A WDM (Wavelength Division Multiplexing) technology is a new optical technology, providing multiple wavelengths at the rate of 10 Gbps on the fiber. IP (Internet Protocol) over WDM networks where IP packets are directly carried on the WDM network is expected to offer an infrastructure for the next generation Internet. For IP over WDM networks, a WDM protection mechanism is expected to provide a highly reliable network (i.e., robustness against the link/node failures). However, conventional IP also provides a reliability mechanism by its routing function. In this paper, we first formulate an optimization problem for designing IP over WDM networks with protection functionalities of WDM networks, by which we can obtain IP over WDM networks with high reliability. Our formulation results in a mixed integer linear problem (MILP). However, it is known that MILP can be solved only for a small number of variables, in our case, nodes and/or wavelengths. We therefore propose two heuristic algorithms, min-hop-first and largest-traffic-first approaches in order to assign the wavelength for backup lightpath. Our results show that the min-hop-first approach takes fewer wavelengths to construct the reliable network, that is, all of lightpaths can be protected using the WDM protection mechanism. However, our largest-traffic-first approach is also a good choice in the sense that the approach can be saved the traffic volume increased at the IP router by the link failure.

We have proposed and fabricated a new poly-Si TFT employing the selectively doped regions in the active layer. In the proposed poly-Si TFTs, the selectively doped regions where doping concentration is identical to that of the source/drain, reduce the effective channel length during the on-state. Under the off-state, the selectively doped regions may reduce the lateral electric field induced near the drain and reduce the leakage current considerably. The experimental data of the proposed TFT exhibit high on-current, low leakage current and low threshold voltage. The fabrication of the proposed TFT is rather simple; the required steps for the proposed TFT are reduced because high dosage ion-implantation for the source/drain and the selectively doped regions is performed simultaneously prior to excimer laser irradiation step.

In this paper, we propose path accommodation methods for unidirectional rings based on an optical compression time-division multiplexing (OCTDM) technology. We first derive a theoretical lower bound on the numbers of slots and frames, in order to allocate all paths among nodes. Three path accommodation algorithms for the all-optical access are next proposed to achieve the lower bound as closely as possible. Path splitting is next considered to improve the traffic accommodation. Finally, we analyze the packet delay time for given numbers of slots/frames, which are decided by our proposed algorithms. Numerical examples are also shown to examine the effectiveness of our proposed algorithms including path accommodation and path splitting methods.

This work presents a frame-structure, referred to as CATM (CATV ATM), to serve as a wireless network infrastructure. The widespread CATV (Community Antenna TV) networks are attractive infrastructures for next generation wireless networks. Providing interactive broadband services over CATV networks is a major trend in communication and ATM (Asynchronous Transfer Mode) networks with broadband communication features well fitted to be the backbone of CATV networks. Based on the proposed network architecture, this work addresses and investigates the problems of call setup and handoff handling. This work also proposes a wireless signaling protocol for establishing mobile connections over the CATM-based wireless networks. To enhance bandwidth utilization, the proposed scheme attempts to keep the path resulting after handoff as short as possible. The protocol also evolves a seamless handoff scheme (denoted as SHSW-CATM), that can preserve data continuity, is transparent to other mobile terminals, and produces a shorter path. Analytical results reveal that the SHSW-CATM has a high probability of obtaining an optimal path (that is, a non-elongated path) following mobility.

A sufficient condition for a code to be optimum on discrete channels with finite input and output alphabets is given, where being optimum means achieving the minimum decoding error probability. This condition is derived by generalizing the ideas of binary perfect and quasi-perfect codes, which are known to be optimum on the binary symmetric channel. An application of the sufficient condition shows that the code presented by Hamada and Fujiwara (1997) is optimum on the q-ary channel model proposed by Fuja and Heegard (1990), where q is a prime power with some restriction. The channel model is subject to two types of additive errors of (in general) different probabilities.

This paper investigates noise enhancement factors of a zero-forcing detector and a decision feedback detector for synchronous Multiple Input Multiple Output (MIMO) channels. It is first shown that the zero-forcing and decision feedback detectors can be implemented in a vector digital filter form, and the noise enhancement factors with the detectors can easily be calculated by using the vector digital filter form. This paper then applies the zero-forcing and decision feedback detectors to the signal detection of a frequency-overlapped multicarrier signaling (FOMS) system. The normalized noise enhancement factor, which is given as a product of the noise enhancement and bandwidth reduction factors, is shown to be smaller with the decision feedback detector than the zero-forcing detector. Results of computer simulations conducted to evaluate bit error rate (BER) performances with the two detectors are also shown together with the BER performance with a conventional channel-by-channel detector.

