Although a lot of works for location management in wireless networks have been reported in the literature, most of the works have been focused on designing per-user-based strategies. This means that they can achieve the performance enhancement only for a certain class of mobile users with a specific range of CMR (call-to-mobility ratio). However, these per-user-based strategies can actually degrade the performance if a user's CMR changes significantly. Therefore, an efficient uniform location management strategy, which can be commonly applied to all mobile users regardless of their CMR, is proposed and analyzed in this paper. The motivation behind the proposed strategy is to exploit the concepts of the two well-known existing strategies: the location caching strategy and the local anchor strategy. That is, the location caching strategy exploits locality in a user's calling pattern, whereas the local anchor strategy exploits locality in a user's mobility pattern. By exploiting these characteristics of both strategies together with the profile management at the HLR (home location register), the proposed strategy can reduce the frequent access to the HLR, and thus effectively results in significant reduction in terms of the total location management cost. The analytical results also demonstrate that the proposed strategy can be uniformly applied to all mobile users, while always maintaining the performance gain over the IS-41 standard regardless of a user's CMR and the network traffic conditions.

We propose and experimentally demonstrate an all-optical broadband wavelength conversion scheme with simultaneous power amplification based on a pump-modulated fiber optic parametric amplifier (FOPA). All-optical tunable wavelength conversion from one to two wavelengths was achieved with ≥13 dB extinction ratio and <2.7-dB power penalty, accompanied by a high (≥37 dB) and flat ( 3 dB variation) FOPA gain spectrum over 47 nm.

A system which employs a stylus as an input device is suitable for creative activities like writing and painting. However, such a system does not always provide the user with a GUI that is easy to operate using the stylus. In addition, system usability is diminished because the stylus is not always integrated into the system in a way that takes into consideration the features of a pen. The purpose of our research is to improve the usability of a system which uses a stylus as an input device. We propose shortcut actions, which are interaction techniques for operation with a stylus that are controlled through a user's hand motions made in the air. We developed the Context Sensitive Stylus as a device to implement the shortcut actions. The Context Sensitive Stylus consists of an accelerometer and a conventional stylus. We also developed application programs to which we applied the shortcut actions; e.g., a drawing tool, a scroll supporting tool, and so on. Results from our evaluation of the shortcut actions indicate that users can concentrate better on their work when using the shortcut actions than when using conventional menu operations.

We propose a new methodology of DOA (direction of arrival) estimation named SPIRE (Stepwise Phase dIfference REstoration) that is able to estimate sound source directions even if there is more than one source in a reverberant environment. DOA estimation in reverberant environments is difficult because the variance of the direction of an estimated sound source increases in reverberant environments. Therefore, we want the distance between microphones to be long. However, because of the spatial aliasing problem, the distance cannot be longer than half the wavelength of the maximum frequency of a source. DOA estimation performance of SPIRE is not limited by the spatial aliasing problem. The major feature of SPIRE is restoration of the phase difference of a microphone pair (M1) by using the phase difference of another microphone pair (M2) under the condition that the distance between the M1 microphones is longer than the distance between the M2 microphones. This restoration process enables the reduction of the variance of an estimated sound source direction and can alleviates the spatial aliasing problem that occurs with the M1 phase difference using direction estimation of the M2 microphones. The experimental results in a reverberant environment (reverberation time = about 300 ms) indicate that even when there are multiple sources, the proposed method can estimate the source direction more accurately than conventional methods. In addition, DOA estimation performance of SPIRE with the array length 0.2 m is shown to be almost equivalent to that of GCC-PHAT with the array length 0.5 m. SPIRE can executes DOA estimation with a smaller microphone array than GCC-PHAT. From the viewpoint of the hardware size and coherence problem, the array length is required to be as small as possible. This feature of SPIRE is preferable.

A new elliptic-function bandpass filter (BPF) is proposed, which utilizes an inter-digital coupled line (IDCPL) as a left-handed transmission line. The IDCPL is employed in order to realize a negative coupling between non-adjacent resonators in a wideband BPF. As the authors' knowledge, the left-handed operations of the IDCPL has rarely utilized before, although the IDCPL itself has been widely used in many microwave circuits without being paid attention to the left-handed operations. Measured characteristics of two BPFs are presented in this paper, one is targeted for 3-4 GHz WiMAX systems, and the other is for 3-5 GHz ultra wideband communication systems (UWB).

