Broadband ISDN, using asynchronous transfer mode, are expected to carry traffic of different classes, each with its own set of traffic characteristics and performance requirements. To achieve the quality of service in ATM networks, a suitable buffer management scheme is needed. In this paper, we propose a buffer management scheme using a priority service discipline to improve the delay time of delay-sensitive class and the packet loss ratio of loss-sensitive class. The proposed priority scheme requires simple buffer management logic and minor processing overhead. We also analyze the delay time and the packet loss ratio for each class of service. The results indicate that the required buffer size of the proposed priority scheme is reduced and the delay time of each class of service is controlled by a parameter. If the control parameter is appropriately chosen, the quality of service of each class is improved.

The Memory-Based Reasoning (MBR) is one of the mainstay approaches in massively parallel artificial intelligence research. However, it has not been explored from the viewpoint of hardware implementation. This paper demonstrates high robustness of the MBR, which is suitable for hardware implementation using Wafer Scale Integration (WSI) technology, and proposes a design of WSI-MBR hardware. The robustness is evaluated by a newly developed WSI-MBR simulator in the English pronunciation reasoning task, generally known as MBRTalk. The results show that defects or other fluctuations of device parameters have only minor impacts on the performances of the WSI-MBR. Moreover, it is found that in order to get higher reasoning accuracy, the size of the MBR database is much more crucial than the computation resolution. These features are proved to be caused by the fact that MBR does not rely upon each single data unit but upon a bulk data set. Robustness in the other MBR tasks can be evaluated in the same manner as discussed in this paper. The proposed WSI-MBR processor takes advantage of benefits discovered in the simulation results. The most area-demanding circuits--that is, multipliers and adders--are designed by analog circuits. It is expected that the 1.7 million processors will be integrated onto the 8-inch silicon wafer by the 0.3 µm SRAM technology.

We consider an asymptotically sparsely encoded associative memory. Patterns are encoded by n-dimensional vectors of 1 and 1 generated randomly by a sequence of biased Bernoulli trials and stored in the network according to Hebbian rule. Using a heuristic argument we derive the following capacities:c(n)ne/4k log n'C(n)ne/4k(1e)log n'where, 0e1 controls the degree of sparsity of the encoding scheme and k is a constant. Here c(n) is the capacity of the network such that any stored pattern is a fixed point with high probability, whereas C(n) is the capacity of the network such that all stored patterns are fixed points with high probability. The main contribution of this technical paper is a theoretical verification of the above results using the Poisson limit theorems of exchangeable events.

A fail-safe logic operation refers to such a processing operation that the output assumes the logical value zero when the operation circuit fails. The fail-safe multiple-valued logic operation is proposed as one method of logic operation. Section 2 defines the fail-asfe multiple-valued logic operation and presents an example of method for accomplishing the fail-safe multiple-valued logic operation. Section 3 describes the method of designing a fail-safe threshold operation device (window comparator) as basic device in the fail-safe multiple-valued logic operation in consideration of LSI implementation and shows an example of prototype fail-safe window comparator. This operation device has higher and lower thresholds. It oscillates and produces an operational output signal only when the input signal level falls between the higher and lower thresholds. Unless the fail-safe window comparator is supplied with input signals of higher voltage than the power supply voltage, it dose not form a feedbadk loop as required for it to oscillate. This characteristic prevents the device from erroneously producing an output signal when any failure occurs in the amplifiers comprising the oscillation circuit. The window comparator can be built as a fail-safe threshold operation device. The fail-safe characteristic is utilized in its LSI implementation. Section 4 verifies the fail-safe property of the prortotype fail-safe window comparator. It is shown that even when the LSI develops failures not evident from outsid (latent failures), it does not lose the operational function and maintains the fail-safe characteristic.

Broadband ISDN based on ATM technologies is expected to offer enhanced and sophisticated services to customers. Since ATM will first be introduced in the business communication world, it will be worth to discuss the future image of desirable ATM customer premises network (CPN). In this paper, we first consider the possible migration scenario of Broadband CPN and some important requirements for the realization of the scenario. Then, we discuss the key issues to be solved for future ATM-CPN, which include network topology, traffic control and connectionless communication services.

In general, the work on developing an expert system has relied on domain experts to provide all domain-specific knowledge. The method for acquiring knowledge directly from experts is inadequate in oriental medicine because it is hard to find an appropriate expert and the development cost becomes too high. Therefore, we have developed two effective methods for acquiring knowledge indirectly from sample cases. One is to refine a constructed knowledge base by using sample cases. The other is to train a neural network by using sample cases. To demonstrate the effectiveness of our methods, we have implemented two prototype systems; the Oriental Medicine Expert System (OMES) and the Oriental Medicine Neural Network (OMNN). These systems have been compared with the system with the knowledge base built directly by domain experts (OLDS). Among these systems, OMES are considered to be superior to other systems in terms of performances, development costs, and practicalness. In this paper, we present our methods, and describe our experimental and comparison results.

