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This paper discusses a λ/4-type wave absorber for the microwave band made with conductive paper, which is paper with a coating of conductive material. A simplified wave absorber of this type is first designed and constructed for the X band and Ku band. Using the resulting absorption characteristics, experimental formulas are derived for the relative permittivity and surface resistance. These formulas are then used to design and construct a more practical wave absorber, whose absorption characteristics are measured. Excellent absorption characteristics, better than 20 dB, are verified in the intervals from 8.2 to 10.6 GHz and from 14.1 to 17.2 GHz for wave absorption in the X band and Ku band, respectively, although there is a difference of approximately 0.4 dB between the designed matching frequency and the measured value. Design guidelines for such a microwave absorber using a conductive coating are then presented. © 2003 Wiley Periodicals, Inc. Electron Comm Jpn Pt 1, 86(10): 100–107, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecja.1180 [ABSTRACT FROM AUTHOR]

This paper proposes a beam pattern selection diversity technique using an adaptive array antenna. In the system using an adaptive array antenna, beam control in the uplink is carried out for all terminals in the cell. Hence, it is necessary to determine the antenna weights for all terminals at the base station, so that the amount of computation is increased and the base station configuration becomes complex in a cellular system that seeks to be capable of handling as many terminals as possible. In this paper, the beam patterns are generated only for a limited number of terminals in the cell, while other terminals share the generated radiation patterns, so that the amount of computation can be reduced substantially. In general, in a system using an adaptive array antenna, the interference suppression capability is significantly affected by the angle of arrival of the propagation channel. In this paper, the angle of arrival of the channel is modeled by a normal distribution and the proposed system is investigated in a micro-cell environment. As a result of numerical simulation, it is found that the proposed method can reduce the processing effort by 20% in the micro-cell environment, while the characteristics are sufficiently competitive with the results obtained when optimum radiation patterns are generated for all terminals. © 2003 Wiley Periodicals, Inc. Electron Comm Jpn Pt 1, 86(5): 32–41, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecja.10020 [ABSTRACT FROM AUTHOR]

In applying satellite circuits to a large domestic telephone network, it is necessary to study channel assignment and dimensioning methods that take advantage of broadcast communication features. This paper shows that for a large-scale telephone transit network which has hierarchical structure, in order to absorb traffic fluctuation, it is attractive to apply satellite circuits to high-usage trunks in combination with terrestrial final trunks, by taking the Japanese telephone toll network as an example. Assuming this network construction, this paper considers three different satellite channel assignment schemes-Pre-Assignment, Timed Pre-Assignment, and Demand Assignment-and introduces a circuit capacity dimensionsing method to minimize the total network cost for each assignment. Finally, a comparison of channel capacity and network cost is made among these assignments under some traffic variation patterns. It was found that Timed Pre-Assignment is the most effective and economical scheme. Demand Assignment is a future technology and its application field is clarified in comparison with other schemes, with the cost increase for realizing Demand Assignment as a parameter. [ABSTRACT FROM AUTHOR]

Recently a few studies have been made of distributed coupled-line type digital frequency multipliers which multiply the repetition frequency of a square input wave. The transfer functions of an n-section distributed coupled-line constant-resistance network and an n-section distributed-constant bridged-T network have the form of a rational function of order n with respect to delay operator Z-1. We develop our discussion on the basis of this transfer function. The theory is developed for the coefficients of the rational function and the output response in a stationary state can be determined by the coefficients of both the denominator and numerator. The obtained results can be applied to all networks having the transfer functions treated in this paper, but the detailed realization condition for each individual network is not discussed. The experiments and calculations shown in Figs. 4 - 7 are conducted using the distributed coupled-line constant-resistance network as an application example. The network described here can be a digital frequency multiplier for two incident impulse trains, 1111 and 1-11-1. The behaviors of the multiplier in the frequency domain as well as in the time domain are investigated and it is shown that a faster impulse train can be obtained at the output in the time domain by adequately thinning out the discrete frequency components of the incident impulse train. [ABSTRACT FROM AUTHOR]

