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In accordance with the diversification and efficiency promotion of visual communication, various new services have been desired recently. One such service is facsimile which can transmit both black-and-white pictures and photographic pictures. However, it is rather difficult to process these two kinds of pictures with a single algorithm. To fulfill the demand for high transmission efficiency and high quality of the reproduced pictures, it is desirable to segment the documents into two categories and process them separately. For this purpose, the extraction of the photographic area included in documents becomes a very important theme. In this paper an extraction algorithm of the photographic area from the document images using the characteristics of edge elements and background gray levels is proposed. The features of this algorithm are: 1) automatic setting of parameters adaptable for each picture is possible; 2) area segmentation corresponding to the various gray levels of backgrounds is possible; and 3) segmentation accuracy is rather high. In the experiment presented in this paper, 125 document images which consist of 512 × S12 pixels with 7-bit gray levels have been used. The background gray levels of these images are 27, 36, 42, 57 and 77, and into these images photographic images, which occupy 50, 60, 70, 80 and 90 percent of the total area have been inserted. Experimental results show that in every image the photographic areas have been segmented successfully in the sense of practical use. For 93.8 percent of the images, the differences between the inserted areas and extracted areas are only 0–7 blocks (0–27 pixels), and the usefulness of this algorithm has been proved categorically. [ABSTRACT FROM AUTHOR]

This paper considers the semiconductor integrated circuit, and proposes a solution to the decision problem for the optimum design, where circuit-element values are determined so that the yield is maximized. The spherical surface random number is employed in the calculation of the yield. Although various nonlinear programming methods can be applied to the optimization problem, this paper applies Newton's algorithm to the optimization algorithm. It is shown that the first- and the second-order derivatives of the yield to the design value, which are needed in the calculation of the search vector in Newton's method, can also be derived using the spherical surface random numbers. I is also shown that the center of the element value determined by the design specification can be calculated using the spherical surface random hi, hers, and the optimization can be performed efficiently using the center as the initial point for the optimization. Applying the proposed method to the 5th-order leap-frog-type switched-capacitor filter, the processing time is reduced to approximately one-fourth compared with the case of the Monte­Carlo method. [ABSTRACT FROM AUTHOR]

Radon discussed the reconstruction problem of a two-variable function from its line integrals and the algebraic representation of this problem. He also discussed the reconstruction from curved-line integrals curved-line integrals and extended the discussion to the reconstruction problem of a multivariable function from its hyperplane integrals. For the first two of these problems, reconstruction algorithms have been developed. They have been applied to X-ray CT (Computed Tomography). The third problem has been studied in connection with ultrasonic CT. On the other hand, very little engineering development has been reported on the fourth problem. However, in a practical problem, it is desired to find a three-dimensional structure based on its projections measured as plane integrals. Also, in statistical analysis, a joint probability density function of multiple variables is often desired based on its marginal distributions. Moreover, the reconstruction problem in multidimensional spaces is of mathematical interest. In this paper, a foundation to this problem and theoretical formulas for a filtered back-projection method for reconstruction are given in a simple form based on a discussion similar to that in CT. For numerical calculation filtering is usually implemented by convolution in CT. In this paper, extensions of the kernel functions for convolution to the multidimensional problem are also presented. [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 proposes a high-performance noiseless data compression model which can compress strings generated by a binary Markov information source without prior knowledge of the source. The adaptive expression of the existing universal codes is described by a model with separated sampler and encoder, and the learning structure of each code and the encoding process are described. Through such a discussion, the intuitive reasons are clarified as to why the codes, despite their asymptotic optimality, do not compress well at the start, pointing out room for improvement. Then, the MDL criterion is introduced into each encoder, to improve the performance, while keeping the sampler fixed. The MDL criterion is an estimation for the minimum code length, including the representation cost of the parameters. Based on this criterion, the Markov order which is to be assumed for each symbol is adaptively determined. Since the same determination can be made at the time of decoding, the unique decodability is guaranteed. In the second half of this paper, more detailed techniques are discussed, and a remarkable improvement is demonstrated by a computer simulation. tt is also shown that the sampler of the proposed universal code is of a high-performance, realizing two kinds of encoders. [ABSTRACT FROM AUTHOR]

In a coherent optical fiber communication with a single-mode fiber and an optical heterodyne detection for improved receiver sensitivity, degradations of the receiving sensitivity due to fluctuation of the polarization condition of the received light are a problem. As a possible solution to this problem, this paper proposes a polarization diversity system with an error-detecting code or an error-correcting code. Its characteristics are analyzed and optimum design values are obtained. [ABSTRACT FROM AUTHOR]

A gain/shape vector quantizer for orthogonal transform domain has been designed based on a previous paper [11] on a gain/shape vector quantizer for a spherically symmetric random source. Such a design method is used in the design of a discrete cosine transform encoder with gain/shape vector quantizer. This encoder is similar to that described in [7] except in the following: (i) it has a gain/shape codebook; and (ii) its normalized coefficients of discrete cosine transform are modeled as having spherically symmetric distribution. The S/N rendition of this encoder is 1.0 - 2.5 dB better than that of the DCT coding scheme with Max-type scalar quantizer at the same bit rate. Furthermore, in spite of its similarity to the conventional discrete cosine transform coding scheme with vector quantizer [7], the encoder introduced in this paper delivers higher S/N using the same number of multiplications for the quantization of normalized coefficients, and/or the same amount of memory for the codebook. [ABSTRACT FROM AUTHOR]

