In this paper, a scheme for recoverability of protocols, which have more than one process and can be modelled by communicating finite state machines, is studied. Normal operating states of a protocol are defined as the set of global states that can be reached by executing state transitions in which error events have not occurred. After some error events have occurred, sequences of state transitions enter abnormal operating states. If the protocol is recoverable, then the sequences revert back to a normal operating state. In real recoverable protocols, the sequences often return to a typical normal operating state, that is, an initial state while retaining consistency in the exchange of messages. This paper proposes a new rollback-recovery scheme for recoverable protocols. In this scheme, the sequences can return not only to an initial state but also to an intermediate state which was reached in the past while retaining consistency in the exchange of messages. In addition, protocols can efficiently return to the intermediate state using a broadcast mechanism. The proposed scheme is therefore effective for recoverability of protocols with more than one process. This paper also presents a recovery sequence generation system which has been developed for designing recoverable protocols and some experiments are carried out to show effectiveness of the proposed scheme.

The integer labeling method is a simplicialtype homotopy method for solving systems of nonlinear equations with global convergence. Since this method does not require matrix operations, it is very simple and is suited to parallel computation on array processors. However, the computation time of the integer labeling method grows exponentially with the dimension n, because it uses simplicial subdivision and the number of simplices in an n-dimensional rectangle grows with n!. In this paper, we propose an efficient integer labeling method for solving systems of nonlinear equations with partially-separable mappings. Partially-separable mappings appear in various fields of science and engineering, such as nonlinear programming problems. In our method, the number of function evaluations is largely reduced by making use of the partial separability of nonlinear mappings. That is, function values of separable terms need not be evaluated as long as the labeled simplex is moving within the identical rectangle. Hence, as the number of separable terms increases, considerable improvement of the computational efficiency can be achieved.

In this paper we present a predictor-corrector tracing curve algorithm for analysis of nonlinear circuits. In order to tracing the curves having sharp turning points efficiently, we introduce a norm Σd i/ds as the parameter to control the tracing step size. This parameter more precisely reflects the sharp degree of the turning points on a curve. In addition that, the Hermite polynomial is used for extrapolation in predictor stage, and the Brown iteration method is used to solve the system of equation in corrector stage. The numerical examples show which computational efficiency is greatly improved, so that this algorithm can be used for DC analysis of nonlinear circuits, efficiently.

Diversity combining and error correction coding are powerful means to combat the multipath fading encountered in mobile radio communications. In this paper, we theoretically analyze the joint effects of postdetection diversity combining and convolutional coding with soft decision Viterbi decoding for QDPSK signal transmissions. The union bounding formula is used for average BER performance calculation taking into account the additive white Gaussian noise (AWGN), cochannel interference, and multipath channel delay spread. Symbol puncturing is applied to produce higher rate codes from original 1/2-rate convolutional codes. Numerical calculations are presented for the required average signal energy per bit-to-noise power spectrum density ratio (Eb/No), required average signal-to-interference power ratio (SIR) and tolerable rms delay spread needed to achieve a certain average BER. Spectrum efficiency of cellular systems is also calculated.

High bit rate data transmission in land mobile communication is essential for supporting more convenient and attractive services. For such transmission, however, a means to cope with frequency selective fading is indispensable. This paper surveys recent developments in Japanese adaptive equalizers which effectively compensate for such fading, and introduces its algorithm, parameter optimization, performance, and some technical improvements in adaptive equalizing performance. We also comments on problems to be solved in the future.

This paper demonstrates results of a numerical experiment on bifurcation phenomena in a two-degrees-of-freedom Duffing's type forced oscillatory system. The regions in the parameter plane (amplitude B and angular frequency ν of the external force) are given, in which various phenomena; chaos, hyperchaos, Hopf-bifurcations, doubling of torus, crisis and windows are observed. Existence of chaos and hyperchaos is confirmed by calculating the Lyapunov exponents. Bifurcations from invariant closed curves to chaotic attractors are also considered. For this system, two types of bifurcations from invariant closed curves to chaotic attractors through doubling of torus are observed; in one case, the doubling is interrupted by modelocking, then a chaotic attractor appears suddenly, in another case, the doubling seems to continue infinitely.