With the development of mobile communication, active research is being done on the small-sized antennas such as microstrip antennas (MSAs). Moreover, MSAs normally are placed on spherical or cylindrical surfaces as a conformal antenna. Conformal MSAs are expected to have different characteristics compared to planar structure. In this case, numerical analysis is needed before the actual experiment. The method of analysis which has wide applications may be considered as efficient for this purpose. One such method is the conformal grids finite-different time-domain method (FD-TD method). In this paper, an MSA on a curved surface is analyzed using the conformal grids FD-TD method. Moreover, comparison with the experimental values also is performed. The experimental results and the analytical results ate in close agreement which shows the validity of the method of analysis. As a result, it is confirmed that in the range of this paper, the input impedance and radiation pattern varies from their values for the planar patch when the patch surface is curved. [ABSTRACT FROM AUTHOR]

This paper proposes an application method of the cooperative distributed multiagent model in multipath allocation algorithm and confirms its valid calculation results by realizing this model in a distributed computer environment. The multiagent model in this paper is an environment where each agent has the same function of asynchronous and parallel calculation and no globally controlling agents exist. To realize this model, this paper proposes an appropriate dividing method of the multipath allocation problem for asynchronous and parallel calculation, a unifying method of each agent's answers end interagent communication protocols. It also compares the required calculation time and the number of allocated paths of a single agent with that of the multiagents end shows the practical calculation ability of the multiagent model. [ABSTRACT FROM AUTHOR]

The control of the cell contention is a technical problem in the input queueing ATM cross-connect switch. This paper considers this problem and proposes a scheduling control method which dynamically assigns the cell transmission time. A construction of the distributed scheduling circuit also is proposed based on Batcher's sorting network. The proposed method processes the cells in the order of their arrivals, as in the conventional three-phase algorithm but has an advantage in that the throughput can he increased by approximately 26 percent without increasing the number of control processes per cell. Mother merit is that multirate ports can directly be contained in the switch. In this paper, the approximate model for the proposed method is constructed, and the mean delay and the cell loss probability are calculated theoretically. The actual operating performance is evaluated by a computer simulation. By combining the proposed method with the conventional self-routing spatial switch, a distributed switching circuit can he constructed as a whole, which is useful in developing an economical large- capacity ATM cross-connect switch. [ABSTRACT FROM AUTHOR]

This paper considers the highly efficient coding of the gray-level image. The extrapolative prediction-discrete sine transform scheme, which was previously proposed by the authors for the case of one-dimensional coding, is extended to the case of two-dimensional coding. In the proposed method, the image is partitioned into square blocks. The correlations among blocks are eliminated by applying the two-dimensional extrapolative prediction for each block from the restored boundary pixel. The correlations the block is eliminated by applying the orthogonal transformation to the prediction errors. In this paper, the correlation function of the image is assumed as the isotropic exponential function, and a two-dimensional extrapolative prediction method is derived, which can be realized as a simple manipulation. The transformation of the prediction errors is performed by the variable-separation type two-dimensional extrapolative prediction-discrete sine transform, where the one-dimensional extrapolative prediction-discrete sine transform is applied to rows and columns. Then the rate-distortion characteristic is calculated, indicating that the proposed method is useful. It is shown that the proposed method with 4 × 4 block size has almost the same coding efficiency as the discrete cosine transform coding with 16 × 16 block size. A computer simulation was made for the actual image, leading to a result validating the theoretical estimation. The proposed method requires less computation per pixel, compared with the discrete cosine transform coding. The method is especially useful from the viewpoint of hardware implementation, since the block size is as small as 1/16. [ABSTRACT FROM AUTHOR]

