bluuebunny/crossref_metadata_2025_split huggingface dataset:
Channel coding performance of an adaptive DCT image coding in combination with m‐transform
Authors: Yamane Nobumoto , Morikawa Yoshitaka , Hamada Hiroshi , Fukuda Hideki 
Published: July 2007

AbstractIn the conventional adaptive discrete cosine transform (ADCT) using the fixed length code, it is known that the source coding performance can be improved greatly by the combined use of the M‐transform (MT). This method is called ADCT‐MT. The purpose of this paper is to evaluate the effect of the combined use of MT from the viewpoint of the channel coding performance. In the conventional ADCT, as well as in the scene adaptive coding (SAC) using the variable length code, the damage in the reconstructed image due to the channel error often is manifested as the local block distortion. In ADCT‐MT, the damage is diffused and distributed uniformly by the inverse MT over a large number of blocks, making the damage less noticeable.A subjective evaluation experiment is conducted (five‐step score) assuming the binary symmetrical channel. A simple error‐correcting code is applied to the coding data of the additional information and DCT dc component. When the bit‐error rate is 10−3, the average score is approximately 3.5 for ADCT and 1.2 for SAC, while it is above 4.5 in ADCT‐MT. Thus, in ADCT‐MT, the damage is little noticeable.
A method of reconstructing front‐looking radar using long‐wavelength holography
Authors: Sakamoto Yuji , Aoki Yoshinao 
Published: July 2007

AbstractWhen the synthetic aperture method is applied to the imaging of objects in the front direction of a moving vehicle, a problem arises in that, if the objects are at positions symmetrical to the direction of movement, the Doppler frequencies change in the same way. Consequently, ghosts symmetrical to the axis are produced in the reconstructed image. From another viewpoint, when an object exists in the direction perpendicular to the direction of movement, the change of the Doppler frequency depends on the position of the object. Then the rate of change is not kept constant and the processing based on the FFT algorithm, as in the general cases of synthetic aperture radar and long‐wavelength holography, cannot be employed.This paper proposes an imaging method for the front‐looking radar based on the principle of long‐wave‐length holography. The proposed method can solve the ghost problem for the objects symmetrical to the direction of movement using a small number of antennas in the azimuth direction. An algorithm also is proposed for high‐speed image reconstruction from the data acquired by the system. The theoretical resolution and the range of maximum possible imaging are discussed. Furthermore, the validity of the proposed method is verified by a computer simulation and an experiment using microwaves.
Characteristics of grid ferrite electromagnetic wave absorber
Authors: Naito Yoshiyuki , Anzai Hiroki , Mizumoto Tetsuya , Takahashi Michiharu 
Published: July 2007

AbstractA novel ferrite grid electromagnetic wave absorber composed of sintered ferrite is proposed. Based on the condition that the return loss should be above 20 dB at 30 MHz, its wideband characteristics for suppressing reflections compared to a single‐layer absorber are demonstrated by computer simulation.Calculating the return loss by varying the geometrical parameters of the ferrite grid, an optimum structure is determined which gives the maximum frequency band. In addition, it is found that the return loss of the grid absorber is impaired by an air gap between the ferrite and conductor. Moreover, the operating characteristics of the grid absorber are demonstrated by experimental models.
Full wave calculation method of VLF wave radiated from a dipole antenna in the ionosphere‐analysis of joint experiment by HIPAS and akebono satellite
Authors: Nagano Isamu , Miyamura Kazutoshi , Yagitani Satoshi , Kimura Iwane , Okada Toshimi , Hashimoto Kozo , Wong Alfred Y. 
Published: July 2007

AbstractA method has been developed for numerically calculating, by means of the full‐wave method, the electromagnetic field intensity distribution on the ground and at the satellite altitude (∼2000 km) using the electromagnetic wave radiated by an infinitesimal dipole placed in a lower ionosphere. The amplitude and polarization are analyzed for the simultaneous observation data on the ground and the Akebono satellite for the VLF wave radiated in the ionosphere heating experiment by a high‐power HF wave. The values computed by the full‐wave method agreed well with the observed data if the VLF sources by the heating experiment are at an altitude of 66 km along the east‐west direction and the current moment is 4.3 × 104 Am.
Hierarchical video coding scheme using mean‐separated normalized vector quantization
Authors: Hanamura Tsuyoshi , Sekiguchi Shunichi , Tominaga Hideyoshi 
Published: July 2007