Quantization error is one of the important measures that determine the performance of the differential PCM. This paper investigates the DPCM quantization error characteristic and the exact determination of the stationary error density. The input signal considered is a time-discrete increment process which is similar to the Wiener sequence, but with Laplacian increments. A system of equations satisfied by the characteristic function of the prediction error is derived first and the exact formulas are derived for error probability distributions. Using these distributions the mean-squared error, the entropy of the quantized outputs, and the probability of granular error are determined. For the obtained optimum quantization step size, it is shown that the granular error exceeds the slope overload error, that the distribution of quantized outputs is nearly geometrical, that the quantization error is almost equal to that of increments for a large number of quantization levels, and that the results agree with rate distortion theory. The present analysis will be useful to performance analysis of DPCM with stationary non-Gaussian autoregressive inputs. [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]

This paper discusses the design of the regulator using output feedback, and describes a method of control using the observer. In the regulator using the observer, the evaluation function is increased, compared with the state-feedback control. In this paper, the minimax evaluation is adopted, which considers the worst case in regard to the initial state. Consequently, the optimal observer, i.e., the minimax observer can be determined by the proposed method, in the sense that the worst value in regard to the initial state is minimized. Since the initial state is not known in the regulator problem using the output feedback control., the minimax evaluation is practically very important. This paper discusses first the discrete-time system, and the design of the minimax observer is discussed for the linear quadratic form and the model-following control problems. Then, the result of applying the idea to the continuous-time system is shown. It is also possible to design the minimax observer for the continuous-time system, in the same way as for the discrete-time system. The proposed method can be applied, not only to the observer with the minimum dimension but also to the observer with the same dimension. As the numerical example, a solution of the minimum problem is presented using the proposed method. [ABSTRACT FROM AUTHOR]

In a wavelength-division-multiplexing transmission systems optical signals with different wavelengths can be transmitted in multiplex via one optical fiber. Since this system not only increases the transmission capacity but also permits two-way transmission an simultaneous transmission of heterogeneous signals, it is being studied as an effective technique for optical transmission. This paper describes a basic design method for an optical wavelength-division-multiplexing transmission system. Types and wavelengths of optical sources and the wavelength dependence characteristics of multi/demultiplexer are designed so that the two criteria of optical receiving power and optical S/X satisfy required system configurations. This paper also presents experimental results for a fabricated multi/demultiplexer designed for a 4-wavelength multiplexed optical subscriber loop system. The experimental results of this multi/demultiplexer optimental are in good agreement with the designed performance and the proposed design method is shown to be effective. [ABSTRACT FROM AUTHOR]

This paper discusses the bifurcation of the almost periodic oscillation and the generation of chaos in a parametic excitation circuit. The system to be considered is described by a third-order nonautonomous differential equation. Here, the original equation is converted into an autonomous system by using the everaging method. Then the behavior of the solution curves is examined by the phase-plane analysis. The bifurcation of the almost-periodic oscillation and the generation of chaos under varying amplitude of the external excitation are discussed in detail. The feature of the method of analysis of the autonomous system used in this paper is that the solution trajectory can be obtained easily. Since the analysis is a kind of approximate method, the result is compared with that of the mapping method which produces an accurate solution. It was verified that the limit cycle obtained in the autonomous system corresponds to the invariant closed curve of the mapping method, and that the bifurcation of the limit cycle leading of the almost-periodic oscillation and its transition to chaos also agree with the result of numerical computation obtained by the mapping method. [ABSTRACT FROM AUTHOR]

This paper demonstrates that the IIR digital phase can be designed by linear programming. The phase network is used not only to compensate the phase distortion of the signal by the filter, but it is used also in various other problems in communication area. In particular, the network with chirp characteristics is well known. There are IIR and FIR digital phase network, but it is difficult to design completely flat amplitude characteristics for the latter. The design problem for the IIR digital phase filter has been considered as a nonlinear programming problem. By reducing this problem to that of linear programming, the optimal solution can be obtained, if it exists, without any particular consideration for the convergence of iteration or the initial values. This paper also discusses the order of the digital phase network so designed, and it is shown that the order is determined from the given design examples are illustrated, indicating that the proposed method is effective. [ABSTRACT FROM AUTHOR]

This paper defines that globally there exists a state equation when a dynamical system of time-invariant nonlinear network can be described only by capacitor voltages and inductor currents. A sufficient condition is presented for the state equation to exist globally, if the capacitor voltage and the inductor voltages. Then the effect of the parasitic resistance or parasitic reactance on the existence of the state equation is discussed. When only parasitic resistances are added, the existence of the global state equation is preserved. However, the existence of the global state equation based on the capacitor currents and the inductor voltages is related to the eventual passivity of the original network. The latter half of this paper discuses the effect of perturbation of the branch characteristics constituting the network on the existence of the global state equation. Especially, it is shown that when the element is strictly locally passive, both the existence of the global state equation and the strictly local passivity are not affected by the perturbation. [ABSTRACT FROM AUTHOR]

