bluuebunny/crossref_metadata_2025 huggingface dataset:
On principal partition of matroids with parity condition into strongly irreducible minors pairs
Authors: Onozava Akira , Inoue Masayuki , Oishi Shin'Ichi , Horiuchi Kazuo
Published: July 2007

The matroid parity problem is a common generalization of the matching problem for graphs. The matroid intersection problem and its engineering applications are also known. It has been shown that the matroid parity problem is generally unsolvable in a polynomial‐bounded running time. The concept of principal partition has recently been extended to matroids with parity condition as well as to 2‐polymatroids and a certain class of matroids for which the matroid parity problem can be solved by a polynomial bounded algorithm has been charcterized. This paper shows that the central minor plays an important role when using the concept of principal partition in the matroid parity problem and generalizes the concept of principal partition of a matroid into its strongly irreducible minors pairs. Then we characterize the properties of strongly irreducible minors pairs and the critical sets pairs which give these minors pairs. Finally, we give a class of matroids for which one can show the existence of such a principal partition and solve the parity problem by a polynomial‐bounded algorithm by using the concept of the so‐called F0‐strongly irreducible minors pairs. At the same time, we show that a strongly irreducible minor called the F0‐ minimal central minor plays an essential role in the theory of principal partition in parity problems.
Extended formulas of sampling theorem on band‐limited waves and their application to the design of digital filters for data transmission
Authors: Kida Takuro , Fukuda Yutaka
Published: July 2007

The paper presents an extension of the sampling theorem with nonuniform sampling points to band‐limited waves where the spectrum of the obtained interpolation functions is differentiable to any desired degree. The adopted series of sampling points, in general, is a periodic repetition of K nonuni‐formly spaced sampling points. It is then shown that, neglecting shift along the time axis, there is no need of K different interpolation functions and that these functions are discrete orthogonal under certain conditions. Next, general formulas are derived to evaluate interpolation error due to moderate band limitation and simplified forms of the formulas are derived at K = 2 for each frequency interval. These formulas are also used as examples for an intuitive explanation. As a typical example of data transmission filters, a digital Nyquist filter is considered and a design method for it is introduced by applying Bellanger's method to some of the low‐rate subsystems while the remaining ones are supplied by interpolation. As an example, two out of five low‐rate subsystems are designed by the proposed method and are shown to require about 40% less hardware than the filters designed by Bellanger's method.
Interactive fuzzy goal programming for multiobjective nonlinear programming problems
Authors: Sakawa Masatoshi
Published: July 2007

This paper considers the situation where the decision‐maker has a fuzzy goal for each of the object functions in a multiobjective nonlinear programming problem, and proposes the interactive fuzzy goal programming which can determine the satisfying solution ensuring the Pareto‐optimality of the decision maker. The decision‐maker has a fuzzy goal for each of the object functions in the multiobjective nonlinear programming problem. For example, “The function should nearly be a or less,” or “The function should be approximately b.” Such a fuzzy goal of the decision‐maker is determined by evaluating interactively the corresponding membership function. After determining the membership function for each of the object functions, the decision‐maker sets the goal membership value for each membership function on a subjective basis. Then the difference between the membership function value and the goal membership value is minimized, determining the corresponding Pareto‐optimal solution. The decision‐maker is either satisfied with the given Pareto‐optimal solution, or subjectively updates the goal membership value by noting the difference between the membership function value for the obtained Pareto‐optimal solution and the goal membership value. By this process, the satisfying solution is derived eventually for the decision‐maker, ensuring the Pareto‐optimality. Based on the proposed algorithm, an interactive computer program was constructed, which is shown in this paper, together with the example of computer output for numerical example.
A consideration on a design for optical collimating system using rod lens
Authors: Kishimoto Ryozo , Toba Hiromu
Published: July 2007

Optical circuits with low loss and stable operation are needed for developing optical communications systems with single‐mode optical fibers and laser diodes. The Gaussian beam field is analyzed by means of the beam expansion method and the Hermite generating function when the beam is incident on a rod lens off‐axis and obliquely. The coupling loss of the optical collimating system is obtained both experimentally and theoretically and the optimum design method is found. With rod lenses which have a radius of curvature of 2.5 mm and thickness of 5.5 mm, the insertion loss is as low as 0.4 dB for lens intervals larger than 100 mm. It is also shown that there is an optimum configuration which minimizes the increase in coupling loss when two connecting single‐mode fibers are displaced in opposite directions perpendicular to the optical axis.
Twin delta loop antenna and its application to antenna with plane reflector
Authors: Tsukiji Takehlko , Kumon Yasunori , Tou Shigefumi , Okubo Masaokl
Published: July 2007