AbstractA highly effective video coding method is proposed for application in a wide range of fields that utilize video information and in multimedia systems where data must be easily manipulated. The proposed video coding scheme is a hierarchical system that uses vector quantization and which also incorporates many of the basic coding components of the internationally standardized lowrate MPEG 1 coding system. In addition to providing the special data handling operations of MPEG 1, the new system incorporates a multiresolution hierarchical decomposition that permits the user to select a desired resolution level at the decoder. Source coding is achieved with mean‐separated normalized vector quantization applied to image blocks that contain fundamental image patterns. However, instead of using separate codebooks for each of the different prediction modes of the coding system, this paper shows that it is possible for various prediction modes to share codebooks to achieve a more efficient implementation. The coding efficiency of the new system is estimated and compared with the performance of a DCT based system. Although the signal‐to‐noise ratio of the VQ system falls short by 0.5 to 1.2 dB, subjectively, the two coding systems give about the same performance. Methods for improving the quantitative signal‐to‐noise ratio performance are also considered.
Development of VLSI of entropy coding for digital video
Authors: Fujiwara Hiroshi , Sakaguchi Toshifumi , Saito Ryuji , Maruyama Masanori 
Published: July 2007

AbstractWith the recent development of the digital electrical communication network and the advent of low‐cost large‐capacity digital storage media, an effort is made toward the digitization of the TV signal. Along with this, the image coding technique is becoming more important, where the research emphasis is shifting from the low bitrate pseudodynamic image representation, to high‐resolution, high‐quality images. Among various image coding methods, the feature of the entropy coding based on Huffman coding [1–3] is that a large amount of image data can be compressed efficiently by combining discrete‐cosine transform (DCT) and the motion‐compensated interframe coding, and is used presently as the indispensable element of the algorithm.To apply the method to the future digital dynamic image with a high image quality requirement and to realize the real‐time processing, it is necessary to develop a fast processing architecture for the Huffman coding, together with its VLSI implementation. With this as background, this paper describes the fast processing architecture for the Huffman coding developed by the authors, together with its VLSI implementation.
Proposal and evaluation of time critical communication protocol on LAN
Authors: Koui Yuuji , Seno Shoichiro , Takada Yoshinori , Ishizaka Michihiro , Ideguchi Tetsuo 
Published: July 2007

AbstractIn the field of control and communication using LAN, such as plant control, there exists a requirement for the time critical property that the data transfer should be completed in the specified time (time window), in addition to the requirement for the high speed. In the timed token protocol (TTP) that has been used in FDDI and other systems, however, the transfer time increases when the input traffic exceeds the system specification, making it impossible to maintain the time‐critical property.This paper proposes an extension of TTP where only the data that can be transferred within the time window are allowed to transverse by applying dynamic distributed management to the data transmission queue in each node. to demonstrate the performance of the proposed protocol, simulations are executed under various conditions; and it is verified that the protocol is effective when applied to the time‐critical communication.
Multicast routing scheme adequate for virtual path environment
Authors: Tode Hideki , Yamamoto Miki , Okada Hiromi , Sakai Yasuharu 
Published: July 2007

AbstractThe problem of accommodating multicast traffic in a virtual path (VP) environment under asynchronous transfer mode (ATM) conditions is examined. A network structure scheme suitable for all possible multicast communications is proposed. the expected result, statistical multiplexing effects during the accommodation of multiple multicast traffic over a VP should reduce hardware costs associated with the accommodation of multicast traffic. Multicast routing algorithms (the carrier‐to‐noise ratio (CNR) algorithm and the improved CNR algorithm) for an ATM network environment are proposed here. the efficiency of these algorithms is tested using their basic characteristics in computer simulations.
An error‐correction method of FM multiplex broadcasting for mobile reception
Authors: Kuroda Toru , Takada Masayuki , Yamada Osamu 
Published: July 2007

AbstractFM multiplex broadcasting for mobile reception can provide new services such as traffic information, graphics, and characters by multiplexing new digital signals with a frequency band higher than the baseband signal for existing FM stereo sound broadcasting. From the standpoint of efficient frequency use and simplicity of broadcasting equipment, the transmission path for traffic information service should be such that it may be established quickly.As a method of digital detection of FM multiplex broadcasting for mobile reception, level controlled minimum shift keying (LMSK) has been reported [1], where the amplitude of the digital signal has been controlled by the level of difference signal (L‐R signal) of the stereo sound.In this paper, comparison between the (272, 190) shortened difference‐set cyclic code [4] which is used for television character multiplex broadcasting [2] or for FM multiplex broadcasting for fixed reception [3] and the one‐half convolutional code which has high error‐correction capability is performed, and an error‐correction method of FM multiplex broadcasting for mobile reception is proposed. As a result, the product code of the (272, 190) code has shown better performance as an error‐correction method of FM multiplex broadcasting for mobile reception. Moreover, laboratory transmission and field transmission experiments have been performed using this method, and it is confirmed that the mobile reception is possible within the service area of FM stereo sound broadcasting by repeating the reception three times.
System unavailability and quality degradation during available time for mobile satellite systems in the mobile ISDN era
Authors: Karasawa Yoshio , Matsudo Takashi , Minamisono Kenichi , Shiokawa Takayasu 
Published: July 2007