This paper describes simple OHP equipment as an aid in the teaching of physics, for example, electromagnetics by demonstrating centrifugal spherical waves and a group of minute articles radially progressing, A Moiré pattern is produced by using two grated transparencies having certain lattices, one fixes, and the other rotated. In this paper, rotating type Moiré patterns are used since they are east to operate. Each lattice is designed as a function of the propagation velocity of each phenomenon to be demonstrated. The model of the movements of a group of minute articles is used for the divergence in a vector analysis. A reversal Moiré is used for this model. This paper discusses the method of designing the grated transparencies required for these models. Another model for demonstrating the electric force around a dipole is described, formed by overlapping two identical transparencies in a slightly shifted position. It is proven in this paper that this overlapped pattern agrees with the pattern of an electric field formed by a set of parallel lines charged positively and negatively, respectively, and with a homogeneous density. The responses of students to this equipment are analyzed via factor analysis, and the factor size representing “idea” gains a relatively high mark. [ABSTRACT FROM AUTHOR]

This paper describes a method of non-stationary analysis based on the geometrical orthogonal projection with least-squares estimation for a linear model. In the past, local stationary analysis and adaptive methods which successively estimate the parameters have been used for this purpose. How- ever, in application to the nonstationarity case as in biomedical signals these methods have the disadvantage that it is difficult to see the physical significance of the parameters. In consideration of this, the present paper defines the backward prediction error space (Ens) consisting of the backward prediction error vector in each dimension and proposes to handle the nonstationarity by expanding the property into the orthogonal states in each dimension. The backward prediction error vectors constitute an orthogonal system in the least-squares estimation and the reflection coefficient is the parameter directly related to this system. The orthogonality can be interpreted in direct relation to the independence of physical functions. As a measure of the non-stationarily, the angle between the vectors is adopted in the BPES. When the parameters which were optimum in the stationary interval are applied to an arbitrary interval, the angle is an exact expression of the discrepancy due to the nonstationarity. By an example of analysis of biomedical signals it is verified that the angle is useful in evaluation of the nonstationarity, especially of that arising from the change of orders. Thus, it is anticipated that the deterministic non- stationary analysis by BPES will provide new information about biological systems. [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]

FMCW (frequency-modulated continuous wave) radar is a radar system which can achieve high resolution by relatively low signal processing load. The authors have reported on clutter suppression by FMICW (FM interrupted CW) radar, where the transmission/reception of FMCW radar in pulse waveform is switched in order to assure transmission/reception isolation and to suppress undesired waves from short distances. This paper proposes the FM staggered PRI system, in which the pulse repetition interval (PRI) is randomized for each pulse in order to suppress the interference when FMICW radars are congested within the search distance. The target-signal in the FM staggered PRI system is formulated. Conditions such as the average PRI and the possible range of staggering are derived from requirements such as the maximum search distance. The output S/I is statistically evaluated by computer simulation, with the average PRI, the pulse width, the number of interference waves, and the input S/I (signal-to-interference ratio) as variables. The effectiveness of the FM staggered PRI system is demonstrated. © 2007 Wiley Periodicals, Inc. Electron Comm Jpn Pt 1, 90(12): 86–100, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecja.20326 [ABSTRACT FROM AUTHOR]

Interstitial microwave hyperthermia is one of the modalities for cancer treatment that insert a thin microwave antenna into the affected part to selectively heat only the tumor. The authors are investigating this technique with an aim of clinical applications of this medical treatment for brain tumors. In the clinical treatment of brain tumors, it is more critical that “only the tumor parts be heated” than for the treatment of other tissues. Therefore, an antenna that can generate a localized heating pattern on the tumor is required. Although the heating pattern can be controlled here in the longitudinal direction of the antenna by using multiple antennas to form an array applicator, control of the heating pattern in the axial direction is relatively difficult. In this paper, to enable the heating pattern to be controlled in the axial direction, the authors introduced a coaxial-dipole antenna and improved its structure. In addition, they assumed that it was actually applied in the medical treatment of brain tumors and used a numerical calculation model that included a tumor created from MR images to verify the effectiveness of the improved coaxial-dipole antenna according to numerical calculations. © 2007 Wiley Periodicals, Inc. Electron Comm Jpn Pt 1, 90(12): 31–38, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecja.20390 [ABSTRACT FROM AUTHOR]

This paper considers a connectionless (CL) packet switching network, such as IP, and proposes a method in which unused addresses are used as labels for packet flows with various granularities, which are transferred along explicitly specified routes. Generally, in CL packet-switched networks, the next packet is selected and relayed to arrive at the destination host on the basis of the destination address attached to the packet. Consequently, it is impossible to transfer packets which have the same destination address but different requirements along separate routes. One technique for performing such a transfer is multi-protocol label switching (MPLS) and is based on a different transfer paradigm. The cost of this method is high because the transfer schemes of each participating router must be modified. To address this problem, this paper proposes a method for flow-based explicit route transfer. In the proposed method, a particular packet flow is allocated to an unused address so that an explicit route is composed from the unused address and the destination address of the packet is translated. In this method, the transfer scheme is kept essentially the same and explicit route transfer is realized only through a simple extension to the router. Depending on the mode of application, it is unnecessary to modify internal routers; the method can easily be applied to existing networks. In this paper, an application of the method to IP, as a typical CL packet switching network, is described, and the features of the proposed method are discussed. © 2007 Wiley Periodicals, Inc. Electron Comm Jpn Pt 1, 90(9): 78–89, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecja.20308 [ABSTRACT FROM AUTHOR]

