bluuebunny/crossref_metadata_2025_split huggingface dataset:
Notes on capability of demultiplexing coded packets on a collision channel
Authors: Inaba Hiroyuki , Kasahara Masao 
Published: July 2007

AbstractPacket exchange methods have come to play a central role as exchange methods in various networks. Especially, the random access method has been attracting attention since networks can be constructed comparatively easily by this method without having to establish special control offices. However, a collision of packets is inevitable with the random access method, which becomes a major factor in decreasing network efficiency. In past access methods, collided packets, in general, are retransmitted.In this paper, a method of considering a collision of packets as collision error, correcting this error, and demultiplexing (isolating) into original packets is proposed. In this method, demultiplexing (isolating) collided packets as well as detecting and correcting the transmission path error occurring simultaneously is possible. In addition, the method has a characteristic of superior compatibility with conventional systems. In addition, it has been clarified that the performance is improved greatly when the proposed method is applied to a random access network, by taking the ALOHA system as an example.
Design and performance of optical fiber identification system for optical fiber transfer splicing system
Authors: Shimizu Masatoshi , Kobayashi Hideo , Chijiwa Youichi , Takashima Seiji 
Published: July 2007

AbstractBoth the expansion of optical networks and their maintenance techniques are becoming increasingly important During optical fiber cable transfer work, while securing user's services, it is very important to develop optical cable transfer splicing systems for efficient cable transfer which raises the possibility of low‐cost maintenance.In this paper, the realizable configuration of the optical fiber identification equipment used in the optical cable transfer splicing system is investigated. The structures of the two identification systems of local injection/local detection and end‐face injection/local detection is proposed and the required functions together with the design guidelines of these two systems are clarified. Further, the design method and characteristics of the local injection and local detection equipments together with evaluation method of the transfer connection losses are presented.Finally, it is shown that the allowable distances of the local injection/local detection and end‐face injection/local detection systems are 11 km and 29 km, respectively.
Propagation characteristics of very low latitude whistlers by ray tracing
Authors: Ohta Kenji , Tomomatsu Tooru , Takahashi Osamu , Hayakawa Masashi 
Published: July 2007

AbstractSimultaneous measurement made in South China in January 1988 has already indicated that the nighttime whistlers observed at very low latitudes (geomagnetic latitudes, 10° to 14°) are attributed to field‐aligned propagation. On the other hand, a few researchers have suggested, based on the ray‐tracing computations, that nighttime whistlers at very low latitudes are due to nonducted propagation.To solve the discrepancy between the authors' experimental results and the previous ray‐tracing studies, extensive two‐dimensional ray‐tracing calculations have been made for the nonducted propagation of whistlers in the inner plasmasphere in a wide frequency range (1 to 10 kHz). The conditions for nonducted whistlers to penetrate through the ionosphere onto the ground have been discussed to clarify the difference from the experimental results reported here.
Multislotted ALOHA scheme for high‐efficiency transmission of variable‐length packets
Authors: Kawazoe Katsuhiko , Kazama Hiroshi , Kato Shuzou , Masamura Tatsurou 
Published: July 2007

AbstractThe paper proposes the multislotted ALOHA (MS‐ALOHA) as a new random access scheme which can improve the throughput in variable‐length packet signal transmission. This scheme is to improve the throughput in the variable‐length packet signal transmission by controlling the transmission timing according to the packet‐signal length.The throughput performance of the proposed scheme for the variable‐length packet transmission is formulated for the infinite station model and the finite station model. The proposed scheme is compared to the traditional slotted ALOHA with the single transmission timing by computer simulation. It is shown that the throughput of the proposed scheme is larger independently of the signal length and the performance is stable against the variation of the signal‐length distribution.When the signal length is distributed uniformly, the maximum throughput is improved by approximately 20 percent compared to the traditional scheme. The application of the retransmission slot‐control scheme to the proposed scheme is considered. Here, the transmission slot for the retransmission packet is assigned to each transmitting station. As a result of analysis by computer simulation, it is shown that a higher throughput is obtained than the ALOHA scheme with the selective rejection retransmission protocol.
Adaptive array antenna based on estimation of arrival angles using DFT on spatial domain
Authors: Yim Choonsik , Kohno Ryuji , Imai Hideki 
Published: July 2007