AbstractIt is expected that mobile‐radio systems will play an important role in realizing general personal communication networks through ISDN. In the near future, the so‐called mobile ISDN era, it is necessary to have common performance objectives between mobile radio links and fixed (or fiber) links and have a common assessment method for data transmission quality.In this paper, based on the ITU‐T definition, unavailability statistics are examined in mobile‐satellite systems which are characterized by low margin systems. the characteristics of signal degradation due to propagation impairments in maritime, aeronautical, and land mobile satellite services are examined. Through this analysis, the importance of differentiation between “unavailability” and “signal degradation in available time” is emphasized when the digital signal transmission quality is evaluated.
Variable bit‐rate video transmission under usage parameter control
Authors: Kawashima Masahisa , Inoue Masahiro , Tominaga Hideyoshi 
Published: July 2007

AbstractThis paper proposes a method of video bit‐rate control for the case where the average transmission bitrate is constrained, considering the usage parameter control in an ATM network. By a simulation, the video quality and the network congestion probability of the variable bit‐rate (VBR) transmission system, with the constrained average bit‐rate, are compared to those of the conventional constant bit‐rate (CBR) transmission system or the VBR transmission system without the rate control. the relations among the length of the sliding window (SW) to monitor the average bit‐rate, the video quality, and the network congestion probability are analyzed.With respect to the video quality, it is shown that the VBR transmission with the average bit‐rate control exhibits a stable image quality when SW is long and exhibits a better image quality than the CBR transmission for the cases of scene change and the panning scene. When the scene changes, the image quality changes and the VBR transmission with the bit‐rate control.With respect to the network congestion probability, it is shown that the probability is decreased greatly by constraining the average bit‐rate and the probability becomes less when SW is made shorter.Finally, it is shown that SW should desirably be long to stabilize the video quality but the permissible length of SW depends on how many video signlas can be multiplexed in the network.
Construction of operation platform for optical subscriber cable network using object‐oriented design
Authors: Kashima Norio , Kokubun Toshinao , Yamamoto Yoshikazu 
Published: July 2007

AbstractIt is anticipated that additions of wideband services and automated operation modules, as well as modification of optical cable networks, will be made in optical subscriber systems. For this purpose, the flexibility to add or modify new tasks and automated operation modules is required for future optical subscriber operation systems. A discussion follows on the development of an operation platform for the subscriber loop that is used to establish the flexible operation system by referring to the operation platform concept proposed for advanced network operation. Especially, it is precisely discussed in the field of optical subscriber cable networks; additionally, the necessary functions for flexibility and integration have been derived. Based on these discussions, an operation platform of optical subscriber cable network is designed and its prototype has been constructed. Constructed system flexibility and priority access control efficiency are confirmed through an evaluation of the constructed prototype system.
A method for estimating end‐to‐end blocking probability and traffic flow based on information on links
Authors: Matsumoto Kimihide , Yokoi Tadahiro 
Published: July 2007

AbstractIn circuit‐switched networks (e.g., telephone networks and ISDN), it is important to manage both the quality of the network elements and the end‐to‐end quality. This paper proposes a method of estimating endto‐end blocking probability based on traffic data measured on the links (e.g., the amount of traffic volume or the number of calls). an end‐to‐end blocking probability is an important measure for telecommunications quality management. In circuit‐switched networks, generally, there are many end‐to‐end routes used to connect any two customers. For efficient network management, statistics on the utilization of these routes are also important (this is called end‐to‐end traffic flow). an estimation method for this end‐to‐end traffic flow also is proposed.The proposed estimation method combines link‐blocking probabilities in accordance with the network configuration and the routing policy of the network considered. the method can be applied to a wide class of networks. Computer simulations of some network models show the properties and the accuracy of the proposed method.
Performance of complexity reduced DFE with improved bidirectional equalization and inverse interpolation
Authors: Kamio Yukiyoshi , Sasaoka Hideichi , Sampei Seiichi 
Published: July 2007

AbstractIn land mobile communications, a frequencyselective fading due to multipath propagation greatly deteriorates the transmission characteristics, especially in high‐speed transmission. As a means to cope with such a frequency‐selective fading, the decision feedback equalizer (DFE) is studied. In the QPSK/TDMA system, a simplified DFE is already proposed for interpolating the preamble and postamble tap coefficients.This paper discusses the application of the DFE to 16 QAM/TDMA, which has a high spectral efficiency. In this case, the error rate performance is deteriorated due to the decrease of the distance between signals, as well as the error propagation of the decision error.From such a viewpoint, a system is proposed which contains the bidirectional equalization and the inverse interpolation based on the timing detection function for the delayed wave in the backward equalization. By this scheme, the number of taps is reduced and the irreducible error rate is improved for the case where there does not exist a delayed wave or there is the effect of a delayed wave.The proposed system is examined by a computer simulation. the computational complexity of the proposed method is compared to the conventional method. As a result, it is seen that the proposed method can achieve a satisfactory equalization performance with onetenth the computational complexity of the conventional method.
A PSK transmission system employing transmitting and receiving butterworth filters with optimized noise performance
Authors: Okada Takahiro , Miyauchi Kazuhiro , Hangai Seiichiro 
Published: July 2007

