bluuebunny/crossref_metadata_2025_split huggingface dataset:
Electromagnetic polarization and its expression
Authors: Hosono Toshio 
Published: July 2007

AbstractBefore 1950, Maxwell's phenomenological theory was used widely in the study of electromagnetics. In spite of the number of works published, none of them adopted electron theory to the study of electromagnetics.Not until after 1950 did the electron theory become popular among electromagnetic researchers. The author has developed an axiomatic electromatic theory (hereafter called EM theory) in which Lorentz' electron theory was taken as one of the axioms.This paper clarifies the problem in the old definitions of polarization and proposes a new definition using formulas which hold rigorously at the microscopic level. Based on this definition, the physical and mathematical meanings of polarization are clarified to establish firmly the EM theory.
New block demodulator with an automatic equalizer
Authors: Matsui Minoru , Hagiwara Masafumi , Nakagawa Masao 
Published: July 2007

AbstractThe block demodulation method recently has received considerable attention because of its high data transmission efficiency and superior performance. However, the conventional block demodulators do not consider the distortions of amplitude and phase in a transmission channel. As a result, the conventional block demodulators cannot compensate such distortions.In this paper, a new block demodulator with an automatic equalizer is proposed. A two‐dimensional block equalizer is used in the proposed demodulator. The overall performance is improved greatly by the repeated estimation method of combined automatic equalization and carrier estimation. In addition, the number of taps in the equalizer is changed for further improvement.The computer simulation result indicates that the mean‐square error by the proposed demodulator is about 1/100 compared with that of the conventional one when SNR = 30 db.
A star‐type local area network having simultaneous multiple transmission capability
Authors: Saito Tadao , Aida Hitosi , Inoue Ichiro 
Published: July 2007

AbstractIn the conventional header‐driven storageless LAN (HDSL), the simultaneous multiple transmission, in general, is impossible, which made it difficult to cope with the increase of the traffic due to the system expansion and other situations. This study proposes a star‐type LAN (multistar LAN) which realizes multiple simultaneous transmission by providing the center node with the multiple simultaneous switching function. In the multistar LAN, HDSL‐type communication is realized by the switching function of the center node. The assignment of the usage of the switching function is determined through the contention and arbitration among the data units sent from the grouped end node.This paper first outlines the structure and operation of the multistar LAN, and presents the theoretical and experimental evaluation of the traffic‐delay characteristics. The features of the multistar LAN features are that the delay for low traffic is small, the performance is less deteriorated for high traffic, and there is a flexibility in accommodating the increase of the traffic.
Optimization of the coherent integration number in a tracking system consisting of a radar sensor and a kalman filter
Authors: Nomoto Kohei , Fujisaka Takahiko , Kirimoto Tetsuo , Ohashi Yoshimasa , Kondo Michimasa 
Published: July 2007

AbstractA tracking system consists of an observation part such as a radar and a filter part such as a Kalman filter. To date, numerous adaptive filters have been studied for improving the tracking accuracy. However, the parameters related to the observed data have been fixed. If, on the other hand, one uses a digital beamforming (DBF) radar as the observation part so that the coherent integration number has a degree of freedom, these observation parameters can be adjusted according to the situation to improve the accuracy of the tracking system.From the viewpoint of requirement on the filter, the observation period and the observation accuracy, both of which are functions of the coherent integration number, are opposite to each other, and hence the optimization of the integration number is a problem. In this paper, a DBF radar is used for observation and a Kalman filter as the filter, and a study is made to determine how the angular position prediction accuracy in such a tracking system varies by the coherent integration number. It is shown that there exists an optimum coherent integration number for the entire tracking system.
Effects of antenna pointing errors on the design of heterodyne optical intersatellite communications
Authors: Goto Koji , Araki Ken'Ichi , Yasukawa Koji 
Published: July 2007

