A highly reliable, operated efficiently, and scalable switching node is required for multivendor system management networks. This paper presents techniques for applying the Telecommunications Management Network (TMN) concept to a distributed switching node. First, we select the TMN protocol structures so as to minimize the command response time. To ensure efficient operation and flexible design of the operation, administration and maintenance (OA & M) software, we propose a command-message handling function for mapping managed objects (MOs) to the OA & M software. We have designed MO classes for switching-system-specific devices with a redundant configuration that ensures highly reliable system operation. The feasibility of these techniques have been confirmed on a prototype system.

We developed a parallel bordered-block-diagonal (BBD) matrix solution for parallel circuit simulation. In parallel circuit sumulation on a MIMD parallel computer, a circuit is partitioned into as many subcircuits as the processors of a parallel computer. Circuit partition produce a BBD matrix. In parallel BBD matrix solution, diagonal blocks are easily solved separately in each processor. It is difficult, however, to solve the interconnection (IC) submatrix of a BBD matrix effectively in parallel. To make matters worse, the more a circuit is partitioned into subcircuits for highly parallel circuit simulation, the larger the size of an IC submatrix becomes. From an examination, we found that an IC submatrix is more dense (about 30% of all entries are non-zeros) than a normal circuit matrix, and the non-zeros per row in an IC submatrix are almost constant with the number of subcircuits. To attain high-speed circuit simulation, we devised a data structure for BBD matrix processing and an approach to parallel BBD matrix solution. Our approach solves the IC submatrix in a BBD matrix as well as the diagonal blocks in parallel using all processors. In this approach, we allocate an IC submatrix in block-wise order rather than in dot-wise order onto all processors. Thus, we balance the processor perfomance with the communication capacity of a parallel computer system. When we changed the block size of IC submatrix allocation from dot-wise order to 88 block-wise order, the 88 block-wise order allocation almost halved the matrix solution time. The parallel simulation of a sample circuit with 3277 transistors was 16.6 times faster than a single processor when we used 49 processors.

A new Hybrid-ARQ scheme with a convolutional code and the Viterbi decoding is proposed, which uses the packet combining technique and a retransmission criterion based on an estimated decoding error rate. The throughput and bit error rate are evaluated by theoretical bounds and computer simulations. It is shown that a given error rate tolerance can be attained with good throughput for any signal to noise ratio, i.e. for the slow time-varying channels. Furthermore, the throughput performance can be improved by retransmitting not all but a part of packet.

In this paper, we compute entropies and average mutual informations for a 'choseong,' a 'jungseong,' and a 'jongseong' in multi-syllable Korean words. In these computations, we consider the property that each Korean syllable is divided into a 'choseong,' a 'jungseong,' and a 'jongseong' which are a consonant, a vowel, and a consonant, respectively, without exception. We compute entropies and average mutual informations for a 'choseong,' a 'jungseong,' and a 'jongseong' from the cumulative frequency of Korean syllables with respect to word length and syllable location in a word. We compute average mutual informations for a syllable and for a 'choseong,' a 'jungseong,' and a 'jongseong' between the two adjacent syllables in a word. The correlation between the two adjacent syllables in a word is not large on the average.

Let L{0,1}* be a language and let λL : {0,1}*{0,1} be the characteristic function of the language L, i.e., if x ∈ L, λL (x) = 1; otherwise,λL (x) = 0. In this paper, we consider an adaptive checker with a single program F (resp. noncommunicating multiple programs F1, F2,...) for λL that works even when an incorrect program F* (resp. incorrect noncommunicating multiple programs F*1,F*2,...) for λL adaptively behaves according to inputs previously provided to the program F* (resp. the programs F*1,F*2,...). We show that (1) for any language L, there exists an adaptive checker with a single program for λL iff L and respectively have competitive interactive proof systems; and (2) that for any language L, there exists an adaptive checker with noncommunicating multiple programs for λL iff L and respectively have function-restricted interactive proof systems. This implies that for any language L, adaptive chekers with noncommunicating multiple programs for λL are as powerful as static ones with a single program for λL.

Mobile communication networks need public key cryptosystems that offer both low computation cost and user authentication. Tatebayashi et al. showed a key distribution protocol for such networks at Crypto'89 based on low exponent RSA. This paper shows that their protocol is not secure. We also present two types of secure and efficient key distribution protocols.

We discuss ISDB (Integrated Services Digital Broadcasting) which has a transport structure to meet the technical requirements such as the flexibility and the extensibility of broadcasting in the future. The basic configuration of the ISDB transmission signal for distribution into various transmission channels is shown. Hybrid multiplexing, which uses common fixed-length packets and structured transmission units called "slots," is introduced to construct a transmission signal for low-cost signal processing in ISDB receivers. We show that a fixed packet length of 40-240 bytes results in high transmission efficiency in a diverse range of service arrangements. Furthermore, we use transmission control methods, which show the relationship between programs and packet IDs, to select the desired program with certainty and ease.

