bluuebunny/crossref_metadata_2025 huggingface dataset:
Evaluating the performance of a message transmission system on meteor burst channel
Authors: Fukuda Akira , Yamashima Hiroyuki , Mukumoto Kaiji
Published: July 2007

This paper evaluates the performance of the two‐way message transmission system on the meteor burst channel developed and tested by the authors. First, the usual channel model is simplified and then the system is analyzed. It is shown through simulations that the errors introduced by the new channel model and by the approximated analysis method are negligible and the proposed method can be used to design and evaluate the system.

The performance of the system having packets with subblocks is compared to that of one with usual packets. It is shown that, by using packets with subblocks, robustness of the system performance against changes of channel parameters as well as a shorter time needed to transmit a message can be obtained. The method of performance evaluation shown in this paper has adequate generality and is also applicable to many other meteor burst communication (MBC) systems.
Prediction of the number of coherent signals for mobile communication systems using autoregressive modeling
Authors: Minamisono Kenichi , Shiokawa Takayasu
Published: July 2007

One effective technique for reducing multipath fading in mobile communications is introduction of directional diversity with the help of adaptive arrays. This technique requires direction of arrival (DOA) estimation of coherent signals and relative time delay estimation. Eigenvector analysis or maximum likelihood localization is an efficient technique to estimate DOA. However, for coherent signals, spatial smoothing preprocessing is required and information about the number of signals is needed.

This paper proposes to use spatial autoregressive modeling and final prediction error (FPE) to estimate the number of coherent signals. Since FPE drastically decreases with p when the length of prediction filter p is less than the number of coherent signals k and FPE converges to a constant value determined by C/N when p is greater than k, the number of coherent signals can be estimated. Moreover, by appropriately defining the FPE threshold, the number of dominant coherent signals can be estimated under the C/N concept. Numerical experiment indicates that this technique can estimate the number of signals and DOA with sufficient accuracy. Further, by appropriately defining the FPE threshold, the number of dominant coherent signals can be estimated.
Testing method for in‐service line of optical subscriber loops with optical time domain reflectometer
Authors: Takasugi Hidetoshi , Suzuki Hideki , Tomita Nobuo , Chida Ryouichi , Oguchi Taisuke
Published: July 2007

With the development of communications service for high performance and for wider bandpass widths, a single‐mode optical fiber has been started to be utilized in subscriber loops in addition to connection loops. An optical fiber cable has an advantage of huge transmission capacity, as compared to a conventional metal cable and, therefore, any breakdown in a cable may cause significant impact on the society. In this sense, a test capability of optical cables without causing any service interruption is needed.

In this paper, a system using the optical time domain reflectometer (OTDR) which can perform such testing is discussed. The optical filter characteristics such as cutoff loss, transmission loss, and bandpass width are discussed. A prototype of the system consisting of optical filter parts has been made in the present study. The influence of the OTDR test light on transmission signal and that of the transmission signal on the OTDR waveform are examined. No degradation of the transmission quality was found. Furthermore, no disturbance in the OTDR waveform was observed. Therefore, it is concluded that a test without disturbing the transmission output signal can be performed by using the present method.
A small 42‐ghz transmitter and receiver for a wireless HDTV (hi‐vision) camera
Authors: Mizuno Haruhiko , Mitsumoto Hideo , Nakakita Hisao , Yazawa Norihiko
Published: July 2007

A transmission system suitable for a small Hi‐Vision wireless camera is proposed and a small transmitter and receiver for the 42‐GHz band is developed. In the present system, no signal processing is performed on the camera output which is directly frequency modulated. Orthogonal circular polarizations are co‐used for transmission.

By means of this system, miniaturization and weight reduction of the equipment (with a transmitter of 5 kg) are attained. At the same time, the transmission bandwidth is reduced to 80 MHz. Also, as the key 42‐GHz devices for realization of the present equipment, a direct FM modulator (modulation sensitivity of 20 MHz/ V), an HEMT power amplifier, an orthogonal circular polarization feed system (with a cross‐polarization discrimination ratio of more than 23 dB), a low‐noise down‐converter (with a noise figure of less than 5 dB) and a simple IF cross‐polarization interference equalizer are developed.

The antenna for the transmitter automatically adjusts its direction by means of the signal returned from the receiver at 10 GHz. The present equipment has a transmission distance of about 250 m with a transmitter output of 25 mW and the signal‐to‐noise (SN) ratio is 48 dB (Y signal). Also, the equipment can be unified with the Hi‐Vision two‐thirds inch small CCD camera developed in our laboratory and can be operated for close to one hour with one battery.
Multipath allocation algorithm for the distributed computer environment
Authors: Minato Kenji , Okumura Yasuyuki , Kishimoto Ryozo
Published: July 2007

This paper discusses the multipath allocation problem in the communication network and proposes a multipath allocation algorithm suited to the distributed environment. The multipath allocation problem is a problem where multiple paths are to be allocated without a conflict. This problem has been difficult to solve in the distributed environment since relations among various routes must be considered. The algorithm proposed in this paper solves this point by realizing the asynchronous path search.

