This paper describes a planning method for ATM networks. The method is based on evaluation of two design items, VC routing and VP routing, as well as on consideration of VPI constraints. In the evaluation, VC routing is compared with VP routing in separate case studies undertaken from the point of view of various parameters such as traffic volume, cost function and network scale. The results suggest the vertical relationship between VC and VP levels in optimally designed ATM networks. VC and VP network levels are then studied separately, and design methods are proposed for individual levels. In addition a perturbation method is proposed for the VC and VP routing use, whose optimum is varied as a function of the parameters described above. Evaluation results show the proposed perturbation method provides cost-effective networks.

To realize Broadband ISDN, which provides multi-media services, ATM (Asynchronous Transfer Mode) has been standardized by CCITT and the development of the system is accelerating towards the 21st century. The packet-oriented information transfer based on fixed size blocks called cells provides a very flexible allocation of transmission capacity to different connections. On the other hand, to ensure the QoS (Quality of Service) for all established connections it is necessary to monitor and regulate the input traffic from each user based on usage parameters which are negotiated between user and network at connection set-up, i.e., a policing function is required. In this paper some requirements for a policing function will be given. Accuracy of the policing decision for violating and well-behaving sources, tolerance with respect to cell delay variation (CDV) which is caused by multiplexing functions between the source terminal and the policing device, time to detect arriving violating cells, implementation complexity, and amount, i.e., cost effectiveness, are discussed mainly. We present simulation results for five policing mechanisms, Leaky Bucket (LB), Jumping Window (JW), and Moving Window (MW) which have been already well-known, Pseudo Jumping Window (PJW), and Pseudo Moving Window (PMW) which are proposed mechanisms. PJM and PMW mechanisms required a pseudo cell buffer with finite queueing capacity to the corresponding JW and MW mechanisms, respectively. These two mechanisms can be expected as advanced methods from view points of the accuracy of the policing for long-term fluctuated compliant source, fast reaction ability and restrictness to long burst traffic comparing with the above existing methods. We compare the five mechanisms based on the above requirements and show that the PJW and the LB are the most effective mechanisms for mean rate policing in ATM networks.

The performance of various ARQ protocols has recently been analyzed for multidestination environments. In all previous work, the round-trip delays between the transmitter and each of the receivers are assumed (or forced) to be equal to the maximum one, to simplify the analysis and/or the operation. This assumption obviously will sacrifice the system performance. In this paper, we evaluate the throughput efficiencies of three multidestination GBN ARQ protocols under unequal round-trip delays. In the investigated protocols, multiple copies of each data block are (re)transmitted contiguously to the receivers. Tight lower bounds are obtained for the throughput efficiencies of the schemes in which each data block is transmitted with the optimum number of copies. Results show that assuming all the round-trip delays to be equal to the maximum one may sacrifice the performance significantly. We also compare the performances of the three investigated protocols. In general, the performance becomes better as the transmitter utilizes more of the outcomes of previous transmission attempts.

This paper presents a method for verifying safety property of a communication protocol modeled as two extended communicating finite-state machines with two unbounded FIFO channels connecting them. In this method, four types of atomic formulae specifying a condition on a machine and a condition on a sequence of messages in a channel are introduced. A human verifier describes a logical formula which expresses conditions expected to be satisfied by all reachable global states, and a verification system proves that the formula is indeed satisfied by such states (i.e. the formula is an invariant) by induction. If the invariant is never satisfied in any unsafe state, it can be concluded that the protocol it safe. To show the effectiveness of this method, a sample protocol extracted from the data transfer phase of the OSI session protocol was verified by using the verification system.

Until now, in a communication system which deals with multiple processes, system behavior has been described by a fixed number of processes. The state reachability problem for specified processes was generally deliberated within a pre-defined number of processes, and was analyzed by essentially searching for all possible behaviors. However, in a system whose number of processes is arbitrary, a given state which is not reachable in some situations which consists of a small number of processes might be reachable in another situation which consists of a larger number of processes. This article discusses the above problem, assuming that the behavior of a system is described by an arbitrary number of processes. After discussing the relationship between our model and the Petri net model, we clarify the properties between the set of reachable states and the number of processes involved in the system, and show an algorithm to obtain a sufficient number of processes for resolving the reachability problem.