Web services are a unified framework that enables the exchange of information among distributed applications using existing World Wide Web communications technologies. Web services offer the benefit of simplifying the sharing of information among different applications that are operated via remote terminals. However, when multiple services exist that provide the same functionality, a mechanism for automatically selecting the most appropriate service from those on offer is necessary. Unfortunately, the majority of automatic selection mechanisms are designed to use a fixed set of indicators as the selection criteria and are therefore unable to adapt to the diverse demands of users. In this paper we propose a new mechanism for automatically performing such service selection that integrates a wide range of different indicators. Specifically, we assign attributes to each of the services that can be used as evaluation criteria; we then gather these attributes at the user's client. We can compute a rating for each service on the basis of the attributes that have been collected and select the service that is assigned the highest rating. In this paper we introduce the concept of an attribute database (an attribute repository) and define a new communications protocol to enable the registration and searching of attributes in order to deal with variation in the attributes used by different services. In addition, using a simulation of a distributed applications environment, we perform evaluations and demonstrate that the proposed selection mechanism is able to reduce execution times as compared to a random selection mechanism. We also implement the proposed mechanism in an experimental environment and show that it can be used in practice for automatically selecting services on the basis of attribute values. © 2007 Wiley Periodicals, Inc. Electron Comm Jpn Pt 1, 90(8): 40–49, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecja.20284 Copyright © 2004 Wiley Periodicals, Inc.Copyright © 2007 Wiley Periodicals, Inc. [ABSTRACT FROM AUTHOR]

In this paper, the authors propose a new control scheme in which the output voltage is fed back into a triangle waveform of a control circuit to improve the transient response of a switching converter. The circuit structure of the proposed system is very simple and will therefore reduce the size and weight of the apparatus and have reduced production costs. Also, because an error amplifier is not used, the circuit is not affected by switching noise or the like and the circuit is easy to design. In this paper, the proposed system is applied to a synchronous rectifying buck converter; the basic properties are analyzed and the system is verified experimentally. As a result, it was confirmed that the proposed scheme has superior regulation properties and transient response characteristics. © 2007 Wiley Periodicals, Inc. Electron Comm Jpn Pt 1, 90(7): 52–59, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecja.20256 [ABSTRACT FROM AUTHOR]

Delay variation of packets is a significant performance measure in IP networks. Both active and passive measurements can evaluate delay variation. Among these, passive measurement is more advantageous because it can monitor the performance experienced by users without disturbing network load. Meanwhile, a shortcoming of using passive measurement is an extremely large storage space required to record packets and timestamps. This problem is solved by feeding a portion of each packet to a hash function as its input and recording the output to identify the packet. Since the data length of the hash function output is very short, such an approach effectively decreases the storage space. However, this approach still needs a considerably large storage space to record time-stamps. Additionally, the collisions among hash output values may bring unacceptable measurement errors. This paper proposes a method to decrease the storage space required to record timestamps for hash-based delay variation measurement. This decrease is achieved by a variable length coding of timestamps. The paper also presents methods to avoid measurement errors brought by hash value collisions. Through experiments, it is shown that the proposed techniques correctly measure delay variation as well as effectively reduce the storage space. © 2006 Wiley Periodicals, Inc. Electron Comm Jpn Pt 1, 90(3): 21–32, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecja.20328 [ABSTRACT FROM AUTHOR]

In this paper, we propose a simple method for accurately calculating the probability distribution of the largest eigenvalue of the correlation matrix of a MIMO propagation channel in a Nakagami–Rice fading environment including direct signals. The results determined by the proposed approximation method were compared to the results of a computer simulation and exhibited accurate matches. We discuss the channel capacity in a Nakagami–Rice fading environment. In this environment, the largest eigenvalue clearly dominates, and maximum ratio combining transfers are clearly useful. © 2006 Wiley Periodicals, Inc. Electron Comm Jpn Pt 1, 89(11): 68–77, 2006; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecja.20210 [ABSTRACT FROM AUTHOR]

Bluetooth is a short-range wireless system using the 2.4-GHz band, but has the problem of degradation of communication quality caused by the noise radiated by microwave ovens which share the same frequency band. In this paper, we theoretically and experimentally study the impact of microwave oven noise on Bluetooth. Time variations in the bit error rate with a fixed channel frequency are theoretically evaluated applying the time domain oven noise model represented by frequency and amplitude modulated wave to the theoretical equation of the bit error probability for frequency shift keying (FSK). The average bit error rate and the average packet error rate with the frequency hopping spread spectrum (FH-SS) scheme are also evaluated. The results of theoretical study show that (1) microwave oven noise using an inverter power supply (inverter-type) degrades average packet error rate more seriously than does a microwave oven not using an inverter power supply (transformer-type), and that (2) FH-SS is less effective in mitigating interference from inverter-type oven noise compared with transformer-type oven noise. Experiments are conducted using Bluetooth terminals. Error rates are measured using actual ovens and oven noise simulator based on the noise model. The effectiveness of the noise model applied in this paper in the evaluation of the Bluetooth transmission characteristics during microwave oven noise interference is demonstrated. © 2006 Wiley Periodicals, Inc. Electron Comm Jpn Pt 1, 89(11): 24–34, 2006; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecja.20275 [ABSTRACT FROM AUTHOR]