In this paper, the basic characteristics of the proposed algorithm are described through the comparison between the proposed and the traditional algorithms for the case of serial computation under the centralized control. Then the proposed algorithm is applied to several kinds of distributed cooperative multiagent models, and it is demonstrated that the proposed model can easily be applied to the distributed environment. A simulation is executed actually using several workstations, and it is shown that the proposed algorithm is desirable as a solution method for the multipath allocation problem in the distributed environment.
Satellite communication applications to B‐ISDN
Authors: Kawai Makoto , Nakaya Kenji , Hojo Hiroshi , Okada Kazuyasu
Published: July 2007

The terrestrial communication network is making progress from the analog public network based mostly on telephone traffic to the N‐ISDN. The development to BISDN also is considered, aiming at an integrated network which can provide large‐scale file transfer, high‐speed data communication such as the communication between high‐speed LAN, and dynamic image communication such as TV and HDTV. This paper proposes the application of the multibeam

Satellite communication to such B‐ISDN, and presents such technical subjects as the satellite communication. First, the purpose of application of the satellite communication to B‐ISDN is described. The requirement in the application to B‐ISDN is presented. Then, aiming at the fulfillment of the requirement, the technical subjects and evolution are shown for the configuration of the communication system, the channel control system, the synchronization control system, OAM system, and the interface to the terrestrial network.
Radiation from the multibranching point of a transmission line
Authors: Nakamura Takashi , Ozawa Akiyoshi , Yokokawa Senji
Published: July 2007

In this paper, branching configuration in a parallel two‐wire transmission line is considered as the cause of the unwanted electromagnetic wave generation and the analysis and experiment are carried out on the radiation characteristics of the discontinuity. Understanding by a simple radiation mechanism is intended. The discontinuity of the traveling‐wave current on the conductor of the transmission line is considered as the radiation source.

By means of the principle of pattern multiplication, the expression of the radiation field from the junction of the transmission line is derived. It is shown that the reflection and transmission coefficient of the traveling wave at the branching point are important factors to determine the radiation pattern. Two types of branching line configurations are treated. One of them is a reflectionless configuration while the other is made of identical transmission lines. The radiation characteristics due to the difference of characteristic impedance are derived. It is shown that there are electric field components radiating strongly in the traveling direction of the current of the branching line and the one radiating strongly into the intermediate direction. By means of the experiment for a T branching line, the validity of the theoretical results is confirmed.
Cornish's expansion analysis of characteristics of a communication system with an optical amplifier
Authors: Mieda Hiroyuki , Yoshino Takayuki , Hirano Nobuo
Published: July 2007

The Laguerre density and its distribution function which represent the noise in communication systems with an optical amplifier are evaluated by the Cornish expansion and it is found that the result is sufficiently useful for practical applications.

The variable transition, skewness, excess, and mode are used as figures of the difference between the Laguerre and Gaussian functions. Then the error rate and decision level on the optimum and quasi‐optimum conditions of a digital on‐off keying (OOK) communication system are analyzed. Assuming the noise to be Gaussian, the error rate is overestimated by about one order. This result agreed with one reported elsewhere.
Consideration of effects of handover during data communications and error reduction
Authors: Uchiyama Hiroki , Miyachi Tatsuo , Kasuga Masao
Published: July 2007

Efficient handover during both mobile telephone and portable telephone communication is a technology essential in implementing ideal mobile communications. However, there exists the possibility of a transmission data slip during the process of circuit switching, which has become a problem in communication using terminal machines such as data modems and FAX machines connected to mobile telephones and portable telephones.

In this paper, a transmission data slip accompanying route changes inside digital exchanges in a handover during telephone communications is assumed; it is shown on the basis of this assumption that a lag in synchronism occurs in the receiver terminal equipment.

Then a sync lag of the receiver terminal modem during handover has been confirmed by tests using actual analog cellular phones and a transmission data slip has been shown on the basis of the results of the tests. In this paper, a synchronism control method minimising the sync lag has been studied. The efficacy of this method has been confirmed as a result of applying the method to a mobile telephone FAX modem.
The barrel switch: An ATM switch architecture for high‐speed switching
Authors: Shobatake Yasuro
Published: July 2007

This paper proposes a new asynchronous transfer mode (ATM) switch architecture called a “barrel switch.” The barrel switch is constructed from n/2 × n identical element switches which are placed out around a cylinder and connected to each other.

The features of this proposed switch are as follows.