AbstractMultipath fading is a factor degrading the communication quality in mobile communications. It has been reported that an adaptive array antenna can enable elimination of the effect of delayed signals by an appropriate control of the radiation pattern. In this paper, it is recognized that an optimum weight of the array antenna can be computed if the direction of arrival and the signal‐to‐noise ratio of the received signal are known. By using the spatial frequency derived by the discrete Fourier transform (DFT) of the received signal which is spatially sampled by the array antenna, an algorithm is proposed in which the directions of arrival and the signal‐to‐noise (SN) ratio of the desired and interference waves are estimated and an optimum weight coefficient of the antenna is computed. This algorithm is different from those in the conventional adaptive digital filter algorithms such as the LMS algorithm. It requires no reference signal and can follow quickly changes in the communication channel. Further, a method is proposed to improve the estimation accuracy of the direction of arrival and the SN ratio with a limited number of elements by using the property of the DFT. To confirm the principle of the proposed algorithm, the basic characteristics are evaluated by computer simulation.
Methods for constructing a management information base (mib) in transmission network operations
Authors: Yoda Ikuo , Fujii Nobuo 
Published: July 2007

AbstractMethods of realizing a management information base (MIB) under a CMIS/CMIP environment using RDBMs for realizing a transmissions network operations system using the OSI management techniques are presented. A method of constructing an MIB by an attribute unit table with respect to the restrictions of CMIP without a specific object class in the operations process is proposed. Corresponding to management information that has become complicated with the times, this method proposes a mechanism of global searching independent of management object definitions by deriving a general procedure required for attribute operations within an agent system to make the CMIS processing codes as independent management object definitions and storing the forementioned procedure in an MIB. In addition, this construction method was evaluated by using an MIB constructed experimentally and the realizability of the proposed method of construction of MIBs and the performance of the experimental MIB evaluated by the experiment are presented. This MIB construction method is applicable to high‐level agent systems that are complicated and of large scale.
Analysis of switching converters with switched snubber
Authors: Noguchi Seiichi , Sakamoto Hiroshi , Harada Koosuke 
Published: July 2007

AbstractIt is considered that the key to miniaturization of switching power supplies is in high frequency. With respect to the high frequency of switching power supplies, the losses and surge during switching are frequent problems. In switched snubber circuits constructed from parallel connection of a switching element and condenser, it is reported that there is essentially no loss and the surge suppression effects are excellent.In this paper, with respect to converters incorporating switched snubber circuits, general state equations taking into account low‐frequency characteristics are determined by the state averaging method. As a consequence, while taking into account parasitic inductances such as the leakage inductance of transformers and floating inductance of wiring, a unified analysis was made of buck type, boost type, and buck‐boost type. Moreover, the general state equations taking into account the parasitic elements of the smoothing condenser were determined by transformation into simple equivalent circuits. The suitability of the analysis was verified by using a flyback converter. The fact that the parasitic inductance in the circuit increases the output impedance is verified quantitatively.
Conditions for a rotationally symmetric aperture mapping in dual reflector antennas—a new category of reflector systems allowing double‐offset configuration
Authors: Nomoto Shinichi , Mizuguchi Yoshihiko 
Published: July 2007

AbstractThe aperture mapping in general dual reflector antennas including the shaped‐reflector type is studied based on the geometrical optics. The condition for a rotationally symmetric aperture mapping is derived. As a result, it is found that there exists a curved surface system which is completely different from the rotational quadratic surfaces for realizing a rotationally symmetric aperture mapping. This new surface system category has higher degrees of freedom in design than the conventional rotated quadratic surfaces (Cassegrainian/Gregorian). It is possible to realize a rotationally symmetric aperture mapping even in a double‐offset reflector arrangement in which no symmetric plane exists.
Phase‐diversity receiver using two pairs of three wires for data transmission over a low‐voltage distribution line
Authors: Hashimoto Naoki , Arai Toshio , Ozawas Yoshitaka , Kohno Ryuji , Imai Hideki 
Published: July 2007

AbstractIntensive efforts have been observed in recent years on the development of data communication technology, aiming at the effective utilization of such existing transmission lines as the in‐house distribution line. The automatic consumption meter reading, for example, uses the low‐voltage distribution line as the transmission channel.This paper aims at the improvement of the receiver demodulation performance in the data transmission using the low‐voltage distribution line and proposes the phase‐diversity reception using two phases (red and black) of the single‐phase, three‐wire system. In the data transmission using the low‐voltage distribution line, stray signals are produced between the two phases of the single‐phase, three‐wire lines and two signals with different signal‐to‐noise (SN) ratios are received. If a simple scheme such as the addition is employed, a problem arises in that the reliability of the demodulated data is deteriorated.To cope with this problem, this paper proposes a phase‐diversity reception, where the time‐varying phase difference is adjusted to zero using an adaptive phase shifter and the SN ratio is improved by synthesizing the two‐phase received signals. The proposed scheme is implemented on a digital signal processor (DSP), and a robustness against the channel noise and the periodic attenuation is realized by the feedback (FB) control.As a result of an experimental evaluation, it is shown that the SN ratio is improved by 2.7 dB at the maximum for the stationary phase error, compared to the traditional simple addition and the addition/subtraction selection schemes. Thus, it is verified that the receiver demodulation performance of the low‐voltage distribution line data transmission can be improved.
On efficiency of optical modulations for optical channel with noise
Authors: Watanabe Noboru 
Published: July 2007