With the development of such communication networks as INS in recent years, the communication protocol has become more complicated, and efficient description and validation are becoming more important. This paper proposes a new method of description and validation for the communication protocol, which realizes the merits of both the composite state-transition diagram and the high-level language. The method describes the communication protocol using the SL diagram, which is the complete state-transition diagram with built-in logical expressions. Using the SL diagram, it is easy to verify the existence of the deadlock by utilizing its graph-theoretic features. On the other hand, by regarding the SL diagram as a flowchart, the inductive assertion (technique used in proving the validity of the program) can be applied to validate the parameter functions. A method is also shown which can efficiently locate the invalid loop using the SL diagram. In this paper, the loop is defined as invalid if the transfer of a packet is continued without progressing the communication. Furthermore, it is pointed out by applying the proposed method that there exists in invalid loop in the standard protocol HDLC. An improvement of HDLC is proposed to eliminate such an invalid loop. [ABSTRACT FROM AUTHOR]

This paper shows that a fundamental signal called a 'minimum norm signal' can be defined for a class of piecewise continuously differentiable signals in the time domain; the energies of the original signals and differentiated signals are both finite. Making use of minimum norm signals, this paper also presents an efficient signal approximation method. The minimum norm signal approximation method. The minimum norm signal is defined as a waveform of minimum norm which takes specified sample values at given sampling points. The proposed approximation algorithm adds a new sampling point at a position which minimizes the integrated square error between the original signal and an approximate signal. This method adds the optimal sampling point at each stage and sequentially constructs the minimum norm signal with small approximation errors. Compared with a conventional approximation method using the orthogonal function system, the proposed method does not require integral calculation and is free from numerical integration error. Moreover, the sequence of approximate signals uniformly converges to the original signal as the number of sampling points tends to infinity. [ABSTRACT FROM AUTHOR]

The existence problem for solution of a nonlinear resistive circuit and the problem of identifying the number of the solutions are classic and basic problems in circult theory. In their paper "On the application of degree theory to the analysis of resistive nonlinear networks" (int. J. Cir. Theor. Appl., 5, pp. 35-68 (1977)), Cbua and Wang presented a unified theory for the existence of solutions for nonlinear circuit equations. That is, on the basis of the degree theory the existence of solutions of many nonlinear resistive circuits can be guaranteed in a unified manner by showing that the circuit equations are homatopic to certain odd fields. Their arguments are, however, not constructive. In this paper, an algorithm based on the fixed-point algorithm theory is presented and it is proved that by this algorithm at least one solution can always be constructed for nonlinear circuit equations whose solutions are guaranteed to exist by Chua and Wang's theorems. Usefulness of the algorithm is also demonstrated by a few examples. [ABSTRACT FROM AUTHOR]

This paper presents the results of a study of the OFDM adaptive modulation technique. The adaptive modulation technique, which selects the modulation scheme according to the transmission conditions, is effective in improving system throughput. Then, it is important to study evaluation function under various propagation conditions. In this paper, we propose an adaptive modulation technique using the instantaneous DUR (desired signal to undesired signal ratio) per packet as the performance measure of the transmission path, in which the intersymbol interference (ISI) and intercarrier interference (ICI) power of delayed waves exceeding the guard interval are used under the assumption of convolution coding and soft-decision Viterbi decoding. A DUR estimation method is also proposed. The effectiveness of the approach is confirmed by numerical simulation. © 2005 Wiley Periodicals, Inc. Electron Comm Jpn Pt 1, 89(3): 36–45, 2006; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecja.20254 [ABSTRACT FROM AUTHOR]