1. This switch has an architecture suitable for high‐speed (2.4 Gbps and more) cell switching.

2. It is a multistage self‐routing and nonblocking switch.

3. Copy connections can be realized with this switch.

4. The building‐block method is applicable to switch implementation, which ensures a full scalability.

Cell loss rate and delay characteristics of this switch also are discussed using computer simulation results. Simulation results under random traffic prove that a 64 × 64 barrel switch has adequate cell loss rate and mean delay characteristics to an actual ATM switching system.
Communication and radio determination system using two geostationary satellites
Authors: Morikawa Eihisa , Kimura Kazuhiro , Wakana Hiromitsu , Miura Ryu , Ohmori Shingo , Matsumoto Yasushi , Wakao Masayoshi
Published: July 2007

With the recent development of satellite communication and the diversified demands for communication, there has been increasing demand to utilize the position of the mobile object as the information. This idea is proposed and has been developed in various countries of the world as the radio determination satellite system (RDSS).

This paper outlines the hybrid communication/ positioning system using two geostationary satellites. The system has been developed by the Communication Research Laboratory in collaboration with the R & D Center for Radio System, together with the result of basic experiments.

Two kinds of experimental systems with different modulation/demodulation methods are constructed. One is the method based on the offset QPSK (called SCPC), and the other is based on the spread‐spectrum (called SS). The former transmits the narrowband signal for distance measurement, in addition to the communication signal. Consequently, this method can easily be introduced into the SCPC satellite communication system presently used in practice, although the accuracy of the positioning is slightly deteriorated. Compared to the former, the latter has the advantage that a highly accurate positioning can be realized since a high‐speed positioning signal is employed using a wide transmission bandwidth. However, the system configuration becomes complex. A field experiment is conducted for each system using the Engineering Test Satellite V (ETS‐V) and the Inmarsat satellite. The positioning accuracy of 2 to 8 km for low altitude and 1 to 2 km for middle altitude is obtained in SCPC. The position accuracy of 400 to 600 m is obtained near Japan by SS.
SAW filter matrix for SS/FDMA system
Authors: Shinonaga Hideyuki , Ito Yasuhiko
Published: July 2007

The configuration and function of a surface acoustic wave (SAW) filter matrix used on board a satellite to implement a subchannel switched FDMA (SS/FDMA) system is described. The function and configuration of the SAW filter matrix (SFM) are described. Conditions imposed on the amplitude and phase of two adjacent subchannels to provide a broad channel by combining the outputs of the subchannels are investigated. Electrical and transmission characteristics of an SAW filter matrix used in four‐beam SS/FDMA system with a subchannel‐combining function are presented, demonstrating its technical feasibility.

When implementing an SFM, it is important that the devices used for a satellite‐based SS/FDMA router are sufficiently reliable for the design life of the satellite. A methodology is shown that gives a redundant configuration with the lightest mass and that achieves the targeted reliability. Example calculations for a four‐beam SS/FDMA router are given.
Time‐domain analysis of yagi‐uda antennas using the FD‐TD method
Authors: Kashiwa Tatsuya , Tanaka Shuichi , Fukai Ichiro
Published: July 2007

The fundamental importance of the Yagi‐Uda antenna is its structural simplicity and its director and reflector actions. To fully comprehend the working principle of this antenna, it is important to be able to visualize the radiation mechanism directly in the time domain. In this paper, transient analysis of the Yagi‐Uda antenna is performed using the FD‐TD method. First, the input impedances and directivities obtained by this method are compared with the moment method, good agreement was found between the two methods, and the validity of this method was demonstrated. Next, the quasi‐impulse responses of the antenna are calculated. The field pattern obtained by this method was visualized in the time domain. The radiation from the antenna edge is shown in the early time responses, and dispersion of the pulse shape with the passage of time is shown in late time responses. Moreover, the difference of characteristics due to the length of parasitic elements is shown by time‐domain observation.
Generalized product codes and their performance
Authors: Hatamori Toshifumi , Kasahara Masao
Published: July 2007

Product codes show improved correcting capability by a comparatively simple method of combining codes and are also effective in correcting bursty errors. In this study, product codes using several kinds of single‐error correcting and double‐error detecting (SEC‐DED) codes, different by rows, are proposed. A method of probabilistically correcting bursty errors by using SEC‐DED codes different by rows and utilizing the differences in these error‐correcting characteristics is proposed. In addition, a decoding method that can correct random errors of the type that could not be corrected by the conventional product codes for this code is proposed.
Frequency‐offset compensation for MPSK differential detection by using double differential encoding
Authors: Ishikawa Hiroyasu , Kobayashi Hideo
Published: July 2007

Although differential detection methods having superior fading resistance and, in general are effective in digital land mobile communications systems, phase shifts due to frequency offsets become a major factor that deteriorates the error rate in these differential detection methods. Although various frequency‐offset compensating methods have been studied and developed, the maximum amount of frequency offset that can be compensated is limited due to the ambiguity of the phase, which has become a problem in estimating the phase shift due to a frequency offset.

