bluuebunny/crossref_metadata_2025_split huggingface dataset:
Asymptotic analysis of whispering‐gallery mode radiation from the aperture of cylindrical concave conducting boundary
Authors: Goto Keiji , Ishihara Toyohiko 
Published: July 2007

AbstractAn asymptotic analysis is discussed for the radiating field when a whispering gallery (WG) mode is radiated from the edge aperture plane of a cylindrical concave conducting boundary and is propagated as a beam. the integral representing the radiation field derived by the method similar to the one used in the problem of diffraction of a plane wave from a semiinfinite conducting plane is evaluated by means of the saddle point method taking into account the existence of the poles and the residue theorem.An asymptotic representation for the beam wave is a combination of the geometric optical ray and the edge diffracted ray. the phenomenon of the radiation of a geometric optical ray from the edge aperture and the phenomenon of diffraction of the modal ray at the terminating edge are clarified. the asymptotic solutions applicable in the shadow boundary, reflection boundary, and the nearby transition region caused by the incidence of the modal ray onto the edge are compared with those obtained by the Fresnel‐Kirchhoff formula so that the effectiveness of the asymptotic expression is determined. Also, it is demonstrated numerically that the radiation field expression based on the diffraction coefficients by the GTD cannot provide good results in the transition region. Further, propagation phenomena of beam fields are clarified from numerical results and the geometrical picture obtained from the ray tracing technique.
Pre‐interference canceller for digital microwave radio systems
Authors: Watanabe Kazuji , Uwano Syuta , Matsue Hideaki 
Published: July 2007

AbstractAs radio communication has progressed, reduction of intersystem interference has become a problem. In a conventional interference canceller, the interference signal as a source of cancellation is obtained at the receiving station and the interference component in the desired signal is canceled based on this interference signal. However, the interference signal for cancellation may not be obtained at the receiving station. As a remedy, an extraction and reinjection‐type interference canceller has already been proposed.In this paper, a pre‐interference canceller is proposed in which, if the transmitting station of the desired signal and that of the interference signal are identical, the interference signal is mixed with the desired signal from the transmitting station beforehand and the interference signal leaking into the desired signal is cancelled at the receiving station.First, the applicable range and the fundamental configuration of the present canceller are presented. Subsequently, the method for determining the amplitude and phase of the interference signal injected into the desired signal of the transmitting station and the method for evaluation of the cancellation effect are presented theoretically.Next, an experiment is carried out with the desired signal of 16 QAM or 256 QAM and the interference signal of 256 QAM. Interference improvement by about 20 dB is obtained for both the 16 and 256 QAM signals. Also, the response speed of control for the fading is 60 ms. In addition to the validity of the theoretical results, effectiveness of the proposed canceller is shown.
Picture coding making use of B‐spline surfaces
Authors: Watanabe Toshiaki 
Published: July 2007

AbstractWhen the B‐spline surface is used in the image representation, it suffices only to apply the image processing to the polygon vertices to derive the same result as in the processing of the whole original surface. If a compression method is established in which the points on the B‐spline surface are considered as the original image data and polygon vertices are regarded as coding data, the image processing can directly be applied to the compressed data, i.e., the polygon vertices. This results in more efficient storage, transmission, and display of the image. However, no study has been made concerning the application of the B‐spline to the compression coding of the surface.This paper considers the application of the B‐spline with the forementioned features to the compression coding of the image and discusses the application techniques and performances. As a result of simulation, it is seen that by adaptively determining the parameters for the surface generation and the number of polygon vertices according to the context of the image, a performance equivalent to or better than the performance of the conventional discrete cosine transform (DCT) can be realized. In other words, the B‐spline surface can well be applied to the compression coding.
A reception scheme switching between equalization and differential detection in frequency‐selective fading mobile radio channels—delay‐spread detection and adaptive reception control
Authors: Suzuki Hiroshi , Fukawa Kazuhiko 
Published: July 2007