As the frequency used in electronic devices increases, limitations on the lumped element type components for prevention of radiated emission appear. Methods for suppression of radiated emission from printed circuit boards by means of differential mode transmission have been studied. However, most of these studies are centered on theoretical analysis. There has been no investigation from both the experimental and theoretical points of view in the high-frequency regions. In this paper, with a view to easily deriving the suppression effect of radiated emission, the electromagnetic fields radiated from differential mode transmission and common mode transmission are derived by the method of moments from a model of parallel micro-strip lines with the effective relative permittivity and the equivalent wires. The suppression of radiation from the differential mode transmission is studied in comparison with the measured data. It is found that the difference between the measured and calculated values of the maximum radiated electric field is less than about 3 dB in the range of 100 MHz to 3 GHz, except near 2 GHz in the case of the common mode transmission. With regard to the suppression effect, the difference between the measured and calculated values is less than 5 dB at 1 to 3 GHz. An investigation with this analytical model found that the radiation suppression effect can be improved by 5 to 10 dB at 1 to 3 GHz by changing the spacing between parallel microstrip lines to 1 mm from 5 mm, that the suppression effect is degraded by about 5 dB due to curvature, and that the radiation suppression effect is decreased by 5 to 20 dB at 1 to 3 GHz if the deviation of the transmission line lengths of a pair of parallel microstrip lines measured from one end reaches 10%. © 2005 Wiley Periodicals, Inc. Electron Comm Jpn Pt 1, 89(2): 36–46, 2006; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecja.20227 [ABSTRACT FROM AUTHOR]

In this paper, the electrical constitutive parameters of various amorphous mixed materials are derived. The effective permittivity of the mixed materials can be expressed simply by the geometric mean of the permittivity of the series combination and that of the parallel combination of each material according to a dielectric layered model. In this expression, it is not necessary to specify the host material as was previously the case. The solution of various mixed materials can be directly expressed in the closed form. It is shown that there is a significant difference between the effective permittivity in this paper and that in the conventional theory depending on permittivity and loss of mixing materials. The validity of the approach is confirmed experimentally. © 2005 Wiley Periodicals, Inc. Electron Comm Jpn Pt 1, 88(10): 1–9, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecja.20229 [ABSTRACT FROM AUTHOR]

The slot array antenna with backward excitation is promising as a constituent element of a planar multisector antenna. This paper deals with a slot array antenna with backward excitation that prevents radiation into the backside by installing a cavity. With a view to simplifying the fabrication process, all slots in the array share one cavity. A design guideline is discussed for reducing mutual coupling between the elements. It is found that the cavity width should cause the TE10 mode to be cut off. For a four-element array with a cavity satisfying this condition, the characteristics are evaluated by the spectral domain moment method. It is shown that a beam tilt toward the end fire direction can be obtained, similarly to the case without a cavity. The antenna characteristics are evaluated in terms of cavity length and depth. It is demonstrated that the effect of the cavity length on the antenna characteristics is significant and that the cavity thickness can be reduced. Further, a test experiment is conducted at 19 GHz to confirm the validity of the numerical study. © 2002 Wiley Periodicals, Inc. Electron Comm Jpn Pt 1, 85(11): 68–76, 2002; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecja.1139 [ABSTRACT FROM AUTHOR]

The main problem of an indoor infrared (IR) wireless system via diffuse infrared link is bit error rate (BER) performance degradation due to intersymbol interference (ISI) induced by multipath distortion. In the previous study, only a rectangular pulse was employed as a transmitted pulse. However, multipath distortion tends to make the nondirected diffuse indoor IR channel have a low-pass frequency characteristic, and thus a rectangular pulse, whose spectrum has a form of sinc function, induces much ISI. In this paper, we analyze the BER performance of indoor IR wireless system via diffuse link employing different kinds of pulse waveforms, such as a Gaussian pulse and a raised cosine pulse, and consider the effect of ISI. Moreover, we analyze the BER performance employing a return-to-zero (RZ) pulse which has a guard interval in a slot. It is shown that the RZ Gaussian pulse is effective in mitigating the effect of ISI. © 2000 Scripta Technica, Electron Comm Jpn Pt 1, 83(9): 33–43, 2000 [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]

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]

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, 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]

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]

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]

In asynchronous transfer mode (ATM) networks, each user requests a call setup with the traffic descriptor which describes its own traffic characteristics. Since network resource control is carried out by this traffic descriptor, it would be necessary that the traffic generation is monitored by the network, which is the so-called usage parameter control (UPC). In this paper, three methods are evaluated analytically for implementing the UPC function: a discarding method, a tagging method, and a hybrid method. The last method is proposed anew in the paper and the comparative results for the three methods are offered from a viewpoint of performance of the cell multiplexer when the output traffic from UPC is super. [ABSTRACT FROM AUTHOR]

