bluuebunny/crossref_metadata_2025_split huggingface dataset:
Evaluation of radio frequency immunity test facilities based on the scattered field of a conductive sphere
Authors: Akiyama Yoshiharu , Kuwabara Nobuo , Ideguchi Tsuyoshi , Tokuda Masamitsu 
Published: July 2007

AbstractIn the radiation immunity test for telecommunication equipment, an electromagnetic applicator such as chamber, a transmission electron microscopy (TEM) cell and a general transmission electron microscopy (GTEM) cell are used. Characteristics that include a semianechoic uniformity of the electromagnetic field without a device under test have been evaluated. However, characteristics that include an electromagnetic field in the presence of the device under test have not been reported.In this paper, it is recognized that these electroamgentic applicators are designed in such a way that they can generate an electromagnetic field simulating a plane wave. Based on the electric field distribution generated by the plane wave incident on a conducting sphere, the electric field is evaluated and compared in the case in which the device under test is placed within the applicator. Further, evaluation results are included for the size of the device under test for which the immunity test is possible in each applicator. The evaluation method first derives the theoretical value of the scattered electric field when a plane wave is incident on the conducting sphere in free space.Next, these theoretical values are compared with the measured electric field values around the conducting sphere in each electromagnetic applicator. It was found that the difference between the measured and the theoretical results is the smallest and the frequency dependence is the lowest in a semianechoic chamber. In the case of a TEM cell and a GTEM cell, it was found that the difference between the measured and the theoretical values is less than +6 dB if the magnitude of the device under test is less than one‐third the spacing between the inner and outer conductors.
Real‐time air traffic flow management: Expectations and probabilities of delay
Authors: Qiao Mu , Morikawa Hiroyuki , Mizumachi Moriyuki 
Published: July 2007

AbstractAir traffic flow management is carried out with a view to maintaining smooth aircraft traffic. Real‐time air traffic flow control is to carry out the air traffic flow control responsive to a real situation in real time by express use of the present situation of the desired terminal region and the radar information.With a view to such real‐time air traffic flow management, this paper derives equations for the holding delay time expectation value of aircraft requesting take‐off, the delay time expectation value within the terminal, holding generating probability, delay generating probability in the terminal, and the flight delay generating probability. If in the future any departure‐regulating procedure for reducing the flight delay time of the aircraft requesting take‐off is developed based on the values found from these equations, it becomes possible to carry out the air traffic flow management adaptively to a real situation.
Application of millimeter‐wave radar traffic observation system
Authors: Shimoi Nobuhiro , Nakamura Yatsuka 
Published: July 2007

AbstractTraffic monitoring systems employ, as sensors, infrared image systems, visible light image systems, and so on. But observation with such monitoring systems are limited to highway interchange areas and intersections of large roads. Also, such systems often fail to detect vehicles hidden by obstacles such as roadside trees because the sensors are easily affected by weather conditions such as rain and dense fog.This paper discusses sensors using 94‐GHz millimeter‐wave radar in traffic observation systems. These sensors make it possible to observe hidden cars and to reduce the influence of weather and are unaffected by night and day conditions.In addition, it is possible to improve the observation ability by using both the current system and the 94‐GHz millimeter‐wave radar for unattended observation of traffic within the range of 1 km.
Still image transmission using unequal error protection coding in mobile radio channel
Authors: Matoba Naoto , Yoshida Susumu 
Published: July 2007

AbstractWith the advent of multimedia mobile communication, image transmission in the fading channel is becoming more and more important. This paper discusses the highly efficient coding where the image coding and the channel coding are integrated. More precisely, the following hierarchical image transmission is proposed. Assuming Joint Photograph Experts Group (JPEG) progressive image coding, discrete cosine transform (DCT) transform coefficients or the bit planes are divided into groups so that the unequal channel coding rates are assigned according to the effect of the channel error on the image quality. The proposed system is examined and evaluated by a computer simulation. As a result, it is shown that the reconstructed image suffers from less deterioration compared to the case where the channel coding rate is assigned uniformly.
Traffic design method for switched telecommunication networks with double homing and combined switching
Authors: Mase Kenichi , Kawano Hiromichi 
Published: July 2007

AbstractThis paper proposes the concept of partially combined switching which is useful in a network design with double homing and combined switching. Partially combined switching makes some of the switches that are found in a certain switch office play the same role as in a different switching office. With partially combined switching, both improvement in switch utilization efficiency and reduction in the number of switches are expected. The concept of hierarchy, such as traffic network, circuit network, etc., is introduced; within this framework the theory of network design with partially combined switching is developed. The changes in network topology and routing tables necessary in order to realize partially combined‐switching are shown here. A traffic assignment method is also shown for circuit networks with partially combined switching. It is pointed out that techniques such as one‐sided homing and combined hierarchy used for the present digital telephone network are examples of partially combined switching. Finally, numerical examples are presented to show that the partially combined switching is effective to reduce the number of switches in the network.
A fast traffic simulation method using vector operation
Authors: Tanaka Yoshiaki , Shimizu Sheyu , Kojima Akihiro , Tomochika Takeshi 
Published: July 2007