AbstractA new reception scheme in which an adaptive equalization‐linear reception circuit and delay detectionlimiter reception circuit are switched optimally on a frequency‐selective fading mobile radio channel with a varying delay spread is proposed. First, the two‐path frequency selective fading propagation model is classified into a fixed delay model and time‐varying delay model in which delay varies according to Markov process. Next, a receiver state model suitable for these propagation models is proposed. the receiver consists of three states: (i) limiter amplifier and delay detection; (ii) linear amplifier and equalizer; and (iii) linear amplifier and baseband delay detection. In addition, a delay spread sensor detecting the delay wave component ratio for state transitions is proposed.Finally, various characteristics have been clarified by computer simulations. It has been clarified that the ratio for selecting adaptive equalization under flat fading can be less than 0.4 and 50 percent with one symbol delay frequency‐selective fading in a delay‐fixed model, and characteristics are infiuenced by the time constant of the processing in a delay transition model.
Performance analysis of a fully digitized multilevel modem for high‐capacity digital radio systems
Authors: Okada Takashi , Aikawa Satoru , Shirato Tadashi 
Published: July 2007

AbstractThis paper considers the modem which has the features of high precision, high‐level functions, adjustment‐free operation, and low cost, to provide high‐capacity transmission and to cope flexibly with various radio communication systems. A fully digitized modem is investigated, in which the digital signal processing techniques are applied up to the IF band.This paper shows the effects of the quantization level, the aperture effect and the clock jitter, which are the major deteriorating factors of digital signal processing (DSP), on the multilevel modem. an analysis method based on the equivalentC/Ndegradation is proposed, and fixed degradation of the modulation/demodulation systems is calculated quantitatively. It is verified as a result that when the method is applied to the devices on the market, the fixed degradation is approximately 2 dB in 256 QAM, which is nearly the same as in the modem with the conventional configuration.It is seen also that the effect of the degrading factors depends on the number of levels. When the number of levels is small, the quantization level has the dominant effect, and when the number of levels is large, the aperture effect, as a factor for the waveform distortion, is the dominant effect. Finally, a fully digital modem is constructed experimentally. As a result of the performance evaluation, the validity of the analysis method is verified by experiment.
Approximation of video cell traffic by AR(1) + IPP‐model
Authors: Onth Kazuyuki , Nakagawa Kenji 
Published: July 2007

AbstractFor a network design and a cell traffic control in an asynchronous transfer mode (ATM) system, it is significant to construct a stochastic model to represent bursty cell streams. As models of bursty cell streams, a Markov modulated Poisson process (MMPP) model and an autoregressive process of order 1 (AR(1)) model have been studied. the MMPP is a process which is based on the Poisson processes, so the MMPP allows the exact queueing theoretic analysis to provide some performance measures. However, it is not capable of expressing the autocorrelation of the cell stream directly. Moreover, the MMPP requires considerable calculation time to achieve the exact analysis.The AR(1) process has advantages of a simple form and the capability of directly expressing the auto‐correlation of the cell stream. However, it cannot follow a rapid change of the cell stream.This paper adopts the AR(1) as a model of the basic cell stream and combines the interrupted Poisson process (IPP) to follow a rapid change. the AR(1) + IPP is proposed to model a video cell traffic, which is the most important source in ATM networks. By applying an approximation technique, the cell loss probability of the system is analyzed. With respect to the accuracy and the calculation time, the proposed model is compared with other conventional models to confirm that the proposed model is superior to the others.
Traffic design method for large‐scale switched telecommunication networks
Authors: Masey Kenichi , Kawano Hiromichi 
Published: July 2007

