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In a low-antenna-height line-of-sight (LOS) microcell, the delay spread characteristic strongly depends on the road shape, the location of the transmitting and receiving points, and so on. To analyze this propagation mechanism, it is necessary to deal with location-specific properties. This paper describes analyzed results for the multipath delay mechanism in a rectilinear street with intersections where both transmitting and receiving stations exist. Special focus is placed on reflection at LOS building walls and on diffraction at building corners at street intersections, and their effect as a factor creating multipath delay is investigated numerically. We show that waves created by their reflection and/or diffraction are significant multipath delays making a major contribution to delay spread in microcells. This paper also presents a comparison between the calculated and measured delay spread, and discusses the effectiveness of the propagation mechanism described. © 1998 Scripta Technica, Electron Comm Jpn Pt 1, 82(4): 56–70, 1999 [ABSTRACT FROM AUTHOR]

This paper proposes a new loop antenna for circular polarization with a single feed. It is an unloaded loop antenna with a peripheral length of one wavelength and uses a compound-wire loop in which adjacent wires have different cross-sectional structures. This antenna is considered as a transmission line above a ground plane and analyzed as an equivalent circuit in which the different cross-sections of the wires are represented by different characteristic impedances. Using the transmission-line model, the condition for circular polarization is derived in terms of the characteristic impedances and the antenna height. Then, as a simple example, a loop antenna with composite radius and a circular cross-section is designed, and the relations among the antenna height, radius ratio, and the input impedance are investigated. The results are discussed and compared to the results of numerical analysis by the method of moments. Then, providing a proof of the effectiveness of the proposed method, an experiment considering the feeding structure is also described; the results agree well with the theory. © 1999 Scripta Technica, Electron Comm Jpn Pt 1, 82(5): 42–50, 1999 [ABSTRACT FROM AUTHOR]

The M-sequence (maximum length sequence) is often used as a ranging signal in radar and other systems. This paper considers the case where an M sequence ranging signal is detected by an MPD (matched pulse detector), which is a digital correlator, and analyzes the probabilities for miss detection and for false detection due to bit error. Previously, this correlation function has not been derived analytically. In this paper, a procedure is presented where the threshold for the miss detection and false detection probabilities is determined by a simulation result for the correlator. An experiment is attempted in which a single M-sequence is detected in satellite communication using VSAT (very small aperture terminal). It is shown that the experimental results and analysis almost agree for a single M-sequence with a 31-bit code length. © 1998 Scripta Technica. Electron Comm Jpn Pt 1, 82(2): 82–89, 1999 [ABSTRACT FROM AUTHOR]

This paper focuses on the three-dimensional frequency characteristics of inter-field signal processing closed in a frame. This is a form of inter-field image processing using two fields of one frame (also called field-merge processing) that is employed in digital image compression. This often-used closed-frame processing occurs when signals are processed in frame-based image simulations. It is a time-variant system, i.e., the field of a frame used in processing alternates between past and future. A conventional signal analysis approach cannot be used to analyze its frequency characteristics. This paper introduces a new method that we have developed to express inter-field signal processing closed in a frame (hereafter referred to as closed-frame signal processing) by a time-invariant system. The results of analyzing the three-dimensional frequency characteristics are also presented. Closed-frame signal processing is being used to improve the quality of HDTV MUSE pictures. With this new method, we were able to calculate the three-dimensional frequency characteristics of the new MUSE system. We also measured the three-dimensional frequency characteristics in an experiment, and compared the measurements with theoretical values. © 1998 Scripta Technica, Electron Comm Jpn Pt 1, 82(4): 23–32, 1999 [ABSTRACT FROM AUTHOR]

With the realization of broadband integrated service digital networks (B-ISDN), broadcast services will occupy a large part of the network traffic. In these services, the same information is distributed to many subscribers through the point-to-multipoint connection paths. This connection form is quite different from that of conventional point-to-point services. Since the conventional network structure is designed for point-to-point services, the current network topology may lower the quality of service or may increase construction costs. In this paper, the hierarchical broadcast network topology is optimized under certain assumptions: the cost functions, the population distribution, and the percentage of broadcast services are treated as parameters. The result shows that the ring-star-star or ring-ring-star topologies can be better than the conventional mesh-star topology in some cases, and can be much better when the viewing ratio of broadcast services increases. © 1998 Scripta Technica, Electron Comm Jpn Pt 1, 82(2): 48–56, 1999 [ABSTRACT FROM AUTHOR]

Distributed databases in general-purpose business software such as groupware widely use a method for simultaneously updating the replicas of other databases owned by each database according to the replication routing schedule. In this paper, a replication routing schedule is discussed in which the time required for updating the replica is the minimum in the distributed database. Specifically, an optimization problem is first formulated for deriving the replication routing schedule with minimum update time. Next, in the cases of even and odd numbers of distributed databases, an algorithm providing a replication routing schedule as an optimum solution is presented in the even case, while a heuristic algorithm providing an approximate solution is shown for the odd case. These algorithms are extremely simple and are practical since the required amount of computational processing is small. © 1998 Scripta Technica, Electron Comm Jpn Pt 1, 82(2): 11–20, 1999 [ABSTRACT FROM AUTHOR]

A shared multi-buffer ATM switch is cost-effective, since it uses low-access-speed memories when compared with a shared single-buffer ATM switch. Due to the low access speed, however, the switch cannot read several cells from a buffer during a single access. Such an access conflict provides a high cell loss rate. In this paper, we propose several cell storage methods that avoid the access conflict, and we compare our approach via simulation with the previously proposed cost-ineffective solution that uses high speed memories under various load conditions. The results show that one of the proposed methods in this paper provides an almost equivalent cell loss characteristic to the previously proposed approach. ©1998 Scripta Technica, Electron Comm Jpn Pt 1, 82(2): 39–47, 1999 [ABSTRACT FROM AUTHOR]