It is known that the impedance characteristics of polygonal loop antennas (e.g., triangular or rectangular loop antennas) vary considerably with the loop shape. This feature is considered to be an advantage of the polygonal loop antenna in designing practical antennas since the characteristics required for the intended purpose can be obtained by appropriate choice of the loop shape. Investigation of the polygonal loop antenna shows that an isoceles triangular loop antenna driven at its apex exhibits relatively broadband impedance characteristics. Utilizing this feature, we propose a twin‐delta‐loop‐antenna (TDLA), which is a coplanar twin triangular loop antenna that provides broadband properties with respect to both impedance and gain. This TDLA can be easily applied to a plane reflector antenna or the Yagi‐Uda array antenna to develop an antenna system with higher performance.

In this paper, for wider application of the TDLA we present the detailed fundamental characteristics of impedance and directive gain of the TDLA. In addition, the design procedure for a plane reflector antenna using the TDLA is demonstrated for an example of practical application of the TDLA with low VSWR for coaxial cable without using a balun or impedance transformer.
Secret ballot systems using cryptography
Authors: Akiyama Minoru , Tanaka Yos Hiaki , Kikuchi Toshio , Uji Hiroaki
Published: July 2007

Several problems arise when an electrical communication system is utilized to realize a secret ballot. For example, double voting is easy. Even if cryptography is used, the content can be deciphered by voters who know the key to the cryptography. This paper proposes and discusses a system which can solve those problems and can realize a secure secret ballot by electrical communication. The divided‐vote secret ballot system is considered first. In this system, the individual votes represented by integers are divided into several sets and are distributed to ballot managers who process the subsets and announce the total. Deciphering and counterfeiting are impossible. Then the sum‐round‐opening secret ballot is discussed. In this system, the vote is enciphered using the GS public‐key system, and are totaled in the enciphered form. The separate‐round‐opening secret ballot is also discussed in this paper. The system is a modification of the sum‐round‐opening type so that the individual votes can be opened separately. Deciphering, counterfeiting and impeding are impossible in this system.
Optimal predictive control of linear discrete‐time stochastic systems
Authors: Yahagi Takashi , Sakai Katsuhito
Published: July 2007

This paper considers the regulator problem for the linear discrete‐time stochastic system represented by the input‐output relation. The methods of optimal predictive control based on the prediction of output, when the output contains a delay in relation to the input, is described. In the control system, in general, there exists a delay inherent in the plant, and this delay apparently is increased with the decrease of the sampling period. There may also be produced a control delay due to the computation time when it is not negligible. From such a viewpoint, the predictive control is very important. In this paper, the input‐output relation is represented by the equivalent state and output equations based on the observable canonical form, and a quadratic objective function containing output and control input is adopted. This choice of state variables is useful in that fewer computations are required in the derivation of the optimal control input, compared with other methods. By comparing the proposed method with a Kalman filter, either method can arrive at the optimal prediction, thereby minimizing the mean‐square error under the specified condition. However, the proposed method is better in the number of computations when an adaptive control by digital computer is to be realized. For example, simulations are made by the proposed method from various viewpoints, indicating that satisfactory control can be realized by suitably selecting the objective function according to the property of the plant.
Analysis of input control based on discrete monitoring in mixed input queueing model
Authors: Fukuda Akira
Published: July 2007

This paper analyzes input control with discrete monitoring in a queueing system involving two input systems. One stream with Poisson arrivals (Poisson stream) can enter the system when waiting room is not full. For the other stream with arrival of general distribution (GI stream), entry into the system is controlled as follows. The system is monitored at Poisson epoch, and when the number of calls in the system at the beginning of each interval is beyond the threshold, the arriving calls are regulated and lost during that interval. The holding time for both of the streams obeys an identical exponential distribution. The model is analyzed using piecewise Markov process theory and the stationary state probabilities at GI call arrival speech and Poisson call arrival epoch are obtained. Next, using these probabilities, regulation probability, regulation action frequency, individual loss probability, and mean waiting time are evaluated. By some numerical examples, this input control is compared with no control and input control with continuous monitoring. As a result, the following are revealed: (i) Under this control, the loss probability for Poisson stream and its mean waiting time are reduced compared with no control case; (ii) Regulation action frequency of this control is far smaller than that of the continuous monitoring control and is little affected by the Inter‐arrival time distribution of GI call.
Double‐thin‐film waveguides for acoustic surface waves
Authors: Hayashi Yukinari , Hayata Kazuya , Koshiba Masanori , Suzuki Michio
Published: July 2007

