Users of computer communication systems and their requirements are rapidly increasing and changing. It is desirable to have a development method which helps to make small changes in a design of a system to obtain another system which satisfies new requirement changes. We propose a flexible synthesis method which adopts designers' requirement changes in formal protocol specifications designed in LOTOS.

A new method is proposed for generating synchronizable test sequences which can be applied in the distributed test architecture for protocol conformance testing. The method consists of a duplex digraph technique and a rural Chinese postman tour algorithm to generate a minimum-length synchronizable test sequence using distinguishing sequences.

In this paper, the error performance of block coded 8-PSK modulation systems of length 32, designed for unequal error protection (UEP) of messages transmitted over a Rayleigh fading channel, is investigated. Computer simulation are reported showing that, with transmission over a Rayleigh fading channel, a good improvement in coding gain is obtained by the use of a binary linear UEP (LUEP) code as a constituent code in the multilevel construction, compared with conventional block coded modulation (BCM) of the same length.

In bandlimited QPSK and QAM transmission systems, phase jitter occurs in the output of a carrier recovery circuit that uses a fourth-power multiplier. To analyze the phase jitter, an exact expression was derived for the autocorrelation function and power spectral density for the case in which bandlimited Gaussian noise and a QPSK or QAM signal with random modulation and arbitrary waveform are simultaneously applied to the fourth-power multiplier. Using this expression, the rms phase jitter of the recovered carrier in root-cosine-rolloff transmission systems for QPSK, 16QAM, 64QAM and 256QAM was calculated. It was shown that the conventional theories for rectangular waveforms are special cases of our theory.

Firstly we show a usuful property of the fast algorithm for computing linear complexities of p-ary periodic sequences with period pn (p: a prime). Secondly the property is successfully applied to obtain the value distribution of the linear complexity for p-ary periodic sequences with period pn.

The defects in the cold rolled strips have textural characteristics, which are nonuniform due to its irregularities and deformities in geometrical appearance. In order to handle the textural characteristics of images with defects, this paper proposes a surface inspection method based on textural feature extraction using the wavelet transform. The wavelet transform is employed to extract local features from textural images with defects both in the frequency and in the spatial domain. To extract features effectively, an adaptive wavelet packet scheme is developed, in which the optimum number of features are produced automatically through subband coding gain. The energies for all subbands of the optimal quadtree of the adaptive wavelet packet algorithm and four entropy features in the level one LL subband, which correspond to the local features in the spatial domain, are extracted. A neural network is used to classify the defects of these features. Experiments with real image data show good training and generalization performances of the proposed method.

Photonic integrated circuits (PICs) are required for future optical communication systems, because various optical components need to be compactly integrated in one-chip configurations with a small number of optical alignment points. Bandgap energy controlled selective metal organic vapor phase epitaxy (MOVPE) is a breakthrough technique for the fabrication of PICs because this technique enables the simultaneous formation of waveguides for various optical components in one-step growth. Directly formed waveguides on a mask-patterned substrate can be obtained without using conventional mesa-etching of the semiconductor layers. The waveguide width is precisely controlled by the mask pattern. Therefore, high device uniformity and yield are expected. Since we proposed and demonstrated this technique in 1991, various PICs have been reported. Using electroabsorption modulator integrated distributed feedback laser diodes, 2.5 Gb/s-550 km transmission experiments have been successfully conducted. Another advantage of the selective MOVPE technique is the capability to form narrow waveguide layers. We have demonstrated a polarization-insensitive semiconductor optical amplifier that consists of a selectively formed narrow (less than 1 µm wide) bulk active layer. For a four-channel array, a chip gain of more than 20 dB and a gain difference between TE and TM inputs of less than 1 dB were obtained. We have also reported an optical switch matrix and an optical transceiver PIC for access optical networks. By using a low-loss optical waveguide, a 0 dB fiber-to-fiber gain for the 14 switch matrix and 0 dBm fiber output power from the 1.3 µm transceiver PIC were obtained. In this paper, the selective MOVPE technique and its applications to various kinds of PICs are discussed.

