bluuebunny/crossref_metadata_2025 huggingface dataset:
A direction‐finding algorithm of reflected waves using small‐sized data series measured in fresnel region and its evaluation
Authors: Wang Jianqing , Echigo Hiroshi , Takagi Tasuku , Sato Tsugio
Published: July 2007

To find the unwanted reflection characteristics of a Fresnel region wave from a building and a wall, it is necessary to know the direction of the reflection source. This paper proposes an algorithm which estimates successively the direction of arrival of the reflected wave in the Fresnel region, based on the study of the characteristics and the shape of the spatial series in that region. This algorithm is realized by a combination of the maximum entropy method in which a spectrum can be estimated at a high resolution with a few data and an error correction by the Newton‐Raphson method for solution of a nonlinear equation. To confirm the validity, a computer simulation and experimental results are shown. In the computer simulation results, the reflection direction was estimated with an error of 0.1° ‐ 2.9° from 40 measured data for an aperture of 5 wavelengths. In the experiment, the reflection direction was estimated with an error of less than 0.5°. From these results, it is found that this algorithm can be applied for direction finding of the reflected wave under an actual electromagnetic environment.
Properties of tapered circular waveguide cutoff filters for TE01 mode millimeter‐waves
Authors: Shirasaki Hirokami , Ishihara Fujio
Published: July 2007

A differential equation is derived for the TE01 mode of a tapered waveguide by satisfying all boundary conditions at the connecting parts of the waveguide. The reflection and transmission coefficients are obtained by the Runge‐Kutta method for cutoff filters using circular waveguides with the linear and n‐th power cosine tapers for millimeter waves. Using the previously published experimental data, the validity of the authors' method was examined by comparing their results for attenuation, phase and delay characteristics with those experimental values. Design charts were constructed for cutoff filters. As an example, the profile for a miniaturized high‐pass filter which satisfied the given specifications for transmission of millimeter waves was determined.
Approximate analysis of memory contention in a multiprocessor system with a single bus
Authors: Nogami Shinya , Sumita Shuichi
Published: July 2007

This paper considers a multiprocessor system in which a memory module and two groups of processors with different access rates to the memory are connected through a single bus. The holding time in the common bus is assumed to follow the general distribution. A new approximate analysis method is proposed. When the holding time in the common bus follows the same exponential distribution, the problem reduces to the BCMP queueing network model, for which the analysis is easy. However, when the processing discipline is FIFO, and the holding time of bus follows the general distribution, a strict analysis is difficult since there is no product‐form solution. For such a case, the system is modeled as a closed queueing network, and a group of processors is aggregated to a single processor with the equivalent common bus occupancy. Then the object model is replaced by a small‐scale model for which the analysis is easy. Using such a model and known results, the approximate solution is obtained for the characteristic parameters by iterative calculations. At the last stage, a numerical example is presented for the case where the holding time of the bus is assumed as constant. Comparing the result with the result of simulation, the range of application for the approximate method is indicated.
Equivalent transmission lines of wire antennas and the radiation mechanism
Authors: Nakamura Takashi , Oda Keisuke , Yokokawa Senji
Published: July 2007

This paper proposes a new analysis method for a linear antenna by obtaining its equivalent nonuniform line. Based on the theory of transmission lines, the radiation mechanism of the linear antenna was clarified. The traveling‐wave mode method which was effective for the analysis of meandering lines was extended. Its equivalent distributed constants are complex variables depending on frequency and position. The calculated results for various antenna characteristics agreed with those by the moment method, providing a proof of the effectiveness of the present analysis method. The effective power on the conductor based on the equivalent nonuniform line for the antenna thus obtained was determined. The radiation mechanism of the antenna through the attenuation of the power was examined. As a result, in a standing‐wave type antenna, it was shown that the transmission component which was radiated gradually from the entire part of the antenna and the storage component which radiated at the terminal part, could be handled separately. In a traveling‐wave type antenna, the transmission component radiated from the entire antenna. However, a dominant radiation in the vicinity of the bending when the angle of bending becomes large was clarified.
Reflection and transmission of gaussian beam of a uniaxially anisotropic medium
Authors: Sonoda Takahiro , Kozaki Syogo
Published: July 2007

Reflection and transmission when a three‐dimensional Gaussian beam is launched obliquely into a uniaxially anisotropic medium whose optical axis has arbitrary direction are analyzed. This problem is solved by using Fourier transforms. Solutions of reflected and transmitted beams having integral form are calculated numerically by using a numerical integral. As a result, physical considerations are presented and the G‐H shift (negative) is discussed.
Aircraft‐and satellite‐borne synthetic aperture radar images of ocean waves in orbital motions
Authors: Sakata Tetsu , Wakasugi Koichiro , Matsuo Masaru
Published: July 2007

