bluuebunny/crossref_metadata_2025_split huggingface dataset:
Performance evaluation of packet voice multiplexer with selective packet‐discarding control
Authors: Niu Zhisheng , Akimaru Haruo , Machihara Fumiaki , Ide Ichiro 
Published: July 2007

AbstractThis 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

AbstractSpread 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

AbstractRecently, 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

AbstractAn 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

AbstractIn 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

AbstractIn 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

AbstractThis 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

AbstractA 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

AbstractA 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

AbstractFor 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

AbstractA 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

AbstractThis 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

AbstractThis 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

AbstractThe 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

AbstractA 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

AbstractThis 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

AbstractTo 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

AbstractThe 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

AbstractThis 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

AbstractThis 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.