AbstractRecently, in parallel with the advancement of lightwave technology, there has been a considerable amount of research and development work in the system engineering aspects of optical communication, including important basic research. Various types of modulation have now been applied in real optical communication systems. In this paper we introduce a scale that can be used to measure the efficiency of optical modulation in terms of the quantum entropy. With the aid of this scale, we then discuss the efficiency of information transmission in various types of optical pulse modulation (PAM, PPM, PWM) for particular photon number states of the input system and for an optical channel with noise.
Digital modulation scheme for FM multiplex broadcasting with mobile reception
Authors: Kuroda Toru , Saito Tomohiro , Takada Masayuki , Yamadas Osamu 
Published: July 2007

AbstractThe FM multiplex broadcasting is one of the broadcasting configurations for providing a new service, where digital signals are multiplexed by utilizing the empty spectrum of the baseband signal in the FM stereo broadcasting. The fixed reception FM multiplex broadcasting system, where reception is done by setting up an antenna has already been developed and used in practice, and its broadcasting has been started. On the other hand, it would be desirable to develop a mobile reception FM multiplex broadcasting system with a certain amount of transmission capacity, where the broadcast can be received by a car or portable radio, for an application to the traffic information transmission. As to the digital transmission to moving objects, interferences such as fading and multiple paths are known to be present and the technical difficulty is increased with the increase of the bit rate. Furthermore, there are difficulties in the FM multiplex broadcasting such as the cross‐talk from the sound signal, due to the nature of the multiplex signal. Only a very low bit‐rate system of about 1 kbit/s has been developed such as RDS (Radio Data System) [1] in Europe for practical applications to the mobile reception. This study aims at the development of a mobile reception FM multiplex broadcasting system with a higher bit rate. An FM multiplex transmission simulator is constructed first, and the transmission characteristics inherent to the FM multiplexing are analyzed. A digital modulation method suited to these transmission characteristics is presented. By laboratory and field transmission tests, the effectiveness of the proposed digital modulation scheme is demonstrated.
Evaluation of input traffic control in atm networks
Authors: Sakamoto Nobuo , Ohba Yoshihiro , Murata Masayuki , Miyahara Hideo 
Published: July 2007

AbstractThis paper evaluates a leaky‐bucket‐type control method as a means of policing control of input traffic in ATM networks. In an ATM network, a user reports parameters specifying traffic characteristics to each traffic source at the time of making a request for a call connection and the network determines whether or not to accept the call on the basis of these parameters. In addition, after the call reception, input traffic after a call connection must be controlled such that the cell arrivals from the traffic source conform with the reported parameters. In this paper, as a method of controlling input traffic, the mean arrival rate and burstiness of input traffic are evaluated quantitatively using the leaky‐bucket method and problems associated with introduction of such an input control system to an ATM network are discussed.
Cell delay variation smoothing methods for atm‐based sdh signal transport system
Authors: Uematsu Hitoshi , Ueda Hiromi 
Published: July 2007

AbstractIf the synchronous digital hierarchy (SDH) signal is converted into asynchronous transfer mode (ATM) cells to be transmitted through the ATM transport network, the efficiency of the operation/management/maintenance of the network will be improved in addition to maintaining the economy and reliability of the network. This is one of the advantages of the ATM transport network.This paper considers the system where SDH signal is transported by ATM technique. The delay variation produced in the ATM transport network is evaluated. Then the buffer readout control and the required buffer capacity are discussed. The order of processing between the delay variation smoothing function and other required functions in the proposed system is analyzed.
Analysis of a magnetic resonance imaging antenna inside an RF shield
Authors: Ochi Hisaaki , Yamamoto Etsuji , Sawaya Kunio , Adachi Saburo 
Published: July 2007

AbstractOptimization of an antenna for magnetic resonance imaging (MRI) requires an accurate analysis of antennas located inside a conducting cylindrical RF shield. A Galerkin‐moment method analysis which can be used for an arbitrary‐shaped shield is used. The surface current on a conducting plane is expanded by means of surface patch segments based on Richmond's method. Numerical results are compared with measured input impedance, which confirms the validity of the proposed method. Furthermore, a relation between the dimension of shield and the sensitivity of the antenna is discussed theoretically.
Scattering from a periodic array of arbitrary shaped elements on a semiinfinite substrate
Authors: Kominami Masanobu , Wakabayashi Hideaki , Sawa Shinnosuke , Nakashima Hiroshi 
Published: July 2007