AbstractWith the widespread telephone service and the introduction of various services, the scale of the switched telecommunication network is expanding. the adequate traffic design of the switched telecommunication network is important in improving the efficiency of the use of the communication network facilities.This paper considers the large‐scale switched tele‐communication network with various local structures and proposes a method for the traffic design. First, it is intended to simplify the design of the large‐scale switched telecommunication network without introducing the network partitioning or the unrealistic concept. For this purpose, the hierarchical concept composed of the traffic network and the circuit network is introduced. Then, the methods for the network structure design and the traffic assignment are presented for the traffic network and the circuit network, respectively. For the former, the design is considered with the specification by the designer as the minimum requirement for the locally inhomogeneous network structure. A method is shown to realize the whole network as a combination of basic elements. For the latter, the minimization of the number of additions in traffic counter is considered. A detailed algorithm is presented, and the effectiveness is shown through numerical examples.
A simulator using transputers for evaluation of multilayered protocols
Authors: Saito Tadao , Aida Hitoshi , Fujita Hirofumi , Saadan Zokaei 
Published: July 2007

AbstractBecause of the trend toward high‐speed data communication, various protocols have been proposed. the behaviors of those protocols are complex and therefore various studies have been made on the performance evaluations. the authors have been studying the theories and the evaluations of the protocols for the cases where the bit error rate is negligible. However, it was difficult to evaluate the cases where the bit error rate is not negligible yet is low enough for use.To evaluate those cases, a protocol simulator was made which uses the transputer for the network nodes and the network links. In this paper, the configuration and the implementation of the simulator are explained in detail and the result of the simulation is discussed briefly.
Optical DPSK/Heterodyne‐. Detection scheme using two polarization planes
Authors: Tsukamoto Katsutoshi , Kuwano Shigeru , Morinaga Norihiko 
Published: July 2007

AbstractThis paper proposes the dual polarization DPSK (DPDPSK) as an extension of the polarization modulation to the narrowband system. the basic performances are examined. First, it is shown that the proposed scheme occupies half of the signal bandwidth of the polarization modulation scheme, the receiver configuration is the same as that of the polarization modulation, and the phase noise insensitivity, which is the feature of the polarization modulation, is utilized effectively in the proposed system.Assuming a receiver with the double‐filtering configuration, a theoretical analysis for the receiver error rate is presented, considering the envelope fluctuation due to the phase noise at the bandpass filter (BPF) output, as well as the additive noise suppression by the lowpass filter (LPF) in the demodulator. It is shown that the optimal BPF bandwidth exists that maximizes the receiver sensitivity.
Performance evaluation of a lightweight logical link control protocol in slotted ring networks
Authors: Hirabayashi Koji , Ishibashi Yutaka , Tasaka Shuji 
Published: July 2007

AbstractThis paper evaluates the performance of a fast select connection oriented (FS‐CO) logical link control (LLC) protocol in slotted ring networks. the FS‐CO‐LLC protocol is one of the light‐weight protocols. It employs a method of implicit connection establishment and release to reduce overhead of connection control. l'his paper analyzes the performance (throughput and average response time) of a slotted ring network in which a single slot circulates by means of Equilibrium Point Analysis. the performance in the case of plural slots is evaluated by simulation. This paper also compares the FS‐CO‐LLC protocol with connection‐oriented (CO) and connection‐less (CL) LLC protocols. Numerical results show that the performance of FS‐CO‐LLC and CL‐LLC protocols is superior to that of CO‐LLC protocol when the average message length is smaller than the buffer size. On the other hand, when the average message length is larger than the buffer size, CO‐LLC protocol has the best performance. It is also shown that the per formance of FS‐CO‐LLC protocol does not‐degrade but CL‐LLC protocol does, even if the average message length becomes larger.
An antenna tracking method for land‐mobile satellite communications system
Authors: Yamamoto Shin‐Ichi , Tanaka Kenji , Wakana Hiromitsu , Ohrnori Singo 
Published: July 2007