AbstractThe supercomputer is used widely at present in various research institutions, and it is quite usual to employ the supercomputer in the simulation. The performance of the supercomputer is improved steadily. A problem in the conventional traffic simulation, however, is that little vector computation is included and the speed of improvement of the simulation has been difficult even if a supercomputer is used.This paper aims at the effective use of the supercomputer in the traffic simulation. A vectorized simulation method is proposed where the simulation clock is advanced for each unit of time, and the call origination and the use of link are represented by a matrix or a vector.Simulation models actually are considered for the circuit‐switching network and the packet‐switching network. The vectorized simulation is applied to those models, and the performances are assessed, compared to those of the conventional method, in terms of the computation time, the call loss probability and the waiting probability. It is shown as a result that the execution speed is improved greatly within a certain range of the error, indicating that the proposed vectorized simulation is effective.
Indoor propagation calculation taking into account antenna patterns using geometrical optics method
Authors: Uehara Kazuhiro , Seki Tomohiro , Kagoshima Kenichi 
Published: July 2007

AbstractAn algorithm to compute the effects of the radiation patterns and polarizations of arbitrary transmit and receive antenna is added to the conventional geometrical optics analysis procedure to study indoor propagation delay characteristics. A method is presented in which the angular information needed for the calculations of the foregoing in a rectangular room can be derived easily from the geometrical nature of the room. By moans of the present procedure, the delay wave suppression effect of a narrow‐beam antenna in a multipath propagation environment is shown quantitatively. For instance, in the case where both transmit and receive antennas are omnidirectional, the delay spread can be reduced to almost one‐tenth if a pencil beam with a half‐power beamwidth of 30° is used. By means of these results, a design procedure for antenna half‐power beamdwidth and the polarization was developed for realization of high‐transmission quality in an indoor high‐speed wireless data communication.
Reachability analysis for communication service specification descriptions in global state transition rules
Authors: Sato Masakazu 
Published: July 2007

AbstractThis paper discusses fundamental characteristics in reachability analysis of communication service specifications defined by means of production rules. In the conventional service specifications, reachability has been analyzed within a finite number of communication processes. However, it is necessary to deal with infinite processes to verify state reachability of the global transition description of the production rules. If the reachability state as a reachable subglobal state constructed with a number of processes is defined, the size of the reachability state set depends on the number of processes at the initial state. In general, the system is analyzed on the assumption of an infinitive number of processes to verify reachability. This paper presents the relationship between the size of the reachable set and the number of processes in the system. It also shows the existence of the upper bound of the reachable state set and a method to obtain the minimum number of processes that gives the upper bound of the reachable set. This study makes it possible to analyze the reachability of an infinite number of processes by a reachability problem of finite number of processes.
Frequency agility radar with doppler processing
Authors: Maeda Seiichi , Sueda Hachirou , Itoh Toshiharu 
Published: July 2007

AbstractIn the frequency agility radar in which the transmit frequency of the radar can be changed at an ultrahigh speed, not only is excellent electronic counter countermeasure (ECCM) performance obtained but also improvement of the detection probability of the object with a fluctuating reflection cross section is expected. However, in the conventional‐type radar, the frequency is modified at a high speed so as to change the entire pulse. However, the standard Doppler process is not possible.In this paper, in order to add a Doppler processing function to a frequency agility radar, the clutter is suppressed with one pulse and the obtained object signal is integrated coherently. The method and the simulation results are presented.
Air traffic control data tables for conflict alert system
Authors: Miura Akira , Morikawa Hiroyuki , Mizumachi Moriyuki 
Published: July 2007

AbstractThe conflict alert system was developed for air traffic control to detect and warn of the danger of aircraft collisions. This paper presents a configuration for air traffic control data tables that increases the efficiency of the conflict alert system, which was devised to predict what instructions to give for preventing collisions. Air traffic control data tables are constructed mainly from air route data and aircraft data. The aircraft are controlled by the air route unit, and all data as well as the relationships between the data (i.e., between aircraft, between aircraft and air routes, etc.) are updated continually in real time for the data tables in question. As a result: (1) the relationship between the aircraft and the air route can instantly be grasped, thereby improving the accuracy of the course prediction for the aircraft; and (2) when judging if two aircraft are possibly in conflict, the efficiency of the conflict detection process can be improved by rapidly being able to grasp the relative relationships of aircraft on adjacent air routes and the relationship between the leading and last aircraft on the same course. The feasibility of the points (1) and (2) is demonstrated through computer simulation.
Performance of modulation‐level‐controlled adaptive modulation systems
Authors: Otsuki Shinya , Sampei Seiichi , Morinaga Norihiko 
Published: July 2007

