Currently, many efforts are underway to design wideband mobile communication system. The system is one of alternative of Future Public Land Mobile Telecommunication Systems (FPLMTS). In this paper, we clarify received signal level characteristics for wideband mobile radio channels in line-of-sight (LOS) microcells. The results from urban-area field experiments, where received signal levels for various receiver bandwidths and power delay profiles were measured, show that the depth of fading of the-received signal decreases as normalized RMS delay spread, defined as the product of receiver bandwidth and RMS delay spread, increases. These results are useful in designing wideband microcell systems for urban areas.

Secure communications via chaotic synchronization is experimentally demonstrated using 3-pieces of commercial integrated circuit phase-locked loops, MC14046. Different from the conventional chaotic synchronization secure communication systems where one channel is used, our system uses two channels to send one signal to be concealed. Namely, one channel is used to send a synchronizing chaotic signal. The other channel is used to send the informational signal superimposed on the chaotic masking signal at transmitter side. The synchronizing chaotic signal is applied as a common input to two identical PLL's located at both transmitter and receiver sides. It has been shown previously by us that the VCO inputs of almost identical two PLL's driven by a common chaotic signal become chaotic, and synchronized with each other. This synchronization is only possible for those who knows exact internal configuration and exact parameter values of the PLL at transmitter side. Therefore, we can use the synchronized VCO input signal as a masking signal which can be used as a key for secure communications. The advantage of this method compared to the previous one channel method is that informational signal frequency range does not affect the quality of recovered signal. Our experiments demonstrate good masking and recovery characteristics for sinusoidal, triangular, and square waves.

In order to provide a fuzzy system with learning function, numerous studies are being carried out to combine fuzzy systems and neural networks. The self-tuning methods using the descent method have been proposed. The constructive and the destructive methods are more powerful than other methods using neural networks (or descent method). On the other hand the destructive method is superior in the number of rules and inference error and inferior in learning speed to the constructive method. In this paper, we propose a new learning method combining the constructive and the destructive methods. The method is superior in the number of rules, inference error and learning speed to the destructive method. However, it is inferior in learning speed to the constructive method. Therefore, in order to improve learning speed of the proposed method, simplified learning methods are proposed. Some numerical examples are given to show the validity of the proposed methods.

A method is proposed for locating large gas leaks in subscriber cable networks composed of different type cables and/or branch cables that uses pressures periodically measured at several points. Theoretical pressure curves corresponding to these measured pressure curves are calculated using a model representing the actual cable network. These curves are called the calculated pressure curves. The position of the leak is varied in the calculation model and where the measured and calculated pressure curves coincide the most, the leak position in the calculation model indicates the estimated leak position. The calculated pressure curves are based on the Laplace transform and an analogy between the pneumatic characteristics in cable networks and the electrical characteristics in electrical transmission networks. An experiment using a cable network about 910m long resulted in a location error of less than 30m.

Frequency demodulation of a single side-band signal with a carrier is discussed and a new demodulation method is proposed. Compared with the conventional RZSSB (real zero single-side band) demodulator, there are no even-order distortions in the demodulated output signal of the proposed method and the third-order distortion can be canceled very easily without any Hilbert transformer as is required in the conventional RZSSB demodulator. Since the carrier can be reproduced completely from the input signal by the proposed method, it can be used for not only an RZSSB signal but also a full-carrier SSB signal or a low-carrier SSB signal. Compared with transmitting an RZSSB signal, it more efficiently transmits a low carrier SSB signal since the carrier does not include any useful information. By this means, the transmission efficiency can be greatly improved by adopting the proposed method.

This paper presents a new learning method to improve noise tolerance in Fuzzy ART. The two weight vectors: the top-down weight vector and the bottom-up weight vector are differently updated by a weighted sum and a fuzzy AND operation. This method effectively resolves the category proliferation problem without increasing the training epochs in noisy environments.

Theoretically, corresponding pairs of feature points between two stereo images can determine their 3-D locations uniquely by triangulation. In the presence of noise, however, corresponding feature points may not satisfy the epipolar equation exactly, so we must first correct the corresponding pairs so as to satisfy the epipolar equation. In this paper, we present an optimal correction method based on a statistical model of image noise. Our method allows us to evaluate the magnitude of image noise a posteriori and compute the covariance matrix of each of the reconstructed 3-D points. We demonstrate the effectiveness of our method by doing numerical simulation and real-image experiments.

On a simple model, the quality of the security tag is simulated theoretically and experimentally. A simple correction makes both results correspond exactly and a simulation formula is provided. By using novel insulating film, a small-sized tag of high quality is developed.