AbstractA new satellite‐tracking method is proposed for a directional antenna installed on a car for L‐band land‐mobile satellite communication. This method uses both a fiber optic gyroscope (FOG) and a magnetic compass (MC) with an open‐loop control algorithm, which com pensates for the disadvantages of individual sensors. Since FOG can detect the angular velocity precisely but cannot detect the absolute azimuthal direction, this type of sensor has inherent errors due to accumulating the angular velocities necessary to obtain the azimuthal direction. Cumulative errors caused mainly by a disagreement between the FOG axis for measuring rotation and the vertical axis during turning curves can be compensat ed by MC. the disadvantage of MC is that errors due to magnetic disturbance are caused by magnetized bridges and trucks. In the proposed method, the occurrence of a magnetic disturbance is detected from a statistical analysis of MC acquired data and FOG is used to control the antenna direction when a car turns either right or left. According to an analysis of the three‐dimensional motions of cars, it was determined that only azimuthal antenna tracking can provide the precise control required to obtain good tracking performance, even when using an 91 L‐band directional antenna with an antenna gain of ap proximately 13 dBi.
MAC address test protocol for a reconfigurable dual‐ring local area network
Authors: Nakayashiki Susumu , Kashio Jiro , Harakawa Takeshi 
Published: July 2007

AbstractThe address of the ring local area network (LAN) station most be unique in the ring. This paper considers the distributed control‐type ring LAN with the configuration management function and proposes an MAC layer address test protocol, which can avoid the duplication of MAC addresses. In the ring LAN, the number of stations contained in the ring is increased or decreased by contraction or expansion of the ring.The duplication of addresses can occur due to the change of the stations, i.e., the set of MAC addresses. Consequently, the proposed system executes the duplicat ed address test being aligned to the ring connection of the station or the ring reconfiguration. the station executes the duplicated address test by the same protocol for various topologies of the ring LAN, such as the single ring, the simple dual ring, and the dual ring with the hierarchical star‐ring structure. By the proposed protocol, it is possible to construct the ring LAN so that the stations have an inherent MAC address no matter how the ring may be reconfigurated.The proposed algorithm is described by the finite‐ state machine (FSM), and a series of processing flows is shown for the address test accompanying the ring reconfiguration. the proposed protocol is included in the IEEE Recommended Practice for the duplicated address test in the dual‐ring LAN with the ring reconfiguration function.
A method to place micro radio zones in mobile packet communication with a chained isolated radio zone network system
Authors: Take Keijiro , Mita Yasuhiro , Oh‐ishi Tetsuya , Tominaga Hideyoshi 
Published: July 2007

AbstractThe authors have already explored a mobile packet communication system for car drivers in which navigational information (maps, pictures, and voice) and stored information (voice message, facsimile, and data) could be sent by common format packets. Because the radio zones in these systems are isolated from each other, efficient use of radio frequencies is desirable. However, since traffic distribution and automobile speeds differ at different locations, the position and number of radiozones has a large effect on system efficiency. This paper describes a method in which radio zones are placed on a given route network by using a car traffic flow simulator that is applicable to mobile communication. Car motion and speed are simulated; the volume of traffic in each radio zone and the traffic that can be processed in each zone are calculated using a model that is quite close to an actual route network. These values are compared with transmission efficiency in a single radio zone. Radio zones are located by deleting existing radio zones that have had poor transmission; relevant results are then discussed.
Equivalent permittivity analysis for periodic wedge‐type absorber using transmission mode approximation
Authors: Aoyagi Takahiro , Nishikata Atsuhiro , Shimizu Yasutaka 
Published: July 2007

AbstractTo obtain a matching over a wide frequency range, pyramid‐type and wedge‐type matching layers are used in front of the multilayered wave absorbers. In this paper, a transmission mode approximation is proposed in which the period of the wedges and the incident polarization direction are taken into account in the calculation of the characteristics of a wedge‐type wave absorber. the degree of difference of the equivalent permittivity derived by the propagation mode approximation from the one by the conventional method (corresponding to the low‐frequency limit) is presented by numerical calculations. It is also shown that there is a difference from the wave absorber characteristics derived by the conventional method even at a wavelength longer than the wedge period. the tendency of the reflection to increase at the higher frequency side is visually explained by replacing it with the taper shape.
Effect of number of packets sent simultaneously to the same output and input buffer
Authors: Yoshihashi Nobutomo , Sasase Iwao 
Published: July 2007