In this paper, a method for compensating frequency offset by double differential encoding of transmission data sequences, which allows a resolution of the forementioned problem even when a large frequency offset occurs, is proposed and the error rate performance in the application of a /4‐shift QPSK scheme is evaluated by computer simulation. As a result, it is shown that the proposed method has superior compensating performance on land mobile communications channels.
An application of chirp to spread‐ALOHA system
Authors: Enomoto Masaru , Takahata Fumio
Published: July 2007

This paper proposes a spread‐ALOHA system using chirp. the system is composed of the modulator containing the chirp filter and the demodulator containing the chirp matched filter, the quasi‐coherent detector and the block demodulator. In the proposed system, the data transmission is realized by using the chirp signal with phase information corresponding to binary data and then, using the chirp effect, the frequency component of the transmitted signal is spread continuously. In addition, since the respective bits composing a packet are compressed in time by the correlation processing using the chirp matched filter, the multiplexed packets are separated in individual packets based on the timing difference among the received packets.

The carrier synchronization, which is required in the demodulation process, is achieved by quasi‐coherent detection and the block demodulation. the frequency and the phase offset occurring in the quasi‐coherent detection are corrected by a method of highly accurate frequency detection based on the fast‐Fourier transform in the block demodulator. Furthermore, assuming various conditions, quantitative evaluations are made on the bit‐error rate performance by means of computer simulation. It is verified that a high interference immunity is realized by the frequency spread using chirp, and frequency offset generated in the quasi‐coherent detection is well estimated and corrected.
Design algorithm for packet‐switching networks with different classes of packets‐capacity, priority, and flow assignment under endto‐end packet delay constraint
Authors: Sugano Masashi , Takashina Hiromitsu , Yokohira Tokumi , Okamoto Takuji
Published: July 2007

This paper proposes a design algorithm for packet‐switching networks with different classes of packets under end‐to‐end packet delay constraint and a design algorithm for fault‐tolerant networks. the former is a heuristic capacity, priority, and flow assignment algorithm which locally minimizes the network cost while satisfying a constraint that the average transmission delay of each class of packets between two arbitrary nodes never exceed a value predetermined for the class.

This algorithm is composed of three subalgorithms and the cost minimization is pursued by iterating these algorithms as long as the constraint is satisfied. the latter is a design algorithm for a fault‐tolerant network which satisfies the foregoing constraint even if an arbitrary single link fails. With this algorithm, an assignment with relatively large cost but satisfying the constraint is obtained first. Then a procedure of reducing the capacity of a link whose effect on cost reduction is great but whose effect on path delay increase is not so great is iterated to reduce the network cost as long as the constraint is satisfied.
Adaptive karhunen‐loeve transform coding and its design method
Authors: Ohzeki Kazuo
Published: July 2007

Specific models have been conventionally used to switch between various Karhunen‐Loève (KL) transform matrices to adapt to local characteristics of nonstationary images. Here, the superior characteristic of the KL transform (mean square error minimization) is extended over all parts of the design process as an evaluation criterion. Further, by using actual images as training data, a design process is established that reflects the nature of real images. In order to compare the adaptive matrix‐switching KL transform coding method with previous simple discrete cosine transform (DCT) coding methods, a transform is proposed that does not cause mean value separation. the effectiveness of this type of adaptive transform is determined by computer simulation. Also, since the resulting coding characteristics do not depend on the training images, it is estimated that the construction of a system that includes common nonstationary characteristics has been achieved. Examination of intermediate steps of this design process show that, in fact, all generated eigenvalues are practically positive and the stability of the design process is guaranteed.
Rate control strategies for high‐priority data in two‐layer packet video transmission
Authors: Kawashima Masahisa , Inoue Masahiro , Tominaga Hideyoshi
Published: July 2007

To transmit the video image with the two‐layer transmission by utilizing the priority cell control of the ATM network, the required bandwidth varies depending on the rate control scheme for the high‐priority information. Therefore, several high‐priority rate control schemes can be considered such as the scheme in which the ratio of the high‐priority bit rate to the entire bit rate is kept constant or the scheme in which the peak rate is specified for the high‐priority information. Therefore, for these two schemes, the optimum layering parameters will be derived in order to keep the minimum bandwidth requirements and to compare the bandwidth requirements by using the optimum layering parameters. As the result of the comparison, it was concluded that the peak rate control is superior when the number of multiplexed video sources (terminals) in the network is low and when the bandwidth requirements for the low‐priority information is not strict. It was concluded also that the scheme to keep the ratio of the high‐priority information fixed is superior when the number of multiplexed video sources in the network is high and when the bandwidth requirements for the low‐priority information is strict.
Single‐reflector‐type wide beam‐spacing multibeam antennas
Authors: Naito Izuru , Makino Shigeru , Furuno Takayoshi , Katagi Takashi
Published: July 2007