In this paper, a layered network that interconnects a distributed queue subnetwork with another distributed queue bridge network is considered. As slot control scheme in this network, a loopback retransmission scheme preventing slot discarding and an adaptive node load control function are proposed. In the communication within the subnetwork, no transmitted slot is discarded during processing. However, it is necessary to consider protection against discarding due to buffer overflow in the bridge of the distributed queue bridge network interconnecting the subnetworks. In order to prevent reduction of slot use efficiency caused by discarding in the bridge, it is desirable to eliminate discarding. Also, in order to prevent discarding of slots arriving at the bridge from the subnetworks, slot transmission at each node must be controlled. In this paper, in order to prevent slot discarding caused by buffer overflow of the bridge, a method is proposed for loopback retransmission of the slot on the bridge network or subnetwork. It is shown that discarding can be eliminated. Also, the effectiveness of the method is confirmed by computer simulation. © 2006 Wiley Periodicals, Inc. Electron Comm Jpn Pt 1, 89(11): 35–45, 2006; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecja.20267 [ABSTRACT FROM AUTHOR]

The demand for video service in mobile communications systems is increasing. In response to this demand, wireless P-MP (Point-to-MultiPoint) video transmission, in which a given video is transmitted to several moving terminals via a single channel, has been studied. This scheme can make effective use of bandwidth, power, and spreading codes. In this paper, as wireless P-MP video transmission schemes effective in the CDMA system, we propose MCAP (MultiCode Assignment algorithm for P-MP transmission) and the P-MP video transmission system. In MCAP, the mobile terminals receiving the identical video are divided into two groups, high quality and low quality, based on the channel quality. By performing transmission power and transmission rate control for each group, the transmission rate can be improved. Also, by using multicode transmission, transmission rate control and the channel allocation are carried out in a unified fashion. In this paper, by means of simulations, it is demonstrated that the proposed scheme can substantially improve the transmission rate without increasing the number of spreading codes and the power. Several schemes are compared as power control base selection schemes needed for MCAP. An optimum scheme is determined from the comparative evaluation results. © 2006 Wiley Periodicals, Inc. Electron Comm Jpn Pt 1, 89(8): 14–25, 2006; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecja.20280 [ABSTRACT FROM AUTHOR]

In wavelength division multiplex (WDM) systems for long distance and large capacity, it is desirable that the modulation format be tolerant to degradation by nonlinear effects and achieve high frequency utilization efficiency. This paper compares modulation formats by numerical calculation from the viewpoints of frequency utilization efficiency and tolerance for fiber nonlinearities. It is shown that duobinary, RZ-DQPSK (0.5) and CSRZ-DQPSK achieve high transmission performance in DWDM (dense WDM). It is also shown that NRZ-DBPSK, RZ-DBPSK (0.5), and CSRZ-DQPSK achieve high transmission performance in CWDM (coarse WDM). Before concluding, various methods of bit-error rate calculation are compared and discussed, aiming at the correct evaluation of the bit-error rate. The application of the Q method to the differential quadrature phase-shift keying format is shown to be feasible. © 2006 Wiley Periodicals, Inc. Electron Comm Jpn Pt 1, 89(8): 50–64, 2006; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecja.20236 [ABSTRACT FROM AUTHOR]

Over the past few years, content delivery services using the Internet have been noted as a new business. In this type of data delivery, we consider services providing multiple classes having different data waiting times based on priority control. The utility to all users is thought to change with the number of classes under priority control and the traffic load ratio per class. Therefore, in this paper, we quantify the relationship between the waiting time and user utility in data transfers with priority control by employing a utility measurement function, and study the traffic load ratio of each class when provided with priority classes and maximizing the utility for all users. Then we analyze the conditions for maximizing utility for each data transfer method and the user utility measurement function, and demonstrate the optimum network efficiency through numerical examples. The results clearly show that a method providing multiple classes rather than a single class and using priority control increases the utility for all users. With priority control, the maximum utility is not reached at 100% network efficiency, but the maximum utility results when a few lines are free. © 2006 Wiley Periodicals, Inc. Electron Comm Jpn Pt 1, 89(7): 49–61, 2006; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecja.10225 [ABSTRACT FROM AUTHOR]

SR (Selective-Repeat) ARQ (Automatic Repeat reQuest) is employed to recover packet errors on a satellite channel effectively. This SR ARQ has the problems of large resequencing delay and bursty packet departure due to the resequencing function. To solve these problems, this paper proposes the PFRS (Per Flow ReSequencing) scheme, which performs resequencing for each flow independently, while lost packet detection and associated retransmission are performed on the basis of whole flows. This paper shows the effectiveness of the proposed scheme by a simulation in which a number of upper layer flows, such as TCP and UDP, are multiplexed over SR-ARQ performed in layer 2. The effectiveness of this scheme includes a decrease in the average packet delay, a decrease in receiving buffer occupancy, suppression of burstiness in output packet streams, and an increase in end-to-end TCP throughput. © 2006 Wiley Periodicals, Inc. Electron Comm Jpn Pt 1, 89(7): 24–34, 2006; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecja.20258 [ABSTRACT FROM AUTHOR]