AbstractIn conjunction with a recent increase in information density, radio wave communication becomes more complex and more varied. Hence, effective use of radio wave resources is required. Under such a situation, the frequency‐selective screen (FSS) with which a single antenna is capable of receiving multifrequencies at the same time has drawn attention. The FSS consists of conductors placed periodically on a dielectric substrate.In this paper, the spectral domain moment method is applied to the problem of scattering from infinitely many conductors with arbitrary shaped elements on a semiinfinite dielectric substrate. From the results, the effect of the surface resistance of the conductor and the characteristics due to the conductor shape are investigated. Various scattering characteristics by linearly and circularly polarized incidences are discussed.
An analysis of atm cell loss probability based on virtual queueing system
Authors: Sato Shohei 
Published: July 2007

AbstractNumerous methods have been employed to analyze the traffic characteristics of an asynchronous transfer mode (ATM) communication system when multiplexed bursty traffic is applied to a single server. Some of the well‐known methods include solving a state equation numerically, approximating the arrival process by Markov modulated Poisson process (MMPP), and a fluid‐flow approximation method.This paper proposes a new approximating analysis technique employing fluid‐flow approximation that requires very small computational quantity. It also focuses on a queue where constant bit‐rate cell traffic and multiplexed N‐independent bursty cell traffic are applied to a finite buffer single server.The characteristics of cell generation during a cell‐overload period and a cell‐underload period are studied to derive a virtual queueing system. If the burst length and the burst interval of the original queue are distributed exponentially, it will be shown that this virtual queue is a GI/GI/1 queue.Finally, a method of calculating the cell loss probability by approximating this virtual queue is presented and it is shown that the results agree with the results of simulations and existing theories.
Adaptive antennas using a kalman filter
Authors: Wang Jinkuan , Takano Tadashi 
Published: July 2007

AbstractThis paper proposes an application of a Kalman filter for an adaptive array antenna. This method has an advantage in that the control gain can automatically be adaptable to the variation of the arriving signal and the convergence speed is high. The convergence condition to optimum weight coefficients is analyzed in the case where a Kalman filter is used for the control of the weight coefficients. By means of a simulation for a four‐element array antenna, it is confirmed that the directivity control error is small and the convergence is swift. The effect of the initial value of the unknown weight coefficient vector W(0) and the initial value P(0) of the estimated error covariance matrix on the convergence characteristics is studied. By means of the simulation, the range of allowable values is indicated. If W(0) and P(0) are chosen appropriately, the maximum error for the directivity control can be restricted to less than 1.5 degrees.
Unique word detection using quantized soft‐decision data
Authors: Sasai Hiroyuki , Takeyabu Masato , Minomo Ken , Takahata Fumio , Ogikubo Junichi 
Published: July 2007

AbstractThe efficacy of applying quantized soft decision data to unique word (UW) detection, which plays an important role in frame synchronization in digital radio transmission systems, is discussed considering hardware implementation. This UW detection method represents the received signal vector using representative points within a multidimensional space and measures the Euclidean distance from the vector point corresponding to the UW pattern.Probability calculations are employed for obtaining theoretically UW detection characteristics such as missed detection and false detection, assuming that white Gaussian noise is added to the signal during transmission. These various characteristics are then compared quantitatively with the characteristics obtained by the conventional UW detection method using hard decision data. In addition, the UW detection characteristics obtained experimentally using hardware are presented. As a result of the quantitative evaluations, it has been clarified that the application of soft decision data is effective in reducing the UW length required for objectives of the UW detection performance associated with frame synchronization characteristics.
Design of optical connectors with ID modules
Authors: Ohtsuki Fumio , Yamashita Katsuya , Yamamoto Yoshikazu 
Published: July 2007

AbstractTo improve the present conventional management system for further expansion of line facilities, a new system which has an automated, real‐time updating capability of system data has been proposed. The design principle and the result of SC2‐ (in‐house single wire) and MT‐type (outside, single∼multiwires) optical connectors with ID modules, which are the key components for this proposed system are presented in this paper. For the design of those connectors, the requirement for the ID module memory device is clarified and a serial‐type electrically‐erasable programmable ROM (EEPROM) is demonstrated to be the most suitable as a memory element.For further designing an integrated structure with connectors to avoid the degradation of the operationality, the packaging is discussed. As a result, the SIP‐type ID modules are located at one side of a connector. To minimize the contact‐loss fluctuation, the design for the structural and mechanical characteristics is discussed where a lateral force or electrode insertion force required to attain a desirable electrical resistance is evaluated. A prototype connector has been fabricated, which exhibits a contact loss change of ‐0.01 dB (SC2) and +0.02 dB (MT) and also a dynamic loss fluctuation level of less than 0.1 dB at the time of a connector insertion. Further, a contact resistance of less than 4 mμ (target: less than 40 mω), the package density of 1.5 to 1.8, and the connector loading time of 1.0 to 1.08 were obtained, which are comparable to the conventional case.