Because of its all‐weather capability and high resolution, the synthetic aperture radar (SAR) is very effective for remote sensing of the ocean. However, for a moving target such as ocean waves, they affect the SAR images as a phase distortion. This paper considers the orbital motion of the ocean waves. By modeling the waves with an ensemble of the moving points, the SAR image is computed. Previously, the discussions were limited to the case of snapshot observation of the slowly moving ocean waves with a rather long wavelength by a high‐speed SAR such as that on a satellite for simplicity of the model. In this paper, this restriction is removed and the estimate and study of the SAR image become possible including a low‐speed SAR such as the one on an aircraft and waves with a short wavelength. As a result, it is pointed out that the phase velocity of the ocean waves cannot be neglected in a low‐speed SAR so that the wavelength of the SAR image is expanded or compressed and that the SAR image is strongly dependent on the ocean waves and the SAR parameters.
Basic characteristics of variable rate interframe video coding
Authors: Nomura Mitsuru , Fujii Tetsurou , Ohta Naohisa
Published: July 2007

Recently, interest has been increasing greatly in the various services and possibilities offered by the new communication media. At the same time, the demand for higher‐speed communication also has increased. Therefore, flexible systems based on ATM (asynchronous transfer mode) have received particular attention because they can meet these demands by transmitting various types of information in a unified form. In this case, the transmission method can utilize effectively the variable rate characteristics of the information sources. Thus, the understanding of basic characteristics of the coded information sources becomes important. This paper investigates the basic characteristics of the variable rate video coding from this viewpoint. The interframe coding method is considered and the burst characteristics of the information as well as the improvement due to variable rate coding are analyzed, using simulation methods. The results relating to video conference scenes show that the peak rate is about three times as much as the average rate and the quality improvement expressed in minimum SNR is about 5 to 10 dB.
Electromagnetically coupled microstrip antennas with circular polarization
Authors: Kominami Masanobu , Yasuda Hirohiko , Uchibori Takuji , Rokushima Katsu
Published: July 2007

Recently, electromagnetically coupled microstrip antennas have been studied extensively. This paper proposes a new microstrip circularly polarized antenna in which an orthogonal mode with a phase difference of 90° is generated on a radiating element via the path length difference of the traveling wave currents on the strip transmission line coupled electromagnetically at two points with the radiating element. By experiments and numerical calculations, the operations of the circular loop and square patch circularly polarized antennas based on the present principle are confirmed. The radiation pattern, input impedance and current distribution are studied. The proposed circularly polarized antenna employing electromagnetic coupling has less spurious radiation from the transmission line than the direct coupled two‐point fed structure and is enabled to provide an excellent circular polarization with a simple construction. Circular polarization can be obtained in a wide angle. If the input and load terminals are interchanged, the direction of the circular polarization can be switched easily.
A crossed‐slot antenna backed by a rectangular cavity
Authors: Itoh Kiyohiko , Iizuka Hiroshi , Ogawa Yasutaka , Baba Hiroshi
Published: July 2007

A shallow cavity‐backed slot antenna has been used as a flushmounted antenna in a high‐speed moving object since it is resistant to vibration and shock. This paper presents a theoretical analysis for a circularly polarized antenna consisting of a crossed‐slot along the diagonal line on the surface of a rectangular shallow cavity. As a method of analysis, the reaction matching method has been used which was developed by Richmond as a form of the moment method by Harrington. By means of this method, the input impedance can be obtained over a broad frequency range in the case where an offset feed and a multiple feed are used. In this paper, an offset symmetric two‐point feed is used so that the impedance matching can be realized easily. The input characteristics and the radiation characteristics of the antenna element are obtained numerically and the obtained results are discussed.
Fluid model to analyze overload characteristics of a telephone network
Authors: Ohta Masataka
Published: July 2007

To study overload characteristics of a telephone network, a simple and useful method using fluid approximation is presented. Taking a two‐stage telephone network as an example, it is shown that the circuit trunk part is congested under an overall overload and the outgoing register part is congested under a focused overload. Since under overload conditions the number of calls in a telephone network is large enough that the law of large numbers is applicable, the traffic flow can be regarded as a deterministic continuous process. Specifically, a fluid approximation can be applied. The calculation time of this method is much less than that of the simulation method. Accordingly, the overload characteristics of a telephone network, which have been analyzed mainly through simulation, can now be analyzed by simple numerical calculation. This fluid model can be applied to the overload analysis of not only telephone networks, but also other communication networks.
High‐speed thermal printing and document feed technique for facsimile using MMR coding scheme over telephone network
Authors: Nakamura Koozoo , Kojima Yasuyuki , Tadauchi Masaharu , Sakata Kunihiro
Published: July 2007