As a structure that reduces radiation from a transmission line with input and output ports, a transmission line with a side plate is proposed in this paper. The radiation field by the traveling wave current on the transmission line is derived and the radiated power is analytically derived. From this analysis, it is found that in order to reduce radiation loss, (1) the transmission line height should be reduced, (2) the characteristic impedance be increased, (3) the propagation constant of the current be increased, and (4) the distance to the side plate be reduced. Further, a transmission line with a side plate is fabricated and the effect of radiation reduction is compared with the theoretical result and demonstrates the validity of the paper. © 2006 Wiley Periodicals, Inc. Electron Comm Jpn Pt 1, 89(6): 1–10, 2006; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecja.20274 [ABSTRACT FROM AUTHOR]

This paper considers a multicarrier system performing burst transmission and discusses the channel estimation method, together with the estimation accuracy. In a multicarrier system such as OFDM, the channel state information of each subcarrier is estimated using a known signal, and then the signal is detected. Consequently, the accuracy of channel estimation has a large effect on transmission performance. Furthermore, in an MC-CDMA system in which OFDM is combined with code spreading in the frequency domain, the signal is also synthesized by using subcarriers in the receiver on the basis of the subchannel information. Thus, the signal quality after despreading depends greatly on the accuracy of channel estimation, and it is an important issue to establish a channel estimation method suited to a multicarrier system and to evaluate its accuracy. This paper considers channel estimation in the time domain based on correlation calculation for the known signal and channel estimation in the frequency domain using the FFT of the known signal. The accuracy of estimation is derived analytically, and a method of reducing the computational complexity is proposed. Finally, the receiver performance is derived quantitatively by computer simulation, assuming that these channel estimation procedures are applied, and the effects of these methods on the quality of the received signal are analyzed. © 2005 Wiley Periodicals, Inc. Electron Comm Jpn Pt 1, 89(4): 10–21, 2006; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecja.20261 [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]

A new pulse compression filter design technique to realize theoretical minimum S/N loss with zero range sidelobe was indicated in our previous paper. In succession, we have verified in this paper the performance of this pulse compression filter applied to discrete phase-coded waveforms modulated by Barker code or P4 code via numerical simulations. As a result, we have concluded that the filter derived by our proposed formula surely realizes zero range sidelobe even in the case of oversampling in one code chip, the compressed pulse width is almost the same as the code chip length, and the degradation caused by the Doppler effect is inevitable but equivalent to traditional pulse compression filters. © 2005 Wiley Periodicals, Inc. Electron Comm Jpn Pt 1, 89(3): 10–20, 2006; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecja.20263 [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]

The application of adaptive array antennas in wireless base stations in cellular mobile communication systems is studied to improve frequency utilization. Since the propagation path information differs in the uplink and the downlink in Frequency Division Duplex (FDD) where the carrier frequencies in the downlink and uplink differ, the method for generating the antenna weights for the downlink is an important topic of study. In this paper, we propose a method that measures the location of the mobile station via the uplink (direction and distance from the base station) and controls the antenna weights of the downlink based on that information. Then we clearly show the improvement in the receive CINR performance in the mobile station when the proposed method was applied to a DS-CDMA cellular system. © 2005 Wiley Periodicals, Inc. Electron Comm Jpn Pt 1, 89(2): 57–68, 2006; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecja.20199 [ABSTRACT FROM AUTHOR]

This paper discusses methods of sending messages from a source that created a mobile agent (MA) to the MA, which has moved. These methods include the Home-Proxy method and Broadcast method. However, with these techniques, it is possible that the transmitted messages may not be delivered to an MA that is frequently moving around on the network. A method for resolving this problem has been proposed by Murphy and Picco (hereafter termed the Murphy method). Although the Murphy method can reliably deliver messages to the MA, it does not take into consideration the time that elapses until the messages are delivered to the MA. The authors propose a method for delivering messages in the shortest possible time (hereafter termed the clustering method) by partitioning the entire network into multiple areas (clusters) to improve this Murphy method. This paper, proposes the clustering method precisely and in detail. In addition, the validity of this method is certified by performing a logical verification. Simulation experiments are performed to compare the method and Murphy method to prove the effectiveness of the method by verifying that the time required to deliver messages to the MA decreases if the time that an MA stays at a node is not short and that the number of messages decreases if the time that an MA stays at a node is short. © 2005 Wiley Periodicals, Inc. Electron Comm Jpn Pt 1, 89(1): 67–80, 2006; Published online in Wiley InterScience (www.interscience.wiley. com). DOI 10.1002/ecja.20184 [ABSTRACT FROM AUTHOR]

In the past few years, there has been a focus on clean energy and the installation of solar cell modules on the walls of high-rise structures such as buildings. Solar cell modules embedded in window glass, which occupies a large portion of the walls of high-rise buildings, are being studied. However, solar cell modules easily reflect electromagnetic waves and the effect of electromagnetic wave interference cannot be ignored. Therefore, in this paper, we study a method for suppressing electromagnetic wave interference in the frequency bandwidth of terrestrial digital broadcasts when using solar cell modules embedded in window glass. By appropriately selecting the structure of the solar cell module and the shapes of the wires connecting solar cell pairs, at least 10-dB reflections can be suppressed in the frequency range from 470 MHz to 770 MHz of terrestrial digital broadcasts while preserving the lighting function of the window glass. © 2005 Wiley Periodicals, Inc. Electron Comm Jpn Pt 1, 88(10): 28–34, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecja.20206 [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]