AbstractAn approximate numerical analysis to evaluate the mean waiting time and the blocking probability of the packet switch under first‐in/first‐out (FIFO) policy with speedup factor is performed. the improved input buffer control policy with speedup factorCis proposed to achieve small mean waiting time by computer simulation and compare the performance with conventional FIFO policy and longest queue policy. Under the proposed model, there are N/2 pairs of input buffers; if one input buffer is empty, the second packet in the queue of the other buffer is transferred to the other empty buffer. It is shown that speedup factor and proposed input buffer control policy can reduce the waiting time compared with conventional FIFO policy and longest queue policy.
Analysis on the mechanism of a tuning stub for circular‐polarized annular microstrip antenna
Authors: Ishii Nozomu , Itoh Kiyohiko 
Published: July 2007

AbstractIt is often not possible to operate a microstrip antenna with a probe feed with a zero reactance at the designed frequency because the self‐inductance of the probe is added to the input impedance. It is proposed that by means of matching stubs added on the periphery of the patch, this excess reactance is cancelled. Few examples exist on the analytical studies of the operating principle of such a proposal. In the present paper, it is noticed that this matching stub resembles by shape the metal piece added for separating the degeneracy in the design of a circularly polarized annular microstrip antenna with a one‐point feed. Then the effects of these two metal pieces and the feed pin are analyzed by the eigen function expansion method and the perturbation method. It is found that the excitation amplitude ratio of the two principal modes can be varied and the phase of the input impedance can be controlled by adding the matching stubs. Further, the design of areas and locations of the two metal pieces are investigated for generation of a circular polarization.
Remote node placement in optical fiber access networks
Authors: Iwashita Motoi , Tanaka Chihaya , Ikeuchi Noriyuki 
Published: July 2007

AbstractThis paper describes the principles of remote node placement for providing narrowband services in access networks. the system composite network configuration of the following three system configurations is clarified in terms of installation costs. Among the parameters considered are regional conditions (such as the area comprising an access network) and the number of demands to be made of the system.In single star configuration (SS), a copper pair is directly installed between a switching node and a customer; in a double star configuration (DS), a remote node is installed between a switching node and customers and an optical fiber is used between the switching and the remote nodes; and in a triple star configuration (TS), two remote nodes (upper and lower remote nodes) are installed in tandem.
Nondestructive optical fiber talk set
Authors: Azuma Yuji , Hasebe Mitsunori , Inaba Toyoaki , Kuwaki Nobuo 
Published: July 2007

AbstractCommunications between maintenance workers who work with nonmetallic optical cables must be conducted through optical fibers. Conventional communications were conducted by cutting the fiber at the cable joint. However, this reduces both operational efficiency and reliability. Based on the bending loss characteristics of optical fibers, we found that the light propagating in an optical fiber can be intensity modulated by U‐bending the fiber and changing the bending radius slightly. Then a nondestructive optical fiber talk‐set was developed without having to cut these fibers. In this paper, the relationship between the bending loss and modulation characteristics is investigated experimentally and the optimal bending width is determined. A talk system has been designed using terminal and intermediate talk‐sets. the required minimum modulation index and the insertion loss of the intermediate talk‐set are discussed considering the difference among fibers. the maximum line length and the allowable number of the intermediate talk‐sets are calculated based on the parameters. It is found that the allowable line length from terminal talk‐set to intermediate talk‐set and from intermediate talk‐set to intermediate talk‐set can be extended up to 80 km by adding repeater functions to the terminal talk‐sets.