This paper proposes a new class of error locating codes which corrects random single-bit errors and indicates a location of an erroneous b-bit byte which includes e-bit errors, where 2 e b, called SECSe/bEL codes. This type of codes is very suitable for an application to memory systems constructed from byte-organized memory chips because this corrects random single-bit errors induced by soft-errors and also indicates the position of the faulty memory chips. This paper also gives a construction method of the proposed codes using tensor product of the two codes, i.e., the single b-bit byte error correcting codes and the single-bit error correcting and e-bit error detecting codes. This clarifies lower bounds and error control capabilities of the proposed codes.

We study all-to-all broadcasting in hypercubes with randomly distributed Byzantine faults. We construct an efficient broadcasting scheme BC1-n-cube running on the n-dimensional hypercube (n-cube for short) in 2n rounds, where for communication by each node of the n-cube, only one of its links is used in each round. The scheme BC1-n-cube can tolerate (n-1)/2 Byzantine faults of nodes and/or links in the worst case. If there are exactly f Byzantine faulty nodes randomly distributed in the n-cabe, BC1-n-cube succeeds with a probability higher than 1(64nf/2n) n/2. In other words, if 1/(64nk) of all the nodes(i.e., 2n/(64nk) nodes) fail in Byzantine manner randomly in the n-cube, then the scheme succeeds with a probability higher than 1kn/2. We also consider the case where all nodes are faultless but links may fail randomly in the n-cube. Broadcasting by BC1-n-cube is successful with a probability hig her than 1kn/2 provided that not more than 1/(64(n1)k) of all the links in the n-cube fail in Byzantine manner randomly. For the case where only links may fail, we give another broadcasting scheme BC2-n-cube which runs in 2n2 rounds. Broadcasting by BC2-n-cube is successful with a high probability if the number of Byzantine faulty links randomly distributed in the n-cube is not more than a constant fraction of the total number of links. That is, it succeeds with a probability higher than 1nkn/2 if 1/(48k) of all the links in the n-cube fail randomly in Byzantine manner.

The throughput performance of the non-persistent carrier sense spread spectrum with overload detection (NP-CSSS/OD) protocol is analysed and compared with that of the conventional non-persistent and one-persistent carrier sense multiple access with collision detection (NP-CSMA/CD and 1P-CSMA/CD) and the one-persistent carrier sense spread spectrum with overload detection (1P-CSSS/OD) protocols. We also introduced utilization measurements and did some performance comparisons between these protocols. At high offered loads, the NP-CSSS/OD protocol is found to offer the best throughput and utilization performances amongst them.

In this paper we present a system for secure communications based on chaos synchronization. Unlike the existing systems for communication via chaotic synchronization, our system extracts the information at the receiver without error. A possibility for secure communications using Lorenz system is given. A practical algorithm for secret-key cryptography is suggested and is evaluated through statistical tests that have not shown any weakness. Furthermore, the algorithm is extremely simple for implementation in a program.

A 0.5 µm CMOS embedded function type gate array family with high speed modules was developed. This family has: an effective basic cell; high speed, compiled type metallized and diffused RAMs; PLL (Phase Locked Loop); and GTL (Gunning Transceiver Logic) to realize operation of over 100 MHz at 3.3 V. This paper describes the basic cell architecture and the compiled type metallized RAM. A divided MOS transistor type basic cell is effective for metallized modules such as metallized RAM and internal logic circuits. The appropriate basic cell size (height) can be decided from the viewpoints of the relationship between the number of usable basic cells and the basic cell height, and the logic circuit speed. Propagation delay time of the 2-input NAND is 200 ps at a standard load of fan out=2 and metal length=1.4 mm. For the universal ASIC, the compiled RAM is indispensable. Single port and multi-port metallized RAMs which are structured by using the basic cells are discussed. The new single port memory cell circuit which has a differential write and single end read operating method is introduced. This memory cell circuit can be realized using one basic cell. The diffused layer region of the NMOS transfer gates for the read operation is shared between neighbor memory cells. So, the capacitance of the bit line becomes smaller, and a high speed access time can be achieved. The measured access time of 1 kbits is 4.2 ns. The new multi-port memory cell circuits which have a single end write and single end read operating method are introduced. The read operating method is the same as that of the single port memory cell circuit. The access time shows very high speed operation comparable to that of the single port memory. This 3F (Flexible, Fast, and Friendly) ASIC family can be applied to high speed processors in workstations and graphics equipment.