Modified MR (MMR) coding is the coding method for G4 facsimile. It has a better compression performance than the MR (modified read) code, which is a coding scheme for G3 facsimile. Consequently, the facsimile using the MMR code is expected to realize a high‐speed transmission. In the facsimile using MMR code, a high‐speed printing is also required to achieve such a highspeed transmission. From such a viewpoint this paper discusses the high‐speed thermal printing, suited to the facsimile over the telephone network using the MMR code. A high‐speed transmission by the black ratio control is considered, where the printing speed is varied according to the number of black pixels in the line. Detailed parameters are presented for the black ratio control which can realize almost the same printing speed as the transmission speed. Next, as the means toward a practical system, a high‐speed document feed technique is considered, together with its realization, where the document feed is performed smoothly following the change of the printing speed. It is shown by computer simulation that the loss of the printing time due to this mechanism is at most 10 percent for the usual document. Finally, to reduce the number of feed stops in a page, a high‐speed document feed is proposed where the maximum feed speed is limited according to the number of buffered coded bits. It is verified by computer simulation that a high‐speed and smooth document feed can be realized without a stop for the usual document.
Measurement accuracy of carried traffic for the loss system with heterogeneous inputs
Authors: Yamada Hiroshi
Published: July 2007

The integrated service digital network aims at providing communication service by various kinds of media, such as speech, data and image, by a single communication network, realizing higher‐level convenience and economy compared with the communication networks for individual services. In its design and management, the traffic problem must be solved for the sharing of a system by heterogeneous traffic. This paper discusses especially the measurement accuracy for the carried traffic when the channel is shared by heterogeneous traffic, which is important in the management of traffic statistics. To discuss the measurement accuracy of the carried traffic, the autocovariance function which represents the correlation between measured values with the time difference of the scanning period must be determined. As a fundamental model, the strict solution is derived for the autocovariance function of the simultaneous connections in the loss system with two kinds of inputs. Using the result, the relation between the variance of the measured values and the scanning period is determined, and the determination of the optimal scanning period is discussed. Since the calculation of the strict solution becomes difficult with the increase of the number of channels, a practical approximation expression is proposed for the autocovariance function.
Electromagnetic wave propagation in a two‐dimensional tunnel with a modified cross‐junction
Authors: Matsunaga Toshiaki , Uchida Kazunori , Noda Takeaki
Published: July 2007

This paper investigates theoretically and experimentally the electromagnetic wave propagation in a two‐dimensional tunnel with a modified cross‐junction in connection with radio communications in tunnels, underground, urban areas with high‐rise buildings and others. Modal expansions and Fourier transform are used as an analytical method, and the surface impedance model is employed as a boundary condition on the tunnel walls. The results presented here can be applied to special tunnels such as the T‐type, modified T‐type, L‐type and step‐type. Experiments based on a microwave simulation are performed by using tunnels composed of concrete slabs. It is found that, concerning electric field intensity, experimental and theoretical results agree well.
Design of two‐stacked circular loop yagi‐uda array antenna
Authors: Korekado Toshikazu , Okuno Kiyoshi
Published: July 2007

A broadband multiple element Yagi‐Uda two‐stacked circular loop antenna is proposed in which two circular loop antennas with a high gain and a broadband are stacked in the broadside direction. In the two‐stacked structure, circular dual‐loop antennas are used in which the loops are connected with a parallel twin wire only for projector and are fed at the center. The antennas are analyzed numerically by setting equivalent antennas consisting of the loops and the parallel twin wire. Detailed design data for each parameter are obtained.

The effect of the stack spacing of the loops on the radiation characteristics is significant. An optimum value is obtained at Dij = 0.45 – 0.60 λ. It is shown that the impedance loss can be compensated by the stab method. Also, an example of the design of a high gain antenna based on the design data is presented.

The validity of the design procedure is confirmed experimentally. With an eight‐element array, a sharp beam is obtained with an H‐plane half‐power angle of about 30 degrees. The maximum actual gain is 11 dB, and the 3‐dB bandwidth is about 270 MHz. This high gain and broadband antenna is an improvement of the actual gain by more than 4 dB in comparison with a dipole array with the same dimensions. At present, this antenna is in the class of broadband antennas with the maximum gain.
Traffic analysis of an integrated voice/data system by means of pseudo‐data call concept
Authors: Akiyama Minoru , Ichiya Yasuo
Published: July 2007

Since the model for the voice/data multitraffic processing system was proposed, various analyses have been made for the system. However, the traditional analysis derived only the average and the variance of the data call queues.

A general and practical method of analysis has not been presented for the waiting time distribution of the data calls, which is important as the service criterion. This paper proposes an approximate method of traffic analysis for the integrated voice/data system, which is applicable to data calls with the holding time following the general probability distribution.

The method is to represent the holding time distribution of the data call following the general probability distribution as a sum of several pseudo‐data calls following exponential distributions. By this method, not only the average waiting time but also the distribution of the waiting time can be calculated relatively easily.