This paper proposes an asymmetric traffic accommodation scheme using a multihop transmission technique for CDMA/FDD cellular communication systems. The proposed scheme exploits the multihop transmission to downlink packet transmissions, which require the large transmission power at their single-hop transmissions, in order to increase the downlink capacity. In these multihop transmissions, vacant uplink band is used for the transmissions from relay stations to destination mobile stations, and this leads more capacity enhancement in the downlink communications. The relay route selection method and power control method for the multihop transmissions are also investigated in the proposed scheme. The proposed scheme is evaluated by computer simulation and the results show that the proposed scheme can achieve better system performance.

In this paper we show some new look at large deviation theorems from the viewpoint of the information-spectrum (IS) methods, which has been first exploited in information theory, and also demonstrate a new basic formula for the large deviation rate function in general, which is expressed as a pair of the lower and upper IS rate functions. In particular, we are interested in establishing the general large deviation rate functions that are derivable as the Fenchel-Legendre transform of the cumulant generating function. The final goal is to show, under some mild condition, a necessary and sufficient condition for the IS rate function to be derivable as the Fenchel-Legendre transform of the cumulant generating function, i.e., to be a rate function of Gartner-Ellis type.

Luby et al. derived evolution of degree distributions in residual graphs for irregular LDPC code ensembles. Evolution of degree distributions in residual graphs is important characteristic which is used for finite-length analysis of the expected block and bit error probability over the binary erasure channel. In this paper, we derive detailed evolution of degree distributions in residual graphs for irregular LDPC code ensembles with joint degree distributions.

Wireless ad hoc communications such as ad hoc networks have been attracting researchers' attention. They are expected to become a key technology for "ubiquitous" networking because of the ability to configure wireless links by nodes autonomously, without any centralized control facilities. Adaptive array antennas (AAA) have been expected to improve the network efficiency by taking advantage of its adaptive beamforming capability. However, it should be noted that AAA is not almighty. Its interference cancellation capability is limited by the degree-of-freedom (DOF) and the angular resolution as a function of the number of element antennas. Application of AAA without attending to these problems can degrade the efficiency of the network. Let us consider wireless ad hoc communication as a target application for AAA, taking advantage of AAA's interference cancellation capability. The low DOF and insufficient resolution will be crucial problems compared to other wireless systems, since there is no centralized facility to control the nodes to avoid interferences in such systems. A number of interferences might impinge on a node from any direction of arrival (DOA) without any timing control. In this paper, focusing on such limitations of AAA applied in ad hoc communications, we propose a new scheme, Forward Interference Avoidance (FIA), using AAA for ad hoc communications in order to avoid problems caused by the limitation of the AAA capability. It enables nodes to avoid interfering with other nodes so that it increases the number of co-existent wireless links. The performance improvement of ad hoc communications in terms of the number of co-existent links is investigated through computer simulations.

In this paper, two new clustering algorithms based on fuzzy c-means for data with tolerance using kernel functions are proposed. Kernel functions which map the data from the original space into higher dimensional feature space are introduced into the proposed algorithms. Nonlinear boundary of clusters can be easily found by using the kernel functions. First, two clustering algorithms for data with tolerance are introduced. One is based on standard method and the other is on entropy-based one. Second, the tolerance in feature space is discussed taking account into soft margin algorithm in Support Vector Machine. Third, two objective functions in feature space are shown corresponding to two methods, respectively. Fourth, Karush-Kuhn-Tucker conditions of two objective functions are considered, respectively, and these conditions are re-expressed with kernel functions as the representation of an inner product for mapping from the original pattern space into a higher dimensional feature space. Fifth, two iterative algorithms are proposed for the objective functions, respectively. Through some numerical experiments, the proposed algorithms are discussed.