This paper proposes a new small multisector antenna called MS-MPYA (multisector monopole Yagi-Uda array) for wireless LANs. MS-MPYA consists of a multisector monopole Yagi-Uda array on a circular finite ground plane. The horizontal radiation pattern of the MS-MPYA is largely determined by the multisector array setting effect. A numerical analysis shows that setting metallic fins between arrays is effective in eliminating the strong reflection that would otherwise cause pattern instability; when the metallic fins are set, the beamwidth is reduced in the horizontal plane due to mutual sector interaction. The MS-MPYA design method considers the variables of array length, ground plane length, reflector height, and fin length. We clarify that the MS-MPYA offers a much lower profile than corner reflector or horn antennas. © 1998 Scripta Technica, Electron Comm Jpn Pt 1, 81(12): 80–90, 1998 [ABSTRACT FROM AUTHOR]

Telecommunications Information Networking Architecture (TINA) is aiming at reusability and interoperability of software by use of location/fault transparency of objects based on distributed processing and object orientation technologies. Currently many attempts to realize TINA commercial systems are ongoing all over the world. As the first step of those attempts, the TINA Trial (TTT) is scheduled to be realized in 1998. To achieve the quality to be used for the commercial systems, quality study not only of software but also of hardware platforms becomes key. This paper intends to clarify the requirements of TINA-based high-quality multimedia networks and possible solutions by considering the TTT system which the authors are developing. The requirements from the perspective of quality are effective usage of system processing capability by effective multiprocessing without any processing overhead and improvement of system stability by fault management achieving autonomous system reconfiguration. This paper shows the desirability of applying stream-oriented data-driven processor to the TINA system so as to satisfy these requirements. © 1998 Scripta Technica. Electron Comm Jpn Pt 1, 81(8): 51–58, 1998 [ABSTRACT FROM AUTHOR]

This paper proposes a new network architecture, ALPEN (ATM multi-protocol emulation network), based on a new concept for realizing full-scale multimedia communication networks. In ALPEN, various communication protocols, such as ABR (available bit rate), FRM (fast resource management), or SHM (short hold mode), can be handled using a single, simple transit network. Each protocol is emulated at the edge node of the WAN (wide area network), and the status of the transit network is checked by periodically examining the residual bandwidth information of each route. ALPEN is a cost-effective and flexible network architecture because it enables us to implement new services or protocols easily by modifying only the edge nodes. In ALPEN, since individual edge nodes periodically obtain the bandwidth information, it is possible to respond promptly to a user's request to change his bandwidth. In particular, when the network's RTT (round trip time) is long, as in a WAN, ALPEN is a promising way to resolve the problem of performance responsibility. Although each edge node periodically checks the disperse information to all destination edge nodes on a residual bandwidth, the information might be old, or it might be necessary to process it independently at the multiple edge nodes. Therefore, the parameter of “effective residual bandwidth” is estimated by a statistical method; the estimation also considers that bandwidth resources may be overbooked by multiple edge nodes. The statistical method is described in this paper. The ALPEN introduced in this paper is an effective architecture that makes it possible to implement new or various unforeseeable network services in the future multimedia era, in which various services and protocols may exist simultaneously. © 1998 Scripta Technica. Electron Comm Jpn Pt 1, 81(8): 19–31, 1998 [ABSTRACT FROM AUTHOR]

Backpressure control is one of several effective traffic control schemes for ATM-LAN. Comparing an input queuing switch with an output queuing switch, backpressure control in a congested input queuing switch has the ability to selectively control the output port of the front stage of the input queuing switch. This paper compares an input queuing switch with an output queuing switch for single and multiple stage configurations by using a computer simulation. The output queuing switch controls all the output ports of the front switch. The input queuing switch, however, can selectively control the congested output port of the front switch. This paper evaluates and compares the performance of the switches for burst traffic. © 1998 Scripta Technica. Electron Comm Jpn Pt 1, 81(7): 38–46, 1998 [ABSTRACT FROM AUTHOR]

Small receivers such as pagers are used in various situations due to their portable nature. These portable units are subject to changes in situation and shift of location so that the receiving gain of arriving wave changes significantly. In this paper, the characteristics of planar loop antennae are studied in detail. We proposed that polarization characteristics can be improved significantly by switching the shorting location of the planar loop antenna. In order to study this effect more realistically, polarization characteristics are measured and evaluated using a model that includes a switching circuit and an oscillator. © 1998 Scripta Technica. Electron Comm Jpn Pt 1, 81(6): 24–30, 1998 [ABSTRACT FROM AUTHOR]

To achieve increased output and frequency stability in solid-state oscillation it is necessary to reduce the oscillator noise. Measures that may be employed to achieve this include operation of a number of oscillators in parallel, external injection locking, self-injection locked operation or a combination of such measures. The purpose of this paper is to clarify the nature of the mechanism which causes improved stability or improved noise characteristics due to injection-locked operation and to develop an intuitive grasp of the stability and noise characteristics of such complex oscillator circuits. In the analysis technique we consider oscillators operating above the microwave band using traveling waves. The Rifle diagram of the oscillator is transformed so that the traveling wave analysis can be performed and a graphical presentation is used to show how arbitrary frequency components of noise are outputted. It is clearly shown how the oscillator output signal (angular frequency ω0) interacts parametrically with the noise equivalent input signal (ω0 + ωn) due to the input signal amplitude dependence of the Rieke diagram, producing a noise output signal of angular frequency ω0 - ωn. We are also able to show on the Riske diagram how the noise characteristic varies with the magnitude and frequency of the injection signal. [ABSTRACT FROM AUTHOR]

