Future cellular communication systems will be called upon to provide multimedia services (voice, data, and video) for various user platforms (pedestrians, cars, and trains) that have a variety of mobility characteristics. Knowledge of mobility characteristics is essential for planning, designing and operating communication networks. The position data of selected vehicles (taxis) have been measured by using the Global Positioning System at 1-s intervals. Those data are used for evaluating mobility characteristics, such as probabilistic distributions of speed, cell dwell time, and cell crossover rate of vehicles, assuming that cells are hypothetically laid over the loci of the vehicles. The cell dwell time of vehicles is found to follow a lognormal distribution, rather than a conventionally-presumed negative exponential distribution. When the holding time distribution and random origination of calls along the loci are assumed, the properties of the cell dwell time and the handoff rate of terminals communicating in the hypothetical cellular systems are also estimated from the measured data.

This paper describes a method of predicting transmission performance to be obtained by applying RAKE reception and parallel transmission in realistic urban multipath environments. Delay profiles measured in metropolitan Tokyo at microwave frequencies were used to obtain the impulse responses of radio channels, and the closed-form equations corresponding to the performance of these anti-multipath techniques were derived, by means of the characteristic function method, under the assumption that the phases of the impulse responses are uniformly distributed. Results show that RAKE reception provides bit error rates 100 times lower than bare transmission does, whereas the improvement obtained by using parallel transmission should be especially valuable in broadband communication systems, such as those operating at data rates above 10 Mb/s.

The effect of surface roughness is crucial for contact recording and proximity recording. In this paper a probability model is developed for investigation of the influence of surface roughness on flying performance and the contact force of the slider. Simulations are conducted for both the contact recording slider and the proximity recording slider, and the results are well coordinated with the reported experimental results and the self-conducted experimental results. Studies are further extended to the characterization of the roughness of the air bearing surface and the disk surface that may support head/disk spacing between 5 nm and 15 nm.

We propose a new technique that is able to extract the small-signal equivalent-circuit elements of high electron mobility transistors (HEMTs) without causing any gate degradation. For the determination of extrinsic resistance values, unlike other conventional techniques, the proposed technique does not require an additional relationship for the resistances. For the extraction of extrinsic inductance values, the technique uses the R-estimate, which is known to be more robust relative to the measurement errors than the commonly used least-squares regression. Additionally, we suggest an improved cold HEMT model that seems to be more general than conventional cold HEMT models. With the use of the improved cold HEMT model, the proposed technique extracts the extrinsic resistance and inductance values.

This paper proposes a method to construct smaller binary decision diagrams for characteristic functions (BDDs for CFs). A BDD for CF represents an n-input m-output function, and evaluates all the outputs in O(n+m) time. We derive an upper bound on the number of nodes of the BDD for CF of n-bit adders (adrn). We also compare complexities of BDDs for CFs with those of shared binary decision diagrams (SBDDs) and multi-terminal binary decision diagrams (MTBDDs). Our experimental results show: 1) BDDs for CFs are usually much smaller than MTBDDs; 2) for adrn and for some benchmark circuits, BDDs for CFs are the smallest among the three types of BDDs; and 3) the proposed method often produces smaller BDDs for CFs than an existing method.

Wireless communication systems are affected by several factors in the indoor environment. The complexity of this environment, however, has hampered the development of methods for analyzing it. Reported here is our investigation of the relationship between the propagation characteristics and performance of a 2.4-GHz ISM-band wireless LAN in various indoor environments. Our objective was to develop guidelines for designing ideal indoor environments for wireless LANs. A booth constructed of a ceiling, floor, and wall materials that could be changed was used for our investigation. The transmission loss and delay spread were measured for four environments; they were calculated by using a ray-tracing method to verify the effectiveness of the ray tracing calculation. The throughput and BER characteristics were measured for the same environments. The following results were obtained. (1) The transmission loss and delay spread could be estimated by using this ray tracing method because the deviations between the calculated and measured data were within 5 dB for the transmission loss and within 10 ns for the delay spread. (2) Reflections from the walls caused a serious interference problem: throughput was 0.0 at more than 30% of the positions along the center line of the booth when the walls were constructed of high-reflection-coefficient material. (3) The throughput and BER were closely correlated with the delay spread; the number of positions meeting a certain throughput was estimated by the method based on the delay spread calculated using the ray tracing method. It was within 10% of the number measured. The results obtained can be used to design ideal indoor environments for 2.4-GHz ISM-band LAN systems.

