bluuebunny/crossref_metadata_2025 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

An 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

As 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

When 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

A 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

This 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

For 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

With 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

Because 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

This 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

This 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

A 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

The 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

The 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

To 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

An 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

It 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

This 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

Communications 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.
Calculation on complex multiple reflection in optical fiber transmission lines
Authors: Tachikura Masao
Published: July 2007

Calculation techniques have been developed for the accurate evaluation of the relative intensity noise due to forward reflection in optical transmission lines. Discrete reflections at connection points and Rayleigh backscattering in fibers are taken into account in the calculations. Formulas for simplified models and a numerical calculation algorithm for practical models are investigated.

Numerical results for a typical subscriber loops with a total fiber length of 7 km reveal for the first time that Rayleigh backscattering has a strong influence due to its interactions with discrete reflections. Variations in the total amount of forward reflection caused by variations in the reflectance of connection points, the connection loss, and the connection spacing also are analyzed by computer simulation.
Digital phase‐locked loops with a wide locking range using a fractional divider
Authors: Sato Fumiyo , Saba Takahiko , Mori Shinsaku , Park Duk‐Kyu
Published: July 2007

Digital phase‐locked loops (DPLLs) are currently used widely in communications. However, conventionally used DPLLs have narrow locking ranges and long acquisition times. Although various types of DPLLs capable of overcoming these problems have been proposed, most of the DPLLs proposed have complicated circuit structures without significantly improved locking ranges. This paper proposes a new broadband DPLL with simple circuit configuration, a very wide locking range and fast acquisition time. to implement a wide locking range, the DPLL uses a fractional frequency divider that eliminates frequency error by changing the high‐speed clock according to the input frequency. After eliminating frequency error, the DPLL adjusts the phase of both the input and output signals by resetting the frequency divider in order to implement a fast acquisition time. This eliminates initial phase error. In addition, this system has a very simple configuration; only a fractional frequency divider is added to the simplest conventional binary quantized DPLL. the proposed DPLL is very practical because of its very wide initial locking range and the fact that the design of the DPLL does not depend on the system requirement as is the case with a conventional DPLL.
Capacity expansion problems based on fuzzy dynamic programming
Authors: Ueda Tohru
Published: July 2007

This paper discusses capacity expansion problems for telecommunication network facilities, based on fuzzy dynamic programming. Although cost functions, discount rates, demand functions, and so on should be given, they usually cannot be defined clearly because of technical developments or business fluctuations. This paper represents undefined factors by fuzzy numbers with triangular membership functions (TFN). Multiplication or division of TFN does not give rigid TFN, but we approximate them to TFN for ease of calculation. Three methods based on this approximation are compared, using numerical examples. Approximation accuracies are confirmed by strict calculation using removal of defining orders of fuzzy numbers.
A mobile packet communication with a chained isolated radio zone network system
Authors: Take Keijiro , Mita Yasuhiro , Oh‐Ishi Tetsuya , Tominaga Hideyoshi
Published: July 2007

A mobile packet communication with a chained isolated radio zone network system is proposed that provides nonrealtime media services including voice messages, images, and navigation information, etc., to terminals in cars. In this system, microradio zones are located along a road to establish the communication between a radio base station and a terminal by using packets in a common format. A terminal receives the signal by the paging channel covering a wide area and transmits packets sequentially when a terminal passes radio zones. Therefore, only three radio frequencies, inbound, outbound, and paging channels, are enough and location registration of all terminals is not necessary to realize the proposed system. When transmission and reception of multiple packets is not completed in a single radio zone, it can be done in other radio zones. Since every terminal has a different staying time in each radio zone, the relationship between staying time and throughput, and the relationship between staying time and message transmission ratio are examined and evaluated by the simulation.
Phase‐tracking viterbi demodulator
Authors: Serizawa Mutsumu , Asakawa Shigeru , Murakami Junzo
Published: July 2007