To increase the degrees of freedom in the design of a thin‐film surface acoustic waveguide, this paper proposes a waveguide of new configuration in which two kinds of strip thin films are placed on the substrate. Specifically, a double‐thin‐film waveguide is considered which consists of a Y‐cut Z‐propagation LiNb 03 substrate with a chromium coat and an additional gold coat on top of it. The velocity dispersion of the Rayleigh wave and the particle displacement distribution as a measure of the guiding effect have been studied theoretically. The results are compared with the structure coated with gold only or with chromium only. From the utility viewpoint, it is desirable to make the velocity dispersion small and the guiding effect substantial. The chromium‐coated structure has a smaller velocity dispersion but the guiding effect is smaller. On the other hand, the gold‐coated waveguide has a larger guiding effect but the velocity dispersion is also large. In the double‐thin‐film configuration, the velocity dispersion can be reduced without significantly degrading the guiding effect. This double‐thin‐film waveguide and the one coated with gold only have been fabricated and the experiments have been performed. It has been confirmed that the numerical results for the velocity dispersion are accurate.
Automatic construction of consonant recognition rules using binary decision unit
Authors: Aikawa Kiyoaki
Published: July 2007

In conventional rule‐based speech recognition, the rules have been constructed in a heuristic way. In that method, the rules with high accuracy have been difficult to construct when the recognition algorithm is complex, as in the case of consonant recognition. To cope with this problem, this paper presents a method for automatically constructing the recognition algorithm in the form of a set of rules. The method is a compromise between the transparency of the algorithmic representation by rule‐based representation and the high accuracy by the optimization of the automatic construction.

The unit of the rule is represented by if (condition), then (branch 1), and else (branch 2). The condition is a threshold logic using the discrimination parameter with clear meaning. The set of rules is constructed by the iterative procedure of selecting the optimum discrimination parameter and the threshold, for partitioning the consonant training samples into two sets. By connecting the constructed rules, a binary decision tree is formed. The consonant is recognized by iterating binary decisions on the tree and examining upon each which terminating node is arrived at. By constructing the rules depending upon each succeeding vowel, a set of rules with a higher accuracy can be obtained. By the evaluation experiment, it was seen that transparent rules with higher accuracies can be constructed. The obtained rules are in agreement with the empirical rules of phonology. Furthermore, using the rules, the consonant recognition rate in 100 city succeeding vowel‐dependent names uttered by 50 subjects was improved from 72.4 to 80.0 percent.
LSP‐CV speech synthesis via CV‐syllable positioning rule
Authors: Arai Yasuhiko
Published: July 2007

Traditional rule‐based synthesized speech has such problems as being unsatisfactory in articulateness and in naturalness of the rhythm inherent to the Japanese language. This paper proposes a CV‐syllable positioning rule based on the auditory evaluated data. The LSP‐CV rule speech synthesis based on the proposed principle is described. The positioning interval of CV‐syllable (i.e., the interval between the auditory perceptual timing points determined by auditory test) is affected by the succeeding syllable. Deviations are produced in the word‐top syllable, syllabic nasal, double consonant, long vowel, diphthong and devocalized sound. The deviations are represented by a correction factor to be combined into the rule in a simple form. By this rule, both rhythm and tempo can be controlled. To improve the sound articulation, the unvoiced part is excited by the original residual signal, the transient part is excited by the adaptive correlation function excitation, and the voiced part is excited by the representative correlation function excitation. As a result, a more natural rhythmicity was realized than in the case of isochronous positioning of CV‐syllable. A rule‐based synthesized speech, which is clear and easy to hear (the single sound articulation score being 95.5%), was obtained. A hardware configuration is realized in which the CV‐syllable concatenation processing is performed on μCPU and the LSP synthesis operation is performed on DSP. Then the frame period can be reduced to 3.2 ms, indicating that the interval between auditory perceptual timing points can be controlled with a high accuracy.
Synchronization method employing a cyclic redundancy check in an asynchronous transport system
Authors: Kitami Tokuhiro
Published: July 2007

This paper proposes a synchronization method in an asynchronous transport system. In this method, the cyclic redundancy check (CRC) code inserted in each cell for error control is also used for cell alignment recovery. Then frame alignment is established using cell alignment signals. The analyses include CRC detection probability in an out‐of‐synchronization mode, and cell/frame alignment recovery performance. The analyses also include the performance for an extended frame structure in which frame length is not divisible by cell length. This method has the following advantages: (a) this system shows good synchronization performance without using additional synchronization patterns; (b) frame alignment recovery time is reduced considerably using cell alignment signals; (c) this technique is also applicable to the forementioned extended frame structure and performs well.
Electromagnetic polarization and its expression
Authors: Hosono Toshio
Published: July 2007

Before 1950, Maxwell's phenomenological theory was used widely in the study of electromagnetics. In spite of the number of works published, none of them adopted electron theory to the study of electromagnetics.