The one-dimensional map is the simplest system in which there can be produced a random orbit called chaos. In the theoretical discussion o chaos, it is important to examine statistics and statistical properties of the chaotic orbit. In general, however, it is difficult, except for some special one-dimensional maps, to examine analytically the statistics. This paper proposes a new method of time-series analysis in order to obtain approximately the various kinds of statistics of the chaotic orbit, such as invariant density, autocorrelation function, power spectrum, and K-S entropy. The essential idea of the proposed method is to replace the integral operator by the finite-dimensional constant matrix P, which Is the finite-element approximation to the integral operator. The approximate expressions for the statistics are given explicitly by the eigenvalues and eigenvectors of P. Applying the proposed method to several mixing one-dimensional maps and determining their statistics, it is concluded that the proposed method is useful in the tine-series analysis of the chaos in the mixing one-dimensional map. [ABSTRACT FROM AUTHOR]

As a method of solving the electromagnetic scattering by perfectly conducting cylinders, the discrete singularity method is discussed. For this method, a finite number of singular points is distributed within the scatterer and the wave function composed of a linear combination of solutions (each of which is derived from a helmholtz equation with each single singularity among the many) is matched with the incident wave function on the boundary. The remaining important problem in this method is how to distributed these singularities in order to obtain the accurate solution with faster convergence and with fewer number of singular points for an arbitrary configuration of the scatterer. The purpose of this paper is to present a reasonable solution to this problem. The essential of the method is that by making as unknown quantities, not only the unknown amplitude coefficients involved in the linear combination of the solutions, but also the coordinates of the singularities, the scattered wave is matched on the boundary in the sense of the least squares. This problem is linear in the amplitude coefficient but nonlinear in the singularity coordinate. Thus we solve this problem by using the algorithm by marquardt et al, of a nonlinear optimization process. This paper considers the general description and indicates its effectiveness by showing a few examples of the scattering problem of rectangular cylinders. [ABSTRACT FROM AUTHOR]

The microwave displacement meter based on the principle of phase interferometer has a high sensitivity in detection, However, in the conventional system the measurable displacement width is limited to the order on e haft-wavelenght of the microwave, and quantitative information can not be obtained without calibration. In the system proposed in this paper, a two-phase microware Doppler sensor (10.525 GHz) is used for detecting the reflected signal from the object as a vector, and displacement is measured directly from the phase.Which the high sensitivity of the phase interferometric method is maintained, the measurable width is improved significantly and quantitative measurement is possible. However, in the present method, the offset caused by the existence of unwanted reflectors other than the object can be a problem. Since this is depent on the measurement environment, the problem is expecially severe for biological measurement. In the this papers, this offset is calculated by estimation and is shown to be removable. Next, a recurrence formula is derived that is used calculating the displacement from the phase of the signal vector. The propotype system can measure the displacement width of 36 cm with the resolution of 90 um. As an example of biological measurement, two-dimension body movement measurement in the balacing function test is presented. Finally, the accurancy and resolution of the present method are studied. [ABSTRACT FROM AUTHOR]

In block interleavers which reorders digits of pulse sequence in a block, pulse distance distribution and interleaving delay time characteristics depend greatly on reading and write-out methods of block inter-leaves and the phase relation between observed pulse sequence and an interleaved block. Hence, it has become necessary to choose an interleaving method in accordance with the purpose. So far, little study has been made which takes account of this condition. This paper analyzes (b,q) interleaver by choosing pulse distance and minimum coding delay time criteria, and shows that effective block interleavers can be classified into four classes. Futhermore, kinds of new (b,q) block interleavers which make the pulse distance greater than q - 1, and these methods maximize the minimum pulse distance among (b,q) block interleavers. Finally, an application example to smear transmission systems is presented and it is shown that the proposed (b,q) block interleavers make it possible to suppress more greatly the burst impulse noise than the conventional (b,q) block interleavers. [ABSTRACT FROM AUTHOR]

In attempt to detect glottic cancer patients by voice information, this paper discusses the properties of the perturbation quotient defined on the pitch period and the amplitude sequences obtained from the outer-tracheal vibration in the sustained utterance of a vowel. Examinations were made for 42 glottic cancer patients and 39 aged normals. As a result, the following observations were made: (1) The glottic cancer patients beyond T2 in T-classification can fairly accurately be detected. (2) Applying the linear discriminant function to the perturbation quotients, the discrimination score between the glottic cancer and the normal is almost equal to that of a specially trained laryngologist, who listened to the same sample voices and determined the existence of hoarseness. (3) The perturbation quotient is almost independent of the age of a speaker and the kind of vowels spoken. This paper describes a new algorithm to estimate accurately the pitch period and the amplitude sequences, as well as the evaluation of the discriminating capability of the perturbation quotients, taking into consideration the variations within the same speaker. [ABSTRACT FROM AUTHOR]