Pipelined protocol processors are used in high-speed networks such as FDDI for achieving high-throughput data communications between end users. In this paper, we present a model for computing the maximum throughput that can be delivered by such processors. The parameters of the model are: input packet length, length of PDU (Protocol Data Unit) and SDU (Service Data Unit) headers, packet processing time of pipeline stages, capacity of the FIFO channels that inter-connect stages, and average number of packets assembled/segmented at a stage. As an example, the maximum throughput of an idealized pipelined processor that executes the FDDI, LLC Class I, IP, and TCP protocols is computed. Also, we show that the formulas given in [1] and [2] are particular cases of the formulas presented in this paper. In a typical application of the proposed model, some desired, or measured, throughput characteristics of a protocol processor will be given, and the parameters of the processor will be computed. [ABSTRACT FROM AUTHOR]

This paper evaluates the performance of the two-way message transmission system on the meteor burst channel developed and tested by the authors. First, the usual channel model is simplified and then the system is analyzed. It is shown through simulations that the errors introduced by the new channel model and by the approximated analysis method are negligible and the proposed method can be used to design and evaluate the system. The performance of the system having packets with subblocks is compared to that of one with usual packets. It is shown that, by using packets with subblocks, robustness of the system performance against changes of channel parameters as well as a shorter time needed to transmit a message can be obtained. The method of performance evaluation shown in this paper has adequate generality and is also applicable to many other meteor burst communication (MBC) systems. [ABSTRACT FROM AUTHOR]

This paper studies the system performance of a zone-structured packet radio network with mobile terminals to which the slotted ALOHA protocol is applied. Conventional performance analyses of the zone-structured packet radio network have not considered the effect of terminal mobile speed. Here, a model is developed for such a zone-structured network where a Markov model is used as the mobility model of a terminal and analytical techniques to evaluate static and dynamic performance of the system are presented. Numerical results and their intuitive interpretations are discussed to examine the effect of zone overlapping, mobile speed, etc. [ABSTRACT FROM AUTHOR]

In the multichannel frequency division multiplex (FDM) optical transmission, the intermodulation distortion generated by the nonlinearity of the LD is a problem. In this paper, it is analyzed that fin the number of transmission channel, N, and the optical modulation index per channel, m, the CSO and CTB are constant for a different value of N if the effective optical modulation index, m√N, is maintained. The results are compared with experiments. In the present analysis, two types of nonlinearity of the current-to-optical conversion characteristics are considered. One of them is the nonlinearity near the bias current of the LD and is predominant in the region of a small effective optical modulation index. Another is the nonlinearity at the threshold value of the LD and is dominant when the effective optical modulation index is large. It is shown by means of the probability density function that the CSO and CTB degrade suddenly if the effect of the nonlinearity of the threshold value appears. In the FM-FDM optical transmission. many distortions in the transmission bandwidth behave as the white noise due to frequency modulation when the carrier is frequency modulated by a video signal. Hence, the CN ratio is effectively degraded. In this paper, it is further presented that the CN ratio degraded by the distortions can be derived from the CSO and CTB by taking into consideration the frequency allocation of the FM signal. [ABSTRACT FROM AUTHOR]

This paper considers a slotted ALOHA network which consists of a central base station and many mobile terminals. In classical performance analyses of random access networks, a channel between the station and a terminal is assumed to be always in a good state. However, this is not the case in mobile radio networks since the channel suffers from many factors such as fading, shadowing, and so on. Moreover, the channel condition changes with the terminal location. In this paper, a simple channel model is used to consider the effects of time-varying channels in a random access network. The channel model assumed in this paper has three states: shadowing, good, and bad. The transitions between the channel states are described by a Markov chain. The dynamic performance of a slotted ALOHA network over such time-varying channels is evaluated by means of the equilibrium point analysis. Then the influence of the time-varying channel on the throughput performance of a slotted ALOHA network is studied. [ABSTRACT FROM AUTHOR]