The sensitivity degradation due to unmatched quantum efficiencies is theoretically investigated for coherent optical POLSK heterodyne, homodyne and balanced receivers with shot noise, thermal noise and LO intensity noise. This analysis is based on the exact expressions of the probability density function (PDF) of the noise process to calculate the bit-error-rate (BER) considering LO intensity noise and unmatched quantum efficiencies. We derive the optimum LO power to minimize the power penalty for POLSK receivers. The theoretical results clarify the relation between the unmatched quantum efficiencies and sensitivity degradation due to the LO intensity noise. Based on this analysis, it is found that the balanced receiver is preferable for the design of POLSK receivers.

Long term phase noises are characterized for network synchronization using two time domain measurement techniques: the Maximum Time Interval Error (MTIE) and Time Variance (TVAR). First, the characteristics of previously measured fiber delay variations are evaluated. The diurnal and annual delay variations and the long term noise feature of random walk phase modulation are well represented by the TVAR technique. The delay variation due to the AU pointer operation is then measured using commercial SDH demultiplexing equipment and compared with the simulation result; the simulation result agrees well with the experimental result. The delay variation in the SDH equipment is simulated using the thermal fiber delay variation measured in the actual network as the input phase of the equipment. It is shown that the SDH equipment sometimes generates delay steps of 617ns, which are larger than the normal pointer operations of 154ns. The long term delay variation, periods over 107s, due to the threshold spacing between the positive and negative stuffing is described. We also show that TVAR is suitable for evaluating the phase noise feature and MTIE can clearly show the peak value of phase noise. The long term phase noises evaluated in this paper are the dominant sources that degrade network synchronous performance. The results of this paper will be useful in designing the equipment synchronous specification.

Throughout the paper, the nearest-neighbour (NN) interconnection of switches within a multistage interconnection network (MIN) is analysed. Three main results are obtained: (1) The switch preserving transformation of a 2-D MIN into the 1-D MIN (and vice versa) (2) The rearrangeability of the MIN and (3) The number of stages (NS) for the rearrangeable nonblocking interconnection. The analysis is extended to any dimension of the interconnected data set. The topological equivalence between 1-D MINs with NN interconnections (NN-MINs) and 1-D cellular arrays is shown.

In a hybrid coder which employs motion compensation and discrete cosine transform (MC-DCT coder), up to 90% of bits are used to represent the quantized DCT blocks. So it is most important to represent them with as few bits as possible. In this paper, we propose an efficient method for encoding the quantized DCT blocks of motion compensated prediction (MCP) errors, which adaptively selects one of a few scanning patterns. The scanning pattern selection of an MCP error block is based on the motion compensated images which are always available at the decoder as well as at the encoder. No overhead information for the scanning patterns needs to be transmitted. Simulation results show that the average bit rate reduction amounts to 5%.

This paper presents the results of a study made to determine the line length coverage of the high-bit-rate digital subscriber line (HDSL) present in NTT's local networks. The HDSL carries one bi-directional 784 kbit/s channel per pair and supports the digital interface at 1544kbit/s by using two cable pairs. The primary purpose of this study is to estimate the range limits for candidate transmission schemes considering line installation conditions, and to determine the most promising transmission scheme and its feasibility given the environment of NTT's local networks. Pulse amplitude modulation (PAM) and quadrature amplitude modulation (QAM) transmission schemes are compared for HDSL implementation. It is shown that 2B1Q-PAM and 16-QAM generally achieve better performance than the more complicated PAM and QAM given the presence intra-system crosstalk interference (interference between identical transmission systems). The range limits determined by inter-system crosstalk interference (interference between different transmission systems) with basic rate access (BRA) implementing a burst-mode transmission method are also estimated. This paper concludes that 2B1Q-PAM achieves the best overall performance in NTT's local networks. A feasibility study of 192-6144 kbit/s transmission is also described.

There are two approaches to implementing the international standard video coding algorithms such as H.261 and MPEG: a programmable DSP approach and a building block approach. The advantages and disadvantages of each are discussed here in detail, and the video coding algorithms and required throughput are also summarized. For more complex standard such as MPEG-, VLSI architecuture became more sophisticated. The DSP approach incorporates special processing engines and the building block approach integrates general-purpose microprocessors. Both approaches are capable of MPEG- NTSC coding in a single chip. Reduction of power consumption is a key issue for video LSIs. Architectures and circuits that reduce the supply voltage while maintaining throughput are summarized. A 0.25-µm, 3-GOPS, 0.5-W, SIMD-VSP for portable MPEG- systems could be made by using architecture-driven voltage scaling as well as feature-size scaling and SOI devices.