In the signal transmission of land mobile communication, the received electric field is affected by multipath fading due to multipath propagation, and the transmission quality is degraded. A diversity reception of some type can be an effective technique against this fading. This paper analyzes theoretically the improvement possible using two-branch switched diversity against the cochannel interference and thermal noise when voice signals are processed by compander and are transmitted by PM. When the baseband SNR (signal-to-noise ratio) under fading is 15 dB, the improvement effects against thermal noise and cochannel interference are 9 dB and 4.5 dB, respectively. When the SNR is 10 dB, they are 7dB and 3 dB. Furthermore, we show that the optimum switching level maximizing the baseband SNR exists and depends on CNR (average carrier-to-noise ratio), and CIR (average carrier-to-interference ratio), and the modulation level. [ABSTRACT FROM AUTHOR]

Recently, many attempts have been made to increase the bandwidth and the gain of circularly polarized antennas constructed on printed circuit boards. In a previous paper, a wide bandwidth was achieved for a circularly polarized array antenna composed of strip dipoles and slots (CP-PASS), although its actual gain was rather low. In the present paper, the gain of CP-PASS is enhanced by adopting an end-fed strip dipole as a strip element, and a basic design procedure and some experimental results of CP-PASS are shown. First, it is verified by experiments that the end-fed strip dipole has some advantages; for example, it has a sufficient gain, its crosspolar radiation level is low, and it is easy to control the radiation resistance. Second, an approximate analysis is made for a basic radiating-element pair for CP-PASS, and a basic design procedure of CP-PASS is obtained by applying the analysis. Finally, several CP-PASS are made and measures, and the design procedure is found to be useful. For a six-pair CP-PASS, its actual gain, 3-dB gain bandwidth, and axial-ratio bandwidth are about 12 dBi, 11% and 12%, respectively. It is found also that CP-PASS requires only a slight correction to the element lengths when a reflector is placed. In addition, it is obtained that the gain of CP-PASS may be increased further. [ABSTRACT FROM AUTHOR]

This paper presents a new method of analysis with numerical results for plane-wave scattering by a layer with inhomogeneous permittivity ε (x) and permeability µ (x). The analysis is based on the following idea (1) we construct a periodic structure, an iteration of the given layer and apply Maxwell's equation for this structure; (2) the electromagnetic fields in this periodic structure are expanded into Fourier series, and the obtained characteristic equation is transformed into an eigenvalue equation; (3) the electromagnetic field in the original inhomogeneous layer is expanded by the solutions of the eigenvalue equation, and the reflected and the transmitted waves are computed by using the boundary conditions. We call this method the Fourier series expansion method (FEM). When the differential equation obtained in the first step of FEM contains dεp(x)/dx (or dµp(x)/dx), Hill's matrix method cannot be applied for the profile for which d²εp(x)/dx² (or d²µp(x)/dx²) is discontinuous. By contrast, FEM in this paper can be applied even if εp(x) (or µp(x)) is continuous, dεp(x)/dx (or dµp(x)/dx) is discontinuous. Even if ε(x) (or µ(x)) of the original inhomogeneous layer is discontinuous we can always construct a periodic structure with continuous ε(x) (or µ(x)), so that FEM can be applied. By numerical analysis, the usefulness of the method is evaluated from the viewpoint of the accuracy of the solution vs. the number of terms in the expansion of the comparison with already reported results. As an example of application, reflectivity is computed for the concrete layer with inhomogeneous permittivity and permeability containing magnetic particles. [ABSTRACT FROM AUTHOR]

This paper assumes a situation where the state of a plant cannot be measured directly, and discusses the problem to construct the internally stable model-following linear system without using a state observer. The problem consists in constructing a compensator (dynamic compensator plus feedback) for the plant so that the transfer function matrix of the obtained closed-loop coincides with that of the model, and the closed-loop system (the model-following system) is internally stable. This paper shows the necessary and sufficient condition for the problem to be solvable, using a geometric approach, and a construction method is presented for the stable model-following system without using an observer. In contrast to the existing methods, the construction method proposed by this paper does not require any additional condition, and can construct the stable model-following system with the given parameters without repeating the trial-and-error procedures. [ABSTRACT FROM AUTHOR]

In the discussion of the two-class feature extraction problem in pattern recognition, Malina [7] proposed recently a new criterion for overcoming the defects of Fisher's criterion. The discussion in this paper focuses on the effectiveness of Malina's criterion and at the same time points out the problem in his feature extraction method, indicating how to avoid the difficulties. First, no clear definition is made in Malina's method for the coordinate system in the feature space, and the coordinate system used is not optimal. Second, the eigenvalue problem must be solved including the solution of inverse matrix in order to determine the feature axis. For the first problem, this paper points out that the coordinate axis di and dj in the coordinate system in Malina's method satisfies diT<∑dj = 0, where Σ is the sum of covariance matrices in the class. Then the optimal coordinate system from that viewpoint is given. For the second problem, the inverse matrix is eliminated by performing a certain transformation (A-1 transformation) to the coordinate system of the original pattern space. The validity of A-1 transformation is shown by the invariance of the distances among classes, and it is shown that the above optimal coordinate system under A-1 transformation is the optimal orthogonal coordinate system satisfying diTdj = 0, i ≠ j. Finally, Malina's criterion is extended to the multiclass case and the problems are discussed. [ABSTRACT FROM AUTHOR]

This paper presents a polynomial-time algorithm which can determine the multicommodity flows in a planar undirected graph G. It is assumed that G remains planar if an edge is added between each source-sink pair. Given positive and real demand to each source-sink pair, the algorithms determines whether or not there exists a multicommodity flow in G realizing the specified demand, i.e., feasibility, and if it exits, the multicommodity flow is determined. It is shown that by solving the maximum-weight matching problem once for a graph which is a modification of the graph dual to the given graph G, the feasibility is determined, and by solving the problem for 0(kn) times, the multicommodity flows are determined. Consequently, if G has a vertices and k source-sink pairs, the computation time required to determine the feasibility is 0(n² log n), and the time required to determine the k-commodity flow is O(kn³ log n). The memory storage required is 0(kn). It is known that the maximum-flow min-cut theorem exists for the case of planar graph considered in this paper. [ABSTRACT FROM AUTHOR]