In this paper, a method for weight control of an adaptive array is proposed for a system using a cyclic prefix in single carrier wireless communications (SC-CP). In the SC-CP system, the delayed wave within the guard interval (GI) can be equalized by discrete frequency domain equalization. Therefore, it is to be expected that the characteristics can be improved with respect to the received signal power by reception of several arriving waves within the GI. On the other hand, reception of several arriving waves leads to generation of zero points in the frequency response so that noise enhancement may be a problem for a discrete frequency domain equalizer with a zero forcing (ZF) reference. Also caused in the SC-CP system are the intersymbol interference (ISI) and interblock interference (IBI) due to the delayed wave exceeding the GI length. In this paper, a weight control method is proposed that simultaneously realizes enhanced received signal power by reception of several arriving waves and avoidance of noise enhancement due to ZF reference equalizer. At the same time, the weight control method to suppress delayed waves outside the GI is theoretically derived and its characteristics are evaluated by a computer simulation. © 2005 Wiley Periodicals, Inc. Electron Comm Jpn Pt 1, 88(9): 38–48, 2005; Published online in Wiley InterScience (www.interscience. wiley.com). DOI 10.1002/ecja.20189 [ABSTRACT FROM AUTHOR]

In multicast delivery in a network environment with various bandwidth limitations, it is effective to apply the layered multicast technique, which realizes delivery at a reception rate matched to each receiver, although the rate is set discretely. This paper assumes a multimedia session such as a multichannel broadcast or a video conference, composed of multiple streams. In such an application, it is desirable from the viewpoint of efficient use of bandwidth that not only should the streams be transmitted with stable quality, but that the rate should be assigned according to requests, such as attention to the speaker. However, it is difficult to achieve the above goal by directly applying the conventional layered multicast rate control technique, since each stream controls the rate independently. From such a viewpoint, this paper presents a session level mechanism covering multiple layered streams. A multiple streams controller (MSC) is introduced into each receiver, and each MSC autonomously controls the reception rate with interstream coordination in the session. The MSC monitors the reception state of the multiple streams simultaneously and estimates the bandwidth information on the bottleneck link and the set of transiting streams, based on the detected congestion data. Based on the estimation, the learning efficiency of the reception rate is improved and rate assignment control over the streams is applied. An evaluation is performed by computer simulation, and it is shown that the reception quality of the stream is improved by applying the proposed method, and that the reception rate can be coordinated among the streams. © 2005 Wiley Periodicals, Inc. Electron Comm Jpn Pt 1, 88(8): 18–31, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecja.20142 [ABSTRACT FROM AUTHOR]

This paper considers the ubiquitous environment, in which a tremendous number of objects, such as physical devices, multimedia contents, and software components, exist everywhere. In order to provide and utilize various services transparently in such an environment, there must be a service synthesis technique that can dynamically construct services by mutually connecting objects. The realization of service synthesis requires a position-independent naming service which can securely and transparently call from the network the functions (functional objects) that act as the service component. The authors designed an interface-based naming service which can perform transparent calling of functional objects on the basis of interface information on the objects. The interface-based naming service not only can call functional objects efficiently from the network, but also can provide several useful features of service synthesis support: when two functional objects are interconnected, the required supplementary functional object is automatically determined, and when a function cannot be found, that function is realized equivalently by using multiple functional objects. This paper describes the architecture of the interface-based naming service, together with its algorithm. The approach is evaluated by simulation and it is shown that the interface-based naming service is a useful system in a ubiquitous environment with an increased number of objects and an enlarged network scale. © 2004 Wiley Periodicals, Inc. Electron Comm Jpn Pt 1, 88(3): 63–75, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecja.10177 [ABSTRACT FROM AUTHOR]

In reliable multicast, the same information is transmitted to specified receiving nodes while maintaining reliability, with the information rate aligned to the receiving node with the lowest throughput by end-to-end control. However, the consideration of the receiving node with the lowest throughput produces the problem that other receiving nodes belonging to the same multicast group are limited to a considerably lower throughput than their own reception limits. This is a problem inherent to multicast communications, where the receiving nodes generally differ in congestion status. This fairness problem for receiving nodes is called intrasession fairness. In reliable multicast, it is impossible to realize intrasession fairness by using only end-to-end control. The purpose of this paper is to realize intrasession fairness by a scheme in which servers independently apply congestion control to the downlink by placing servers in the network and providing network support. The proposed scheme is evaluated by simulation. © 2004 Wiley Periodicals, Inc. Electron Comm Jpn Pt 1, 88(2): 61–70, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecja.10125 [ABSTRACT FROM AUTHOR]

We explain a tracking method that uses a linear filter to estimate the true values of the position and the velocity with the target position as the radar observation. One rep- resentative example is a Kalman filter for three-dimen- sional space. The α-β filter with its easily analyzed performance is widely used in one-dimensional space. In a tracking method, the tracking precision must be evaluated when sufficient time has elapsed since the initial calculation, that is, in the steady state. The equation for calculating the variance of the errors in the predicted position in the steady state has been reported for radar observations of a constant-velocity linear motion target by an α-β filter. In addition, a Kalman filter can obtain the variance of the errors in the predicted position in the steady state by the Riccatti equation. In this case, however, a premise is the presence of drive noise that indicates the ambiguity of the motion model. There is no equation for calculating the variance of the errors in the predicted position in the steady state for the radar observations of a constant-velocity linear motion target. In this paper, we present an equation for calculating the covariance matrix of the prediction errors in the steady state of the position and velocity for the radar observations of the constant-velocity linear motion target in a 3D spatial linear filter. The results calculated in this paper present an extension of a conventional α-β filter. [ABSTRACT FROM AUTHOR]