Not until after 1950 did the electron theory become popular among electromagnetic researchers. The author has developed an axiomatic electromatic theory (hereafter called EM theory) in which Lorentz' electron theory was taken as one of the axioms.

This paper clarifies the problem in the old definitions of polarization and proposes a new definition using formulas which hold rigorously at the microscopic level. Based on this definition, the physical and mathematical meanings of polarization are clarified to establish firmly the EM theory.
New block demodulator with an automatic equalizer
Authors: Matsui Minoru , Hagiwara Masafumi , Nakagawa Masao
Published: July 2007

The block demodulation method recently has received considerable attention because of its high data transmission efficiency and superior performance. However, the conventional block demodulators do not consider the distortions of amplitude and phase in a transmission channel. As a result, the conventional block demodulators cannot compensate such distortions.

In this paper, a new block demodulator with an automatic equalizer is proposed. A two‐dimensional block equalizer is used in the proposed demodulator. The overall performance is improved greatly by the repeated estimation method of combined automatic equalization and carrier estimation. In addition, the number of taps in the equalizer is changed for further improvement.

The computer simulation result indicates that the mean‐square error by the proposed demodulator is about 1/100 compared with that of the conventional one when SNR = 30 db.
A star‐type local area network having simultaneous multiple transmission capability
Authors: Saito Tadao , Aida Hitosi , Inoue Ichiro
Published: July 2007

In the conventional header‐driven storageless LAN (HDSL), the simultaneous multiple transmission, in general, is impossible, which made it difficult to cope with the increase of the traffic due to the system expansion and other situations. This study proposes a star‐type LAN (multistar LAN) which realizes multiple simultaneous transmission by providing the center node with the multiple simultaneous switching function. In the multistar LAN, HDSL‐type communication is realized by the switching function of the center node. The assignment of the usage of the switching function is determined through the contention and arbitration among the data units sent from the grouped end node.

This paper first outlines the structure and operation of the multistar LAN, and presents the theoretical and experimental evaluation of the traffic‐delay characteristics. The features of the multistar LAN features are that the delay for low traffic is small, the performance is less deteriorated for high traffic, and there is a flexibility in accommodating the increase of the traffic.
Optimization of the coherent integration number in a tracking system consisting of a radar sensor and a kalman filter
Authors: Nomoto Kohei , Fujisaka Takahiko , Kirimoto Tetsuo , Ohashi Yoshimasa , Kondo Michimasa
Published: July 2007

A tracking system consists of an observation part such as a radar and a filter part such as a Kalman filter. To date, numerous adaptive filters have been studied for improving the tracking accuracy. However, the parameters related to the observed data have been fixed. If, on the other hand, one uses a digital beamforming (DBF) radar as the observation part so that the coherent integration number has a degree of freedom, these observation parameters can be adjusted according to the situation to improve the accuracy of the tracking system.

From the viewpoint of requirement on the filter, the observation period and the observation accuracy, both of which are functions of the coherent integration number, are opposite to each other, and hence the optimization of the integration number is a problem. In this paper, a DBF radar is used for observation and a Kalman filter as the filter, and a study is made to determine how the angular position prediction accuracy in such a tracking system varies by the coherent integration number. It is shown that there exists an optimum coherent integration number for the entire tracking system.
Effects of antenna pointing errors on the design of heterodyne optical intersatellite communications
Authors: Goto Koji , Araki Ken'Ichi , Yasukawa Koji
Published: July 2007

In the optical intersatellite communication system using a heterodyne detection, the signal level changes by the pointing error of the receiving antenna on the satellite in addition to the pointing error of the transmitting antenna of another satellite. Further, since these antenna pointing errors cause the unavailable state of the optical channel, the unavailability will become a problem. However, to date, nothing has been reported on link design which reflects the unavailability by considering the pointing errors of both the transmitting and receiving antennas.

In this paper, equations for the burst error rate are derived by means of the probability density function of the pointing error distributions of the transmitting and receiving antennas. With this burst error rate, the unavailability is computed. Hence, a link design reflecting the unavailability can be carried out by taking into consideration the pointing errors of the transmitting and receiving antennas at the same time. Further, a link design example is presented in the case where the facing satellites have identical communication systems.
A spatial frequency‐preserving post‐filter for block image coding
Authors: Izawa Yuuji
Published: July 2007

Block image coding, based on the discrete cosine transform (DCT), is used widely for transmission and storage of images and achieves high coding efficiency. However, the blocking effect is generated at low bit rates, and it is the major cause of picture quality degradation.