Japanese commercial communications satellites (CSs), which are 50 to 60 degrees from the Japanese broadcasting satellite (BS), have begun direct broadcasting service. Simultaneous reception of broadcasting from CSs and BS requires a multibeam antenna with wide beam‐spacing. an optimum reflector for a single‐reflector‐type wide beamspacing multibeam antenna is presented on the basis of wave aberration analysis of defocus‐fed reflector without restrictions on reflector symmetry and feed displacement amount.
A spread spectrum cordless telephone
Authors: Tanaka Kiyoshi
Published: July 2007

The United States industrial, scientific, and medical (ISM) band has been released for spread spectrum communication, and various applications for it are being proposed. A spread spectrum cordless telephone set has been developed for domestic use as one of its applications.

In this paper, the design outline and its characteristics are explained. the direct sequence spread spectrum technique with spreading ratio of 16 in the 902‐ to 928‐ MHz ISM band is used. to solve the near‐far problem in the mobile radio communication channel, the frequency division multiple access‐time division duplex (FDMA TDD) technique is adopted where different frequencies can be assigned to each channel. Compact size and low power consumption is achieved by developing a chip in which spread spectrum processing and transceiver multi plexing can be handled on a single ASIC chip.

The voice codec uses ADPCM and provides better voice quality compared to the conventional analog cordless phones. Wider talking range compared to the conventional 46/49 MHz cordless phone is obtained by increasing the amount of transmitted power. Moreover, since the ISM band is used, interference from other sources can be avoided by changing the channel frequencies.
Source‐radiation field analysis in scalar waves‐ electromagnetic scattering in conducting circular cylinder
Authors: Tokumaru Shinobu , Ohgake Ken‐Ichi
Published: July 2007

To enlarge the range of applications of integral equation methods in wave fields, a new source‐radiation field analysis is proposed. In this method, in addition to the conventional Huygens integral representation deriving the radiation field from the source, the Huygens‐Fresoel integral representation deriving the source from the source and the radiation field by means of the conjugate Green's function is added. These two integral equations are solved simultaneously for the source and the radiation field. the source‐radiation field solutions in the scalar waves are formulated. As the simplest example to demonstrate the effectiveness of this method, electromagnetic plane wave scattering by a perfectly conducting circular cylinder is solved.
Errors and correction factors for schelkunoff's shielding effectiveness formula
Authors: Nagao Hiroshi , Nishikata Atsuhiro , Shimizu Yasutaka
Published: July 2007

This paper presents the error of the resistive film approximation and that of Schelkunoff's equation with respect to the rigorous solution. Both of these approximate equations cause errors for the planar shield for which either an infinitesimal electric dipole or an infinitesimal magnetic dipole is the source. Hence, the four types of planar shield with different directions and types of dipole source are investigated.

Next, the conditions for causing the error is studied. When Schelkunoff's equation and the resistive film approximation are rewritten, they become functions of three dimensionless parameters. However, the numerical analysis reveals that only two error‐causing parameters are sufficient if the choice is carefully made. With these two parameters, the correction factors are derived with which the rigorous value is obtained from Schelkunoff's equation or the resistive film approximation. the rigor ous solution is a complicated equation including integral calculation. On the other hand, Schelkunoff's equation is relatively simple. If this correction value is used, a solution equivalent to the rigorous solution can be obtained from Schelkunoff's equation or even simpler resistive film approximation.
Performance of differential parallel combinatory spread spectrum communication systems
Authors: Sasaki Shigenobu , Kikuchi Hisakazu , Zhu Jinkang , Marubayashi Gen
Published: July 2007

This paper proposes differential parallel combinatory spread spectrum (DPC/SS) communication systems; one of the parallel combinatory spread spectrum (SS) communication systems the authors have been studying so far. the parallel combinatory SS system is a spectral efficient SS system in which the system transforms sever al bits of data into a combination of pseudonoise (PN) sequence with modulation of positive and negative signs and transmits them.

The proposed DPC/SS system applies differential encoding to the positive or negative sign modulation of the PN sequences, and then they are transmitted. In the receiver, the combination of a transmitted sequence set is estimated by noncoherent detection and the coded sign is demodulated by differential detection. Thus, the receiver does not need to regenerate the phase of the carrier frequency. the proposed systems will be applicable to a mobile cellular system in which a large phase variation interferes with the communications.