Nonlinear behavior of electromagnetic surface waves propagating along a tangentially magnetized ferrite slab is investigated. The nonlinear Schrodinger equation (NLSE) which describes the temporal evolution of the electromagnetic wave pulses has been derived directly from the Maxwell equations and the equation of precessional motion for the magnetization in the ferrite slab with the aid of the reductive perturbation method without magnetostatic approximation. Based on the formula derived, we have numerically evaluated the frequency-dependence of the nonlinear coefficient in the NLSE for both a magnetostatic surface wave mode and a dynamic mode. As a result, we have confirmed the possibility of the propagation of solitons in the waveguide.

Voltage holding property of liquid crystal (LC) cell for long period was investigated and the experimantal results were analyzed using a microscopic model considered the movement of ions in LC layer. The time dependent voltage decay curve observed in the experiment, which is not driven by the analysis with the conventional equivalent circuit comprised of the capacitance and the resistance, can be well explained by the microscopic model.

This paper proposes an optimal design scheme for photonic transport networks that interconnect multiple wavelength division multiplexing (WDM) self-healing ring systems by using optical cross connects (OXCs). To calculate the number of OXCs required in each hub to interconnect these ring systems, a virtual mesh network is generated, on which the route of each optical path (OP) going through multiple adjacent rings ("ring" is defined as circle in network topology) is determined based on a list of hubs. An integer-programming-based design problem is then formulated that minimizes the overall cost of facilities including OXCs as well as ring systems to accommodate a given demand. By solving this problem, we can simultaneously optimize required number of ring systems in each ring, wavelength assignment within each individual bidirectional ring system, required number of OXCs in each hub, and capacity to be allocated to each OP. Numerical examples show that the ring-based network is more cost-effective than the mesh restorable network when the cost of an OADM is lower than that of an OXC, and the OXC-to-fiber cost-coefficient ratio is sufficiently large.

We are interesting in the error exponent for source coding with fidelity criterion. For each fixed distortion level Δ, the maximum attainable error exponent at rate R, as a function of R, is called the reliability function. The minimum rate achieving the given error exponent is called the minimum achievable rate. For memoryless sources with finite alphabet, Marton (1974) gave an expression of the reliability function. The aim of the paper is to derive formulas for the reliability function and the minimum achievable rate for memoryless Gaussian sources.

High-capacity multiwavelength ring networks with bidirectional WDM add/drop multiplexer (WADM) having built-in EDFAs is analyzed and demonstrated. All WDM channels can be added/dropped independently in each direction. The capacity of a bidirectional ring is found to be approximately twice that of an unidirectional ring. An eight-wavelength WADM is demonstrated for a data rate of 10 Gb/s per channel, providing an overall capacity of 80 Gb/s. The performance of the add/drop multiplexer is not degraded by backward backscattering light. The same WADM is also demonstrated to be able to serve as a bidirectional in-line optical amplifier.

We propose an extraction method of personal features based on on-line handwriting information. Most recent research has been focused on signature verification, especially in the field of on-line writer verification. However, signature verification has a serious problem in that it will accept forged handwriting. To solve this problem, we have introduced an on-line writer verification method which uses ordinary characters. In this method, any handwritten characters (i.e., ordinary characters) are accepted as a text in the verification process, and the text used in the verification process can be different from that in the enrollment process. However, in the proposed method, personal features are extracted only from the shape of strokes, and it is still uncertain how efficient other on-line information, such as writing pressure or pen inclination, is for extracting personal features. Therefore, we propose an extraction method of personal features based on on-line handwriting information, including writing-pressure and pen-inclination information. In the proposed method, handwriting information is described by a set of three-dimensional curves, and personal features are described by a set of Fourier descriptors for the three-dimensional curves. We also discuss the reliability of the proposed method with some simulation results using handwritten data. From these simulation results, it is clear that the proposed method effectively extracts personal features from ordinary characters.

Blind channel estimation algorithm which is applicable to the time-variant channel under frequency-selective fading is proposed. The condition on the blind channel identifiability using temporally and spatially oversampled data is shown. The proposed algorithm consists of two stages. At the first stage, the channel equalization matrix is estimated by taking account of the time-variant characteristics of the channel. At the second stage, the signals and the channel matrix are alternately estimated by using the finite alphabet property of the transmitted symbols. Periodical return from the second stage to the first makes the blind estimation algorithm feasible for the time-variant channel with fast fading. The simulation results confirm the fast convergence property and the effectiveness of the proposed algorithm in coping with the frequency-selective fading.