Queueing problems are investigated for very wide classes of input traffic and service time models to obtain good loss probability and waiting time probability approximation. The proposed approximation is based on the fundamental recursion formula and the Chernoff bound technique, both of which requires no particular assumption for the stochastic nature of input traffic and service time, such as renewal or markovian properties. The only essential assumption is stationarity. We see that the accuracy of the obtained approximation is confirmed by comparison with computer simulation. There are a number of advantages of the proposed method of approximation when we apply it to network capacity design or path accommodation design problems. First, the proposed method has the advantage of applying to multi-media traffic. In the ATM network, a variety of bursty or non-bursty cell traffic exist and are superposed, so some unified analysis methodology is required without depending each traffic's characteristics. Since our method assumes only the stationarity of input and service process, it is applicable to arbitrary types of cell streams. Further, this approach can be used for the unexpected future traffic models. The second advantage in application is that the proposed probability approximation requires only small amount of computational complexity. Because of the use of the Chernoff bound technique, the convolution of every traffic's probability density fnuction is replaced by the product of probability generating functions. Hence, the proposed method provides a fast algorithm for, say, the call admission control problem. Third, it has the advantage of accuracy. In this paper, we applied the approxmation to the cases of homogeneous CBR traffic, non-homogeneous CBR traffic, M/D/1, AR(1)/D/1, M/M/1 and D/M/1. In all cases, the approximating values have enough accuracy for the exact values or computer simulation results from low traffic load to high load. Moreover, in all cases of the numerical comparison, our approximations are upper bounds of the real values. This is very important for the sake of conservative network design.

We analyze frame rates in low bit rate video coding and show that an optimal frame rate can be theoretically obtained. In low bit rate video coding the frame rate is usually forced to be decreased for reducing the total amount of coded information. The choice of frame rate, however, has a great effect on the picture quality in a trade-off relation between coded picture quality and motion smoothness. It is known from experience that in order to achieve an optimum balance between these two factors, a frame rate has to be selected which is appropriate for the coding scheme, property of the video sequences and coding bit rate. A theoretical analysis, however, on the existence of an optimal frame rate and how the optimal frame rate would be expressed has not been performed. In this paper, coding distortion measured by mean square error is analyzed by using video signal models such as a rate-distortion function for coded frames and inter-frame correlation coefficients for non-coded frames. Overall picture quality taking account of coded picture quality and motion smoothness simultaneously is expressed as a function of frame rate. This analysis shows that the optimum frame rate can be uniquely specified. The maximum frame rate is optimal when the coding bit rate is higher than a certain value for a given video scene, while a frame rate less than the maximum is optimal otherwise. The result of the theoretical analysis is compared with the results of computer simulation. In addition, the relation between this analysis and a subjective evaluation is described. From both comparisons this theoretical analysis can be justified as an effective scheme to indicate the optimal frame rate, and it shows the possibility of improving picture quality by selecting frame rate adaptively.

In our preceding paper, I-ISMA (Idle Signal Multiple Access for Integrated services), a combination of ISMA and time reservation technique, was proposed to transmit an integrated voice and data traffic in third generation wireless communication networks. There, the channel capacity of I-ISMA was evaluated by the static analysis. To fully estimate performance of contention-based channel access protocols, however, we also need dynamic analysis to evaluate stability, delay, etc. Particularly, in systems concerning real-time voice transmission, delay is one of the most important performance measures. A six-mode model to describe an I-ISMA system is set up. With some assumptions for simplification, the dynamic behavior of the system is approximated by a Markov process so that the EPA (Equilibrium Point Analysis), a fluid approximation method, can be applied to the analysis. Then, numerical and simulation results are obtained for some examples. By means of the same analysis method and under the same conditions, the performance of PRMA is evaluated and compared briefly with that of I-ISMA.

