This paper describes some dynamical properties of higher order neural networks with decreasing energy functions. First, we will show that for any symmetric higher order neural network which permits only one element to transit at each step, there are only periodic sequences with the length 1. Further, it will be shown that for any higher order neural network, with decreasing energy functions, which permits all elements to transit at each step, there does not exist any periodic sequence with the length being over k + 1, where k is the order of the network. Lastly, we will give a characterization for higher order neural networks, with the order 2 and a decreasing energy function each, which permit plural elements to transit at each step and have periodic sequences only with the lengh 1.

The author once defined the Ω-matrix and showed that it played an important role for estimating the number of solutions of a resistive circuit containing active elements such as CCCS's. The Ω-matlix is a generalization of the wellknown P-matrix. This paper gives the necessary and sufficient conditions for the Ω-matrix.

In this paper, oscillation modes produced in a Josephson circuit and its application to digital systems are described. The analysis is performed using an analog simulator to model the Josephson junction, in addition to computer simulation. The experimental results concerning oscillation modes agree well with the simulation results. The main advantage of the mapping for the oscillation modes is that it allows understanding of the relationships among oscillation modes and circuit parameters at first sight. In addition, a novel application of nonlinear oscillation to digital systems is described.

C1 class smooth interpolation by a fuzzy reasoning for a small data set is proposed. The drafting technique of a human expert is implemented by using a set of fuzzy rules. The effectiveness of the present method is verified by computer simulations and by applications to the practical interpolation problem in a power system.

The importance sampling simulation technique has been exploited to obtain an accurate estimate for a very small probability which is not tractable by the ordinary Monte Carlo simulation. In this paper, we will investigate the simulation for a sample average of an output sequence from a Markov chain. The optimal simulation distribution will be characterized by the Kullback-Leibler divergence of Markov chains and geometric properties of the importance sampling simulation will be presented. As a result, an effective computation method for the optimal simulation distribution will be obtained.

Many activities are being promoted for the coming multimedia age. In this paper, background information for multimedia communications is followed by an outline of joint tests in multimedia communications with some examples of the projects and applications. These trials are also explained from the aspects of project specifications, which include application classifications and details of multimedia-on-demand offerings, as well as technical issues in experimental environments which mainly include those related to ATM technology.

This paper presents a method for mechanically transforming a parallel algorithm on an original network so that the algorithm can work on a target network. It is assumed that the networks are of cube-type such as the shuffle-exchange network, omega network, and hypercube. Were those networks isomorphic to each other, the algorithm transformation is an easy task. The proposed transformation method is based on a novel graphembedding scheme <φ: δ, κ, π, ψ>. In addition to the dilating operation δ of the usual embedding scheme <φ: δ>, the novel scheme uses three primitive graph-transformation operations; κ (= δ-1) for contracting a path into a node, π for pipelining a graph, and ψ (= π-1) for folding a pipelined graph. By applying the primitive operations, the cube-type networks can be transformed so as to be isomorphic to each other. Relationships between the networks are represented by the composition of applied operations. With the isomorphic mapping φ, an algorithm in a node of the original network can be simulated in the corresponding node(s) of the target network. Thus the algorithm transformation is reduced to routine work.

A new ATM switch architecture, named shared multibuffering, features great advantages on memory access speed for a large switch, and overall size of buffer memories to achieve excellent cell-loss performance. We have developed a 622-Mb/s 88 shared multibuffer ATM switch with multicast functions and hierarchical queueing functions to accommodate 156-Mb/s, 622-Mb/s and 2.4-Gb/s interfaces. Implementation of the shared multibuffer ATM switch is described with respect to the four sorts of 0.8-µm BiCMOS LSIs and ATM switch boards. The switch board/type-1, with C1-LSI, allows to accommodate effectively 156-Mb/s and 622-Mb/s interfaces, which is suitable for an ATM access system. The switch board/type-2, with C2-LSI, can provide multicast functions and accommodate a 2.4-Gb/s interface. By using four switch boards, it is possible to apply them to a 2.4-Gb/s ATM loop system.

This paper describes a trial of evaluating the proper characteristics of multiple sound insulatain systems from their output responses contaminated by unknown background noises. The unknown parameters of sound insulation systems are first estimated on the basis of hte linear time series on an intensity scale, describing functionally the input-output relation of the systems. Then, their output probability distributions are predicted when an arbitrary input noise passes through these insulation systems.

The ringing occurred in the step response causes an undesirable stripe pattern in TV signals. A simultaneous approximation with both the frequency and the step response is required in the designing filter which is used in the image signal processing in order to prevent the ringing. The wellknown Remez algorithm for designing FIR filters approximates the response only in the frequency domain. As the result, the filters designed by this algorithm causes the large ringing in the step response. In this paper, we propose the method of design for FIR filters with minimum amplitude in the stopband, under the condition that the step response has no ringing and the prescribed rise characteristics. For this end, we use the constrained successive projections method.

For the successful realization of the multimedia information environment, it is strongly required to develop very cost effective optical access networks. Accordingly, ways of reducing system cost are described. At the same time, the development of attractive new services is indispensable to drive network modernization. The connectionless networking service for community user groups is proposed together with the new concept of group communication.

This paper describes the concept of the regional community network system. The system provides PC connectionless communication services to residential customers and a platform on which customers can construct closed user groups. The proposed system is superior to conventional dial-up PC communications from the viewpoint of quick response and communication charge. A new mechanism of group management using the MAC addresses of the interface cards embedded in the ONU and PC terminals is proposed. Conventional telecommunication services, multi-channel video distribution services, and connectionless computer communication services can be provided simultaneously by utilizing the fiber-optic access system. The regional community network system is promising for the construction of a regional information platform and would be one of the forces driving FTTH.