An algorithm for extracting fundamental frequencies from duet sounds is proposed. The algorithm is based on an acoustical feature that the temporal fluctuation patterns in frequency an power are similar for harmonic components composing a sound for a single musical note played on a single instrument with a single active vibrating source. The algorithm is applied to the sounds of 153 combinations of pair-notes played by a flute duet and a violin duet. Experimental results show that the zone-wize correct identification rate by pitch name are 98% for the flute duet and 95% for the violin duet in the best cases.

In audio-frequency magnetotelluric surveys, electromagnetic radiation from worldwide thunderstorm activity is used as an energy source for geophysical exploration. Owing to its origin, such a signal is inherently transient and short lived. Therefore, special care should be taken in the detection and processing of this transient signal because the interval of time between two successive transient events contains almost no information as far as the audio frequency magnetotellurist is concerned. In this paper, a wavelet transform detection, processing and analysis technique is developed. A complex-compactly-supported wavelet, known as the Morlet wavelet, is selected as the mother wavelet. With the Morlet wavelet, lightning transients can be easily identified in the noisy recordings and the magnetotelluric impedance tensor can be computed directly in the wavelet transform domain. This scheme has been tested on real data collected in the archipelago of Svalbard, Norway as well as on five sets of synthetic data contaminated with various kinds of noise. The results show the superior performance of the wavelet transform transient detection and analysis technique.

This paper compares signal classification performance of multilayer neural networks (MLNNs) and linear filters (LFs). The MLNNs are useful for arbitrary waveform signal classification. On the other hand, LFS are useful for the signals, which are specified with frequency components. In this paper, both methods are compared based on frequency selective performance. The signals to be classified contain several frequency components. Furthermore, effects of the number of the signal samples are investigated. In this case, the frequency information may be lost to some extent. This makes the classification problems difficult. From practical viewpoint, computational complexity is also limited to the same level in both methods.IIR and FIR filters are compared. FIR filters with a direct form can save computations, which is independent of the filter order. IIR filters, on the other hand, cannot provide good signal classification deu to their phase distortion, and require a large amount of computations due to their recursive structure. When the number of the input samples is strictly limited, the signal vectors are widely distributed in the multi-dimensional signal space. In this case, signal classification by the LF method cannot provide a good performance. Because, they are designed to extract the frequency components. On the other hand, the MLNN method can form class regions in the signal vector space with high degree of freedom.

Random fluctuations of the propagation constants of modes along the fiber axis are taken into consideration and the power coupling coefficient between cores of an image fiber is theoretically derived. For the fiber used for the measurement in the previous paper (A. Komiyama, IEICE, vol.E79-C, no.2, pp.243-248, 1996) it is verified that the coupling coefficient can be described in terms of statistical properties of the propagation constants in the cross-section of the fiber.

Multipath interconnection networks can support higher bandwidth than those of nonblocking networks by passing multiple packets to the same output simultaneously and these packets are buffered in the output buffer. The delay-throughput performance of the output buffer in multipath networks is closely related to output traffic distribution, packet arrival process at each output link connected to a given output buffer. The output traffic distributions are different according to the various input traffic patterns. Focusing on nonuniform output traffic distributions, this paper develops a new, general analytic model of the output buffer in multipath networks, which enables us to investigate the delay-throughput performance of the output buffer under various input traffic patterns. This paper also introduces Multipath Crossbar network as a representative multipath network which is the base architecture of our analysis. It is shown that the output buffer performances such as packet loss probability and delay improve as nonuniformity of the output traffic distribution becomes larger.

MPO optical backplane connectors using multi-fiber push-on plugs (MPO plugs) have been developed. MPO optical backplane connector is a connector connecting a printed board to a backplane using MPO plug. MPO plug is held in the housing with self-retentive mechanism. To get same optical performances as standard MPO connector, precision in dimension and mechanism for appropriate connecting-disconnecting sequence are necessary. We have developed a new backplane housing and printed board housing based on previously reported MU connector. The optical performance is similar to that of MPO connectors.