This paper evaluates the error performances. of the DPC/SS systems in additive white Gaussian noise (AWGN) channels and frequency‐nonselective, slowly Rayleigh fading channels. It also evaluates the effect of diversity in the Rayleigh fading channels.

In the AWGN channel, the DPC/SS system is superior by I dB to the differential phase‐shift keying (DPSK) system and to the BPSK system in terms of required signal‐to‐noise ratio at 10‐8 bit error rate (BER) at the same spectral efficiency. In the Rayleigh fading channel, diversity reception in the DPC/SS system gains more improvement in the BER performance, as the number of branches increases, than that obtained in a direct‐sequence spread spectrum system with DPSK.
A signal design method for block‐coded modulation in multipath fading channel
Authors: Okada Minoru , Hara Shinsuke , Morinaga Norihiko
Published: July 2007

This paper considers the block‐coded modulation system in the multipath fading environment and derives the upper bound expression for the bit error rate considering the effects of the interleaving size and the space diversity. Then a signal design is proposed. Here, the set of signals minimizing the upper bound expression is sought using the quasi‐Newton method, which is known as an iterative solution method for the nonlinear progrmming problem. the bit error rate for the signal sequence derived by the proposed signal design is evaluated by a computer simulation, and the effectiveness of the proposed signal design is demonstrated.
Noise augmentation and signal‐to‐noise ratio degradation in in‐line amplifier systems due to the nonlinear refractive index of optical fibers
Authors: Saito Shigeru , Naka Akira
Published: July 2007

Optical noise enhanced by the nonlinear refractive index of optical fibers is one of the major factors limiting the system performance of in‐line amplifier transmission. This paper derives an analytical expression of noise enhancement taking into account group‐velocity dispersion of optical fibers. Evolution of the in‐phase and quadrature‐phase noise field components is expressed by a simple matrix describing the transmission characteristics of optical noise through the basic section composed of an optical amplifier and a transmission fiber. This enables minute investigation of noise evolution in in‐line amplifier systems; approximate characteristics can be learned as well. A noise increase proportional to the third power of a number of amplifiers is verified in the normal dispersion regime while an exponentially rising noise peak is found in the anomalous dispersion regime.

Based on these results, signal‐to‐noise ratios at the receiver and allowable transmission distances are discussed in terms of the dispersion parameter and the amplifier number. From the noise evolution point of view, the longest transmission distance is achieved in the normal dispersion regime.
A new method of designing telecommunications networks using time‐series traffic data
Authors: Matsumoto Kimihide , Nojo Satoshi
Published: July 2007

Telecommunications networks are designed and managed based on statistical traffic data including basic traffic obtained at peak traffic hours. Network links are also designed based on the basic traffic. the network is designed so that the quality of services (network blocking) is at a certain level when basic traffic is applied to the network and the network is managed so that quality of services is maintained for the basic traffic. This conventional method is universal and simple because the required data for design and management are very small. On the other hand, recent telecommunication systems have the ability to measure and collect detailed traffic data.

This paper proposes a new network design method in which time‐series traffic data rather than statistical traffic data is used for network design. Combining the time‐series traffic data and the tariff data for each hour, we can design a network based on total revenue. Unlike the conventional method, the proposed method makes it possible to estimate revenues, costs, and damages. Using time‐series traffic data obtained for every hour of the year, a method is devised that optimizes the number of circuits (i.e., for optimizing network blocking) and thus maximizes profits. This paper also presents a new methodology for traffic data and a new network structure that effectively uses the proposed method.
Design of an asymmetric parabolic cylinder antenna with high aperture efficiency
Authors: Asai Kikuo , Kojima Masayoshi , Misawa Hiroaki , Ishida Yoshio , Maruyama Kazuo , Yoshimi Naohiko , Wakasa Masaaki , Karakida Masue
Published: July 2007

With respect to the asymmetric cylindrical parabola antenna constructed for radio astronomical observation at 327 MHz, the design method and the verification of the design values are reported. The present antenna placed emphasis on the improvement of the receiving sensitivity and is designed to increase the aperture efficiency as much as possible.

To carry out an optimum design of the primary feed made of a dipole array with a corner reflector, the structural parameters of the primary feed have been studied. It was found that there exist optimum values. The reduction of the efficiency due to the transmission loss and the phase error loss of the reflector surface made of stainless wires was derived. The overall aperture efficiency was estimated to be 75.9 percent. In an actually constructed antenna, the aperture efficiency measured with a celestial radio source as the standard radio source was 71 ± 5 percent. It was confirmed that the aperture efficiency derived from the computation and the optimum design values are reasonable.
Path planning for low‐altitude flight by fuzzy reasoning
Authors: Nomoto Kohei , Kameda Hiroshi , Mano Seiji , Tachibana Yasuo
Published: July 2007