The maximum‐likelihood sequence estimation reception system, where the transmitted signal sequence is decided by the maximum likelihood using Viterbi algorithm, from the modulated signal, such as the phase modulated convolution‐coded signal, TCM, and CPM, is considered to be very interesting because of its excellent signal‐to‐noise ratio (SNR) versus error rate performance. Such a system assumes the coherent detection of the received signal in order to realize excellent performance. The reception system, which is expected to follow the carrier with a large offset and a low SNR, has been difficult to realize due to the difficulty of satisfying the requirement. This paper proposes the following system. The phase‐locked loop is provided corresponding to each survival path in the Viterbi algorithm used in the estimation of the maximum‐likelihood sequence estimation. The phase‐locked loop is selected in parallel to the selection of the survived path. In other words, the phase synchronization and the (maximum‐likelihood) sequence estimation are simultaneously achieved. The system is discussed in detail, and it is shown that a stable coherent detection can be realized for a very low SNR.
Relative orbit determination experiment by ground‐based differential angle tracking
Authors: Sawada Fumitake , Kawase Seiichirou
Published: July 2007

When more than one satellite is operated nominally at the same longitude of the stationary orbit, there is a danger of collision. At present, to avoid the collision, the cooperative station‐keeping is applied so that the spacing of the satellite orbits is maintained as evenly as possible. In this method, however, it is difficult to cope with the situation when a larger number of satellites is operated at the same longitude in the future. From such a viewpoint, it is intended to apply the relative orbit determination by the differential angle tracking to the orbit monitoring of multiple satellites.

An experiment for accuracy evaluation is executed using the satellites in operation. The position of the satellite, which is to be used as the reference in the evaluation, is calculated by calibrating the present orbit‐determination system. The orbit is calibrated by observing the close satellites by a large telescope on the same scene and measuring accurately the differential angle between the two satellites. The accuracy of the relative orbit determination is evaluated by the differential angle measurement using the calibrated orbit‐determination system and it is seen that the relative position of the two satellites can be estimated with the accuracy of 1 km. In other words, it is seen that the relative orbit determination by differential angle tracking can be executed practically for monitoring the approach of satellites.
Transmission efficiency of spread ALOHA system using unified spread‐spectrum code
Authors: Sasamori Fumihito , Takahata Fumio
Published: July 2007

This paper considers the direct‐spread ALOHA system using the same spread‐spectrum code where the individual packet signals are separated using the time compression of the output signal from the matched filter in the demodulator. A method is shown to derive theoretically the transmission efficiency of the system and then the performance of the spread ALOHA system of the spread code length of seven chips is shown as an example. The transmission efficiency (channel traffic performance and the throughput) of the system is compared to that of the conventional slotted ALOHA system and discussed quantitatively. It is shown that the spread ALOHA system can realize a good performance with a low peak transmitted power.
Characteristic of linearly polarized aperture array antenna
Authors: Tsukamoto Katsuya , Arai Hiroyuki
Published: July 2007

As a radiating element for a triplate‐type antenna, an array antenna excited by the electromagnetic coupling by the feed probe through an aperture on the upper conductor was analyzed by the spectral domain method under the assumption of a periodicity. From the comparison of the computed results and the measured data, the unloadedQand operating frequency agreed well from the engineering viewpoint so that the effectiveness of the analysis method is confirmed. Further, from the calculations of the electromagnetic field at the resonance of the antenna, it is found that the parallel plate mode under the aperture elements become a standing wave and that the resonance condition is when the field distributions are in phase at the elements. From the findings, it is clear that the antenna becomes highly efficient when the period of the standing wave of the parallel plate mode and the antenna element spacing coincide.
High resolution time‐domain measurements of signals with an exponential amplitude frequency dependence
Authors: Ohshima Kohzoh , Ogawa Yasutaka , Itoh Kiyohiko
Published: July 2007