This paper describes an adaptive array antenna using a signal processing system which is implemented by a systolic array processor (SAP), SAP-AA. Computer simulations show the behavior of the SAP-AA against multipath fading. The SAP realizes a parallel pipelined processing by regularly placing many SAP cells with identical functions and structures so that it achieves the high throughput rate in the data processing. Also, the SAP has many desirable features for very large-scale integration (VLSI) system design and enables miniaturization, weight reduction, and mass production of the processing equipment. In this paper, first, the SAP-AA is described which realizes the least squares (LS) algorithm based on the QR decomposition for the input data matrix using the Givens rotations. In addition, the fundamental performances of the SAP-AA are studied including both the transient response and the steady-state behavior in multipath signal environments. To date, there has been no report which treats the multipath signal suppression performance of the SAP-AA. Finally, it is concluded from the discussion that the SAP-AA is effective for unwanted signal suppression in a multipath signal environment. [ABSTRACT FROM AUTHOR]

Previously, the authors have proposed a design method of a shaped dual-reflector contoured-beam antenna with virtual multihorns with a view to applications to the broadcast satellite BS-3. In such a design, there were discontinuities on the main reflector. In this paper, a method for eliminating these step discontinuities is studied for the dual-reflectors. The current distribution on the main reflector corresponding to the desired radiation pattern is determined by optimization depending on the constraint gain of the far field. Note that the optimization method for the aperture phase distribution was known for a single smoothly shaped contoured-beam antenna. Also, in this paper, an optimization method for the amplitude distribution is proposed anew. Further, by adding a restriction to the phase difference between the adjacent elements in the optimization of the phase distribution, the step discontinuity on the reflector is eliminated. By means of this method, an antenna made of a main reflector with an aperture diameter of 2.3 m is designed at 12 GHz which is the frequency of the downlink of the broadcast satellite. Most of Hokkaido, Honshu, Shikoku, Kyushu, and Okinawa is covered by a radiation pattern with more than 40 dBi and other remote islands with more than 28 dBi. A one-half scale model is fabricated and the radiation pattern is measured at 22 GHz. The results agree well with the numerical results. Also, the sidelobe and the cross-polarization characteristics of this antenna sufficiently satisfy the technical standards in RR.AP 30. [ABSTRACT FROM AUTHOR]

The multibeam transponder allows one to use a smaller ground station in satellite reception system and to make good use of the frequency hand. The redundant system is important for the higher reliability of transponder, especially as the number of the beams increases. This paper considers a redundant system for a multibeam transponder. The concept of the expected system value herein introduced takes the reliability and the transponder weight into account simultaneously. Comparing the performance of eight typical redundant configurations, the importance of the common and active redundancy is shown. [ABSTRACT FROM AUTHOR]

This paper discusses a satellite TDMA system with two dispersive delay lines of opposite characteristics in earth stations and in the satellite transponder to reduce the peak transmitting power of the earth stations. Reduction effect is estimated for available SAW devices and the reduction in peak transmitting power of about 27 dB is achieved in the single-pulse transmission mode. In actual TDMA systems, however, burst pulses must be transmitted and bursts of about 1000 symbols in length are used. Since only relatively short bursts (about 20 symbols long) are allowable in this system, various study subjects are discussed to realize it, such as the increase of burst length, reference time establishment at earth stations, modulation/demodulation and clock recovery. The effects of several kinds of system impairments, such as residual response of modulator, effect of characteristic deviation of dispersive delay lines, and dynamic range of receiver amplifier of transponder are studied. [ABSTRACT FROM AUTHOR]