As in the design for a voice communication network, the integrated network can be designed so that the given service criterion is satisfied by 99 percent of the data calls in the data system. As an example, the case of facsimile as the data source is examined. The result by the proposed method agreed well with the result of simulation, indicating that a practically sufficient accuracy is realized.
High‐speed broadband circuit switching system architecture
Authors: Chiba Yoshikazu , Hiraide Kazuhiro , Kondo Fumio
Published: July 2007

This paper considers the speed of communication where NTSC and HDTV video signal is encoded into digital forms, and proposes a high‐speed broadband circuit switching system which realizes the integrated services covering communication services and distribution services. The former include the end‐to‐end communication such as TV conference and the video retrieval such as image inquiry system, and the latter includes the CATV.

The proposed method has the following features: (1) The communication services and the distribution services are distinguished by using layer 3 of I interface protocol. The video channel selected by the subscriber is transferred between the subscriber and the service processing node of the video distribution system, using the high‐level layer signal; (2) considering the uncertain demand, a building block structure is adopted, where the unit is the small‐scale independent switching and distribution module with several tens to several hundreds of subscribers; (3) the load‐function distributed control scheme is adopted.

In the communication services, the functions are divided into the modules of subscriber accommodation, intermodule connection, inter‐office signal processing and system management. In the distribution services, the divided modules such as the selection of video channel and the interface processing to the video operation center are executed in the almost complete processing within the module, which helps to reduce the communication traffic between modules.
Atm cross‐connect switch using folded banyan switching network with bypass links
Authors: Okamoto Satoru , Obara Hitoshi
Published: July 2007

A high‐speed multiplex transmission system has recently been proposed based on ATM, where the information is divided into fixed‐length blocks called cells, and transmitted on asynchronous multiplexing basis. As the switch to be used in the transit node in such a transmission system, various kinds of switching networks have been proposed, composed of two‐input × two‐output switch elements with internal buffers. Among those, the multistage buffered Banyan structure, which is a cascade connection of two Banyan networks as the distribution and routing networks, is of a distributed structure, being suited to LSI implementation. The network is a promising candidate since it realizes the self‐routing and is stable against a variety of traffic. However, this switching network has a problem in that the delay is increased with the scale of the network, and the in‐service expansion of the switching network is not easy.

This paper proposes a new network topology of the Banyan network with bypass links, together with the self‐routing method, and describes its performance. The network is composed of the distribution and routing networks with bypass links between individual unit switches. By transferring cells from the distribution network to the routing network through the bypass links at appropriate stages, the delay is reduced. The in‐service expansion of the system is made easy.
Trellis coding with improved bit error performance
Authors: Umeda Masatoshi , Murata Masashi , Morinaga Norihiko
Published: July 2007

In a conventional Trellis coded modulation (TCM), the error‐event probability is minimized by designing the Trellis code so as to achieve the maximum free Euclidean distance (ED). This paper proposes a new coding technique which improves the post‐decoding bit error rate without changing the ED‐structure of the conventional TCM code. This is achieved by channel coding with mapped signal sets having minimum Hamming distance (MHD) on information bits for error events generated at free ED.

First, this mapping was obtained by calculating Hamming distances on information bits for error events generated at free ED for all code mappings by using a computer, which requires a large amount of calculation. We show that such codes for multiphase modulation are constructed by a simple coding method without this much calculation. Also, its effectiveness is confirmed by the simulation.
A study on hybrid motion video coding schemes– block size, comparison of dct and vq schemes, loop filter
Authors: Kato Yoichi , Okubo Sakae , Suzuki Yutaka
Published: July 2007

To design a highly efficient video codec, comparisons of available techniques from various viewpoints are necessary so that the coding scheme and parameters are chosen appropriately. In recently presented papers and equipment, many systems use motion‐compensated interframe prediction and DCT or VQ schemes for the prediction error coding. A loop filter often is adopted to improve coding efficiency.

This paper compares DCT and VQ schemes in an interframe coding scheme, on an optimal blocksize for interfreme prediction error signal coding and on the effect of loop filtering from the viewpoints of coding efficiency and reproduced image quality. Simulations using actual image sequences show that the optimal block size is 4 × 4 or 8 × 8, that the loop filter improves significantly the coding efficiency and reproduced image quality, and that DCT and VQ schemes give nearly the same efficiency with an appropriate loop filter.
A digital phase‐locked loop for stuffing synchronization systems
Authors: Rokugo Yoshinori , Goto Masataka , Hirosaki Botaro
Published: July 2007

Stuffing synchronization systems are now being applied actively to new fields such as digital cross‐connect and SONET. In stuffing synchronization systems, however, the analog PLLs are still used for the receive destuffmg circuitry. This paper describes a method of applying a complete second‐order digital phase‐locked loop (PLL) to a stuffing synchronization system. In the PLL used for the stuffing synchronization systems, a buffer memory consisting of an N‐stage frequency divider is provided in order to suppress jitter.