The time‐domain measurement using the multiplication signal classification (MUSIC) algorithm is effective for measuring various electromagnetic circuits and antennas as well as for analysis of electromagnetic wave scattering due to its high resolution. However, conventional methods have been based on the assumption that each signal does not have any frequency dependence other than phase delay proportional to the frequency originating from delay time. Hence, such an assumption cannot be satisfied in the case of diffraction coefficients such as those in the case of electromagnetic wave scattering. In this paper, the solution to this problem is proposed by application of the procedure based on the improvement of the Root MUSIC algorithm for the signals with exponential amplitude frequency dependence. In the exponential frequency dependence of e−αf, α is considered to be an unknown parameter. Delay time and α are estimated simultaneously by means of the modified Root MUSIC algorithm. It is shown that the frequency dependences of the specular return and the creeping wave of a conducting sphere are estimated with sufficiency accuracy.
A large‐scale asynchronous transfer mode switch architecture
Authors: Shobatake Yasuro , Kamitake Takashi
Published: July 2007

This paper proposes an asynchronous transfer mode (ATM) switch architecture to realize a large‐scale ATM exchange to be used for the future spreading era of ATM networks. The proposed switch architecture is based on a three‐stage Clos network which consists of many element switches to obtain a large‐scale ATM switch. In the proposed ATM switch, the element switches at the first‐and last‐stage of the Clos network are the shared buffering ATM switches; the element switches at the second stage are the input buffering ATM switches. Because it is preferable to build various capacities of ATM switches in the same way with the three‐stage Clos network architecture, the element switches of the second stage of Clos network should be scalable. Therefore, it is proposed that the second stage switches are the input buffering ATM switches. On the other hand, the first‐ and last‐stage switches are the shared buffering ATM switches to prevent degradation of cell loss rate. The proposed architecture has been evaluated by computer simulations, and it shows that internal link speed‐up and flow control prevent the degradation of cell loss rate. It also shows that degradation of cell loss rate can be ignored even when the ATM switch size is expanded.
Experimental advanced mobile satellite communications system in the mm‐wave and ka‐band using communications and broadcasting engineering test satellite
Authors: Isobe Shunkichi , Kawamata Fumio , Hamamoto Naokazu , Naito Hideyuki , Takeuchi Makoto , Isogai Mitsuo , Ohmori Shingo
Published: July 2007

It is expected that the demand for personal satellite communications will increase and systems providing various services enabling direct communications between automobiles and portable stations will be in demand in the near future. Load transponders and experimental systems are being developed and studied for the advanced mobile satellite communications systems of the Communications and Broadcasting Engineering Test Satellite (COMETS) expected to be launched in 1997 in order to develop and verify multibeam interconnection technologies and regenerative repeater technologies as technologies required to implement such next‐generational mobile satellite communications systems.

In this paper, the functions required by COMETS experimental systems have first been clarified, assuming future systems. Next, the payload configuration satisfying the required functions and performance has been designed based on the conditions restricting the load. As a result, a batch‐type regenerator using a digital polyphase‐fast Fourier transform (FFT) filter bank, Ka‐band 20‐W solid‐state power amplifier, and a millimeter‐wave low‐noise amplifier (N.F. = 2.4 dB) has been realized. In addition, experiments have been considered employing the experimental system using the foregoing.
Optimization of antenna aperture distribution with ground reflection
Authors: Tajima Hirohisa
Published: July 2007

In general, the radiation pattern in the vertical plane of an antenna requiring a low elevation angle coverage is made to have sharp cutoff characteristics so that the reduction of the electric field intensity by ground reflection, known as “the lobbing effect,” can be avoided. However, the lobbing effect depends on the installation of height of the antenna, and therefore the determination of the optimal antenna pattern for a certain installation environment is difficult.