In this paper, we propose a new watermarking method which spreads an ID pattern with specific sequences and embeds it throughout the spatial domain of an image. A set of the sequences is a key for extracting the ID pattern. As an ID pattern is spread throughout an image, we can extract the ID pattern from a part of the image, that is a clipped image. We can also confirm authenticity by extracting the same ID pattern from several parts of an image. The proposed method is robust to StirMark, which is a benchmark tool to test robustness of watermarked images, as well as disturbance by noise addition and common image processing operations such as edge-enhancement, brightness-contrast conversion, posterization, Gauss filtering, median filtering, gamma correction, JPEG compression and clipping.

The interconnect analysis of on- and off-chips is very important in the design of high-speed signal processing, digital communication, and microwave electronic systems. When the interconnects are characterized by sampled data via electromagnetic analysis, the circuit-level simulation of the network requires rational approximation of the sampled data. Since the frequency band of the sampled data is more than 10 GHz, the rational function must fit into it at many frequency points. The rational function is approximated using the orthogonal least-squares method. With an increase in the number of the fitting data, the least-squares method suffers from a singularity problem. To avoid this, the sampled data are hierarchically approximated in this paper. Moreover, to reduce the computational cost of the circuit-level simulation, the parameter matrix of the interconnects is approximated by a rational matrix with one common denominator polynomial, and the selective orthogonalization procedure is presented.

This paper concentrates on the model useful for analyzing the error performance of M-estimators of a single unknown signal parameter: that is the error intensity model. We develop the point process representation for the estimation error, the conditional distribution of the estimator, and the distribution of error candidate point process. Then the error intensity function is defined as the probability density of the estimate and the general form of the error intensity function is derived. We compute the explicit form of the intensity functions based on the local maxima model of the error generating point process. While the methods described in this paper are applicable to any estimation problem with continuous parameters, our main application will be time delay estimation. Specifically, we will consider the case where coherent impulsive interference is involved in addition to the Gaussian noise. Based on numerical simulation results, we compare each of the error intensity model in terms of the accuracy of both error probability and mean squared error (MSE) predictions, and the issue of extendibility to multiple parameter estimation is also discussed.

A novel method for image reconstruction of a microwave hologram synthesized from one-dimensional data is proposed. In the data acquisition, an emitting antenna is shifted along a line. At every position of the emitting antenna, the amplitude and phase of diffraction fields are measured with a detecting antenna along a line perpendicular to the shifted direction. An equivalent two-dimensional diffraction field is synthesized from the one-dimensional data sets. The conventional reconstruction method applied to the one-dimensional configuration was the Fresnel approximation method. In this paper, an equivalent diffraction is introduced in order to obtain better images than the Fresnel approximation. An experiment made at 10 GHz shows the usefulness of the proposed method.

Cellular Digital Packet Data (CDPD) provides wireless data communication services to mobile users by sharing unused RF channels with AMPS on a non-interfering basis. To prevent interference on the voice activities, CDPD makes forced hop to a channel stream when a voice request is about to use the RF channel occupied by the channel stream. The number of forced hops is affected by the voice channel selection policy. We propose analytic models to investigate the CDPD channel holding time for the the least-idle and random voice channel selection policies. Under various system parameters and voice channel selection policies, we provide guidelines to reduce the number of forced hops.

Program slicing is a technique for statically analyzing a program and extracting an executable sub-program, which is called a program slice, from the original program. This technique has been widely applied to program testing, debugging and maintenance. This paper presents a slicing method for extracting program slices from a program that calls library functions, which are provided as object code. The method this paper presents analyzes dependence relationships between library functions using global data that are referred to by the library functions but not explicitly declared in a program. In this method, before slicing a program with respect to a slicing criterion, a Def-Slice-Use table will be generated that stores slice information for each function in the program by slicing these functions in advance, and then the program can be efficiently sliced using this table. The paper also illustrates some examples of program slicing using a program slicer LibSlicer that implements this method.

Natural language interface systems can accept more unrestricted queries from users than other systems, however it is impossible to understand erroneous sentences which include the syntax errors, unknown words and misspelling. In order to realize the superior natural language interface, the automatic error correction for erroneous sentences is one of problems to be solved. The method to apply the LR parsing strategies is one of the famous approaches as the robust error recovery scheme. This method is able to obtain a high correction accuracy, however it takes a great deal of time to parse the sentence, such that it becomes a very important task to improve the time-cost. In this paper, we propose the method to improve the time efficiency, keeping the correction accuracy of the traditional method. This method makes use of a new parsing table that denotes the states to be transited after accepting each symbol. By using this table, the symbol which is allocated just after the error position can be utilized for selecting correction symbols, as a result, the number of candidates produced on the correction process is reduced, and fast system can be realized. The experiment results, using 1,050 sentences including error characters, show that this method can correct error points 69 times faster than the traditional method, also keep the same correction accuracy as the traditional method.