This paper analyzes first the effects on the DPLL resulting from the incorporation of an N‐stage frequency divider based on a multilevel quantized phase comparator. The characteristics parameters of the complete second‐order DPLL when the N‐stage frequency divider is added are determined. Significant low‐frequency jitter is present in the narrow‐band complete second‐order DPLL. The phenomenon of low‐frequency jitter generation is analyzed and procedures for determining the coefficient values of the complete second‐order DPLL that will result in tolerable levels of low‐frequency jitter are described. Finally, the DPLL parameters are evaluated theoretically and experimentally to determine the suitability of the DPLL design for stuffing synchronization systems.
Performance evaluation of packet voice multiplexer with selective packet‐discarding control
Authors: Niu Zhisheng , Akimaru Haruo , Machihara Fumiaki , Ide Ichiro
Published: July 2007

This paper evaluates the performance of packet voice multiplexer with selective packet‐discarding (SPD) control. The control scheme is based on the embedded ADPCM coding technology wherein the encoded information is grouped into two separate parts: a more significant part (MSP); and a less significant part (LSP).

When the buffer length exceeds a certain threshold, the LSPs of the incoming packets will be discarded to relieve the congestion.

By assuming that the voice packets (cells) arrive at the multiplexer in phase‐type Markov renewal process (PH‐MRP) and that they are all of the fixed length, we model the system under consideration as PH‐MRP(x)/‐Ek/1/m(m1) with sufficiently large k. Using the matrix‐analytic (MA) method, recursion formulas and effective computation algorithms for the performance measures of interest are derived. Numerical examples are illustrated.
Spread spectrum communication method for power line
Authors: Endo Kaoru , Nakamura Tadashi , Tsumura Soichi , Tsuruta Shichiro
Published: July 2007

Spread spectrum (SS) communication is proposed as a high‐speed data transmission system which uses the power line as the transmission channel. However, the power line is not originally a transmission line, the quality of transmission is not guaranteed, and the characteristics are not ideal in general. Especially, the phase characteristics may fluctuate greatly and rapidly in synchronization with the power frequency.

In the traditional SS system, the sequence inversion keying (SIK) and the synchronization control by digital lock loop (DLL) are employed. However, there is a problem in that the stable retaining tracking of the synchronization is not realized for such a channel, thereby preventing normal demodulation. Code shift keying (CSK) is proposed to replaced SIK. An effective synchronization method to replace DLL in the application to power line communication has not been proposed.

This paper proposes the synchronization control method which can establish stable synchronization at the initial stage. Also, the stable synchronization tracking in the deteriorated transmission environment is realized with a fast phase characteristics fluctuation similar to that in the power line, in addition to the demodulation method which demodulates the information stably even if the correlation function is distorted. By an experiment using the artificial power line and an actual home, the effectiveness is verified and the practical usefulness is demonstrated well.
Formulation of dispersive characteristics associated with orientation polarization using the FD‐TD method
Authors: Kashiwa Tatsuya , Ohtomo Youichi , Fukai Ichiro
Published: July 2007

Recently, the usefulness of the three‐dimensional (3‐D) time‐domain analysis has been increased for the analysis of microwave circuits and electromagnetic scattering problems. However, in these methods, the constitutive parameters such as the permittivity and the permeability have been treated as constant regardless of the frequency. Recently, it has become indispensable to formulate the dispersion effects from the viewpoints of the broadband applications of the electromagnetics and of rigorous simulations.

In this study, the equation of motion for the polarization in the medium is used in the FD‐TD method, which is a 3‐D time‐domain analysis technique, so that the frequency dispersive media are treated.

As an example of the frequency dispersion phenomena, the orientation polarization important in the microwave frequency region is discussed. The validity of the present formulation is presented by comparison of the permittivity derived from the waveform propagation analysis by the simulation with the theoretical value. As an example of analysis, water is chosen to be a representative medium with orientation polarization. The two‐media problem with water and air was analyzed in terms of the difference of the waveform propagation of a burst wave in the case with and without the dispersion characteristic of the water.
Effect of timeout retransmissions on end‐to‐end delay in packet switching networks
Authors: Inai Hiroshi , Yokohira Tokumi , Murata Masayuki , Miyahara Hideo
Published: July 2007

An end‐to‐end error recovery scheme is a promising way to obtain low end‐to‐end delays in packet switching networks. However, a too‐short timeout interval may cause unnecessary packet retransmissions even when a packet is transmitted successfully to the receiver. On the other hand, a longer timeout interval may introduce large end‐to‐end delay when a packet is actually lost. Thus, it becomes important to determine an appropriate timeout period in the scheme.