Recently, with the advance of micro-fabrication techniques, extremely many circuits are integrated in a silicon chip. As a result, the power density is increased and the processing of this power density becomes a key to realize a VLSI. As a means to resolve this problem, this paper discusses a method for reducing the power consumption in the entire analog-digital LSI by reusing in the I2L circuit, the current already used in the analog circuit. Several representative analog circuits are studied in this paper and a stacking of the analog circuit and the I2L circuit is investigated. As an example, when an I2L circuit id combined in the constant current source side of the differential amplifier with the signal gain of 36 dB, the noise leakage from the I2L circuit to the output of the differential amplifier is about -14dB (about 2mV). This stacked analog -I2L is applied to an actual integrated circuit. Without losing the function and characteristics of the original integrated circuit the apparent power consumption of the I2L circuit is made zero and the power consumption of the entire integrated circuit is reduced from 65 mW to 34 mW, which is about a 50% reduction. [ABSTRACT FROM AUTHOR]

Recently, for the improvement of reliability of digital communication systems, various kinds of error-correcting codes are being used. To improve system reliability through the use of more capable error-correcting codes it is extremely important to simplify the decoder construction and to reduce the decoding delay. This paper studies a decoding algorithm for a class of simple iterated codes (SI codes) constructed by simply repeating I times a codeword (called block) in a given code (called subcode). Moreover, this paper discusses the decoding delay when this decoding algorithm is applied to decoding the Reed-Muller codes constructed by the superimposing method. [ABSTRACT FROM AUTHOR]

This paper combines the supplementary variable method and the phase method to analyze the steady-state of GI/Ek/I with finite waiting room. Although there have been many studies made on the queue with finite waiting room, there has not been a study of GI/Ek/I which determines the characteristic quantities and discusses the characteristics by numerical computation. This paper defines firs the residual arrival time as the supplementary variable and derives steady-state basic equations for the joint probability density functions of the variable and the total remaining number of phases in the system. Using Laplace transform, the solutions are represented by the joint probability densities for the remaining number of phases and the zero remaining arrival time. The value of joint probability densities is determined, if the distribution function of arrival interval is given, by solving a system of linear equations by numerical computation. Using that solution, various characteristic quantities are represented such as number of customers in the system, actual waiting period length, distribution of idle period length, loss probability and power. Finally, the analytical result for GI/M/1/N is found to be equal to the known result, and as a numerical example characteristic quantities of GI/E4/1/4* are illustrated, together with the discussion for the characteristics. [ABSTRACT FROM AUTHOR]

This paper discusses the communication traffic characteristics of Dynamic Channel Assignment (DCA) in cellular mobile communication systems. In general, it is difficult theoretically to analyze the communication traffic characteristics of DCA. This paper proposes an approximate method called clique packing, for analyzing the blocking probability performance of an idealized DCA. For calculating the blocking probability of clique packing, an approximate formula is derived which is based on the Erlang B formula and is in a simple form. It is shown that the numerical results of the approximate method agree with computer simulation results. An approximate analytical method for calculation of the blocking rate el practical DCA methods such as the first-available method also is proposed. To calculate the blocking rate of the practical DCA methods, the simple formula for clique packing is used after modeling the practical DCA methods as clique packing. It is shown that the modeling is appropriate. This modeling enables the blocking rate of the practical DCA methods to be calculated by using the approximate formula for clique packing. [ABSTRACT FROM AUTHOR]

In the ArM system, all multimedia information, such as voice, picture and data. is divided into packets with the fixed length of 53 bytes, called cells, and the cells are transferred. Intensive studies have been made on the performance of the system, where such multimedia information is multiplexed in the network switch. In the ATM network, the cell loss is not compensated, and it is necessary that the end-user should recover from the errors in order to realize highly reliable data transfer among computers. As one such approach, the error-correcting code (FEC) has been considered interesting. From such a viewpoint, this paper evaluates analytically the data transfer performance when FEC is used. When FEC is used, the redundant cell produces an overhead, which may enhance congestion when the traffic in the network is high and deteriorate the performance. Also, from this viewpoint, this paper considers the priority control, where the redundant cells are discarded positively when the network is congested. The effectiveness of the approach is examined, as in the data transfer performance for the case where the video and the data exist together in the traffic, and it is demonstrated that the control parameters in the priority control are especially important in that case. [ABSTRACT FROM AUTHOR]

With the improvement of the speed of computers in recent years, there is required a local area network (LAN) that can realize a high-speed] broadband communication. For this purpose, asynchronous transfer mode (ATM) LANs bassed on ATM technique is considered important. This paper considers the bandwidth reservation control as a means of traffic control in ATM LAN and evaluates the performance by simulation. The evaluation as made for the following methods of congestion control: ACK/NACK method,based on the ACK/NACK signal which is results when the bandwidth reservation succeeds/ fails; the dynamic ACK/NACK method, which is an improvement so that the control can S adapted to the traffic load; and control method based on the link information from the switch. It is shown for the single-stage switching network that the dynamic ACK/NACK methode has a better performance when the traffic is low but the control method based on the link information has the highest performance when the traffic is high. It also is shown for the three-stage switching network that the control method based on the link information has the highest performance. [ABSTRACT FROM AUTHOR]