In this paper we compare various parallel preconditioners such as Point-SSOR (Symmetric Successive OverRelaxation), ILU(0) (Incomplete LU) in the Wavefront ordering, ILU(0) in the Multi-color ordering, Multi-Color Block SOR (Successive OverRelaxation), SPAI (SParse Approximate Inverse) and pARMS (Parallel Algebraic Recursive Multilevel Solver) for solving large sparse linear systems arising from two-dimensional PDE (Partial Differential Equation)s on structured grids. Point-SSOR is well-known, and ILU(0) is one of the most popular preconditioner, but it is inherently serial. ILU(0) in the Wavefront ordering maximizes the parallelism in the natural order, but the lengths of the wavefronts are often nonuniform. ILU(0) in the Multi-color ordering is a simple way of achieving a parallelism of the order N, where N is the order of the matrix, but its convergence rate often deteriorates as compared to that of natural ordering. We have chosen the Multi-Color Block SOR preconditioner combined with direct sparse matrix solver, since for the Laplacian matrix the SOR method is known to have a nondeteriorating rate of convergence when used with the Multi-Color ordering. By using block version we expect to minimize the interprocessor communications. SPAI computes the sparse approximate inverse directly by least squares method. Finally, ARMS is a preconditioner recursively exploiting the concept of independent sets and pARMS is the parallel version of ARMS. Experiments were conducted for the Finite Difference and Finite Element discretizations of five two-dimensional PDEs with large meshsizes up to a million on an IBM p595 machine with distributed memory. Our matrices are real positive, i.e., their real parts of the eigenvalues are positive. We have used GMRES(m) as our outer iterative method, so that the convergence of GMRES(m) for our test matrices are mathematically guaranteed. Interprocessor communications were done using MPI (Message Passing Interface) primitives. The results show that in general ILU(0) in the Multi-Color ordering and ILU(0) in the Wavefront ordering outperform the other methods but for symmetric and nearly symmetric 5-point matrices Multi-Color Block SOR gives the best performance, except for a few cases with a small number of processors.

We propose and demonstrate a scheme enhancing the performance of optical access networks with Manchester coded downstream and re-modulated NRZ coded upstream. It is achieved by threshold level control of a limiting amplifier at a receiver, and the minimum sensitivity of upstream is significantly improved for the re-modulation scheme with 5 Gb/s Manchester coded downstream and 2.488 Gb/s NRZ upstream data rates.

A Lyapunov-based recurrent neural networks unified power flow controller (UPFC) is developed for improving transient stability of power systems. First, a simple UPFC dynamical model, composed of a controllable shunt susceptance on the shunt side and an ideal complex transformer on the series side, is utilized to analyze UPFC dynamical characteristics. Secondly, we study the control configuration of the UPFC with two major blocks: the primary control, and the supplementary control. The primary control is implemented by standard PI techniques when the power system is operated in a normal condition. The supplementary control will be effective only when the power system is subjected by large disturbances. We propose a new Lyapunov-based UPFC controller of the classical single-machine-infinite-bus system for damping enhancement. In order to consider more complicated detailed generator models, we also propose a Lyapunov-based adaptive recurrent neural network controller to deal with such model uncertainties. This controller can be treated as neural network approximations of Lyapunov control actions. In addition, this controller also provides online learning ability to adjust the corresponding weights with the back propagation algorithm built in the hidden layer. The proposed control scheme has been tested on two simple power systems. Simulation results demonstrate that the proposed control strategy is very effective for suppressing power swing even under severe system conditions.

In this paper, we shall describe about a fuzzy estimation theory based on the concept of set-valued operators, suitable for available operation of extremely complicated large-scale network systems. Fundamental conditions for availability of system behaviors of such network systems are clarified in a form of β-level fixed point theorem for system of fuzzy-set-valued operators. Here, the proof of this theorem is accomplished in a weak topology introduced into the Banach space.

This paper introduces multiple view geometry under projective projection from four-dimensional space to two-dimensional space which can represent multiple view geometry under the projection of space-time. We show the multifocal tensors defined under space-time projective projection can be derived from non-rigid object motions viewed from multiple cameras with arbitrary translational motions, and they are practical for generating images of non-rigid object motions viewed from cameras with arbitrary translational motions. The method is tested in real image sequences.