This paper discusses flight‐path planning for an aircraft flying at low altitude while avoiding terrain crashes. In a past study, several algorithms based on exploratory procedures have been proposed; however, they do not generate practical paths that take into account aircraft inertia. This paper proposes a new algorithm to generate a flight path taking account of the aircraft's inertia; this algorithm does not generate the flight path directly, but determines the aircraft's steering acceleration at every point along the way and then generates the flight path based on the steering acceleration. This algorithm extracts feature parameters representing a relation between the aircraft and the terrain, determines steering acceleration by fuzzy reasoning using the feature parameters, and updates state variables of the aircraft. Furthermore, this paper also proposes a learning algorithm to design the membership values in the fuzzy reasoning from reference flights since it is difficult to optimize them by trial and error. The flight‐path planning by the proposed algorithm is compared with that based on the exploratory procedure. The learning algorithm of the membership values is validated through computer simulations.
Moving target detection by quadrature mirror filter
Authors: Ehara Naoki , Sasase Iwao , Mori Shinsaku
Published: July 2007

For pulse radars, coherent moving target indication processes and discrete Fourier transform‐based Doppler filter banks are used to separate moving targets from stationary objects and clutter. These processes utilize the Doppler frequency shift of the moving target. Because the moving target indication processes and Doppler filter bank processes are performed with the pulse repetition period as a unit, several pulses are required to obtain output from the filter bank. If the search radar considered here uses an electronically scanned antenna, the fact that several pulses are required for one steered beam means that search capability is limited (e.g., the searchable region is narrowed). A method is proposed here that uses the quadrature mirror filter with a range cell as the process unit for the Doppler filter process for high‐speed target Doppler separation to reduce the number of pulses required for each beam. The quadrature mirror filter is a filter that performs the orthogonal wavelet transform. This original signal can be separated without wasting information in the time‐frequency domain. Long transmitted pulses are used in computer simulations to show that the number of pulses needed in the Doppler filter bank can be reduced using this method.
A study on introduction of power spectrum density model for field merged signal and its analysis
Authors: Shishikui Yoshiaki
Published: July 2007

This paper describes a theoretical model of the power spectrum density (PSD) for a field‐merged frame signal and compares the efficiency between the field‐based coding and frame‐based coding which uses the fieldmerged signal. The field‐merged signal has also been used recently as an input signal to the spatial coding process for the coding of interlaced‐scanned television signals. However, the nature of PSD, which is an important basis for high‐efficiency coding, is not sufficiently understood in the area of field‐merged signal. For instance, optimality of the conventional techniques applied to the field‐merged signal is not assured. A theoretical PSD model for the field‐merged signal has been introduced and its properties have been clarified in relation to the motion of the image. The performance of frame based‐coding is calculated using this model.
Radar clutter suppression using notch filter bank in multibeam radar
Authors: Kondo Michimasa , Fujisaka Takahiko , Iwamoto Masafumi , Okada Takamitsu , Tachibana Yasuo
Published: July 2007

A new clutter suppression method is proposed for a multibeam radar with which the profile of the input signal can be estimated with a statistically high accuracy. In this method, the suppression filter is selected adaptively from the discrete notch filter bank on the basis of the estimated clutter bandwidth. As the selection method, the concept of selection probability linked to the bandwidth estimation accuracy is introduced so that the selection algorithm is derived. To evaluate the performance of the system based on this algorithm, the conventional improvement factor is improved by defining the performance function taking into consideration the filter selection probability and the desired detection probability. Based on these factors, a configuration example of a notch filter bank is presented for the model radar.

The system performance is evaluated by the figure of merit (FOM) defined here. The results obtained are: (1) there exists an optimum maximizing the FOM in the clutter bandwidth estimation accuracy and the filter distribution spacing; and (2) if the estimation accuracy is increased in response to the distribution spacing of the filter bank, the FOM is improved as the distribution spacing is reduced.
Performance of an asynchronous transfer mode local area network switch with backpressure function‐maximum throughput analysis
Authors: Ohsaki Hiroyuki , Wakamiya Naoki , Murata Masayuki , Miyahara Hideo
Published: July 2007

As an effective traffic control mechanism of the asynchronous transfer mode (ATM) local area network (LAN) which has been getting attention as the next‐generation high‐speed LAN, the reactive congestion control is considered. In this paper, to obtain such a traffic control mechanism, a scheme to add the function of backpressure to an ATM switch having buffers in both the input side and the output side is evaluated. Also in this paper, the maximum throughput of an ATM switch with backpressure function for burst traffic is analyzed mathematically. Further, a uniform traffic load and a mixture of such traffic occupying the bandwidth in a peak rate as voice and video are analyzed. Moreover, with some numerical data examples, the effect of the output buffer size and the burstiness of the arriving traffic on the system performance is analyzed.
Analysis of characteristics of a cross‐product frequency discriminator in four‐phase‐shift keying systems
Authors: Osuga Katsumi , Miyauchi Kazuhiro
Published: July 2007

Characteristics of a cross‐product frequency discriminator and the responses of an automatic frequency control (AFC) closed loop using the discriminator are analyzed theoretically in this paper for practical four‐phase‐shift keying (4PSK) transmission systems that have band‐limiting filters in their transmitters and receivers. The general expressions for the characteristics and the responses are derived when these filters are assumed to have arbitrary characteristics and three types of 4PSK, i.e., QPSK, offset QPSK, and π/4‐shift QPSK, are assumed.