AbstractIn the optical intersatellite communication system using a heterodyne detection, the signal level changes by the pointing error of the receiving antenna on the satellite in addition to the pointing error of the transmitting antenna of another satellite. Further, since these antenna pointing errors cause the unavailable state of the optical channel, the unavailability will become a problem. However, to date, nothing has been reported on link design which reflects the unavailability by considering the pointing errors of both the transmitting and receiving antennas.In this paper, equations for the burst error rate are derived by means of the probability density function of the pointing error distributions of the transmitting and receiving antennas. With this burst error rate, the unavailability is computed. Hence, a link design reflecting the unavailability can be carried out by taking into consideration the pointing errors of the transmitting and receiving antennas at the same time. Further, a link design example is presented in the case where the facing satellites have identical communication systems.
A spatial frequency‐preserving post‐filter for block image coding
Authors: Izawa Yuuji 
Published: July 2007

AbstractBlock image coding, based on the discrete cosine transform (DCT), is used widely for transmission and storage of images and achieves high coding efficiency. However, the blocking effect is generated at low bit rates, and it is the major cause of picture quality degradation.This paper proposes a spatial frequency‐preserving post‐filter which reduces the blocking effect efficiently without decay of spatial resolution in decoded images. By simulation, the improvement of the picture quality is verified and it is shown that the SN ratio can be improved by 0.7 to 0.9 dB.
A theoretical study of measurement of cross‐polarization power ratio (XPR) in mobile communication environments
Authors: Taga Tokio 
Published: July 2007

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

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

AbstractError rates of block‐coded MPSK and/or MQAM systems with hard‐decision decoding are evaluated theoretically on the Rayleigh fading channel characterizing the land mobile channel. BCH codes are employed as the block codes and analysis is carried out both for nondiversity reception and for dual MRC diversity reception.It is shown that on the Rayleigh fading channel, in contrast to the AWGN channel, BCH‐coded MPSK systems can achieve significant coding gain compared to uncoded BPSK even in the hard‐decision decoding case without changing spectral efficiency. It is shown also that diversity reception is needed for sufficient large coding gain in higher spectral efficiency. Moreover, it is suggested that the code length longer than a threshold is necessary for large coding gain under the given number of multilevel modulation and given spectral efficiency.
Distributed self‐healing network and its optimum spare‐capacity assignment algorithm
Authors: Chujo Takafumi , Komine Hiroaki , Miyazaki Keiji , Ogura Takao , Soejima Tetsuo 
Published: July 2007

AbstractRapid self‐healing under link failure in high‐capacity optical fiber is a basic issue in broadband networks. Failure restoration schemes are being studied which reroute failed paths using the control of path reconfiguration function of the Digital Cross Connect System (DCS). Distributed control schemes based on a flooding algorithm have been proposed to meet real‐time requirements for large‐scale transmission networks, but problems arise, such as message congestion at nodes and internode synchronization.The performance of the self‐healing algorithm depends not only on the algorithm itself but also on physical network topology and spare capacity. In this paper, we propose a distributed restoration algorithm using a flooding technique and a centralized spare‐capacity assignment algorithm minimizing total spare capacity in a network while meeting a given survivability objective.The failure restoration time, restoration ratio, and spare capacity cost of these algorithms will be evaluated by computer simulation.
Optical subscriber loops by nonpressurized optical fiber cable
Authors: Kawase Masaaki , Tomita Shigeru , Kasahara Nobuyuki , Uenoya Takuya 
Published: July 2007

AbstractIn optical‐fiber‐cable networks of Japan, usually dry air is compressed into the cable and joints and gas‐pressure sensors are used for remote‐supervision of pressure maintenance. However, optical fibers are different from metallic lines and penetrating water is not a direct obstacle. Further, the manufacture of gas dams is not as easy as that of the metallic cables, and the gas dams become very large in size so that it becomes difficult to put them in the line. Therefore, the nonpressurized cables with reliabilities as high as those of the pressurized ones have been investigated.This paper discusses first the main factors responsible for the reliability deterioration of nonpressurized optical fiber cables and joints, which are the important elements of an optical system. Then, as the nonpressurized line structure, the waterproof optical fiber cables and the remote supervision of joints are discussed. Using a simple remote‐supervisory structure which consisted of the water sensors and OTDR, it is shown that the realization of reliabilities as high as those of the pressurized cables is possible.
Ranging and positioning test of an aircraft using a geostationary satellite
Authors: Ito Ken , Hoshinoo Kazuaki , Ito Minoru , Nishi Shunji 
Published: July 2007