In this paper, an aperture distribution that takes into consideration the ground reflection is optimized in the case where the height of the top of the DME/P antenna for distance measurement of MLS for aircraft landing is restricted to 3 m. The aperture distribution was evaluated by the minimum values of the electric field intensity at many sampling points around the required coverage area in the presence of ground reflection. The optimization was carried out by maximizing these minimum values using the steepest descent method. As a result, the minimum values of the electric field intensity within the covered region became uniform so that the electric field distribution was improved. In the optimized aperture distribution, the phase center of the antenna is shifted to the upper part of the aperture so that the lowest electric field intensity at the lower coverage edge was improved by 6.5 dB.
A coherent detection system with a suppressed pilot channel for ds/cdma systems
Authors: Abeta Sadayuki , Sampei Seiichi , Morinaga Norihiko
Published: July 2007

This paper proposes a coherent detection system using a suppressed pilot channel to achieve coherent RAKE diversity combining for DS/CDMA up‐link in land mobile communication systems. At the receiver, delay profile is measured using the suppressed pilot channel and simultaneously chip timing is detected by using block demodulation and maximum likelihood estimation, and measured the complex delay profile. The performance of proposed adaptive RAKE diversity is evaluated by computer simulation for quadriphase‐shift keying (QPSK) system. The results show that the performance of the proposed scheme is superior to that of the conventional DPSK/PDI, and it is almost the same as the theoretical performance for the coherent RAKE diversity receivers.
Nearly lossless compression of color still images and its performance evaluation
Authors: Okumura Akira , Suzuki Junji
Published: July 2007

Existing image coding systems can be categorized into lossy and lossless coding methods. Nearly lossless compression, which attains both higher compression performance than lossless compression and higher image quality than lossy compression, is required in applications that include medicine and printing. This paper proposes a nearly lossless coding method in which distortion is restricted to within a predetermined range. The RGB input signals are transformed into one luminance and two chrominance components; the magnitudes of these luminance and chrominance components are adjusted in the encoder so that the reconstructed RGB signals have minimum distortion after inverse color transformation in the decoder. The prediction residual signals of these level‐adjusted components are entropy coded. As a result, the reconstructed RGB signals have coding distortion levels of only +1 or ‐1. This restricted distortion never accumulates even if encoder/decoder couples are connected in tandem because all encoders and decoders operate in synchrony.
Resolving cycle slips with redundant satellites for kinematic global positioning system
Authors: Wang Dun , Morikawa Hiroyuki , Mizumachi Moriyuki
Published: July 2007

The kinematic global positioning system (GPS) is a system that successively executes the positioning of a mobile user with the accuracy of several centimeters by measuring the phase of the radio wave (carrier) from the GPS satellite while moving. A problem in the kinematic GPS system, however, is that the phase‐shift corresponding to the integer multiple of the wavelength (cycle slip) produced during the phase measurement must be eleminated to realize a highly accurate positioning.

For this problem, this paper presents a method that can detect and eliminate the cycle slip with a high accuracy and lobustness by more than four GPS satellite signals which is needed in the positioning. The detection/elimination of the cycle slip based on the update residual error of the Kalman filter and the detection/elimination of the cycle slip based on the redundant GPS signal are integrated and a method to determine the cycle slip with a high accuracy is realized.
A model for a token ring system using jump‐type stochastic differential equations
Authors: Minowa Hiroyuki
Published: July 2007

We propose presents a model for a token ring system using jump‐type stochastic differential equations. We model waiting frames as a queueing system whose mechanism is different from those of conventional queueing systems. In addition, we assume that frame interar‐rival time obeys an exponential distribution, and we show that the number of waiting frames has the same law as M/M/·‐queue. For this case, we obtain stationary distribution, mean cycle time, and mean system time. We also compare these results with simulations.
Conditions for synchronization in multimedia remote presentation systems
Authors: Ohno Ryuichi , Aida Hitoshi , Saito Tadao
Published: July 2007

There is increasing demand for a system that supports various multipoint activities such as a conference and education using multimedia information. This paper considers the situation where such a multimedia remote presentation system is to be constructed and discusses the condition for maintaining the synchronization among the media in the information presentation at each node.