In this paper, the results of numerical analysis based on the theoretical analysis of the self-focusing effect when a microwave beam propagates through the ionospheric plasma from the solar power station (SPS) to the ground are shown. The self-focusing effect of the microwave beam is either caused by the plasma heating by the microwave beam or caused by the spatial gradient of the electromagnetic beam intensity. In this paper, the latter case is discussed. Since the microwave frequency used in the SPS is six orders of magnitude higher than the maximum collision frequency in the ionosphere, the theory used in this paper assumes a collisionless plasma and is derived from Maxwell's equations and the equation of motion. The self-focusing effect of the microwave beam predicted by the theory is determined by five parameters: plasma density and temperature; microwave frequency; intensity; and the spatial gradient of intensity. In this paper, based on the results of the numerical analysis of the theoretical equations, the self-focusing effect under the parameters related to the microwave beam used in the energy transmission of a future SPS is described. [ABSTRACT FROM AUTHOR]

Reconfigurable beam antennas are suitable for onboard antennas from the point of view of frequency reuse, satellite power utilization, and flexibility for traffic demand variation. In this paper, an efficient design method of the feed-array excitation coefficients for arrayfed reflector-type reconfigurable beam antennas is proposed. The feed-array is composed of several subarrays, and only amplitude between subarrays is controlled to achieve reconfigurability. Excitation coefficients of subarrays and amplitude between subarrays are determined efficiently by the proposed design method. The method is verified by a design example for an international communications satellite application. [ABSTRACT FROM AUTHOR]

In a cellular mobile communication system, a service area is divided into many cells for efficient use of channels. It is necessary to take into consideration intercell vehicle movement for teletraffic performance evaluation of such cellular mobile communication systems. Its performance evaluation has been done for a one-dimensional band-shaped area, e.g., a highway, assuming that vehicle movement is one way. This paper presents a theoretical performance evaluation of a one-dimensional band-shaped area, assuming two-way vehicle movement. First, whether steady-state performance for the traffic offered to each cell is constant is analyzed and then the transient characteristic for the case in which traffic varies with time is analyzed. Through a comparison of theoretical and simulation results, the validity of the theoretical result is demonstrated. [ABSTRACT FROM AUTHOR]

This paper addresses some solutions to overcome the problems that arise which optical time domain reflectometry (OTDR) is applied to optical amplifier submarine transmission systems. It designs a backscatter path that feeds the backscattering into the opposite line without causing any degradation in the main signal transmission. This paper proposes a new modulation format, FSKASK, and confirms that the proposed approach can both eliminate optical surge generation and improve OTDR performance. An FSK-ASK OTDR is applied to an 890- km commercial amplifier submarine transmission system with a 90-km span. Field trials successfully demonstrate that the OTDR can locate a fault in all spans with a spatial resolution of 1 km after averaging the sum of 220 measurements. The FSK-ASK OTDR proves to be very useful in maintaining a reliable submarine transmission system because it can locate subtle fiber anomalies along the entire length from a terminal end. [ABSTRACT FROM AUTHOR]

As an effective traffic control mechanism of the asynchronous transfer mode (ATM) local area network (LAN) which has been getting attention as the next-generation high-speed LAN, the reactive congestion control is considered. In this paper, to obtain such a traffic control mechanism, a scheme to add the function of the backpressure to an ATM switch having buffers in both the input side and the output side is evaluated. Also in this paper, the maximum throughput of an ATM switch with backpressure function for burst traffic is analyzed mathematically. Further, a uniform traffic load and a mixture of such traffic occupying the bandwidth in a peak rate as voice and video are analyzed. Moreover, with some numerical data examples, the effect of the output buffer size ad the burstiness of the arriving traffic on the system performance is analyzed. [ABSTRACT FROM AUTHOR]

The antennas for mobile communication handsets have become smaller in shape, which has degraded their electrical performance significantly. To obtain a small but high-performance handset, it is important to increase the antenna efficiency. The important parameter for such a purpose is the radiation efficiency which can be measured easily by the. Wheeler method. This method is carried out based assumption that the input power is equal to power loss if the antenna is covered with a cap of a size on the order of a radian sphere. However, unless this assumption holds, the computed Wheeler efficiency does not give accurate raditon efficiency. When the raditon the radition efficiency is actually measured by the Wheeler method, the measured values often have a dip from the theoretical value. In this paper, the cap is approximated by wire grids and the Wheeler method is simulated on a computer. It is confirmed that the dip is not cause derives from the invalidness of the presumption of the Wheeler method that the internal reactive electromagnetic field not changed when a cap is sleep. It is shown also that the Wheeler method can be used sufficiently even if the size of the cap is larger than the radian sphere. The limit of application is studied. [ABSTRACT FROM AUTHOR]

The conflict alert system was development for air traffic control to detect and warn of the danger of aircraft collisions. This paper presents a configuration for air traffic control data tables that increases the efficiency of the conflict alert system, which was devised to predict what instructions to give for preventing collisions. Air traffic control data tables are constructed mainly from air rout data and aircraft data. The aircraft are controlled by the air route unit, and all data as well as the relationship between the data (i.e, between aircraft and air routes,etc.) are updated continually in real time for the data tables in question. As a result;(1) the relationship between the aircraft and the air route can instantly be grasped, thereby improving the accurancy of the course prediction for the aircraft; and (2) when judgeing if two aircraft are possibly in conflict, the efficiency of the conflict detection process can be improved by rapidly being able to grasp the relative relationship of aircraft on adjacent air routes and the relationship between the leading and last aircraft on the same course. The feasibility of the point (1) and (2) is demonstrated through computer simulation. [ABSTRACT FROM AUTHOR]