Marc Kellner proposed an example problem intending to compare modeling and describing techniques of software process. In this paper, we will describe our approach to understanding and describing the problem, from a process/product relation view, and synchronization/concurrent view. Also, we will show that a description of the problem is translated for execution and its correctness is validated.

We analyze the average bit error probability (BER) performances of BPSK with pilot tone in the frequency-selective Rayleigh fading channel, which can be characterized by the delay power spectrum due to multipath fading. The analysis is based on the error probability conditioned on the receiver input envelope in order to investigate the diversity effects. With taking into consideration of predetection receiving filter characteristic, the average BER is evaluated by treating the normalized standard deviation (rms delay spread), τ0/T (T: digital symbol period), of the delay power spectrum, BT product of predetection filter and power distribution between BPSK signal and pilot tone as parameters. The results show that the optimum power distribution (kopt) can be determined mainly according to the ratio (α) of tone extracting filter bandwidth to predetection filter bandwidth provided that α is small. For fixed α, τ0/T and kopt corresponding to α, optimum BT product, which minimizes the error rate, exists and the value is dependent on signal energy per bit to noise power spectral density ratio (SNR), and is affected slightly by the delay power spectrum shapes. In this paper, one-sided exponential, Gaussian and double spike shapes are treated as delay power spectrum shapes. On the average BER characteristics due to delay spread with fixed α, BT and kopt corresponding to α, the delay power spectrum shape is of no importance for τ0/T0.06. For τ0/T0.06, in the case of double spike delay power spectrum, BER is less than that for the other two spectral shapes. By making use of the selection diversity with 2-branch and predetection filter with optimum BT product, SNR can be improved by 16dB at the average BER of 10-4.

This paper proposes and investigates an adaptive equalizer with diversity-combining over a multipath fading channel. It consists of two space-diversity antennas and a Ts/2-spaced decision-feedback-equalizer (DFE). Received signals from the two antennas are alternatively switched and fed into the feed forward-filter of DFE. We call this structure a Switched Input Combining Equalizer with diversity-combining (SICE). By using an SICE, the receiver structure for combining diversity equalization can be simplified, because it needs only two receiver sections up to IF BPF. The bit error rate (BER) performance of SICE was evaluated by both computer simulation and experiment over a multipath fading channel. We experimentally confirmed the excellent BER performance, around 1% of BER over a multipath fading channel at 160Hz of maximum doppler fading frequency. Therefore, the proposed SICE is applicable to highly reliable transmission in the 1.5-GHz-band mobile radio.

This paper proposes fiber optic link configurations for use in microwave and millimeter-wave transmission Higher frequencies,such as millimeter-waves, are well suited to transmission of broadband signals. Photodiodes can operate simultaneously as optical detectors and microwave frequency mixers thanks to their inherent nonlinearities. This allows us to increase the output radio frequncy. But, this also generates undesired spurious frequencies, necessitating the use of microwave filters. We discuss here two fiber optic link configurations, i.e., balanced/image canceling photodiode mixing links utilizing the combination of microwave functional components and optical devices to suppress the local/image frequency without filters. These configurations are experimentally investigated at microwave frequencies and local/image frequency suppression is successfully demonstrated.

A Decision Feedback Equalizer (DFE) structure with a varying number of tap lengths was used with a recursive least squares (RLS) algorithm to determine tradeoffs between equalizer size and performance in mobile and portable digital radio systems. A mobile channel simulator, SMRCIM, was used to demonstrate how much an equalizer can improve the BER in real world urban channels. The results show that at 850MHz, the DFE is unable to improve the BER when the mobile terminal exceeds speeds of 115km/h for U.S. Digital Cellular systems. The performance of adaptive equalization for indoor high data rate systems was evaluated using the indoor channel simulator SIRCIM, and we found that DFEs have excellent performance for indoor radio channels. For simple structures, the BER is less than 10-3 at 15dB Eb/NO using coherent QPSK modulation. Finally, an equalizer structure for non-coherent π/4 DQPSK modulation was developed and simulation results are presented.

A simple inequality that guarantees stability of perturbed linear state space models is proposed. It is shown that the result is superior to some existing result in sharpness and possesses some advantageous aspects.

This paper describes a new technique for isolated word recognition that uses both pitch information and spectral information. In conventional methods, words with similar phoneme features tend to be misrecognized even if their phonemes are accented differently because these methods use only spectral information. It is possible to improve recognition accuracy by considering pitch patterns of words. Many phonetically-similar Japanese words are classified by pitch patterns. In this technique, a pitch pattern template is produced by averaging pitch patterns obtained from a set of words which have the same accent pattern. A measure for word recognition is proposed. This measure based on a combination of the phoneme likelihood and the pitch pattern distance which is the distance between a pitch pattern of an input speech and pitch pattern templates. Speaker-dependent word recognition experiments were carried out using 216 Japanese words uttered by five male and five female speakers. The proposed technique reduces the recognition error rate by 40% compared with the conventional method using only phoneme likelihood.