In this paper, first, the synchronization semantics is defined based on the information presentation timing between the media information taken out from the storage information source and the live media information such as the user's voice. Then a computation procedure is shown for the buffer size needed in each node in order to satisfy the semantics. Based on those reasonings, the design condition is presented for the buffer size and the command response time.
Lightning surge test generator for telecommunication equipment
Authors: Motomitsu Tamio , Kuwabara Nobuo , Ideguchi Tsuyosi , Tokuda Masamitsu
Published: July 2007

Lightning surge which is induced on a telecommunication cable may damage telecommunication equipment. This paper proposes a design method for a lightning surge generator which can accurately predict reliability for the lightning surges in telecommunication equipment and the quality of the lightning surge generator developed based on this method is described.

First, the characteristics of the lightning surge which is fed to the equipment are determined from such factors as the lightning surge inducing mechanism. Next, the testing surge waveform design method is determined in which evaluations of the lightning surge proof of equipment by the peak voltage, steepness (peak voltage/ front time) and energy of the lightning surge can be performed in one surge test. The testing surge waveform then is determined based on this design method.

A method is described for realizing the lightning surge characteristics and the testing surge waveform using a basic impulse voltage generator circuit which consists of an LRC circuit with few circuit elements. Experimental results demonstrate that the developed lightning surge generator based on the proposed designing method can predict the malfunction rate accurately.

It is shown also that it is highly practical because its size and cost are about one‐tenth that of a conventional testing device.
A packet channel sharing protocol for microcellular mobile communications
Authors: Kayama Hidetoshi , Ichikawa Takeo
Published: July 2007

Because new microcellular systems have high‐speed transmission, they are expected to provide the infrastructure for voice and data communication. To implement packet radio communication on such systems, packet channel sharing protocol for DCA systems (PCSD) scheme is proposed for sharing dynamically assigned TDMA channels with circuit‐switched calls. In this protocol, packet channels are temporally established only when packets are generated. This is done by transmitting downlink signals, consecutively, from a cell station (CS); and subsequent uplink packets are transmitted in accordance with the access control signal associated with each downlink signal. If no packet is transmitted within a predetermined period, the CS stops downlink transmission to release the packet channel. The characteristics of this protocol are evaluated using computer simulations of four‐channel TDMA/TDD. The results indicate that the protocol improves channel capacity by more than 10 percent (when packet throughput is 0.2) compared to individual assignment in which channels are separately assigned to packet and circuit‐switched calls, respectively, without deteriorating packet throughput.
Network design of b‐isdn using the group virtual path scheme
Authors: Omotani Masaaki , Takahashi Tatsuro
Published: July 2007

Issues of network design for the group virtual path (GVP) scheme, such as assignment of objective cell loss rates, algorithms for GVPs and congestion tolerance are discussed. The GVP is a previously proposed bandwidth sharing scheme. This scheme gives better statistical multiplexing efficiency since bandwidth is assigned to a group of virtual paths (VPs) rather than to an individual VP.

Varying the cell loss rates does not have much effect on the acceptable offered load for low virtual channel (VC) peak speed. The cell loss rate for high VC peak speeds were evaluated by simulation and proved similar to virtual channel handlers (VCHs): switches and virtual path handlers (VPHs): cross connects. Therefore, objective cell loss rates should be assigned equally to VCHs and VPHs. Five algorithms are proposed for group VPs. The necessary transmission capacity given by each algorithm is slightly higher than optimum grouping but close to optimum groupings can be achieved by using these algorithms together. Congestion tolerance of the GVP scheme is better than that of the conventional VP scheme if only one VP is congested. If all VPs in a GVP are congested, congestion tolerance worsens. However, the transmission capacity necessary to compensate for congestion tolerance is smaller in the GVP scheme than in the conventional scheme.