AbstractThe multivalued quadrature amplitude modulation (QAM), such as 16 QAM, is a very useful technique in land mobile communication since a high‐speed transmission can be realized without enlarging the transmission band. The technique has a problem, however, in that it is not robust against the decrease of the received signal level due to fading or the effect of the delayed waves, which easily deteriorates the transmission quality. To solve such a problem, this paper proposes an adaptive modulation system where the number of modulation levels is adjusted according to the condition of the channel. In the proposed system, the instantaneousC/N0and the delay spread are estimated as the condition of the channel, using a method based on time division multiple access/time division duplex (TDMA/TDD).When the channel is in a good situation, a highspeed transmission is executed using a larger number of modulation levels such as 256 QAM. When the channel is in a bad condition, a modulation method with a small number of modulation levels, such as quadraphase‐shift keying (QPSK), is used, which is robust against the noise or the delayed waves. By this scheme, it is possible to realize a high‐speed transmission without deteriorating the transmission quality, compared to the conventional system with the fixed number of modulation levels. The transmission performance is evaluated by a computer simulation, and it is shown that a high‐speed transmission can be realized without deteriorating the transmission quality, compared to the QPSK system, in the uniform Rayleigh fading condition as well as in the situation containing delayed waves.
Coefficient‐based adaptive transform coding scheme
Authors: Hamada Takahiro , Matsumoto Shuichi 
Published: July 2007

AbstractA coefficient‐based, adaptive, orthogonal transform coding scheme is proposed to enhance the performance of interframe DPCM/orthogonal transform coding which has currently become the mainstream coding method in use for video signals. In this proposed scheme, the widely used block‐based inter‐ and intracoding modes are supplemented by introducing a new coding mode, the “mixed mode,” that has the characteristic of optimally controlling prediction and quantization on an orthogonal transform coefficient basis. Based on a statistical model of the video signal, it is shown that the prediction coefficients and quantizer of the proposed scheme can be theoretically optimized. Results from computer simulations on real images show that in terms of an objective evaluation measure (weighted signal‐to‐noise ratio) that reflects properties of the human visual system, that a performance gain of 4.6 dB over the H.261 standard is obtained and 3.4 dB gain over MPEG is obtained. From the perspective of subjective evaluations, it is shown that it is possible to greatly reduce block noise, of course, in exchange for some resolution degradation from mosquito noise.
Fault location on optical amplifier submarine transmission systems
Authors: Sumida Masatoyo , Amemiya Masaki , Furukawa Shin‐Ichi , Tanaka Kuniaki 
Published: July 2007

AbstractThis paper addresses some solutions to overcome the problems that arise when optical time domain reflectometry (OTDR) is applied to optical amplifier submarine transmission systems. It designs a backscatter path that feeds the backscattering into the opposite line without causing any degradation in the main signal transmission. This paper proposes a new modulation format, FSK‐ASK, and confirms that the proposed approach can both eliminate optical surge generation and improve OTDR performance. An FSK‐ASK OTDR is applied to an 890‐km commercial amplifier submarine transmission system with a 90‐km span. Field trials successfully demonstrate that the OTDR can locate a fault in all spans with a spatial resolution of 1 km after averaging the sum of 220measurements. The FSK‐ASK OTDR proves to be very useful in maintaining a reliable submarine transmission system because it can locate subtle fiber anomalies along the entire length from a terminal end.
Link control method for improving packet transmission efficiency for store and forward communications by LEO satellites
Authors: Nakayama Tsuyoshi , Hamamoto Naokazu 
Published: July 2007

AbstractFor a communication system using LEO satellites, a simpler method that will improve link transmission efficiency is indispensable in cost reduction. A new link control method is proposed to improve packet transmission efficiency for store and forward communication systems using LEO satellites. With this method, the throughput is improved by controlling the request of user terminals by the control packets from a satellite allocating slots for information packets in reserved frames of variable length. Performance of the proposed method is evaluated by computer simulation; the result has revealed that the method improves the throughput twice as much as the variable calling rate slotted ALOHA system.
A method of designing feed‐array excitation coefficients for array‐fed reflector‐type reconfigurable beam antennas
Authors: Naito Izuru , Chiba Isamu , Makino Shigeru , Mano Seiji 
Published: July 2007