The expression for a deterministic component and the autocorrelation functions for random components are obtained first in the case of an open loop. Those results then are used to obtain the power spectral densities, and the expression for variance of frequency fluctuation is shown. The variance is used to calculate frequency jitter in an AFC closed loop.

The variance of frequency fluctuation consists of three components. The components yielded from a product of noise and noise and a product of noise and signal are independent of the modulations. The component from a product of signal and signal, on the other hand, depends on the modulations. The components for quadra‐phase‐shift keying (QPSK) and for π/4‐shift QPSK are equal, but the component for offset QPSK is larger than that for the others.
Characteristics of mobile communication traffic in a two‐way band‐shaped service area
Authors: Kabasawa Tatsuya , Sengoku Masakazu
Published: July 2007

In a cellular mobile communication system, a service area is divided into many cells for efficient use of channels. It is necessary to take into consideration intercell vehicle movement for teletraffic performance evaluation of such cellular mobile communication systems. Its performance evaluation has been done for a one‐dimensional band‐shaped area, e.g., a highway, assuming that vehicle movement is one way.

This paper presents a theoretical performance evaluation of a one‐dimensional band‐shaped area, assuming two‐way vehicle movement. First, whether steady‐state performance for the traffic offered to each cell is constant is analyzed and then the transient characteristic for the case in which traffic varies with time is analyzed. Through a comparison of theoretical and simulation results, the validity of the theoretical result is demonstrated.
Fundamental characteristics of multiple‐access schemes for satellite communication networks
Authors: Onozato Yoshikuni , Saito Miki , Teruya Ken
Published: July 2007

In multiple‐access schemes for digital satellite communication, a collective arrangement is needed in which all the uncoordinated users may share a single satellite channel. The slotted ALOHA scheme is basically a random access scheme where the time axis is slotted and each earth station transmits packets at random.

In this paper, the stability issues of the slotted ALOHA scheme and its useful limits are discussed first. This gives the useful range of a basic type of random access scheme. Next, the instance conflict scheme is explained where multiple access according to the demands of various users is possible. This scheme can satisfy the basic requirements of the satellite channel according to the demand of various users.
Application of a near‐field measurement to the characteristics verification of a polyhedron approximated antenna
Authors: Hanayama Eiji , Someya Suguru , Takano Tadashi
Published: July 2007

In most of the deployable antennas to be placed on board a satellite, the main reflector is made of planar facets or ruled surfaces. Therefore, an anomaly can be expected in the electric field distribution on the aperture in comparison with the smooth reflector. This paper presents the near‐field measurement method, relevant problems, and measurement results for a polyhedron approximated antenna with a reflector made of planar facets. The near‐field measurement system is of a polarplane scanning type, and the two polar components of the electric field can be measured simultaneously. With this system, the near‐field of the polyhedron approximated antenna is measured. It is experimentally shown that the amplitude is maximum at the junction of the facets; thus, the validity of the previously reported theoretical analysis is proven. Although the near‐field distribution depends on the measurement plane, the results of the transform of such a distribution to the far‐field by the aperture distribution method are identical regardless of the measurement plane. Further, reduction of the near‐field measurement points is discussed. In the case of the present antenna, it is shown to be necessary to use 30 points and 36 points, respectively, of the number of measurement points in the radial and circumferential directions with the measurement scan range at the circumscribing circle of the hexagonal aperture, if the far‐field paraxial radiation characteristics obtained are accurate to within 1 dB.
A packet‐generation model based on communication characteristics in an ethernet system
Authors: Ishida Yoko , Takahara Mikio
Published: July 2007

Some communication characteristics of an Ethernet were measured and investigated for the purpose of creating a packet‐generating model for use in network characteristics simulations. The communication protocols measured were Telnet, X‐Window, NetWare, Apple Talk, and so on. The measured results showed some interesting characteristics for the generated packet‐length distribution and the packet‐generation spacing depending on the communication contents and the terminal types such as Server and Client terminals. Based on the measured data, a variable packet‐length generation model for use in network simulations is created. Some simulated results using the model are shown and differences between the variable and the fixed packet‐length models are investigated for the throughput characteristics.