The paper deals with the evaluation of performance of current cellular systems which are required to accommodate in an already operating system a wide range of new services, with different quality requirements (on delays, retransmission rates, etc.), and often characterised by a high burstiness (i. e. with relatively short traffic bursts, interleaved by comparatively long silence periods). To this end, an extension of packet communications is appealing for its inherent flexibility; standardisation of packet protocols for data transmission over idle GSM channels is in progress, and a similar service exploiting AMPS radio and network resources is already specified as Cellular Digital Packet Data. In both cases voice traffic retains a higher priority. The paper focuses on the evaluation of the effect of this additional traffic on existing voice traffic in a GSM Phase 2+ system. Although voice calls experience the same channel availability, their performance are worsened by the higher co-channel interference due to the higher average channel occupancy. This impairment cannot be tackled, as a matter of course, by increasing the re-use distance as this would affect the overall system capacity. The paper suggests the use of smart planning strategies capable to ease control of interference levels with a negligible impact on system complexity and signalling load.

This paper is a brief survey of mobile applications of meteor burst communications (MBC). Though the capacity of MBC systems is generally not large, this unique long distance communication method has at least two selling points when applied to mobiles. First of all, it is cheap. Secondly, it can easily offer nationwide seamless service. Thus, since the late 1980s, mobile MBC systems have been attracting interests of the industry. Although MBC is today a well established communication technique, there are some difficulties to be overcome before it is widely applied to mobile systems. Two most serious problems are the rather large antenna size and high transmitter power inherent to this beyond line of sight communication which relies on weak reflections of low VHF (typically 35 to 50 MHz) radio waves from ionized meteor trails. Some reduced sized antennas which can be mounted on the roofs of trucks have been tested. The problem of large peak power (a few hundred watts for mobile remotes) is much alleviated by the very low duty cycle (usually less than 1%) of remote transmitters due to their bursty transmissions responding to the probe signals from the master station via infrequent meteor reflections. In this paper, some land and maritime mobile MBC systems are brieflyintroduced.

In this paper, a feasible optical code-division multiple-access (CDMA) technique is proposed for high-speed computer networks using prime codes and optical signal processing to guarantee real-time data communications. All-optical architectures for fastly tunable CDMA encoders and decoders are presented, which can be feasibly implemented in the optical domain by using electrooptic switches and optical delay lines. This can support an ultrahigh throughput and a very fast reconfiguration time. Furthermore, we present a self-synchronized sample technique to ensure the correct phase synchronization between optical clock stream and asynchronous electronic data at each electrooptic modulator of an optical CDMA transmitter.

This letter points out that while a class of conditions presented in Matsuoka K. [1] are truly sufficient for absolute stability of neural networks, the proof of the sufficiency given in [1] is not sound. As a remark, a mathematically rigorous proof of the sufficiency of the class of conditions for absolute stability of neural networks is provided.

This paper discusses how to derive message sequence charts (MSCs) from a set of state transition descriptions. Recently, MSC notation has received much attention in the communications software field because it graphically shows system global behavior, So MSC handling techniques are being widely studied. These studies have recommended the design a system by a set of formal MSCs in the early stages of development and then to convert them into state transition descriptions. However, it is difficult to apply those results to existing communications software products. This is because these systems are designed based on state transition descriptions and there are no formal MSCs for them. In this paper, we propose a method of deriving MSCs based on optimized reachability analysis. This method generates MCSs that avoid state explosion. A case study using Q.931 protocol shows the feasibility of this method.

Multimedia communications, fast growing industry in the world and in Korea, require advanced technology in network, computer, device, and application software. Korean government and industries prepare for this huge opportunity by commitment to national R&D programs. While investing heavily on present multimedia products, private companies also support R&D on future multimedia technologies. This paper surveys key R&D efforts in Korea by programs and organizations.

A CMOS fully balanced current-mode filter is presented. A fully balanced current-mode integrator which is the basic building block is implemented by adding a very simple common-mode-rejection mechanism to fully differential one. The fully balanced operation can eliminate even order distortion, which is one of the drawbacks in previous continuous current-mode filter. Moreover, the additional circuit can work as not only common-mode-rejection mechanism but also Q-tuning circuit which compensates lossy elements due to finite output impedance of MOS FET. A prototype fifth-order low-pass lad-der filter designed in a standard digital 0.8µm CMOS process achieved a cut-off frequency (fC) of 100MHz; fC was tunable from 75MHz to 120MHz by varying a reference bias current from 50µA to 150µA. Using a single 3V power supply with a nominal reference current of 100µA, power dissipation per one pole is 30mW. The active filter area was 0.011mm2/pole and total harmonic distortion (THD) was 0.73 [%] at 80MHz, 80µA amplitude signal. Furthermore, by adjusting two bias currents, on chip automatic both frequency and Q controls are easily implemented by typical tuning systems, for example master-slave tuning systems [1].

In this paper, a super-resolution method based on the Discrete Cosine Transform (DCT) is proposed for a signal with some frequency damage. If the damage process can be modeled as linear convolutoin with a type 1 linear phase FIR filter, it is shown that some DCT coefficients of the damaged signal are the same as those of the original signal except for the DCT coefficients corresponding to the frequency damage. From this investigation, the proposed method is provided for the DCTs with four types as expanding the super-resolution method based on the Discrete Fourier Transform (DFT). In addition,two magnification approaches based on the proposed method are described to improve the conventional approach.