AbstractReconfigurable beam antennas are suitable for on‐board antennas from the point of view of frequency reuse, satellite power utilization, and flexibility for traffic demand variation. In this paper, an efficient design method of the feed‐array excitation coefficients for array‐fed reflector‐type reconfigurable beam antennas is proposed. The feed‐array is composed of several subarrays, and only amplitude between subarrays is controlled to achieve reconfigurability. Excitation coefficients of subarrays and amplitude between subarrays are determined efficiently by the proposed design method. The method is verified by a design example for an international communications satellite application.
Numerical analysis of self‐focusing effect caused by inhomogeneity of microwave energy density in ionosphere
Authors: Shinohara Naoki , Matsumoto Hiroshi , Shklyar David R. 
Published: July 2007

AbstractIn this paper, the results of numerical analysis based on the theoretical analysis of the self‐focusing effect when a microwave beam propagates through the ionospheric plasma from the solar power station (SPS) to the ground are shown. The self‐focusing effect of the microwave beam is either caused by the plasma heating by the microwave beam or caused by the spatial gradient of the electromagnetic beam intensity. In this paper, the latter case is discussed. Since the microwave frequency used in the SPS is six orders of magnitude higher than the maximum collision frequency in the ionosphere, the theory used in this paper assumes a collisionless plasma and is derived from Maxwell's equations and the equation of motion. The self‐focusing effect of the microwave beam predicted by the theory is determined by five parameters: plasma density and temperature; microwave frequency; intensity; and the spatial gradient of intensity. In this paper, based on the results of the numerical analysis of the theoretical equations, the self‐focusing effect under the parameters related to the microwave beam used in the energy transmission of a future SPS is described.
Evaluation of pseudonoise sequence in time spread pulse position modulation/code division multiple access systems
Authors: Date Toshitaka , Zhou Xuping , Oka Ikuo , Fujiwara Chikato 
Published: July 2007

AbstractTo evaluate the processing gain performance of the binary maximal‐length sequence (m sequence), the Gold sequence and the Kasami sequence in a time spread pulse position modulation/code division multiple access (PPM/ CDMA) system, the merit factors of these sequences are calculated and a lower bound on the processing gain of a time spreading filter is derived using the merit factors. It is shown that, under the condition that the sequence length is large, the merit factor of the m sequence approaches 3, the merit factors of the Gold sequence and the Kasami sequence approach 1, the m sequence having the strongest impulse noise resistibility. Furthermore, the cross merit factor between two pseudonoise sequences is defined as a parameter expressing the capability of suppressing multiple access interference. It is shown that the cross merit factors of m sequences, synchronous Gold sequences, and good synchronous Kasami sequences approach 3, and the cross merit factor of bad synchronous Kasami sequence having the strongest multiple access interference suppression capability and the bad synchronous Kasami sequence having almost no multiple access interference suppression capability.
Evaluating the performance of the dynamic bandwidth reservation method using link utilization information in automatic transfer mode local area networks
Authors: Wakamiya Naoki , Murata Masayuki , Miyahara Hideo , Ikeda Chinatsu 
Published: July 2007

AbstractWith the improvement of the speed of computers in recent years, there is required a local area network (LAN) that can realize a high‐speed broadband communication. For this purpose, asynchronous transfer mode (ATM) LANs based on ATM technique is considered important.This paper considers the bandwidth reservation control as a means of traffic control in ATM LAN and evaluates the performance by simulation. The evaluation is made for the following methods of congestion control: ACK/NACK method, based on the ACK/NACK signal which is returned when the bandwidth reservation succeeds/fails; the dynamic ACK/NACK method, which is an improvement so that the control can be adapted to the traffic load; and control method based on the link information from the switch.It is shown for the single‐stage switching network that the dynamic ACK/NACK method has a better performance when the traffic is low but the control method based on the link information has the highest performance when the traffic is high. It also is shown for the three‐stage switching network that the control method based on the link information has the highest performance.
Bit‐error rate performance of block‐coded modulation systems under rayleigh fading
Authors: Okada Minoru , Hara Shinsuke , Morinaga Norihiko 
Published: July 2007

AbstractA block‐coded modulation (BCM) system estimating the complex amplitude variations of a channel by Kalman estimation is proposed and evaluated in this paper. A differential BCM system estimating a channel equivalently by differential encoding, on Rayleigh fading channels, is also presented here. To evaluate the propagation characteristics of the proposed BCM systems accurately, the upper bounds of the bit‐error rate (BER) of BCM are derived, considering the estimation error of the complex amplitude variations of a propagation channel; the BER characteristics of the systems on Rayleigh fading channels are analyzed by the derived upper bounds of the BER and computer simulation. Analyses show that the upper bounds derived are effective in evaluating the BER characteristics of the BCM systems when there are channel estimation errors and the proposed BCM systems operate effectively even when channel estimation errors exist.