In this paper, we propose a new approach to speaker independent isolated-word speech recognition using multisegment multiple vector quantization (VQ) codebooks. In this approach, words are recognized by means of multisegment multiple VQ codebooks, a separate multisegment multiple VQ codebooks are designed for each word in the recognition vocabulary by dividing equally the word into multiple segments which is correlative with number of syllables or phonemes of the word, and designing two individual VQ codebooks consisting of both instantaneous and transitional speech features for each segment. Using this approach, the influence of the within-word coarticulation can be minimized, the time-sequence information of speech can be used, and the word length differences in the vocabulary or speaking rates variations can be adapted automatically. Moreover, the mel-cepstral coefficients based on unbiased estimation of log spectrum (UELS) are used, and comparison experiment with LPC derived mel cepstral coefficients is made. Recognition experiments Using testing databases consisting of 100 Japanese words (Waseda database) and 216 phonetically balanced words (ATR database), confirmed the effectiveness of the new method and the new speech features. The approach is described, computational complexity as well as memory requirements are analyzed, the experimental results are presented.

In this letter we propose a novel method of connection, called the hybrid connection, and find that a resistively coupled oscillator with hybrid connection has stable in-phase and anti-phase synchronized oscillations. Averaging method is used to investigate the stability of the synchronized oscillations. The theory is verified by the experimental results.

This paper discusses crystal-growth and device-design issues associated with the development of high-performance InP/InGaAs heretostructure bipolar transistors (HBTs). It is shown that a highly Si-doped n+-subcollector in the HBT structure causes anomalous Zn redistribution during metalorganic vapor phase epitaxial (MOVPE) growth. A thermodynamical model of and a useful solution to this big problem are presented. A novel hybrid structure consisting of an abrupt emitter-base heterojunction and a compositionally-graded base is shown to enhance nonequilibrium base transport and thereby increase current gain and cutoff frequency fT. A double-heterostructure bipolar transistor (DHBT) with a step-graded InGaAsP collector can improve collector breakdown behavior without any speed penalty. We also elucidate the effect of emitter size shrinkage on high-frequency performance. Maximum oscillation frequency fmax in excess of 250 GHz is reported.

Improvement of the convergence characteristics of the NLMS algorithm has received attention in the area of adaptive filtering. A new variable stepsize NLMS method, in which the stepsize is updated optimally by using variances of the measured error signal and the estimated noise, is proposed. The optimal control equation of the stepsize has been derived from a convergence characteristic approximation. A new condition to judge convergence is introduced in this paper to ensure the fastest initial convergence speed by providing precise timing to start estimating noise level. And further, some adaptive smoothing devices have been added into the ADF to overcome the saturation problem of the identification error caused by some random deviations. By the simulation, The initial convergence speed and the identification error in precise identification mode is improved significantly by more precise adjustment of stepsize without increasing in computational cost. The results are the best ever reported performanced. This variable stepsize NLMS-ADF also shows good effectiveness even in severe conditions, such as noisy or fast changing circumstances.

This paper proposes a novel architecture and MMICs for an integrated 2-32 GHz front-end of a spectrum analyzer. The architecture achieves miniaturization by eliminating the large YIG tracking filter and also achieves multi-octave measurement with less than one octave sweep of the first local oscillator. The MMIC's demonstrate ultra-wideband performances with reduced chip sizes by utilizing newly developed FET cells for power combination, multi-order frequency conversion, low leakage variable resistance, and active impedance translation. The MMIC's are a fundamental/harmonic frequency converter, a variable attenuator, a single-pole triple-throw switch, a single-pole double-throw switch, a distributed pre-amplifier, and an active LC lowpass filter. All the MMIC's are smaller than 1 mm2, except the pre-amplifier and the filter.

This work is concerned with a dynamic analysis of complex uniplanar guide-wave structures for MMICs at millimeter-wave frequencies. The enhanced spectral domain approach is effectively used to model such uniplanar structures with trapezoidal conducting strips involving microshielding enclosures. A wide range of line propagation and impedance characteristics is obtained for slotline and coplanar waveguide (CPW). The effect of different conductor profiles on line characteristics is discussed in detail. Results show an excellent agreement with other works. A class of dispersion-related curves are presented for design consideration.

We have designed and implemented a simple yet powerful declarative synchronization mechanism for a paralle object-oriented computation model. The mechanism allows the user to control multiple message reception, specify the order of message reception, lock an invocation, and specify relations as invocation constraints. It has been included in a parallel object-oriented language, called A-NETL. The compiler and operating system have been developed on a total architecture, A-NET (Actors NETwork). The experimental results show that (i) the mechanism allows the user to model asynchronous events naturally, without losing the integrity of described programs; (ii) the replacement of the mechanism with the user's code requires tedious descriptions, but gains little performance enhancement, and certainly loses program readability and integrity; (iii) the mechanism allows the user to shift synchronous programs to asynchronous ones, with a scalable reduction of execution times: an average 20.6% for 6 to 17 objects and 46.1% for 65 objects. These prove the effectiveness of the proposed synchronization mechanism.