This paper proposes a spatial frequency‐preserving post‐filter which reduces the blocking effect efficiently without decay of spatial resolution in decoded images. By simulation, the improvement of the picture quality is verified and it is shown that the SN ratio can be improved by 0.7 to 0.9 dB.
A theoretical study of measurement of cross‐polarization power ratio (XPR) in mobile communication environments
Authors: Taga Tokio
Published: July 2007

Methods for evaluating the crosspolarization power ratio (XPR) in mobile communication include the one using a crossed dipole, the one using a dipole antenna and a turnstile antenna, and that using a dipole antenna and a loop antenna. However, measurement errors in these methods have not been investigated.

In this paper, the measurement error characteristics of various XPR measurement methods are analyzed theoretically. By finding the factors causing degradation of measurement accuracy, this paper proposes a method with more accuracy and clarifies its measurement error characteristics. It is found that the measurement error depends on the XPR and the measurement accuracy is degraded significantly because the measuring antenna does not have an isotropic characteristic and the antenna for horizontal polarization has a vertical polarization pattern. To improve this deficiency, a method is proposed in which a cylindrical slot antenna is used for the horizontal polarization because the sensitivity of this antenna to the vertical polarization can be made sufficiently low. It is pointed out that the measurement error with this antenna can be improved significantly.
Structure and coding characteristics of adaptive gain/shape vector quantizer for low bit‐rate motion picture coding
Authors: Watanabe Hiroshi , Suzuki Yutaka
Published: July 2007

One of the highly efficient coding methods for motion pictures is to combine the motion‐compensation interframe prediction and the vector quantization. Among such methods, the normalized vector quantization is to represent the motion‐compensated interframe difference signal, to separate the average value and to normalize the amplitude. It has a merit in that the general codebook can be utilized.

This paper shows that the approximation error does not always decrease in those conventional method, even if the vector quantization procedure is iterated. As a solution to this problem, it is shown to be sufficient to employ the vector quantizer with a gain/shape structure. An elaboration is made to the codebook size to handle the input vector amplitude. Then the motion picture coding algorithm is constructed using the proposed adaptive gain/shape vector quantizer. By optimizing the coding parameters aiming at the low bit‐rate coded transmission, practical temporal and spatial resolutions are obtained for TV confeferences and TV phones.
Error‐rate performance of block‐coded M‐ary modulation and hard decision decoding systems on rayleigh fading channel
Authors: Konishi Ken‐Ichi , Miyagaki Yoshiya
Published: July 2007

Error rates of block‐coded MPSK and/or MQAM systems with hard‐decision decoding are evaluated theoretically on the Rayleigh fading channel characterizing the land mobile channel. BCH codes are employed as the block codes and analysis is carried out both for nondiversity reception and for dual MRC diversity reception.

It is shown that on the Rayleigh fading channel, in contrast to the AWGN channel, BCH‐coded MPSK systems can achieve significant coding gain compared to uncoded BPSK even in the hard‐decision decoding case without changing spectral efficiency. It is shown also that diversity reception is needed for sufficient large coding gain in higher spectral efficiency. Moreover, it is suggested that the code length longer than a threshold is necessary for large coding gain under the given number of multilevel modulation and given spectral efficiency.
Distributed self‐healing network and its optimum spare‐capacity assignment algorithm
Authors: Chujo Takafumi , Komine Hiroaki , Miyazaki Keiji , Ogura Takao , Soejima Tetsuo
Published: July 2007

Rapid self‐healing under link failure in high‐capacity optical fiber is a basic issue in broadband networks. Failure restoration schemes are being studied which reroute failed paths using the control of path reconfiguration function of the Digital Cross Connect System (DCS). Distributed control schemes based on a flooding algorithm have been proposed to meet real‐time requirements for large‐scale transmission networks, but problems arise, such as message congestion at nodes and internode synchronization.

The performance of the self‐healing algorithm depends not only on the algorithm itself but also on physical network topology and spare capacity. In this paper, we propose a distributed restoration algorithm using a flooding technique and a centralized spare‐capacity assignment algorithm minimizing total spare capacity in a network while meeting a given survivability objective.

The failure restoration time, restoration ratio, and spare capacity cost of these algorithms will be evaluated by computer simulation.
Optical subscriber loops by nonpressurized optical fiber cable
Authors: Kawase Masaaki , Tomita Shigeru , Kasahara Nobuyuki , Uenoya Takuya
Published: July 2007

In optical‐fiber‐cable networks of Japan, usually dry air is compressed into the cable and joints and gas‐pressure sensors are used for remote‐supervision of pressure maintenance. However, optical fibers are different from metallic lines and penetrating water is not a direct obstacle. Further, the manufacture of gas dams is not as easy as that of the metallic cables, and the gas dams become very large in size so that it becomes difficult to put them in the line. Therefore, the nonpressurized cables with reliabilities as high as those of the pressurized ones have been investigated.