This paper analyzes a tandem queueing network system with blocking due to finite capacity in intermediate nodes and investigates the effect of the timeout period on the end‐to‐end delay performance. It is found that there exists the timeout period minimizing the mean packet transmission delay in the end‐to‐end error recovery scheme. The delay performance between end‐to‐end and link‐by‐link error recovery schemes also is compared and it is found that the delay performances of these schemes are influenced significantly by the node‐to‐node delay.
Design algorithm for survival of fiber optic networks
Authors: Yamato Katsumi , Murata Masayuki , Nishio Shoujirou , Miyahara Hideo , Nishida Takeshi
Published: July 2007

In attempts to realize a highly reliable transmission network using the optical fiber, transmission devices with high‐level communication control functions have been developed. However, no method of network design utilizing the characteristics of such devices has been presented.

This paper proposes a design method for realizing the fiber‐optic network at a low cost and satisfying the service requirements from the network users as far as possible even in the case of a fault by making use of various transmission devices. For this purpose, the components of the fiber‐optic network are modeled and a measure for evaluating the network reliability is introduced. Based on this measure, the design for the highly reliable fiber‐optic network is formulated as an integer programming problem.

An algorithm is presented which can derive a solution with a low cost and that realizes the required performance even in the cause of a fault. Also, the routing method is discussed which is needed in the design of a highly reliable network.

It is shown through numerical examples that the network can be designed at a lower cost for the fault recovery than the traditional shortest path routing by executing the routing so that the traffic is made uniform for all communication paths.
Cell transfer ratio control‐type priority control method for ATM switching
Authors: Tanaka Yoshiaki , Akiyama Minoru , Hosaka Shinichiro
Published: July 2007

In the ATM switching system, various kinds of information are multiplexed and transferred. Thus, priority control is required to satisfy various qualities.

This paper proposes a cell transfer ratio control‐type priority control method in which a buffer is prepared for each quality class and the maximum number of continuously transferrable cells is defined for each class when sending cells from the buffer. Required transmission quality is realized by the class ratio (cell transfer ratio) and the buffer size.

The multiqueue system controlled by this method is analyzed and traffic characteristics such as mean waiting time and cell loss probability at the buffer are evaluated. As a result, the effectiveness of the quality control with the proposed method is shown.
Dividing method for topological design of corporate communication networks
Authors: Ohmae Yoshitsugu , Watanabe Atsushi , Takeshita Miyuki
Published: July 2007

This paper proposes a topological design algorithm for a corporate communication network. The algorithm is more efficient than the traditional heuristic algorithms. In our method we subdivide the overall nodes. We then use branching for a batch of nodes so divided and bounding by traffic and product of traffic and channel distance. We repeat the above procedure until the final desired topological configuration is attained.
Three‐dimensional motion estimation of head in model‐based coding of moving facial images
Authors: Koike Atsushi , Kaneko Masahide , Hatori Yoshinori
Published: July 2007

A model‐based image coding system basically consists of an “analysis” process at the transmitting side and a “synthesis” process at the receiving side. Images are coded by transmitting only information about changes in shape of a three‐dimensional (3‐D) model of an object prepared at both the transmitting and receiving sides. The essential elements in the “analysis” process are recognition of the object from moving images, estimation of the object motion, and detection of changes in its shape.

This paper proposes a method of estimating the motion in 3‐D space of the head in model‐based image coding of moving facial images and confirms the validity of the method by computer simulations.

First, the basic concept of model‐based coding is described. A discussion about the treatment of motion information in moving images is performed from the viewpoints of 3‐D motion of the object and shape changes of object components, and the outline of the basic idea to detect the motion and shape changes is presented. Then the 3‐D motion estimation method using the 3‐D shape model of the object and motion vectors in 2‐D space is described in detail.

Computer simulations are performed on moving facial images, and the results show that the motion of the head in the input moving images is well reproduced as the motion of a 3‐D shape model.

Finally, the relation between precision of depth coordinates and estimation results is considered, and it is demonstrated that the proposed method is effective for estimating 3‐D motion parameters in model‐based coding of moving facial images.
A study on the wave absorber using lossy permittivity materials for coating at cylindrical objects
Authors: Hashimoto Osamu
Published: July 2007

A design method is studied for effective one‐ and two‐layer‐type wave absorbers to be installed on circular cylinders using lossy dielectric materials. Design charts based on this design method are presented for each type of wave absorber. One‐layer‐type cylindrical absorbers are fabricated and measured results for absorbed amounts are presented.
Method of determining the exciting coefficients for the feed array on array‐fed reflector‐type shaped‐beam antennas
Authors: Makino Shigeru , Naitoh Izuru , Urasaki Shuji , Katagi Takashi
Published: July 2007

For a shaped‐beam antenna having a feed array consisting of a reflector and numerous antenna elements, the method is described of determining the exciting coefficients for the feed array which maximize the minimum gain at the earth stations in the service area. In this method, a large effect is seen when the number of antenna elements is greater than the number of earth stations in the service area.