This paper considers the Z-channel, which is known as a channel model for photon communication or semiconductor memory. A new decoding algorithm is proposed and discussed. Recently, studies have been made from various viewpoints on the asymmetrical error-correcting code suited to the Z-channel, which is considered interesting. One of the basic problems in the Z-channel is the performance and the decoding method when the cyclic code with various features is applied, but it has been investigated little. This paper presents first a maximum-likelihood decoding algorithm which is highly efficient for the cyclic code on the Z-channel. It is then shown that by providing a certain threshold for the algorithm, a higher-speed decoding is realized. It is shown also that by setting the threshold above a certain value, the computational complexity can be improved without sacrificing the maximum-likelihood property. Finally, it is demonstrated by numerical calculation that the decoding error probability is improved greatly by the decoding algorithm proposed in this paper, together with a drastic improvement in the computational complexity. [ABSTRACT FROM AUTHOR]

This paper proposes a new method for efficient validation of the telecommunication protocol, containing the internal events, including those for the timer and resource management. The proposed validation method first converts the protocol containing the internal event into the equivalent protocol not containing the internal event. Then the original protocol is validated by applying the already-proposed validation method for the protocol not containing the internal event to the result of conversion. This paper discusses mainly the principle and the algorithm of the protocol equivalent conversion. The features of the proposed validation method are that the protocol is validated with the minimum processes and signals, which reduces the processing time and the memory capacity needed in the validation and also improves the efficiency. [ABSTRACT FROM AUTHOR]

This paper proposes a method to detect a fault location in a faulty paired cable consisting of branching cables and different gauge wires along a length. Calculating an input-admittance of a faulty pair cable involves consideration of cable length, cable secondary constants, branching conditions, and a fault location. Under this principle, a measured input-admittance can be indicated by fault location if cable length, cable secondary constants, and branching conditions are known. In addition, when a calculated input-admittance agrees with a measured input-admittance, the fault can be located. However, a location error appears because actual cable secondary constants are slightly different from those cable secondary constants that are calculated. This paper also describes the location errors caused by secondary constants differences. Furthermore, two improvement methods for location errors have been developed. One method applies the difference between input-admittances before and after fault. The other method refers a measured input-admittance of a fault-free cable to that of a faulty cable. As results, fault location errors in an open fault (a breakdown of wires) and an insulation degradation fault were significantly decreased. [ABSTRACT FROM AUTHOR]

In the conformance test of the communication protocol, it is desired from the viewpoints of strictness and efficiency to generate automatically the test sequence, based on the formal description. Several methods have been proposed for this purpose. All of these methods are based on the two formal descriptions which can be the basis for the test-sequence generation: one is the description based on the order of the input/output events, and the other is the decription based on the finite-state machine model. This paper attempts to compare the applicability of the two description methods to the conformance test. Also, it evaluates the error-detection capability which actually generates the test sequences for the following two cases: (1) The test sequence is generated directly from the specification based on the order of events; (2) The test sequence is generated from the finite-state machine model, which is obtained from the description of (1). In the evaluation, a simulation technique is employed which uses as a testing object a finite-state machine containing random errors. Finally, this paper notes the handling of the undefined transitions contained in a large number in the actual protocol and considers the class of errors pertinent to the actual protocol, such as the redundant state errors or the replicated state errors. [ABSTRACT FROM AUTHOR]

This paper describes the improvement of characteristics of an offset tri-reflector antenna by introduction of reflector surface shaping, and the importance and allowance of suppression of the higher periodic components of the reflector surface distortion caused in the fabrication process. In an antenna with a good wide-angle radiation pattern, degradation of the sidelobe characteristics due to the higher-order periodical components of the surface distortion cannot be taken lightly. In this paper, the angle and the level of the sidelobe peak due to the periodic aperture phase error are expressed in simple formulas. These formulas are combined with an approximate expression of the wide-angle radiation pattern so that the allowance of the periodic reflector surface distortion is given. Next, a design and measured characteristics are described for a shaped offset tri-reflector antenna with its aperture diameter of 3600 mm to be used at frequencies of 3.6 to 6.475 GHz. Two prototypes with difference values of surface accuracy are compared. By means of measured examples, it is pointed out that suppression of higher-order periodic components of the surface distortion is important. By means of reflector shaping, a nonaxisymmetric aperture distortion is important. By means of reflector shaping, a nonaxisymmetric aperture distribution is realized so that the edge level in the horizontal cross section is made small. Further, by suppressing the higher-order periodic components of the surface distortion, an offset tri-reflector antenna with a good wide-angle pattern and a good cross-polarization characteristic was realized. [ABSTRACT FROM AUTHOR]