This paper reviews the application of optical technologies to phased array antennas. The performance of the fibre transmission medium and of sources and detectors is reviewed, leading to simple expressions for transmission loss and noise performance. Both coherent and non-coherent beam forming techniques are considered. Future trends, including the use of optical amplifiers and coherent signal generation, will also be discussed.

An integrator is quite a suitable active element for high-speed filters. The effect of its excess phase shifts, however, is severe in the case of high-Q filter realization. The deterioration due to the excess phase shifts cannot be avoided when only integrators are used as frequency-dependent elements like in leapfrog realization. This paper describes a design of second-order high-speed and high-Q filters with low sensitivity to excess phase shifts of integrators by adding a passive RC circuit. The proposed method can drastically reduce the effect due to the undesirable pole of an integrator, which is the cause of the excess phase shifts, compared to conventional filters using only integrators. As an example, a fourth-order bandpass filter with 5-MHz center frequency and Q=25 is implemented by the proposed method on a monolithic chip. The results obtained here show quite good agreement with the theoretical values. This demonstrates effectiveness of the proposed method and feasibility of high-speed and high-Q filters on a monolithic chip.

This paper mainly concentrates on recent studies on land mobile propagation, considering new trends of the progress of digital and personal land mobile communications. High speed digital transmission for millimeter-wave indoor communication is of another current interest. Microcellular propagation in urban areas and indoor propagation are major research targets at present days. Multipath propagation characteristics such as delay-profiles becomes more and more important measuring items, and some signal processing methods like MUSIC method have been widely introduced to improve the time resolution against the limit of available radio bandwidth. Path-loss characteristics in mobile propagation are extended to the path-loss prediction and are going to be applied to cellular system design in connection with the design of directional base-station antennas. Another recent topic is an extension of target frequency bands for mobile propagation studies, which are spreading from VHP, UHF and SHF to EHF bands.

The inverted slot line (ISL) has been propoaed for millimeter-wave LiNbO3 optical modulator. It is simple in structure, and capable of achieving the perfect velocity matching between carrier and modulating waves. The excellent performance of the ISL optical modulator has been demonstrated at 100 GHz, and the extension into the 50 GHz range is being expected. This paper addresses the analysis of the ISL based on the spectral domain approach. The major results obtained here are the demonstration of the perfect velocity matching not only at 10 GHz but also at 50 GHz, and the characterization of the ISL in terms of effective refractive index, characteristic impedance, overlap integral factor and transmission loss. The depth of optical phase modulation is also estimated at 50 GHz to show a promising performance in the millimeter-wave frequency range. The effective refractive index and the characteristic impedance are found to be theoretically predictable, but the field profile, the overlap integral factor and the transmission loss are not necessarily in good agreement with measurements. As a result of analysis, it can be concluded that the Y-cut substrate is superior to the Z-cut substrate in the following respects: 1. Coupling with the surface wave mode hardly occurs near the operating frequency range. 2. The perfect velocity matching can be attained with a larger spacing between the electrode and the ground plane. 3. The transmission loss is smaller. 4. The field intensity and the voerlap integral factor do not seem to be much deteriorated in the actual ISL.

High Tc superconducting (SC) active antennas made from thin films were produced by the magnetron sputtering method. The SC active antennas are found to be good for detecting 50GHz electromagnetic waves. Furthermore, the improvement of the sensitivity of the SC active antennas is demonstrated with the use of a corner reflector.

Let C{c1, , cm} be a family of subsets of a finite set S{1, , n}, a subset S of S is a co-hitting set if S contains no element of C as a subset. By using an O((log n)2) time EREW PRAM algorithm for a maximal independent set problem (MIS), we show that a maximal co-hitting set for S can be computed on an EREW PRAN in time O(αβ(log(nm))2) using O(n2 m) processors, where αmax{|cii1, , n} and βmax{|djj1, , n} with dj{ci|jci}. This implies that if αβO((log(nm))k) then the problem is solvable in NC.

In this paper, we will define Kleene-Stone logic functions which are functions F: [0, 1]n[0, 1] including the intuitionistic negation into fuzzy logic functions, and they can easily represent the concepts of necessity and possibility which are important concepts of many-valued logic systems. A set of Kleene-Stone logic functions is one of the models of Kleene-Stone algebra, which is both Kleene algebra and Stone algebra, as same as a set of fuzzy logic functions is one of the models of Kleene algebra. This paper, especially, describes some algebraic properties and representation of Kleene-Stone logic functions.