First, the necessary condition is shown for the exciting coefficients for the feed array which maximize the radiated power at the earth station. Based on this result, an algorithm is described which determines the array excitation coefficients. Moreover, the method is verified to be efficient by the calculated and measured results.
Spherical dipole antenna using optical/electrical converter
Authors: Murakawa Kazuo , Kuwabara Nobuo , Amemiya Fujio
Published: July 2007

A spherical dipole antenna is studied as a standard electromagnetic emission source in the EMI measurement. Its radiation characteristics are discussed both theoretically and experimentally. One of the antenna elements of a spherical dipole antenna is constructed in the shape of a shield case in which the electronic circuit is installed. Hence, the electromagnetic analysis can be carried out without considering the shape of the electronic circuit into the boundary of the analysis. It is pointed out that the electromagnetic field in not only the far region but in the near region can be computed numerically with high accuracy by means of the mode matching technique.

By using a nonmetallic optical fiber instead of a coaxial cable as the signal line, the disturbance of the electromagnetic field by the cable can be neglected. Based on the numerical results, a spherical dipole antenna was fabricated and the radiation characteristics were measured at 30 to 1000 MHz. It was confirmed that the measured data and the numerical results agree within 1.9 dB for the vertical polarization and 1.7 dB for the horizontal polarization. From these results, it is clear that a spherical dipole with radiation characteristics as numerically computed can be realized.
Notes on fast maximum‐likelihood decoding‐algorithm of cyclic code on Z‐channel
Authors: Inaba Hiroyuki , Kasahara Masao , Morii Masakatu
Published: July 2007

This paper considers the Z‐channel, which is known as a channel model for photon communication or semiconductor memory. A new decoding algorithm is proposed and discussed.

Recently, studies have been made from various viewpoints on the asymmetrical error‐correcting code suited to the Z‐channel, which is considered interesting. One of the basic problems in the Z‐channel is the performance and the decoding method when the cyclic code with various features is applied, but it has been investigated little.

This paper presents first a maximum‐likelihood decoding algorithm which is highly efficient for the cyclic code on the Z‐channel. It is then shown that by providing a certain threshold for the algorithm, a higher‐speed decoding is realized. It is shown also that by setting the threshold above a certain value, the computational complexity can be improved without sacrificing the maximum‐likelihood property. Finally, it is demonstrated by numerical calculation that the decoding error probability is improved greatly by the decoding algorithm proposed in this paper, together with a drastic improvement in the computational complexity.
A coding scheme of dither image using two types of information
Authors: Tanaka Kiyoshi , Nakamura Yasuhiro , Matsui Kineo
Published: July 2007

This paper presents a data compression scheme which uses the statistical properties of ordered dither image by vector representation. When a part of the dither image corresponding to n x n dithering matrix is described as a vector, it is observed that there is high correlation ratio between neighbor blocks for level information (the number of black pixels in the vector), the resolution information (the number of kinds of vectors) is a few, and their frequency distribution is very biased. Thus, if these two kinds of information on vector are coded separately by the variable length coding scheme, then high compression ratio can be attained for transmission and storage of dither image.
A detector diversity system for land mobile communications
Authors: Sano Hiroyasu , Hagiwara Masafumi , Nakagawas Masao
Published: July 2007

The land mobile communication is affected by fading when the mobile station moves in the multipath transmission environment. On the other hand, there are cases where there is no fading as in the communication with the standing or transported mobile station. It has been understood that the coherent detection using PLL is better in the nonfading environment and the differential detection is better in the fading environment.

From such a viewpoint, this paper proposes a detector diversity system for mobile communication which can cope with the complicated states of the transmission path by switching between the coherent detection (PLL) and the differential detection using the error‐detection code. The proposed system uses a simple error‐detection code, and the two detectors are switched by selecting the detector with a fewer number of detected errors. The feature of the system is that it is simple, being constructed by the existing PLL and the differential detector. The effectiveness of the proposed system is verified by computer simulation.
Criteria of the possibility of multipath interference cancellation
Authors: Kaitsuka Toshiyuki
Published: July 2007

A case exists in which cancellation of interference is not possible with an interference canceler which cancels the interference wave from ground radio stations mixing into the ground station for the satellite communication. It is found experimentally that this is caused by the difference in the frequency characteristics of the input signals to the two antennas by the multipath effects.