Recently there have been many methods for rate control methods as applications of control theory. This paper considers congestion control in an ER system of ABR class in ATM as an example, and proposes a PID-type control rule under the existence of propagation delay. In the ATM switch, we predict the buffer level after time which equals the propagation delay elapsed. Based on the difference between the predicted and target values, a QoS value is calculated. It is stored in the ER field of an RM cell, and sent to each source. The connection sets the transfer rate corresponding to the extent of satisfaction and the QoS service class. We show conditions for the control parame- ters in order to stabilize the buffer level. [ABSTRACT FROM AUTHOR]

It is well known that a large spike error and a bias error occur in the monopulse angle measurement process (of height estimation due to sea surface reflection or road surface reflection) when height estimation of a low-altitude target is carried out with an air traffic control radar or a tracking radar with a monopulse antenna. In this paper, a target height estimation method is proposed that can seek the estimation object with only one parameter of the target height, even if fading prevention by frequency hopping and a subarray configuration of the array antenna based on the maximum likelihood estimation method is used. By means of computer simulation, the S/N dependence and equivalent earth radius error dependence of the target height estimation error are evaluated when the conventional ΣΔ monopulse method, the maximum likelihood estimation method without frequency hopping for four subarrays, and the proposed maximum likelihood estimation method with frequency hopping are used. Even though the evaluation is within the limited conditions, it is confirmed that the proposed method can estimate the target height while fading prevention is attempted in a multipath environment. © 2004 Wiley Periodicals, Inc. Electron Comm Jpn Pt 1, 87(11): 39–48, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecja.10208 [ABSTRACT FROM AUTHOR]

In this paper, an FDTD analysis is carried out for an active integrated antenna with an amplifier. The GaAs FET used in the amplifier is expressed in terms of TriQuint's Own Model (TOM) and the numerical results of its state equation are combined with the FDTD method by way of the voltage source method. As a result of investigation of the method for application of the bias voltage in a 8.5-GHz low-noise amplifier, it is found that convergence to the set voltage is obtained by applying the voltages via shorting pins after all bias circuits are modeled. Also, the analysis and experimental results of the radiation patterns of the active patch antenna are compared. It is found that the cross polarization level is increased due to the currents flowing in the drain bias line placed near the patch antenna. Finally, the radiation characteristics of the active slot antenna are investigated. It is confirmed that the cross polarization can be reduced by separating the radiating part and the circuit part on opposite sides of the substrate. The method proposed in this paper allows design of the entire antenna structure integrated with active devices, including the effect of the coupling between the circuit elements, impedance matching conditions, and radiation patterns. © 2004 Wiley Periodicals, Inc. Electron Comm Jpn Pt 1, 87(11): 21–29, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecja.10213 [ABSTRACT FROM AUTHOR]

In the circularly polarized dielectric resonator antenna (CP-DRA), the one-point feed method with a simplified configuration of the feed system is studied. Although the CP-DRA using a rectangular dielectric body requires a simple fabrication process, the excitation condition for a circular polarization is not clear yet. This paper studies a design method for a CP-DRA generating a circular polarization with one probe placed at the external location of a rectangular dielectric body. As the first step of the design, the procedure used in the design of a conventional circularly polarized microstrip antenna is applied to this CP-DRA. In the second stage of the design, an optimum structure of the CP-DRA generating a circular polarization with matching to a feed system is determined by an iterative analysis of the structure including the excitation section by means of the modal polarization current model method (M-PCMM). It is shown in the second stage of the design that the M-PCMM is useful. © 2004 Wiley Periodicals, Inc. Electron Comm Jpn Pt 1, 87(11): 1–10, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecja.10216 [ABSTRACT FROM AUTHOR]

Channel efficiency can be improved by transmission that integrates voice and the data. When this idea is applied to multicellular systems, channels must be assigned so that the intercellular interference power is minimized. Furthermore, channels must be provided with priority for voice calls, since real-time transmission is required. As a system that considers these requirements, this paper investigates a method of reducing intercellular interference in a circuit switching system with channel segregation in which data are transmitted with priority, using the silent period of voice calls. It is shown by computer simulation that the proposed method can improve performance characteristics such as the interference rate, blocking rate, forced termination rate, and hand-off rate. [ABSTRACT FROM AUTHOR]

This paper considers the application of optical wireless communications to mobile communications. We consider an optical mobile communications system using cycle emission cells and allowing a reduction of the shadowing effect, which is a problem in optical wireless communications. The proposed system uses multiple transmitters with cycle emissions (DTCE). By varying the number of transmitters, the error rate performance is compared via computer simulation. It is anticipated in particular that when the proposed method is applied to mobile communications, multiple transmitters will be placed in the service area, and the distance between the transmitters and the synchronization among the transmitters will greatly affect the error rate performance. The performance is calculated by varying these parameters via computer simulation, and the results are evaluated. Furthermore, the result is compared to other models which have been proposed in order to reduce the shadowing effect, and the effectiveness of the DTCE system regarding optical wireless mobile communications is demonstrated. [ABSTRACT FROM AUTHOR]