The equation of the magnetic shielding effectiveness for a configuration made of a circular (transmitting) coil in a semi-half space on one side of a metal sheet and a magnetic sensor in the space on the other side of the sheet has been derived by Moser for the case where the axis of the coil is perpendicular to the sheet. One of the objectives of the present paper is to derive an equation for the magnetic shielding effectiveness in the case where the coil axis is parallel to the sheet. This paper shows that this effectiveness is smaller by a certain amount than the case where a magnetic dipole is placed at the center of the transmitting coil instead of the coil. The amount of reduction is a function of the ratio of the coil radius to the distance from the center of the coil to the observation point. Another objective of this paper is to determine what kind of quantities can be obtained by the measurement method by the MIL-STD-285 which is used for the measurement of the shielding effectiveness of the wall of the shielded room. In this measurement, the magnetic field shielding effectiveness is derived by measurement of the induced voltage of the receiving coil when the transmitting and receiving coils with a diameter of 12 inches are placed on both sides of the sheet at a distance of 12 inches, respectively, from the sheet in a plane perpendicular to the sheet. It is shown that the result of such a measurement gives rise to a value almost equal to (or smaller by about 0.4 dB than) the magnetic shielding effectiveness in s hypothetical ease where a magnetic dipole is pieced at the center of the transmitting coil and a magnetic sensor is placed at the center of the receiving coil. [ABSTRACT FROM AUTHOR]

The integrated services digital network (ISDN), which is under construction at present, will enlarge the range of communication service by developing radio access systems, with the digital mobile communication systems as the core. The purpose of such a radio access system is to realize the communication capability, which is as flexible as that of the fixed system, while utilizing the features of the radio system. The following problems arise in the traditional access schemes, however, when multiple types of calls with various information characteristics and rates are to be handled. The immediate (circuit switching) system cannot contain efficiently the multiple type of traffic, while the waiting (packet switching) system may produce a delay with a long variation. This paper proposes a new scheme for radio channel access, aiming at a positive integration of the multiple type of traffic. In this scheme, the blank of information is compressed to construct a block (cell) with a constant length, and the physical channel is controlled to be assigned to each cell. The blank is inserted on the receiving side to ensure the time-transparency. Then, the flexibility to various types of immediate and waiting calls, as well as the efficient operation of the channels, are realized. This paper describes also the concept of the scheme and fundamental composition. The channel capacity and the channel occupancy are evaluated by a computer simulation, and it is shown that the proposed scheme has the desirable property that the statistical multiplexing effect is utilized. [ABSTRACT FROM AUTHOR]

This paper describes the estimation of the propagation loss in an urban environment important for channel design of land mobile communication. Conventional methods for intimating the propagation loss in an urban environment gives a representative value of the propagation loss in the urban environment or the propagation loss (median value) within a 500 m ×800 m area obtained by introducing an area factor of occupied buildings. Such a method is not suitable for estimation of the propagation loss depending on the situation near the mobile station. In this paper, the relationship of the measured data of the propagation loss in the Tokyo Metropolitan area at 813 and 1433 MHz with the urban environment parameters such as the base station antenna height, distance, frequency, width of the street where the mobile station exists, direction, average building height, building height on the street side is derived by the multiple regression analysis method. A prediction formula for the propagation loss (median value in the section of about 80 m) including these parameters is derived. The parameter dependencies of the propagation loss, such as the antenna height dependence and the average building height dependence, are described. In addition, the distance dependencies of the propagation loss in this prediction formula and conventional method are compared with the measured values. The prediction formula is expressed in terms of the sum of simple functions of the foregoing parameters. Hence, the estimation of the propagation loss can be carried out easily, taking into consideration the urban environments such as the height of the buildings and width of the streets. [ABSTRACT FROM AUTHOR]