There is increasing demand for a system that supports various multipoint activities such as a conference and education using multimedia information. This paper consider the situation where such a multimedia remote presentation system is to be constructed and discusses the condition for maintaining the synchronization among the media in the information at each node. In this paper, first, the synchronization semantics is defined based on the information presentation timing between the media information taken out from the storage information source and the live media information such as the user's voice. Then a computation procedure is shown for the buffer size needed in each node in order to satisfy the sematics. Based on those reasonings, the design condition is presented for the buffer size and the command response time. [ABSTRACT FROM AUTHOR]

This paper discusses fundamental characteristics in reachability analysis of communication service specifications defined by means of production rules. In the conventional service specifications, reachability has been analyzed within a finite number of communication processes. However, it is necessary to deal with infinite processes to verify state reachbility of the global transition description of the production rules. If the reachability state as a reachable subglobal state constructed with a number of processes is defined, the size of the reachability states set depends on the number of processes at the initial state. In general, the system is analyzed on the assumption of an infinitive number of processes to verify reachability. This paper presents the relationship between the size of the reachable set and the number of processes in the systems. It also shows the existence of the upper bound of the reachable state set and a method to obtain the minimum number of processes that gives the upper bound of the reachable set. This study makes it possible to analyze the reachability of an infinite number of processes by a reachability problem of finite number of processes [ABSTRACT FROM AUTHOR]

Land mobile communications systems that implement spread spectrum are being actively researched. With direct-sequence spread spectrum, performance is predicted to improve by dividing a multipath delay wave into separte paths, using path diversity combining, and so-called path diversity receiver. Generally, although performance improves with an increase in the number of branches in a diversity system, a small number of branches is preferred with the implementation of a receiver. Hence, this paper analyzes the performance when n = 2 for a model of a path diversity receiver where n = paths are selected from M candidate paths in order of the largest instantaneous signal-to-noise (S/N) ratio, and bearing in mind the receiver that produces the maximal ratio combining. The results show that there is no significant differences between n = 4 and n = 2 when M = 4. The average power delay profile shows the number of effective branches when applying a system of n = 2 branches to path diversity for both the exponential and rectangular models. Also, the theoretical value for the BPSK and FSK average bit error rate performance is determined for a primary modulation system with the rectangular model. [ABSTRACT FROM AUTHOR]

To achieve efficient and highly reliable network operation requires a mechanism to monitor and control the states of remote a mechanism to monitor and control the states of remote terminals (nodes) automatically by control operation system (OpS). This paper is an attempt to obtain such a mechanism. Operation and maintenance (OAM) cell is defined that contains the connection information for remote monitoring and the control path to be set. By successively transferring OAM cells according to the connection information, remote monitoring and control virtual paths (VPs) can be obtained autonomously. Based on the proposed idea, this paper discusses the structure of the OAM cell, the functions to be provided in the cross-connect system, and transmission algorithms for the OAM cell. The proposed system well utilizes the unique feature of the ATM cell. The cell routing information (VPI) is transferred within itself. [ABSTRACT FROM AUTHOR]

This paper proposes the differential detection type direct sequence/code-division multiple-access (DS/CDMA) adaptive interference canceller (AIC) that can track the fast fading. The proposed AIC is composed of the fractionally chip-spaced code-orthogonalizing filter (COF) with tap length corresponding to several bit periods and the differential detector. The COF makes adaptively the tap weight orthogonal to all spreading codes of other users as a despreading code of the desired user so that the interferences from other users are cancelled and the signal component of the desired user is extracted. The differential detector compensation the carrier phase variation due to finding in the desired user's signal at the COF output. By such a structure, the tracking performance of AIC to the channel variation can be improved to the limit of the tracking performance of the differential detector. This paper evaluates the basic ability of the proposed AIC in the fast-fading channel. The AIC is especially expected to be utilized in the DS/CDMA mobile communications since the receiver is of the signle-user type, where no information concerning other users is needed. [ABSTRACT FROM AUTHOR]

This paper discusses capacity expansion problems for telecommunication network facilities, based on fuzzy dynamic programming. Although cost functions, discount rates, demand functions, and so on should be given, they usually cannot be defined clearly because of technical developments or business fluctuations. This paper represents undefined factors by fuzzy numbers with triangular membership functions (TFN). Multiplication of division of TFN does not give rigid TFN, but we approximate them to TFN for ease of calculation. Three methods based on this approximation are compared, using numerical examples. Approximation accuracies are confirmed by strict calculation using removal of defining orders of fuzzy numbers. [ABSTRACT FROM AUTHOR]

Telecommunications networks are designed and managed based on statistical traffic data including basic traffic obtained at peak traffic hours. Network links are also designed based on the basis traffic. The network is designed so that the quality of services (network blocking) is at a certain level when basic traffic is applied to the network and the network is managed so that quality of services is maintained for the basic traffic. This conventional method is universal and simple because the required data for design and management are very small. On the other hand, recent telecommunication systems have the ability to measure and collect detailed traffic data. This paper proposes a new network design method in which time-series traffic data rather than statistical traffic data is used for network design. Combining the time-series traffic data and the tariff data for each hour, we can design a network based on total revenue. Unlike the conventional method, the proposed method makes it possible to estimate revenues, costs, and damages. Using time-series traffic data obtained for every hour of the year, a method is devised that optimizes the number of circuits (i.e., for optimizing network blocking) and thus maximizes profits. This paper also presents a new methodology for traffic data and a new network structure that effectively uses the proposed method.