Further, a method is proposed to discriminate whether the arriving interferences can be cancelled. Its effectiveness is confirmed experimentally. Whether or not the interferences can be cancelled can be determined by the amount of variation of the received electric field intensity of the interferences. If there is a signal with a constant‐shaped spectrum, the distortion of the shape can be used for discrimination. As a result, the condition and limit of applications of the interference canceler are found.
Adaptive predictive coding of still images using neural networks
Authors: Ueno Ikuro , Itoh Susumu , Utsunomiya Toshio
Published: July 2007

This paper proposes an adaptive predictive coding method for still images using neural networks. Using a neural network, this method realizes data compression by representing the image in a hidden layer which has a lower dimensionality (i.e., contains fewer units) than the input layer and then quantizing the output of each hidden layer unit. In this method, extrapolative prediction of a 4 ± 4 pixel block is utilized and the prediction residual error is the target of coding. Then, to realize neural networks which possess high versatility, training of the neural networks using training vectors which are generated based on a statistical model of interpolative error signals is performed.

The rate‐distortion characteristics of 11 types of neural networks, having different numbers of units in the hidden layer, are calculated. The optimal relationship between the number of units in the hidden layer and the number of quantization levels corresponding to each unit are explained.

Based on the local statistics within the image and the forementioned rate‐distortion characteristics, the neural networks and the number of quantization levels are controlled adaptively. At the same time, by introducing a variable block‐size method, high encoding efficiency and good reproduction quality are realized. Finally, it is demonstrated that the method presented herein exhibits better encoding performance than the method which performs vector quantization of the same prediction residual error.
Loss‐compensation characteristics and noise performance of distributed erbium‐doped optical fibers
Authors: Wada Akira , Tanaka Daiichiro , Yamauchi Ryozo
Published: July 2007

To realize loss compensated Erbium‐doped (Er‐doped) optical fibers with the intensity deviations of the propagating light signal suppressed below a few decibels, first, numerical simulations of the appropriate Er concentration, the anticipated loss compensation length, and the noise figure are carried out. Hence, the intensity deviations of the light signal of 1.535‐μm wavelength can be kept below 1 to 3 dB at 60 mW pumping power of 1.48‐μm wavelength allowing 30 to 40 km long loss‐compensated fibers to be produced.

Based on these results, an Er‐doped 36.8‐km long fiber actually is manufactured where the intensity deviations of the propagating light signal over the whole length is about 1 dB at pumping power of 66 mW. It is shown experimentally that it is possible to produce loss‐compensated 73.6‐km long fibers using the bidirectional pumping method. The experimental results of the noise figure are in good agreement with those of the simulation ones.
Variable bit rate video coding method
Authors: Kuroda Hideo , Fujimura Makoto , Nataochi Yukihiro , Ikehara Masaaki
Published: July 2007

The NUCLEI (Nagasaki University codec using large interframe prediction errors as important parts) method is proposed in this paper as a new interframe coding method for the asynchronous transfer model (ATM). Characteristics of this method are as follows: 1) interframe predictions are done using a full band, considering the high coding efficiency during the normal state; 2) interframe predictions are done even after cell loss, considering the high coding efficiency after cell loss; and 3) utilizing the fact that the small moving areas are less important than the large moving areas in dynamic images (motion pictures), large moving areas or blocks with large interframe differences are allocated to priority (higher priority) cells as priority blocks and comparatively small blocks are allocated to nonpriority (lower priority) cells as nonpriority blocks. These characteristics are realized by assigning frame memories for storing priority block signals in addition to frame memories storing all images. It is shown by computer simulations that good interframe coding characteristics can be realized in both during the normal state and after a cell loss.
Investigation of radiation characteristics of large deployable antennas using a model antenna
Authors: Hanayama Eiji , Takano Tadashi
Published: July 2007

This paper clarifies the radiation characteristics of a tension truss‐type deployable antenna based on measurements made on its solid model and presents its experimental method. The main reflector of the model antenna is constructed by many triangular plates approximating a paraboloid. As the aperture shape of a tension truss‐type deployable antenna is a hexagon, the difference between the circular aperture of the model antenna and the hexagon is covered with radiowave absorbers. The distribution of mechanical reflector errors which are projected on the aperture plane is formulated and their relations to electrical errors is shown. Data on reduction of gain and grating lobes in the radiation pattern arising from periodic reflector errors are obtained. The measured results are compared with calculated values of radiation characteristics and good agreement is obtained. It is shown that radiation characteristics can be estimated by the aperture integration method by neglecting the disturbance of current distribution at seams of facets.
Theoretical and experimental study on the wave absorber for metal cylinders with mirror‐symmetrical cross section
Authors: Hashimoto Osamu , Inoue Toshikazu , Soh Tetsu
Published: July 2007

This paper presents an analysis method based on the point matching method for the reflection characteristics of a metal cylinder with mirror‐symmetrical cross section coated with a wave absorber. By means of this method, various design charts and the numerical results of the reflection characteristics are shown for wave absorbers that are optimum for the elliptical and oval‐shaped cross sections. The effectiveness of this method was confirmed by a model experiment.