In pattern recognition using neural networks, it is very difficult for researchers or users to design optimal neural network architecture for a specific task. It is possible for any kinds of neural network architectures to obtain a certain measure of recognition ratio. It is, however, difficult to get an optimal neural network architecture for a specific task analytically in the recognition ratio and effectiveness of training. In this paper, an evolutional method of training and designing feedforward neural networks is proposed. In the proposed method, a neural network is defined as one individual and neural networks whose architectures are same as one species. These networks are evaluated by normalized M. S. E. (Mean Square Error) which presents a performance of a network for training patterns. Then, their architectures evolve according to an evolution rule proposed here. Architectures of neural networks, in other words, species, are evaluated by another measurement of criteria compared with the criteria of individuals. The criteria assess the most superior individual in the species and the speed of evolution of the species. The species are increased or decreased in population size according to the criteria. The evolution rule generates a little bit different architectures of neural network from superior species. The proposed method, therefore, can generate variety of architectures of neural networks. The designing and training neural networks which performs simple 3 3 and 4 4 pixels which include vertical, horizontal and oblique lines classifications and Handwritten KATAKANA recognitions are presented. The efficiency of proposed method is also discussed.

The current-voltage characteristics of a single electron transistor (SET) in the resonant transport mode are investigated. In the future when SET devices are applied to integrated electronics, the quantum effect will seriously modify their characteristics in ultra-small geometry. The current will be dominated by the resonant transport through narrow energy levels in the dot. The simple case of a two-level system is analyzed and the transport mechanism is clarified. The transport property at low temperatures (higher than the Kondo temperature) in the low tunneling rate limit is discussed, and a current map where current values are classified in the gate bias-drain bias plane is provided. It was shown that the dynamic aspect of electron flow seriously influences the current value.

Current computing systems are too slow for information processing because of the huge number of procedural steps required. A decrease in the number of calculation steps is essential for real-time information processing. We have developed two kinds of novel architectures for automatic elimination of redundant calculation steps. The first architecture employs the new digit-serial algorithm which eliminates redundant lower digit calculations according to the most-significant-digit-first (MSD-first) digit-serial calculation scheme. Basic components based on this architecture, which employ the redundant number system to limit carry propagation, have been developed. The MSD-first sequential vector quantization processor (VQP) is 3.7 times faster than ordinary digital systems as the result of eliminating redundant lower-bit calculation. The second architecture realizes a decrease in the number of complex calculation steps by excluding useless data before executing the complex calculations according to the characterized value of the data. About 90% of Manhattan-distance (MD) calculations in VQP are excluded by estimating the MD from the average distance.

This paper describes the expanded generalized method of characteristics (GMC) in order to handle large linear interconnect networks. The conventional GMC is applied to modeling each of transmission lines. Therefore, this method is not suitable to deal with large linear networks containing many transmission lines. Here, we propose the expanded GMC method to overcome this problem. This method computes a characteristic impedance and a new propagation function of the large linear networks containing many transmission lines. Furthermore the wave propagation delay is removed from the new wave propagation function using delay evaluation technique. Finally, it is shown that the present method enables the efficient and accurate simulation of the transmission line networks.

It is an important problem in signal processing, system realization and system identification to find linear discrete-time systems which are consistent with given covariance parameters. This problem is formulated as a problem of finding discrete-time positive real functions which interpolate given covariance parameters. Various investigations have yielded several significant solutions to the problem, while there remains an important open problem concerning the McMillan degree. In this paper, we use more general input-output characteristics than covariance parameters and consider finding discrete-time positive real matrix functions which interpolate such characteristics. The input-output characteristics are given by the coefficients of the Taylor series at some complex points in the open unit disk. Thus our problem is a generalization of the interpolation problem of covariance parameters. We reduce the problem to a directional interpolation problem with a constraint and develop the solution by a state-space based new approach. The main results consist of the necessary and sufficient condition for the existence of the discrete-time positive real matrix function which interpolates the given characteristics and has a limited McMillan degree, and a parameterization of all such functions. These are a contribution to the open problem and a generalization of the previous result.

A gate oxide excess current model is described based on the phonon-assisted tunneling process of electrons into neutral traps. The influence on local electric field of charge of electrons trapped by neutral traps in gate oxide is simulated using a two-dimensional device simulator into which the new model is incorporated. FN current is suppressed with an increase in the neutral trap density to over 1019 cm-3. The calculated results reflect the endurance characteristics of flash memories in which erase/write operation speed depends on FN current.

This paper presents an efficient algorithm to compute the characteristic polynomial of a polynomial matrix. We impose the following condition on given polynomial matrix M. Let M0 be the constant part of M, i. e. M0 M ( mod (y,,z)), where y,,z are indeterminates in M. Then, all eigenvalues of M0 must be distinct. In this case, the minimal polynomial of M and the characteristic polynomial of M agree, i. e. the characteristic polynomial f(x,y,,z) | x E M | is the minimal degree (w. r. t. x) polynomial satisfying f(M,y,,z) 0. We use this fact to compute f(x,y,,z). More concretely, we determine the coefficients of f(x,y,,z) little by little with basic matrix operations, which makes the algorithm quite efficient. Numerical experiments are given to compare the algorithm with conventional ones.