The networked reality is defined to be the virtual reality used in networks and using networks. The paper describes several levels of the networked reality and their applications.

When we design a human interface of a computer-mediated communication (CMC) system, it is important to take a socio-behavioral approach for understanding the nature of the human communication. From this point of view, we conducted experimental observations and post-experimental questionnaires to investigate communicative characteristics in a teleconference using Fujitsu Habitat" visual telecommunication software. We experimentally held the following three kinds of small-group conferences consisting of five geographically distributed participants: (a) teleconference using a visual telecommunication system (Fujitsu Habitat"), (b) teleconference using a real-time keyboard telecommunication system of NIFTY-Serve and (c) live face to face physical conference. Analyses were made on (1) effects of the media on utterance behaviors of conference members, and (2) satisfaction of conference members with communicative functions of the media. Satisfaction was measured by a seven-level rating scale. We found that participants in a telconference held by using Habitat showed significant differences in contents of utterances and the rating of satisfaction with nine communicative functions compared with those of conferences held by using a real-time keyboard telecommunication system and a live face-to-face conference. These results suggest some features that could facilitate multi-participant on-line electronic conferences and conversations.

In real life, our sence of social reality is supported by the institutional basis, group/interpersonal basis, and belief/schema basis. In networked life, in contrast, these natural and ordinary bases are not always warranted because of a lack of institutional backup, the fragility of the group or interpersonal environment, and the noncommonality of our common sense. In order to compensate for these incomplete bases, networkers ar seeking adaptive communication styles. In this process, there emerge three types of communication cultures. One is the name-card exchange" type. This type is realized by communicating our demographic attributes verbally, which is useful for reality construction of the institutional basis. The second is the ideographization" type. In this type, the content of customary nonverbal communication is creatively transformed into various pseudo nonverbal or para-linguistic expressions, which strengthen fragile interpersonal relationships. The last type is the verbalian" type. This type never depends on the interpersonal or institutional basis. The networked reality is constructed solely in the attempt for common sense development among members. By analyzing the content of messages exchanged in four public groups called Forums," the author found that patterns of communication are transformed in a manner adaptive to each Forum's reality. Thier adaptation modes are different and depend on the types of communication culture every Forum pursues. This is contrarty to the psychologists' tendency to assume that there must be common characteristics or rules valid throughout all of the electronic communication situations.

The many-user networked virtual world system InterSpace" is described. This system's main purpose is to enhance the user's communication activities. In InterSpace, the real world information is embedded in the shared virtual world as a combination of video and CG images. Users can ovserve and access this information by simply looking and approaching embedded images. The concept of InterSpace and a prototype system of this service are introduced.

We numerically show that the learning time t of the back propagation model with the encoder topology obeys a power law described as t MD (D: constant, 1

This paper describes a design method of stuff synchronization circuit for High-definition Television (HDTV) transmission to reduce stuff jitter, one of the greatest problems in video transmission through plural Synchronous Digital Hierarchy (SDH) networks operating with different frequency sources. First, we determine the quantity of stuff jitter in SDH networks using the pointer mechanism and Administration Unit (AU) pointer bytes. From the results of a subjective test conducted for HDTV, we show that the minimum noticeable jitter is 3.6 nsec in using a color-bar pattern as a test image and a sinusoidal wave as a jitter signal. These results are used to describe the effect of stuff jitter on picture quality. We then introduce a distributed destuffing method at the receiving end, and show that jitter can be reduced by about 32dB in a 622Mbps rate system. Based on these results, we finally show that the cut-off frequency of the clock recovery PLL for distributed destuffing is more than 10 times higher than that required by conventional destuffing. This reduces the pull-in time by more than 99.9%.

The double-stage threshold-type foreground-background congestion control for the common-store queueing system with multiple nonpreemptive priority classes is proposed to improve the transient performance, where the numbers of accepted priority packets in both foreground and background stores are controlled under the double-stage threshold-type scheduling. In the double-stage threshold-type congestion control, the background store is used for any priority packets, and some parts of the background store are reserved for lower-priority packets to accommodate more lower-priority packets in the background store, whereas some parts of the foreground store are reserved for higher-priority packets to avoid the priority deadlock. First, we derive the general set of coupled differential equations describing the system-state, and the expressions for mean system occupancy, throughput and loss probability. Second, the transient behavior of system performance is evaluated from the time-dependent state probabilities by using the Runge-Kutta procedure. It is shown that when the particular traffic class becomes overloaded, high throughputs and low loss probabilities of other priority classes can be obtained.