The paper clarifies the bifurcation mechanism responsible for a repeated appearance of period-one attractors in an R-L-Diode circuit driven by a sinusoidal voltage source E sin 2πft. Extensive measurements are performed to observe bifurcation diagrams in the f-E parameter space. After several simplifications of the dynamics, exact bifurcation equations are derived and analyzed. A major finding is that all the period-one attractors of our interest belong to the same family in the f-E parameter-space.

A new statistical test has been recently presented for determining whether a binary sequence into which a real-valued sequence to be tested is transformed precisely mimics Bernoulli trials B (p, q) with probabilities of 0 and of 1, p and q, or not. This paper gives a theoretical test based on such a stringent test and shows its usefulness. This method uses the ensemble average technique under the assumption that the pseudorandom-number generator is mixing with respect to an absolutely continuous measure. The existence of such a measure permits us to theoretically calculate the ensemble average of several statistics by using the Perron-Frobenius integral operator. Furthermore, this operator releases us from cumbersome and tedious procedures to calculate multivariate distributions, in connection with several statistical tests. Three kinds of tests, the runs test, poker test, and serial correlation test are presented. The Galerkin approximation to the operator on a suitable functional space is also introduced which provides a finite dimensional matrix (referred to as a Galerkin-approximated matrix of the Perron-Frobenius operator). The largest eigenvalue of the matrix, nearly equal to 1, corresponds to the existence of the measure. Each theoretical value of three tests for B (p, q) shows that the magnitude of the second largest eigenvalue plays an important role in determing randomness of the sequence generated by the generation.

Bifurcations of phase-locked modes for diffusively coupled van der Pol equations are investigated. It is known that in-phase and out-of-phase modes are typically observed in the system if two oscillatory equations are identical. There have been many studies on the behavior of diffusively coupled equations of van der Pol type. Many of these, however, persist in the limits of weakly nonlinearity and weak coupling. In this paper we study global feature of bifurcation sets of the modes under relatively wide range of variation of system parameters: coefficient of nonlinear term, parameter related to the frequency of the uncoupled equations, diffusion coefficient and so on.

In statistical tests, the uniform distribution property is frequently requested. Two well-known procedures are discussed for transforming nonuniform good random sequences into uniform ones. Results of a recently proposed randomness tests are also shown to be invariant under these transformations.

Based on the loss behavior of optical fibers coated with high and low thermal expansion coefficient (α) secondary jackets in the -180 to 20 temperature range, the mechanism of loss increase has been discussed. The low α liquid-crystalline-polyester(LCP)-jacketed fiber shows the microbending loss of 5 dB/km at -180, while the high α nylon-jacketed fiber exhibits the maximum microbending loss of about 30 dB/km at -120 and then shows the decrease in loss with decreasing temperature. The relatively low loss increase in the LCP-jacketed fiber arises from crystallization of the primary silicone and slight eccentricity of the LCP jacket. The unusual loss behavior in the nylon-jacketed fiber can be explained in terms of the arrangement of randomly distributed fiber curvature at -120, which is predicted by Yabuta's fiber-buckling model and supported by the occurrence of fiber-strain relaxation.

This paper describes a new simulation-based design methodology for process and device development of submicron MOS VLSIs. The main purpose of this work is to bridge the gap between simulations and actual experimental data through a transformation of the RSF (Response Surface Function) which determines a quadratic relationship between measured device characteristics and process conditions. To achieve the reliable RSF, we have developed two key techniques: (1) Transformation of variable and response before application of the RSM (Response Surface Method) design by simulations. (2) Improvement of the RSF which is determined by process and device simulations, by using the measured data of MOSFET characteristics. The new design methodology is applied to obtain RSFs having good device threshold voltage and maximum drain current. MOS devices fabricated with an experimental 0.8 µm technology are utilized to verify the results. The device parameters are 11-20 nm for the gate oxide thickness, and 0.8-4.0 µm for the gate length. The averaged RMS errors between the obtained RSF and the experimental data are 0.02 V for the threshold voltage and 1.46 % for the maximum drain current. A quantitative explanation on the effect of the transformation technique is given.