A new automated main distributing frame (AMDF) system is developed that reduces operating costs in metallic-cable main distributing frames (MDFs) used for communication networks. In this AMDF system, a robot inserts connecting-pins into the crosspoint holes of matrix-boards. This process allows jumpering to be completed within three minutes and the route-setting for line testing within one minute. The AMDF system provides approximately 2,100 office equipment cable-terminals. Parallel installation of several AMDF systems allows larger MDF systems to be constructed. This system reduces costs and achieves high reliability through three new technologies: high-density matrix-board, precision pin-handling, and a highly reliable system control. Test results for a prototype AMDF system confirm their effectiveness.

High Definition Television (HDTV) is likely to be one of the major services in the Broadband Integrated Services Digital Network (B-ISDN). The transmission of HDTV signals on digital networks requires the adoption of sophisticated compression techniques to limit the bit-rate requirements and to provide high-quality and cost-effective network services. A flexible coding scheme that supports various bit-rates is needed to support the various services expected which will have different requirements. This paper describes the design of an HDTV codec based on a subband DCT coding algorithm that can encode original 1.2 Gb/s HDTV signals to less than 50Mb/s. A configuration that efficiently bridges HDTV and standard TV signals is also proposed. Computer simulation results show that the degradation caused by the bridging function is insignificant. In the coder, first stage quadrature mirror filters (QMFs) decompose the input signal into two bands in the horizontal direction, while the second stage filters decompose the two bands into four bands in the vertical direction. Adaptive DCT (Discrete Cosine Transform) is adopted for horizontal-low and vertical-low (LL) signal coding. High-band signals are coded by adaptive DPCM and PCM. To maximize bit-rate reduction efficiency, DCT coding is adaptively applied to either the intra-field signals, the inter-field signals, or the motion compensated inter-frame signals. Bi-directional inter-frame prediction is applied to the adaptive DCT coding to improve coding performance at low bit rates. The same prediction mode as for LL signal is applied to adaptive DPCM coding of LH and HL signals. Compatibility is realized by a configuration in which both the TV signal components and the residual signal, derived by subtracting the TV signal from the LL signal, are encoded.

A stored channel simulator for digital mobile radio enviroments is proposed, which enables the field tests in the laboratory under identical conditions, since it can reproduce the actual multipath radio channels by using the channel impulse responses (CIR's) measured in the field. Linear interpolation of CIR is introduced to simplify the structure of the proposed simulator. The performance of the proposed simulator is confirmed by the laboratory tests.

A new concept for a positioning satellite system based on a new satellite constellation has been studied. The system needs a minimum of four satellites injected into quasi-geostationary orbit (QGEO) with high inclination. Due to the QGEO characteristic, the satellites are orbiting within continuous visibility range of ground control stations (GCS), from which the satellite time is controlled through the link connections of the feeder and the intersatellite communication (ISC). Consideration is made for the required high accuracy and quality checks against malfunction, wherever the satellites may be positioned. The orbit data processing function, another major function, is performed independently of the time control. The case of global coverage attained by twelve satellites has been studied in this paper. When a constellation of satellites for a global navigation satellite system (GNSS) is designed, conditions to obtain a good geometric dilution of precision (GDOP) at all places and times should be considered. Therefore, the satellites will be spread out in wide directions and are in an asymmetrical arrangement when seen by an observer are considered when setting the parameters of the ephemerides of the constellation. Under the restraints of the designed constellation, the GDOP value distribution for a third of the world map with area time parameters is computed and summarized in histograms for the system evaluation.

This paper describes a novel method to calculate the fields scattered by a polyhedron structure for an incident plane wave. In this method, the fields diffracted by an edge are calculated using the equivalent edge currents which are separated into components dependent on each of the two surfaces which form the edge. The separated equivalent edge currents are based on the Geometrical Theory of Diffraction (GTD). Using this Separated Equivalent Edge Current Method (SEECM) , fields scattered by a polyhedron structure can be calculated without special treatment of the singularity in the diffraction coefficient. This method can be also applied successfully to structures with convex surfaces by modeling them as polyhedron structures.

