuous-wave (FMCW) technique. In order to linearly sweep the optical frequency, we adopt a reference interferometer and an electric phase comparator. The interference beat signal of the reference interferometer is phase-compared with an external reference rectangular signal having a fixed frequency near the interference beat signal frequency by a lock-in amplifier. The error signal from the lock-in amplifier is fed back to the modulating signal of the injection current of the LD. Thus, a phase-locked loop composed of optical and electric circuits can be established, and the beat signal frequency is locked to the frequency of the reference signal. The optical frequency of the LD is, therefore, excellently linearly swept in time. In order to experimentally confirm the linearlity of the proposed method, we apply this light source to the FMCW reflectometry. Resultingly, the improvement of the linearity is estimated to be about 10 dB. And the theoretically limited spatial resolution of the FMCW reflectometry is achieved.

There has been an increasing demand for telecommunication services that satisfy individual users' requirements such as personal telecommunication services and intelligent network services. This demand for advanced telecommunications services is having a great impact on the control architecture and mechanism. In this paper, we propose a new representation of processing power for telecommunications services, using TPS (Transaction Per Second), instead of BHCA, which has been the most commonly used parameter for conventional telephone networks. In developing an IN benchmark, telecommunications services are compared with the TPC-A (Transaction Processing Performance Council-A) benchmark model based on TPS. This benchmark is then used to estimate the requirements for processing power, which, in turn, indicate the necessity for a distributed control. A layered architecture, compatible architecture, and control mechanism for user services are employed to adapt to the distributed network environment.

A stepwise refinement method of communications service specifications is proposed to generate communications software that can conform to any network architecture. This method uses a two-layered language; one layer is a service specification description language (STR), and the other layer is a supplementary specification description language for implementing STR description on a communications system (STR/D). STR specifies terminal behaviors that can be recognized from a perspective outside of the communications systems. With STR, a communications service is defined by a set of rules that can be described without detailed knowledge of communications systems or communications network architectures. Each STR rule describes a global state transition of terminals. Supplementary specifications, such as terminal control and network control, are needed to implement communications services specified by STR rules. These supplementary specifications are described by STR/D rules. Communications services, such as UPT (Universal Personal Telecommunication), are standardized so that they can be provided on a given functional model consisting of functional entities. Specifications for each functional entity in a network are obtained from the two kinds of initially described specifications mentioned above. The obtained specifications are described by STR(L) and STR/D(L) rules, which specify local specifications of a functional entity. These specifications for functional entities are then transformed into software specifications, and finally communications software is generated from these software specifications. This stepwise refinement method makes it possible to generate communications software that can conform to any functional model from service specifications.

In this paper, we propose the architecture of BALANCE (Better Adaptive Load-balancing through Acquiring kNowledge of Characteristic of an Environment) in which users can submit their jobs without acquiring either a status of an environment or characteristics of jobs and servers even in a widely connected heterogeneous network. The architecture of BALANCE includes three types of information bases and two types of daemons. Information bases, namely job, resource, and environment information base, manage the knowledge of job characteristics, available resources for CPUs, and status of the environment, respectively, as a proxy for users. The dispatching daemon selects an adequate server for each job using knowledge stored in the information bases. A service daemon executes each job. On completing each job, a service daemon gets a statistic of the job and returns it to the dispatching daemon where the job came from so that the statistic will be available at the next dispatching time. BALANCE enables an environment (1) to balance the load, (2) to share software functions as well as hardware facilities, and (3) to learn a user's job characteristics. We have implemented a prototype with more than 50 heterogeneous UNIX workstations connected by different networks. Two simple experiments on this prototype are presented. These experiments show a load balancing scheme that takes the characteristics of each job into account.

We introduce a procedure to determine the discrete Fourier spectra of the band-limited function from its irregularly distributed samples. The nonuniform data of the signal are represented by the non-orthogonal basis functions (non-harmonic Fourier functions) and discrete Fourier spectra of the signal. We construct a set of orthonormal basis functions from the above mentioned non-orthogonal basis functions using the Gram-Schmidt procedure. Based on the G-S procedure and the property of the orthogonalization, the spectral components of signal can be obtained by the conjugate transpose of orthonormal basis functions, their coefficients matrix and the nonuniform samples. Thus the desired signal can be obtained by the inverse Fourier transform of the determined discrete Fourier spectra. We apply this algorithm to reconstruct a band-limited low-pass and band-pass signal and show that our method provide more stable and better reconstruction than the matrix inversion method.

With the arrival of B-ISDN, widespread usage of multicast services such as TV broadcasting and video 900 services will increase the possibility of network congestion unless efficient multiple destination routing (MDR) algorithms are used. Current MDR algorithms using link cost based on bandwidth usage or distance to compute the minimum cost routing tree do not take into account the vast amount of information collected by intelligent network (IN) databases. In this paper, we propose a multicast routing algorithm which modifies the way the cost is calculated by using the predicted traffic statistics collected by IN databases. We also show that the traffic handling characteristics vastly improved over conventional MDR algorithms.

Recognizable series is a model of a sequential machine. A recognizable series S is represented by a triple (λ,µ,γ), called a linear representation of S, where λ is a row vector of dimension n specifying the initial state, γ is a column vector of dimension n specifying the output at a state, and µ is a morphism from input words to nn matrices specifying the state transition. The output for an input word w is defined as λ(µw) γ, called the coefficient of w in S, and written as (S,w). We present an algorithm which constructs a reduced linear representation of an unknown recognizable series S, with coefficients in a commutative field, using coefficient queries and equivalence queries. The answer to a coefficient query, with a word w, is the coefficient (S, w) of w in S. When one asks an equivalence query with a linear representation (λ,µ,γ), if (λ,µ,γ) is a linear representation of S, yes is returned, and otherwise a word c such that λ (µc) γ(S, c) and the coefficient (S, c) are returned: Such a word c is called a counterexample for the query. For each execution step of the algorithm, the execution time consumed from the initial step to the current step is O(mN 4M), where N is the dimension of a reduced linear representation of S, M is the maximum time consumed by a single fundamental operation (addition, subtraction, multiplication or division), and m is the maximum length of counterexamples as answers to equivalence queries returned until that step.

Experimental optical gain characteristics of an erbium-doped fiber amplifier have not been explained well by conventional laser schemes in the case of two-channel amplification. Modified simple laser schemes including cross relaxation among degenerate levels were valid for the explanation of the optical gain dependence on input signal power and on the erbium-doped fiber length.

A modified deformable model is presented for constructing bijective topology preserving feature maps. The algorithm can solve the optimization problem in the input space as well as that in the output space. A saturating distance function alternative to the Euclid norm is employed to obtain compact space filling maps.

A design of a high power laser structure is presented which is based on an increase of the cavity length as well as a maximization of the stripe width. This requires a low value for the modal attenuation coefficent and a low optical confinement factor. A model is presented from which the modal gain, the confinement factor, the active region thickness, the stripe width, the length and the reflection coefficients can be calculated. A variant for all design parameters needed to reach 1 W emission in the fundamental lateral mode is given. These values are used to design the epitaxial structure.

To provide personal, intelligent, and multimedia services through a mobile communications network, a Mobile Service Control Point (M-SCP) was developed, which performs both the location register and service control functions. The M-SCP was constructed on a common platform to allow quick introduction of new services. Software techniques to reduce the frequency of process-switching, assign the highest priority to real-time tasks, and operate a multiple-CPU structure provide faster real-time processing. This is confirmed by computer simulation and research in the field.