AbstractIn‐the aeronautical satellite system for the air traffic control in the oceanic area, it is important to know the position of aircraft at the ground earth station. This paper describes the ranging and positioning system using two geostationary satellites (real satellite and a pseudosatellite on the ground).This system is designed to allow ranging and positioning of each aircraft every 0.6 s within the ranging and positioning accuracy of 100 m and 1 km, respectively. Experiments to estimate this system were performed using a real aircraft. Results gave better accuracy than those mentioned in the foregoing.
Design of a directional diversity receiver using an adaptive array antenna
Authors: Kuroiwa Noboru , Kohno Ryuji , Imai Hideki 
Published: July 2007

AbstractIn mobile communication, fading due to multipath is a major factor in the deterioration of communication quality. One strategy for this problem is the adaptive array which eliminates the effect of the delayed waves by beam‐forming or controlling the radiation pattern adaptively. However, in the conventional method, the delayed waves simply are eliminated but are not utilized. It has been pointed out also that the directional diversity reception is effective in reducing the fading effect. In the conventional directional diversity reception method, the radiation pattern of the antenna is fixed.In this paper, it is pointed out that the information identical to that in the direct wave is contained in the delayed wave. A directional diversity method is proposed in which, by means of the radiation pattern of the adaptive array antenna, the direct wave and the delayed waves are separated adaptively or combined.In this system, two sets of antenna weights are included for unknown or time‐varying waves and the radiation patterns of the antenna can be controlled adaptively so that the directions of arrival can be estimated individually. By adaptively combining the direct and delayed waves, the SN ratio can be improved. The basic evaluation of this system is carried out to indicate that the error rate can be improved over that for the conventional adaptive array antenna which does not make use of the delayed wave. A possibility of using the proposed system in mobile communication is discussed.
Urban multipath propagation delay characteristics in mobile communications
Authors: Tanaka Tetsu , Kozono Shigeru , Akeyama Akira 
Published: July 2007

AbstractIn this paper, propagation delay measurements were carried out in Tokyo (metropolitan urban area) where high rises and other buildings are concentrated on a plane and in Kofu (urban area adjacent to mountains) surrounded by tall mountains. The delay characteristics such as delay spread and wave numbers were found.The principal results obtained in these areas are as follows.(1) In a metropolitan urban area, i.e., Tokyo, (a) the average delay spread in a high‐density residential district is less than about 1 μs and the delay profile consists of a group of direct waves arriving directly from the base station; and (b) the average delay spread in a location with high‐rise buildings is also less than 1 μs and the average number of arriving waves is about five with the delay profile consisting of a direct wave group and a reflected wave group from reflecting object.(2) In an urban area adjacent to mountains, i.e., Kofu, the average delay spread is less than about 2 μs and the average number of arriving waves is four. The delay profile consists of a direct wave group and a reflected wave group. The level of the reflected wave group decreases exponentially with the delay time in the case of reflection from buildings, while the level is almost constant within a certain range of delay time and is of a spread shape (rectangular) in the case of reflection from mountains.From these measured results, a simple propagation model consisting of a direct wave group and a reflected wave group is proposed. It is shown that the distance dependence of the delay spread has a peak between the base station and a reflecting object.
Characteristics and prediction methods for the occurrence rate of SES in available time affected by tropospheric scintillation
Authors: Matsudo Takashi , Karasawa Yoshio 
Published: July 2007