This paper proposes a new distortion analysis method for frequency-dependent FET amplifiers, which uses a novel Frequency-Dependent Complex Power Series (FDCPS) model. This model consists of a frequency-independent nonlinear amplifier represented by an odd-order complex power series and frequency-dependent input and output filters. The in-band frequency characteristics of the saturation region are represented by the frequency-dependent output filter, while the in-band frequency characteristics of the linear region are represented by the frequency-dependent input and output filters. In this method, the time-domain analysis is carried out to calculate the frequency-independent nonlinear amplifier characteristics, and the frequency-domain analysis is applied to calculate the frequency-dependent input and output filter characteristics. The third-order intermodulation (IM3) calculated by this method for a GaAs MESFET amplifier is in good agreement with the numerical results obtained by the Harmonic Balance (HB) method. Moreover, the IM3 calculated by this method also agrees well with the measured data for an L-band 3-stage GaAs MESFET amplifier. It is shown that this method is effective for calculating frequency-dependent distortion of a nonlinear amplifier with broadband modulation signals.

We propose an H-plane manifold-type triplexer with closely arranged junctions. Broadband characteristics for each bands are obtained by arranging filters closely near the end of the common waveguide. Three fundamental and sufficient parameters are introduced for numerical optimizations to determine the configuration of the broadband triplexer. The configuration including closely arranged junctions requires an generalized scattering matrix (GS matrix) of an asymmetric cross junction to simulate and design. We expand the mode matching technique (MMT) to be able to analyze this kind of discontinuities by joining two asymmetric steps discontinuities to a symmetric cross junction. This is suitable expressions for numerical calculations. The characteristics of the whole triplexer are obtained by cascading GS matrices of the corresponding discontinuities. The experimental results of the fabricated triplexer were compared with the simulated data, and the results agree well with the simulated one. The characteristics of the fabricated triplexer satisfy the request of the broad band operation and high power-handling capability.

This paper describes the error probability of the second order BAM estimated by a computer simulation and an analytical calculation method. The computer simulation suggests that the iterations to retrieve a library pattern almost converge within four times and the difference between once and twice is much larger than that between twice and four times. The error probability at the output of the second iteration is estimated by the analytical method. The effect of the noise bits is also estimated using the analytical method. The BAM with larger n is more robust for the noise. For example, the noise bits of 0.15n cause almost no degradation of the error probability when n is larger than 100. If the error probability of 10-4 is allowable, the capacity of the second order BAM can be increased by about 40% in the presence of 0.15n noise bits when n is larger than 500.

In this paper we present a complete methodology for efficient electro-mechanical characterization of a CMOS compatible MEMS technology. Using an original test structure, the so-called "U-shape cantilever beam," we are able to determine all mechanical characteristics of force sensors constituted with elementary beams in a given technology. A complete set of electro-mechanical relations for the design of Microsystems have also been developed.

It is confirmed by simulation that SOI-DRAMs can be operated at high speed by using the floating body structures. Several floating body effects are analyzed. It is described that the dynamic retention characteristics are not dominated by capacitive coupling and hole redistribution. And it is described that those characteristics are determined by the leakage current in the small pn-junction region of the floating body. Reducing pn junction leakage current is important for realizing a long retention time. If the pn junction leakage is suppressed to 10-18 A/µm, a dynamic retention time of 520 sec at a VBSG of 0.5 V can be achieved at 27. On those conditions, the refresh current of SOI-DRAMs is reduced by 54% compared with bulk-Si DRAMs.

In this paper, the generalized learning vector quantization (GLVQ) algorithm is applied to design a hand-written Chinese character recognition system. The system proposed herein consists of two modules, feature transformation and recognizer. The feature transformation module is designed to extract discriminative features to enhance the recognition performance. The initial feature transformation matrix is obtained by using Fisher's linear discriminant (FLD) function. A template matching with minimum distance criterion recognizer is used and each character is represented by one reference template. These reference templates and the elements of the feature transformation matrix are trained by using the generalized learning vector quantization algorithm. In the experiments, 540100 (5401 100) hand-written Chinese character samples are used to build the recognition system and the other 540100 (5401 100) samples are used to do the open test. A good performance of 92.18 % accuracy is achieved by proposed system.

Fluctuation characteristics of character centroid intervals in laterally written Japanese sentences are investigated by means of their spatial frequency characteristics. Power spectra of character centroid intervals in their longitudinal and transverse directions are obtained for handwritten and word processor printed sample sentences. It is shown that for fluctuation characteristics in the longitudinal direction, power spectra are inversely proportional to their spatial frequencies for handwritten sentences and proportional to them for word processor printed sentences, and there exists a remarkable difference between handwritten and word processor printed sentences. It is also shown that for fluctuation characteristics in the transverse direction, power spectra are proportional to their spatial frequencies for both handwritten and word processor printed sentences, and there is no remarkable difference between handwritten and word processor printed sentences.