High efficiency amplifier construction techniques are investigated focusing on UHF band transmitting power amplifiers intended for cellular portable telephones and the state of the art amplifiers are presented. First, it is shown that high efficiency amplifiers are indispensable to attain pocket sized portable units through a theoretical analysis using a simple model. When about 1 W of transmitting power is required, it is desirable for the amplifier to operate with an efficiency of over 40%. Secondly, the switching mode scheme is described as the most effective technical means to achieve high amplifier efficiency. State of the art switching mode amplifiers, the Harmonic Reaction Amplifier (HRA) and the Linearized Saturation Amplifier with Bidirectional Control (LSA-BC), are presented as examples of nonlinear and linear amplifiers respectively. Basic operation mechanisms are shown. Experimental HRA and LSA-BC are constructed to determine their practically attainable efficiencies. Power-added efficiencies of 75% and 40% are recorded from a 1.7 GHz band 3 W HRA for CW and a 1.5 GHz band 1 W LSA-BC for π/4 QPSK respectively. These values indicate that these types of amplifier can be applied to pocket sized portable radio units.

A wavelength selective filter using a vertical micro-cavity surface emitting laser is proposed. A 5 µm long GaInAsP/InP micro-cavity with 95% dielectric multilayer reflectors was fabricated. A wavelength bandwidth of less than 10 was obtained at 1.52 µm of operating wavelength. Also, polarization independent filtering characteristics are demonstrated. By introducing an amplification/wavelength-tuning section, a tunable filter with bandwidth of less than 1 is expected.

We show a simple method for the adiabatic elimination, and show a condition on which our method is equivalent to using the Stratonovich stochastic calculus in eliminations.

This paper introduces recent propagation studies on land mobile in Japan. Land mobile communications in Japan are offering various type of services, such as paging, automobile and portable telephones, and cordless phones. These services are rapidly progressing in both capacity and quality at the present time. First, this paper describes the progress of propagation studies supporting the growth of these services. Land mobile radio communications in Japan are now moving in the direction of high capacity, portability and digitalization. In accordance with the progress, this paper describes propagation studies on () high capacity, including radio wave trapping by beam tilting and low height base station antenna, anti-cochannel interference receiving techniques by diversity, and improved prediction accuracy by environmental structure correction factor, () portability, including measurements and prediction results of propagation loss in indoor and outdoor, () digitalization, including multipath delay characteristics in urban and suburban areas, and propagation model to estimate the delay spread. Secondarily, this paper describes propagation study subjects and future propagation approaches to support the expected remarkable expansion of land mobile communications. Propagation studies on land mobile satellite communications systems are also touched upon.

In the following I show how the nonlinear economic dynamics has been developed from the pre-war times to the present. The history of nonlinear economic dynamics may be divided into four broad and somewhat overlapping periods: the 1930's and 1940's, the 1950's, the 1960's and 1970's, and the current period. However, these dates are really just suggestive.

The problem of embedding two-dimensional grids into hypercube parallel computers is the main subject of this work. Two methods (called dilation 1 and dilation 2 embedding) are used to embed a grid and their performances are evaluated. In dilation 1 (d1) embedding a grid edge connecting 2 points is mapped into one hypercube link, and in dilation 2 (d2) embedding there are cases in which one grid edge is mapped into two hypercube links. Generally, this makes the performance of d2 embedding poorer than that of d1 embedding, as communication between some adjacent grid points have to be forwarded through an intermediate link. However, there are cases where d2 embedding allows a more efficient use of the hypercube, as more processors can be used in the embedding. Thus, it is necessary to find out what kind of embedding achieves the best performance. We assume that the number of grid points is larger than the number of processors, and then propose a method to divide the grid in rectangular parts of arbitrary size called fragments, which are actually embedded into a processor. Using the parameters of a commercial hypercube, the performances of several grids embedded under different conditions are evaluated. As a result, the relation between hypercube size and grid size is found to have a strong influence on the choice of the embedding method.

Recently, most of the difficult problems which prevented the realization of soliton communication have been solved by using the so-called erbium-doped optical fiber amplifiers (EDFAs). These amplifiers can provide a larger gain with a lower pumping power than the Raman process. In this paper, we describe how we were able to realize an actual soliton transmission system which utilizes lumped amplifiers instead of distributed amplifiers. A data transmission experiment at 10 Gbit/s 300 km is presented.