Compressible viscous flows past a space plane have been elucidated by parallel computation on the NWT. The NWT is a vector-parallel architecture computer system which achieves remarkably high performance in processing speed and memory storage. We have examined the advantages of the NWT in order to simulate realistic flow problems in engineering, such as the investigation of global and local aerodynamic characteristics of a space plane. The accuracy of the computational results has been verified by comparison with experimental data. The simplified domain-decomposition technique introduced here is easy to apply for parallel implementation to significantly improve the acceleration rate of computations. The larger available memory storage enables us to conduct a grid refinement study through which several points concerning CFD simulation of a space plane are obtained.

We extend the Rabin cryptosystem to the Eisenstein and Gauss fields. Methods for constructing the complete representation class and modulo operation of the ideal are presented. Based on these, we describe the methods of encryption and decryption. This proposed cryptosystem is shown to be as intractable as factorization, and recently presented low exponent attacks do not work against it.

RF integration, until recently the integration of active devices in conventional architectures suitable for discrete-component circuits, is now turning into full-integration based on new architectures developed specifically for an LSI technology. This paper reviews some of the key existing and emerging circuit techniques and discusses the serious problem of crosstalk. In order to develop miniature and low power RF transceivers, direct-conversion and monolithic VCO's will be further studied. Silicon bipolar technology will still be playing major role beyond the year 2,000, and CMOS will also be used in certain applications.

This paper deals with an orthogonal functional expansion of a non-linear stochastic functional of a stationary binary sequence taking 1 with equal probability. Several mathematical formulas, such as multi-variate orthogonal polynomials, recurrence formula and generating function, are given in explicit form. A simple example of orthogonal functional expansion and stationary random seqence generated by the stationary binary sequence are discussed.

Topological sorting is, given with a directed acyclic graph G = (V, E), to find a total ordering of the vertices such that if (u, v) E then u is ordered before v. Instead of finding total orderings, we wish to find out how many total orderings exist in a given directed acyclic graph G = (V, E). Here we call a total ordering as legal sequence and the problem as legal sequence number problem. In this paper, we first propose theorems on equivalent transformation of graphs with respect to legal sequence number. Then we give a formula to calculate legal sequence number of basic series-parallel digraphs and a way of the calculation for general series-parallel digraphs. Finally we apply our results to show how to obtain legal sequence number for a class of extended series-parallel digraphs.

We describe our implementation of the Hypercube variation of the Multiple Polynomial Quadratic Sieve (HMPQS) integer factorization algorithm on a Parsytec GC computer with 128 processors. HMPQS is a variation on the Quadratic Sieve (QS) algorithm which inspects many quadratic polynomials looking for quadratic residues with small prime factors. The polynomials are organized as the nodes of an n-dimensional cube. We report on the performance of our implementations on factoring several large numbers for the Cunningham Project.

We propose an improved orthogonal frequency division multiplexing (OFDM) signal detector which uses the minimum mean-square error (MMSE) noise feedback equalization (NFE). The input bit stream is trellis-coded to form OFDM signal blocks and the maximal ratio combining (MRC) is adopted at the receiver in order to improve the performance of the detector. As a result, we obtain significantly improved detection performance compared with the conventional OFDM receivers as follows. Using the proposed MMSE-NFE in the receiver, we can obtain the performance gain of about 1.5 dB to 2 dB in symbol energy to noise power spectral density (Es/No) for Doppler frequencies of fd=20 and 100 Hz, respectively, over the receiver with the MMSE linear equalization (LE) alone at symbol error rate (SER) of about 10-3. With MRC and trellis coding, the performance gain of about 11 dB in Es/No for fd=20 and 100 Hz at SER of about 10-3 is obtained.