Let M(y) be a matrix whose entries are polynomial in y, λ(y) and v(y) be a set of eigenvalue and eigenvector of M(y). Then, λ(y) and v(y) are algebraic functions of y, and λ(y) and v(y) have their power series expansionsλ(y) = β0 + β1 y + + βk yk + (βj C),(1) v(y) = γ0 + γ1 y + + γk yk + (γj Cn), (2)provided that y=0 is not a singular point of λ(y) or v(y). Several algorithms are already proposed to compute the above power series expansions using Newton's method (the algorithm in [4]) or the Hensel construction (the algorithm in[5],[12]). The algorithms proposed so far compute high degree coefficients βk and γk, using lower degree coefficients βj and γj (j=0,1,,k-1). Thus with floating point arithmetic, the numerical errors in the coefficients can accumulate as index k increases. This can cause serious deterioration of the numerical accuracy of high degree coefficients βk and γk, and we need to check the accuracy. In this paper, we assume that given matrix M(y) does not have multiple eigenvalues at y=0 (this implies that y=0 is not singular point of λ(y) or v(y)), and presents an algorithm to estimate the accuracy of the computed power series βi,γj in (1) and (2). The estimation process employs the idea in [9] which computes a coefficient of a power series with Cauchy's integral formula and numerical integrations. We present an efficient implementation of the algorithm that utilizes Newton's method. We also present a modification of Newton's method to speed up the procedure, introducing tuning parameter p. Numerical experiments of the paper indicates that we can enhance the performance of the algorithm by 1216%, choosing the optimal tuning parameter p.

An all-optical phase multiplexing scheme for phase-modulated signals is proposed and experimentally demonstrated using four-wave mixing (FWM) in a highly-nonlinear fiber (HNLF). Two 10-Gb/s π/2-shifted differential phase-shift keying (DPSK) wavelength-division multiplexing (WDM) signals are experimentally demonstrated to be converted and phase-multiplexed into a 20-Gb/s differential quadrature phase-shift keying (DQPSK) signal with non-return-to-zero (NRZ) and return-to-zero (RZ) formats, respectively. Experimental results show that, due to phase-modulation-depth doubling effect and phase multiplexing effect in the FWM process, a DQPSK signal is successfully generated through the proposed all-optical phase multiplexing with improved receiver sensitivity and spectral efficiency.

The least-squares linear filtering and fixed-point smoothing problems of uncertainly observed signals are considered when the signal and the observation additive noise are correlated at any sampling time. Recursive algorithms, based on an innovation approach, are proposed without requiring the knowledge of the state-space model generating the signal, but only the autocovariance and crosscovariance functions of the signal and the observation white noise, as well as the probability that the signal exists in the observations.

AlN/GaN Metal Insulator Semiconductor Field Effect Transistors (MISFETs) were designed, simulated and fabricated. DC, S-parameter and power measurements were also performed. Drift-diffusion simulations using DESSIS compared AlN/GaN MISFETs and Al32Ga68N/GaN Heterostructure FETs (HFETs) with the same geometries. The simulation results show the advantages of AlN/GaN MISFETs in terms of higher saturation current, lower gate leakage and higher transconductance than AlGaN/GaN HFETs. First results from fabricated AlN/GaN devices with 1 µm gate length and 200 µm gate width showed a maximum drain current density of 380 mA/mm and a peak extrinsic transconductance of 85 mS/mm. S-parameter measurements showed that current-gain cutoff frequency (fT) and maximum oscillation frequency (fmax) were 5.85 GHz and 10.57 GHz, respectively. Power characteristics were measured at 2 GHz and showed output power density of 850 mW/mm with 23.8% PAE at VDS = 15 V. To the authors knowledge this is the first report of a systematic study of AlN/GaN MISFETs addressing their physical modeling and experimental high-frequency characteristics including the power performance.

Scalar multiplication methods using the Frobenius maps are known for efficient methods to speed up (hyper)elliptic curve cryptosystems. However, those methods are not efficient for the cryptosystems constructed on fields of small extension degrees due to costs of the field operations. Iijima et al. showed that one can use certain automorphisms on the quadratic twists of elliptic curves for fast scalar multiplications without the drawback of the Frobenius maps. This paper shows an extension of the automorphisms on the Jacobians of hyperelliptic curves of arbitrary genus.