AbstractA band‐limited phase‐shift keyed (PSK) transmission system satisfying Nyquist's first criterion by an equalizer using Butterworth filters for transmitting and receiving filters is discussed. Minimum noise equalization that minimizes the receiver equivalent noise band width is proposed and the characteristics of such a system are calculated. In addition, minimum noise equalization is compared with reference equalization and roll‐off equalization and it is clarified that minimum noise equalization is better than these equalization method in frequency and power efficiency. It is shown also that the frequency efficiency and the efficiency of transmitting power have a trade‐off relationship in a bandwidth‐limiting and then power‐amplifying scheme and the frequency efficiency is increased without decreasing the transmission power by decreasing the heat loss of a high‐order transmitting filter in a power‐amplifying and then band‐width‐limiting scheme.
Prediction of urban propagation characteristics for low base‐station antennas
Authors: Iwama Tsukasa , Mizuno Mitsuhiko 
Published: July 2007

AbstractEffective use of frequency is extremely important for land mobile communication where the number of users is steadily increasing. One means of achieving frequency efficiency is to employ the microcell in which the service area is subdivided into a minimum unit to increase geographical frequency reuse. One implementation of the microcell system is to position the base‐station antenna at a level below the tops of surrounding build ings. Estimation of the radio wave propagation characteristics is indispensable for implementing such a microcell system.In this paper, a method of estimating the wave propagation characteristics between arbitrary transmission and reception points based on a building database is modeled theoretically on a computer using geometrical optical methods such as the geometrical theory of diffraction (GTD). Up to two reflections and diffractions are considered. Comparison of theoretical and measured results of the estimated propagation loss show that the estimated average error was less than about 10 dB for distances of less than 500 m from the transmitter to the receiver for streets on which the transmitting antenna is visible from the receiving antenna. By contrast, the error was about +20 dB to ‐10 dB within 600 m on a street crossing one where the transmitting antenna is visible.
Bit error rate and power penalty in MSK coherent optical communication systems with a single interfering echo
Authors: Yamaguchi Yoshiaki 
Published: July 2007

AbstractIf an echo is generated during transmission, then along with the principal wave (directly transmitted wave), an echo with a certain time delay arrives at the receiver, which causes degradation of receiver performance.In this paper, the bit error rate for optical MSK communication systems with a limiter‐discriminator‐integrator‐type receiver is analyzed and the influence of echo is evaluated qualitatively as well as quantitatively.In general, there exists a floor value on the error rate curve due to the phase fluctuation of laser light in the coherent optical communication systems, which is not reduced upon increasing the received optical power. It is shown that this floor value increases due to the presence of echo and its value is a maximum when the delay time of echo with respect to the principal wave is an integral multiple of the bit duration. Moreover, when the spectral linewidth of the light with high bit rate is narrow, then the effect of echo becomes even stronger.A relationship between the received optical power and bit error rate is derived, and the power penalty is determined for given echo amplitude, delay time, and linewidth‐bit duration product. the conditions under which the effect of echo cannot be neglected are clarified. Moreover, the optical MSK system is compared with the optical DPSK system and it is shown that the MSK signal is degraded by echo greater than the DPSK‐signal.The special feature of this paper is an exact analysis of the case when some phase correlation exists between the principal wave and echo due to coding considerations.
A multiaccess coherent optical communication system using common optical carrier with star configuration
Authors: Tsukamoto Katsutoshi , Fujii Takashi , Morinaga Norihiko 
Published: July 2007

AbstractA variety of multiaccess optical communication systems with common carrier have been reported recently. This paper proposes a new type of multiaccess coherent optical communication system with star configuration in which a common optical carrier from a single source is distributed by a star coupler. In this system, the carrier is phase‐modulated at each user by an external modulator through a subcarrier signal and the signal is received by an optical heterodyne receiver. A feature of the system is that the distributed optical carrier and the modulated light are directional‐division multiplexed.Theoretical analysis of the carrier‐to‐noise power ratio (CNR) of the system is carried out in this paper taking into account the effect of interference light caused by reflections, backscattering, or insufficient isolation of a circulator used in the system, followed by discussions on the allowable value of the signal‐to‐interference light power ratio and on the relation between transmitter power and maximum user numbers.