This paper discusses first the main factors responsible for the reliability deterioration of nonpressurized optical fiber cables and joints, which are the important elements of an optical system. Then, as the nonpressurized line structure, the waterproof optical fiber cables and the remote supervision of joints are discussed. Using a simple remote‐supervisory structure which consisted of the water sensors and OTDR, it is shown that the realization of reliabilities as high as those of the pressurized cables is possible.
Ranging and positioning test of an aircraft using a geostationary satellite
Authors: Ito Ken , Hoshinoo Kazuaki , Ito Minoru , Nishi Shunji
Published: July 2007

In‐the aeronautical satellite system for the air traffic control in the oceanic area, it is important to know the position of aircraft at the ground earth station. This paper describes the ranging and positioning system using two geostationary satellites (real satellite and a pseudosatellite on the ground).

This system is designed to allow ranging and positioning of each aircraft every 0.6 s within the ranging and positioning accuracy of 100 m and 1 km, respectively. Experiments to estimate this system were performed using a real aircraft. Results gave better accuracy than those mentioned in the foregoing.
Design of a directional diversity receiver using an adaptive array antenna
Authors: Kuroiwa Noboru , Kohno Ryuji , Imai Hideki
Published: July 2007

In mobile communication, fading due to multipath is a major factor in the deterioration of communication quality. One strategy for this problem is the adaptive array which eliminates the effect of the delayed waves by beam‐forming or controlling the radiation pattern adaptively. However, in the conventional method, the delayed waves simply are eliminated but are not utilized. It has been pointed out also that the directional diversity reception is effective in reducing the fading effect. In the conventional directional diversity reception method, the radiation pattern of the antenna is fixed.

In this paper, it is pointed out that the information identical to that in the direct wave is contained in the delayed wave. A directional diversity method is proposed in which, by means of the radiation pattern of the adaptive array antenna, the direct wave and the delayed waves are separated adaptively or combined.

In this system, two sets of antenna weights are included for unknown or time‐varying waves and the radiation patterns of the antenna can be controlled adaptively so that the directions of arrival can be estimated individually. By adaptively combining the direct and delayed waves, the SN ratio can be improved. The basic evaluation of this system is carried out to indicate that the error rate can be improved over that for the conventional adaptive array antenna which does not make use of the delayed wave. A possibility of using the proposed system in mobile communication is discussed.
Urban multipath propagation delay characteristics in mobile communications
Authors: Tanaka Tetsu , Kozono Shigeru , Akeyama Akira
Published: July 2007

In this paper, propagation delay measurements were carried out in Tokyo (metropolitan urban area) where high rises and other buildings are concentrated on a plane and in Kofu (urban area adjacent to mountains) surrounded by tall mountains. The delay characteristics such as delay spread and wave numbers were found.

The principal results obtained in these areas are as follows.

(1) In a metropolitan urban area, i.e., Tokyo, (a) the average delay spread in a high‐density residential district is less than about 1 μs and the delay profile consists of a group of direct waves arriving directly from the base station; and (b) the average delay spread in a location with high‐rise buildings is also less than 1 μs and the average number of arriving waves is about five with the delay profile consisting of a direct wave group and a reflected wave group from reflecting object.

(2) In an urban area adjacent to mountains, i.e., Kofu, the average delay spread is less than about 2 μs and the average number of arriving waves is four. The delay profile consists of a direct wave group and a reflected wave group. The level of the reflected wave group decreases exponentially with the delay time in the case of reflection from buildings, while the level is almost constant within a certain range of delay time and is of a spread shape (rectangular) in the case of reflection from mountains.

From these measured results, a simple propagation model consisting of a direct wave group and a reflected wave group is proposed. It is shown that the distance dependence of the delay spread has a peak between the base station and a reflecting object.
Characteristics and prediction methods for the occurrence rate of SES in available time affected by tropospheric scintillation
Authors: Matsudo Takashi , Karasawa Yoshio
Published: July 2007

The unavailable time percentage and the SES (severely errored seconds) occurrence rate within available time was investigated according to CCITT definition using Ku band low elevation angles satellite system data obtained mainly at the Yamaguchi station. As a result, the CCITT unavailable time percentage was found to agree with the cumulative signal attenuation time percentage as determined by the traditional statistical treatment. This agreement held even in the case of low elevation angles.