With the severe traffic situation in recent years as the background, there are intensive studies on the intervehicle communication system, aiming at the safety improvement of the road traffic system and the smooth control of the traffic flow. The spread-spectrum communication is very useful in the realization of such a system since the data for the distance between vehicles are obtained, which is very important in driving the vehicle, as well as the communication. This paper considers the intervehicle communication network using the spread-spectrum system and proposes the medium access control (MAC) protocol for the autonomous distributed access control. To evaluate the performance of the proposed system, a computer simulation is executed for the environment where the vehicles run freely on a highway. It is shown that stable information exchange can be realized with vehicles running in nearby positions. [ABSTRACT FROM AUTHOR]

No detailed analysis has been available on the return loss characteristics of a pyramidal electromagnetic wave absorber. Therefore, an approximate analysis method for the pyramidal absorber has not been established in a rigorous sense. In this paper, the return loss characteristics for the normal incident on the pyramidal absorber are derived by the numerical simulation based on the spatial network method. Also, as an approximate method for the wave absorber that can approximate the obtained results well, a method called the synthesized capacitance model is proposed. By comparison of the numerical results by the two methods, it is found that the approximate results by the synthesized capacitance model provide more accurate results than those by the previous approximate models. Further, by means of the synthesized capacitance model for the normal incidence, the oblique incidence characteristics of the TE wave were computed and the results agreed well with the measured data. [ABSTRACT FROM AUTHOR]

This paper consider the performance of traffic capacity and handover frequency in a DS/CDMA system under imperfect handover. The effect experienced when the number of base stations observed by the personal station is restricted is estimated. Furthermore, the effect of handover hysteresis also is considered. Simulation models are presented which can evaluate the traffic capacity and the handover frequency under these imperfections. System performance is evaluated by computer simulations using these models. It is found that if the number of observed base stations is 3 and the standard deviation of short-distance medium value variance is 6 dB, the reverse-link traffic capacity is reduced to about 90 percent and the forward-link traffic capacity is reduced to about 85 percent, while the handover frequency is about 90 percent of the frequency of the short-distance medium value variance. It is found also that if the handover hysteresis is 4 dB and σ is 6 dB, the reverse-link traffic capacity is reduced by about 10 percent while the handover frequency is about 10 percent of the frequency of the short distance medium value variance. [ABSTRACT FROM AUTHOR]

This paper proposes differential parallel combinatory spread spectrum (DPC/SS) communication systems; one of the parallel combinatory spread spectrum (SS) communication systems the authors have been studying so far. The parallel combinatory SS system is a spectral efficient SS system in which the system transforms several bits of data into a combination of pseudonoise (PN) sequence with modulation of positive and negative signs and transmits them. The proposed DPC/SS system applies differential encoding to the positive or negative sign modulation of the PN sequences, and then they are transmitted. In the receiver, the combination of a transmitted sequence set is estimated by noncoherent detection and the coded sign is demodulated by differential detection. Thus, the receiver does not need to regenerate the phase of the carrier frequency. The proposed systems will be applicable to a mobile cellular system in which a large phase variation interferes with the communications. This paper evaluates the error performances of the DPC/SS systems in additive white Gaussian noise (AWGN) channels and frequency-nonselective, slowly Rayleigh fading channels. It also evaluates the effect of diversity in the Rayleigh fading channels. In the AWGN channel, the DPC/SS system is superior by 1 dB to the differential phase-shift keying (DPSK) system and to the BPSK system in terms of required signal-to-noise ratio at 10 bit error rate (BER) at the same spectral efficiency. In the Rayleigh fading channel, diversity reception in the DPC/SS system gains more improvement in the BER performance, as the number of branches increases, than that obtained in a direct-sequence spread spectrum system with DPSK. [ABSTRACT FROM AUTHOR]

This paper evaluates the performance of a fast select connection oriented (FS-CO) logical link control (LLC) protocol in slotted ring networks. The FS-CO-LLC protocol is one of light-weight protocols. Is employs a method of implicit connection establishment and release to reduce overhead of connection control. This paper analyzes the performance (throughput and average response time) of a slotted ring network in which a single slot circulates by means of Equilibrium Point Analysis. The performance in the case of plural slots is evaluated by simulation. This paper also compares the FS-CO-LLC protocol with connection-oriented (CO) and connection-less (CL) LLC protocols. Numerical results show that the performance of FS-CO-LLC and CL-LLC protocols is superior to that of CO-LLC protocol when the average message length is smaller than the buffer size. On the other hand, when the average message length is larger than the buffer size, CO-LLC protocol has the best performance. It is also shown that the performance of FS-CO-LLC protocol does not degrade but CL-LLC protocol does, even if the average message length becomes larger. [ABSTRACT FROM AUTHOR]

Efficient handover during both mobile telephone and portable telephone communication is a technology essential m implementing ideal mobile communications. However, there exists the possibility of a transmission data slip during the process of circuit switching, which has become a problem in communication using terminal machines such as data modems and FAX machines connected to mobile telephones and portable telephones. In this paper, a transmission data slip accompanying route changes reside digital exchanges in a handover during telephone communications is assumed; it is shown on the basis of this assumption that a lag in synchronism occurs m the receiver terminal equipment. Then a sync lag of the receiver terminal modem during handover has been confirmed by tests using actual analog cellular phones and a transmission data slip has been shown on the basis of the results of the tests. In this paper, a synchronism control method minimizing the sync lag has been studied. The efficacy of this method has been confirmed as a result of applying the method to a mobile telephone FAX modem. [ABSTRACT FROM AUTHOR]