An approximate but sufficiently accurate high frequency solution is developed in this paper for analyzing the problem of electromagnetic plane wave scattering by an open-ended, perfectly-conducting, semi-infinite parallel-plate waveguide with a thin layer of lossy or absorbing material on its inner wall, and with a planar termination inside. The high frequency solution combines uniform geometrical theory of diffraction (UTD) and aperture integration (AI) methods. The present method has several advantages in comparison with other methods.

Numerical analysis of the electromagnetic radiation from conducting surface structures is concerned. The method of moments is discussed with the surface-patch modeling in which the surface quantities, i.e. the current, charge and impedance are directly introduced and with the wire-grid modeling in which the surface quantities are approximated by the filamentary traces. The crucial element to a numerical advantage of the wire-grid modeling lies in the simplicity of its mathematical involvements that should be traded for the uncertainties in the construction of the model. The surface-patch techniques are generally not only clear and straightforward but also more reliable than the wire-grid modeling for the computation of the surface quantities. In this work, we bring about a comparative discussion of the two approaches while the analysis of a built-in planar antenna is reported. For the purpose of the comparison, the same electric field integral equation and the Galerkin's procedure with the linear expansion/testing functions are used for both the wire-grid and surface-patch modeling.

Statistically improved results of power line radiation (PLR) over Eastern Asia observed at 50 and 60Hz are described in this paper. A total number of 150 orbits, which had been observed from June 1984 to January 1986, by the Japanese scientific satellite OHZORA, are used to detect PLR over Eastern Asia around the Japanese Islands. Depending on the increase in the number of data points, the statistical characteristics of the background noise can be precisely determined by using the improved technique compared with the initial analysis. Statistically reasonable data points are detected as PLR based on the +3 criterion, where is the standard deviation of the background noise. Therefore, the statistical reliability for rejecting the background noise is 99.85%. Then, these detected data are applied to the cause-and-effect test. When the statistically detected data points are placed on the map of Eastern Asia, the points cover Eastern Japan and the east coast of China for 50Hz, and they cover Western Japan for 60 Hz. The maps of the detection ratios and those of the average field strengths indicate the positive correlation with the ground maps of the electric power generation at 50 and 60 Hz. The positive correlation is more clearly seen at 50Hz since the background noise is somewhat weaker than that at 60Hz. This close relationship between the satellite observation and the electric power generation suggests that the detection of PLR is not caused by chance, and that PLR penetrates into the ionosphere and propagates approximately just upward. The decrease of field strength with altitude can be interpreted as the gradual decrease of the refractive index from 400 to 700km. Therefore, the detection ratio and the average field strength with respect to the satellite altitude suggest PLR propagating from the bottom of the ionosphere. According to these observational results, it is concluded that PLR in Eastern Asia is high above the high electric power generating regions over Japan and China, and that the satellite observation is capable of estimating PLR field below the ionosphere. These results are the first direct indication that the PLR field is enhanced over the high electric power generation region, and is penetrating into the ionosphere.

A method for constructing a compact non-blocking, large matrix-size, optomechanical switch is proposed. It can be switched arbitrarily by disconnecting and reconnecting ferrules on the matrix board. A 250500, 25-mm-ferrule-pitch, 800^W855^D945^H (mm) switch is fabricated. Although the space above the board is densely packed with many ferrule-terminated-fibers, because of the way in which they are arranged and the control of their length, there is no discernible excess loss due to fiber bending.

The design of a high speed self-routing network switch module is described. Clock distribution and timing design to achieve high-speed operation are considered. A 88-port self-routing Benes network switch prototype on multi-chip module is fabricated using 44-port space division switch LSIs. The switch module achieves a maximum measured clock frequency of 750MHz under switching operation. Resultant total throughput of the switch module is 12Gbit/s.

For analyzing the transient electromagnetic fields caused by electrostatic discharge (ESD), a new ESD model is presented here. Numerical calculation is also given to explain the distinctive phenomenon being well-recognized in the ESD event.