Further, the ratio of SES occurrence rate within CCITT available time to the conventional cumulative signal attenuation time percentage was found to be much larger than in the case of high elevation angles, and to have a high correlation with tropospheric scintillation. An experimental formula was developed for this ratio as an index of the degree to which tropospheric scintillation affects overall signal deterioration. Using this formula a formula was developed to predict the SES occurrence rate within CCITT available time from the index and the traditional cumulative signal attenuation time percentage. Also, it was confirmed that there was good agreement between the predicted value and the experimental value.
Resource management strategy in an ATM network
Authors: Noguchi Kiyohiro , Okada Tadanobu
Published: July 2007

This paper proposes a system of realtime bandwidth management and call admission control in an ATM network, which guarantees communications quality with high reliability and control simplicity. In this call admission control system, the allocated bandwidth for each bursty class is determined by theX‐percent value of the superposed bursty traffic distribution in each bursty class. Whether a requesting call is accepted or rejected is judged by the total allocated bandwidth of all bursty classes.

Since the communications quality of each class can be approximately estimated from theX‐percent value of the superposed bursty traffic distribution and this probabilityX, a method of determining the allocated bandwidth satisfying quality specification is presented by formulating the probability event that each peak state is superposed.

Bandwidth management, where bursty classes are introduced in order to realize optimal and simple control in accordance with the traffic burstiness and a method of call admission control are also presented. Although throughput performance is too deteriorated to realize the safety‐side bandwidth management, computer simulation confirms that the statistical multiplexing effect can be expected by using the proposed method.
Study of fault‐location expert systems for paired cables
Authors: Koga Hiroaki , Abe Tetsuji , Takeda Kazutoki , Hayashi Akira , Mitsunaga Yutaka
Published: July 2007

No method has been reported for fault location in a length of paired cable which consists of branched cables and wire of different gauges. This paper proposes a fault‐location expert system which comprises a new pulse echo detector and a fault‐location estimation expert system. The new pulse echo detector can locate a fault by the correspondence between theoretical and measured reflected waves. However, there is some degree of error because the transmission characteristics of each paired cable vary slightly.

A more precise fault‐detection technique has also been developed. It is the fault‐location estimation expert system which has a knowledge base including experimental field data and an inference technique based on probability theory. The knowledge is obtained from the fault rate of each cable part in the field. Field tests have clarified that the fault‐location expert system can detect faults successfully.
Dual‐mode equalization for digital mobile radio
Authors: Higashi Akihiro , Suzuki Hiroshi
Published: July 2007

The performance of digital mobile radio systems when transmitting at over several tens of kbit/s severely degrades with the onset of fast fading multipath propagation. This paper proposes a dual‐mode equalization (DME) method to overcome the degradation and experimentally verifies the effectiveness of the method.

The new method uses decision feedback equalizers (DFEs) in two modes simultaneously, a normal mode, and a time‐reversal mode, and selects the best equalization result.

The time‐reversal equalization mode improves the characteristics of equalization and adaptation in the non‐minimum phase condition. It converts the nonminimum phase to the minimum phase condition by the time‐reversal operation.

Principles of dual‐mode equalization, an algorithm for mode output selection, and timing problems are discussed in detail. Experiments demonstrate average BER performance in two‐path and typical multipath environments. The proposed dual‐mode equalization technique improves average BER performance by 2 dBEb/N0.
Transmission delay variation compensation in precision time‐synchronous networks
Authors: Imaoka Atsushi , Kihara Masami
Published: July 2007

This paper analyzes the performance of transmission delay variation compensation between two nodes in precision time‐synchronous networks. The compensation methods predict transmission delay using round‐trip path and compensate delay variations by employing a phase‐locked loop. Two methods for compensating delay variations in the master node (scheme A) and in the slave node (scheme B) are compared.

Results show that scheme B is more accurate and more stable than scheme A. Then the total compensation error, which equals the sum of the delay variation, delay measurement error, and PLL internal noise, is calculated using the measured delay of actual telecommunication lines. Minimum compensation deviation of 2 ns is obtained by optimizing the PLL parameter. This deviation is determined by the flicker phase noise of the difference delay between the outgoing and incoming paths.
Shielding effectiveness of a metal sheet parallel to the axis of a circular loop
Authors: Yamaguchi Takashi , Okumura Yoshihisa , Amemiya Yoshifumi
Published: July 2007

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 a hypothetical case where a magnetic dipole is placed at the center of the transmitting coil and a magnetic sensor is placed at the center of the receiving coil.
High‐speed pull‐in of a digital phase‐locked loop incorporating an and filter
Authors: Inoue Takashi , Tokunaga Manabu , Mori Shinsaku
Published: July 2007

With the rapid progress in high‐speed communication, there is increasing demand for a digital phase‐locked loop (DPLL) with a faster phase acquisition. This paper proposes a DPLL which uses an AND filter instead of a random walk filter (RWF) as the loop filter.