AbstractThe unavailable time percentage and the SES (severely errored seconds) occurrence rate within available time was investigated according to CCITT definition using Ku band low elevation angles satellite system data obtained mainly at the Yamaguchi station. As a result, the CCITT unavailable time percentage was found to agree with the cumulative signal attenuation time percentage as determined by the traditional statistical treatment. This agreement held even in the case of low elevation angles.Further, the ratio of SES occurrence rate within CCITT available time to the conventional cumulative signal attenuation time percentage was found to be much larger than in the case of high elevation angles, and to have a high correlation with tropospheric scintillation. An experimental formula was developed for this ratio as an index of the degree to which tropospheric scintillation affects overall signal deterioration. Using this formula a formula was developed to predict the SES occurrence rate within CCITT available time from the index and the traditional cumulative signal attenuation time percentage. Also, it was confirmed that there was good agreement between the predicted value and the experimental value.
Resource management strategy in an ATM network
Authors: Noguchi Kiyohiro , Okada Tadanobu 
Published: July 2007

AbstractThis paper proposes a system of realtime bandwidth management and call admission control in an ATM network, which guarantees communications quality with high reliability and control simplicity. In this call admission control system, the allocated bandwidth for each bursty class is determined by theX‐percent value of the superposed bursty traffic distribution in each bursty class. Whether a requesting call is accepted or rejected is judged by the total allocated bandwidth of all bursty classes.Since the communications quality of each class can be approximately estimated from theX‐percent value of the superposed bursty traffic distribution and this probabilityX, a method of determining the allocated bandwidth satisfying quality specification is presented by formulating the probability event that each peak state is superposed.Bandwidth management, where bursty classes are introduced in order to realize optimal and simple control in accordance with the traffic burstiness and a method of call admission control are also presented. Although throughput performance is too deteriorated to realize the safety‐side bandwidth management, computer simulation confirms that the statistical multiplexing effect can be expected by using the proposed method.
Study of fault‐location expert systems for paired cables
Authors: Koga Hiroaki , Abe Tetsuji , Takeda Kazutoki , Hayashi Akira , Mitsunaga Yutaka 
Published: July 2007

AbstractNo method has been reported for fault location in a length of paired cable which consists of branched cables and wire of different gauges. This paper proposes a fault‐location expert system which comprises a new pulse echo detector and a fault‐location estimation expert system. The new pulse echo detector can locate a fault by the correspondence between theoretical and measured reflected waves. However, there is some degree of error because the transmission characteristics of each paired cable vary slightly.A more precise fault‐detection technique has also been developed. It is the fault‐location estimation expert system which has a knowledge base including experimental field data and an inference technique based on probability theory. The knowledge is obtained from the fault rate of each cable part in the field. Field tests have clarified that the fault‐location expert system can detect faults successfully.
Dual‐mode equalization for digital mobile radio
Authors: Higashi Akihiro , Suzuki Hiroshi 
Published: July 2007

AbstractThe performance of digital mobile radio systems when transmitting at over several tens of kbit/s severely degrades with the onset of fast fading multipath propagation. This paper proposes a dual‐mode equalization (DME) method to overcome the degradation and experimentally verifies the effectiveness of the method.The new method uses decision feedback equalizers (DFEs) in two modes simultaneously, a normal mode, and a time‐reversal mode, and selects the best equalization result.The time‐reversal equalization mode improves the characteristics of equalization and adaptation in the non‐minimum phase condition. It converts the nonminimum phase to the minimum phase condition by the time‐reversal operation.Principles of dual‐mode equalization, an algorithm for mode output selection, and timing problems are discussed in detail. Experiments demonstrate average BER performance in two‐path and typical multipath environments. The proposed dual‐mode equalization technique improves average BER performance by 2 dBEb/N0.
Transmission delay variation compensation in precision time‐synchronous networks
Authors: Imaoka Atsushi , Kihara Masami 
Published: July 2007

AbstractThis paper analyzes the performance of transmission delay variation compensation between two nodes in precision time‐synchronous networks. The compensation methods predict transmission delay using round‐trip path and compensate delay variations by employing a phase‐locked loop. Two methods for compensating delay variations in the master node (scheme A) and in the slave node (scheme B) are compared.Results show that scheme B is more accurate and more stable than scheme A. Then the total compensation error, which equals the sum of the delay variation, delay measurement error, and PLL internal noise, is calculated using the measured delay of actual telecommunication lines. Minimum compensation deviation of 2 ns is obtained by optimizing the PLL parameter. This deviation is determined by the flicker phase noise of the difference delay between the outgoing and incoming paths.