It is verified that the loop can realize a faster phase acquisition without deteriorating the jitter suppression performance. The jitter suppression and phase acquisition performances are analyzed based on the theory of Markov chain, and it is shown that the proposed loop has a wider locking range. Then the phase acquisition speeds of the proposed loop, the conventional binary quantized DPLL, and the DPLL with inserted AND filter are compared for the same jitter suppression.

It is seen that the proposed loop can drastically improve the phase acquisition performance for a large initial phase difference. The tendency remains the same even if a noise is added, and the jitter is small. Those properties are verified by a computer simulation with satisfactory agreement with the theoretical analysis.
Design of corrugation depth and velocity dispersion characteristics of elliptical corrugated horn
Authors: Shogen Kazuyoshi
Published: July 2007

With a view for use as a primary feed for the shaped beam antenna on board the Broadcast Satellite 3, a design of the corrugation depth and a study of the velocity dispersion characteristics were carried out. The elliptical corrugated horn is approximated with an elliptical corrugated waveguide. The boundary conditions are determined by connecting the electromagnetic field in the corrugation with the hybrid mode in the waveguide at the boundary. From the solution of this boundary condition equation, the analysis other than that for the balanced hybrid mode is possible. By means of this method, a design method is demonstrated for corrugated grooves satisfying the elliptic balanced hybrid condition. Further, the κ‐β characteristics of the elliptic corrugated waveguide fabricated for test are computed and measured.
Synchronization and multiplexing of HDTV signals for transmission in broadband ISDN
Authors: Kinoshita Taizoil , Eto Yoshizumi , Nakahashi Tomoko , Sakaki Masanori
Published: July 2007

When a high‐definition video signal such as HDTV is to be transmitted in a Broadband‐ISDN with a hierarchy, it is desirable that the video transmitter/receiver systems as well as the transmission system operate asynchronously, so that both synthesis and editing of the video are easier. It is also important to realize clock synchronization/transmission multiplexing without a deterioration of picture quality.

From such a viewpoint, this paper first proposes a video stuffing method, which is a video/transmission clock synchronization method based on the concept of the synchronizer. Then the proposed multiplex video transmission system combines the synchronization detection for the video and the transmission in the receiver, based on the integer relation between the video block and the transmission frame. Lastly, the synchronous digital hierarchy (SDH) (STM 4‐frame or STM 1‐frame) transmission is investigated (it uses the HDTV encoding equipment); the SDH can transmit the Broadband‐ISDN signal with H4 × 4 or H4 rate, and the effectiveness of the proposed system is demonstrated. As a result of the experiment, the three clocks for the transmitter/receiver as well as the transmission system operated asynchronously, and a satisfactory video can be transmitted and reproduced without the video synchronization detection in the receiver, and without a deterioration of picture quality.
Performance of trellis‐coded 16‐QAM/TDMA system for land mobile communications
Authors: Sampei Seiichi , Kamio Yukiyoshi
Published: July 2007

The digital cellular telephone system is considered in various countries. It is a system which is more attractive than the conventional analog transmission system in the sense that various data can be transmitted using the same transmission band. In practice, it is very difficult to realize composite transmission of various data or the data transmission of the ISDN terminal. For such a situation, this paper proposes the trellis‐coded, 16‐QAM, six‐channel TDMA system. The proposed system includes various elaborations to improve the transmission characteristics, e.g., the fading distortion estimation by inserting the pilot symbol, the space diversity with maximum ratio combining, the symbol interleaving, and the two‐frequency hopping. A computer simulation is executed for such a system to examine its performance. It is seen as a result that the spectral efficiency is improved greatly and the high‐quality transmission is realized, compared to the systems considered in the United States and in Europe.
3‐GHz band burst mode earth station transmitter
Authors: Saito Takaya , Inoue Takeo , Shimokawa Kiyoshi
Published: July 2007

To reduce the size and the cost of the earth station equipment for satellite communication, a 30‐GHz band burst mode earth station transmitter is developed. In this case, the transmitter can access seven 30/20‐GHz band transponders on the CS‐3 transponder hopping system. Wideband and high‐power characteristics are required for the transmitter with the transponder hopping system. For this purpose, a helix‐type traveling‐wave tube (TWT) transmitter is newly developed to replace the conventional klystron tube, realizing wideband characteristics. The anode voltage switching method is developed and used for the transmitter so that the output of the 30‐GHz band helix TWT is increased. The anode voltage of TWT is made ON/OFF (burst mode) in accordance with a time‐advanced control signal from TDM A equipment to satisfy the thermal condition for the helix slow‐wave circuit and to reduce the power consumption. The major performances are as follows. The output power of 150 W is achieved by combining two tubes under the duty 50 percent or less and the power variation at 150 W is 1 dB/1 GHz or less. The rise and fall time of anode voltage is less than 3 μs.