bluuebunny/crossref_metadata_2025 huggingface dataset:
A reconfigurable wiring concentrator in hierarchical star with dual‐ring LAN
Authors: Nakayashiki Susumu , Kashio Jiro , Harakawa Takeshi
Published: July 2007

The in‐house information communication network using local area network (LAN) is required to cope flexibly with the expansion/modification of the system and to avoid the system‐down in the generation of a fault by detaching the fault domain.

This paper considers the star‐ring LAN with the ring spurs and a dual ring. It proposes also the structure and control of the wiring concentrator of ring LAN with the dedicated automatic reconfiguration control by the ring spur bypass and the ring wrapback. Since the ring contains both the ordinary terminals and WC, the reconfiguration‐dedicated medium access control (MAC) frame is introduced anew and can be sent only by wiring concentration (WC), making unnecessary the specification modification of the MAC layer of the terminal.

The WC which handles the localization and detachment of the fault point is determined by this mechanism. The test ring is automatically expanded from the local ring in WC to the ring containing the ring spur and the ring containing the dual ring successively by testing the conductivity.

Using WC, a ring LAN system with the automatic ring degeneration/expansion function can be realized, while providing the terminal with the function of connection/detachment/shift on LAN (hot‐pluggability). The time required for reconfiguration by the proposed reconfiguration control is evaluated by summing up the times for the major control steps and by experimental examination.
Effects of transmission delay in audiovisual communication
Authors: Kurita Takaaki , Lai Satoru , Kitawaki Nobuhiko
Published: July 2007

To provide audiovisual communication such as television telephone and television conference economically and efficiently, high efficiency coding, satellite communication and asynchronous transfer mode (ATM) are considered for introduction to the communication network. However, these technologies may degrade communication quality since they increase the signal propagation delay time. The effect of the propagation delay on the communication quality has been studied frequently for voice communication by telephone, but there have been few studies on audiovisual communication. Further, the effect on the delay quality by the addition of video to the voice has not sufficiently been understood.
Transmission loss budget design of the optical star‐shaped ring network
Authors: Hakamata Yoshiro , Sueyoshi Yoshinao , Okuno Masayuki
Published: July 2007

One high‐fidelity ring‐type optical transmission network is the star‐shaped ring network having a multi‐port accessory in its hub. The present paper describes the transmission loss budget design for the star‐shaped ring network that takes into account continuously received interference signals. Conventionally, the S/X value, which is the ratio of the main signal power to an interference signal power, has been used to evaluate the degree of interference.

First, the factors responsible for determining this ratio are discussed and then a design chart is derived to correlate the S/X value with the level difference between the transmitter and the receiver for the network. Based on this design analysis, multiport optical accessors are fabricated; and measured results are presented. It is demonstrated that the star‐shaped ring network with, desirable performance can be realized successfully. Finally, a method to lower the level difference between the transmitter and the receiver using multiwavelengths is proposed.
Scattering of circularly polarized waves by a conducting cylinder–a representation in terms of circularly polarized energy flux densities
Authors: Tokumaru Shinobu , Ping Wang
Published: July 2007

To understand the radiation and scattering phenomena of electromagnetic waves visually, streamlines of the electromagnetic energy flux density are drawn. This paper attempts to show the scattering phenomena of circularly polarized waves in the presence of an infinitely long perfectly conducting circular cylinder by graphical presentation of the streamlines. This is based on the Poynting vector and circularly polarized electromagnetic energy flux densities proposed recently.

From the viewpoint of circularly polarized electromagnetic energy flux density, the conversion of a circularly polarized field to a cross‐polarized field on the cylindrical surface is drawn specifically. Even though the structure of the scatterer is two‐dimensional, the streamlines of the electromagnetic energy flux density is threedimensional. This phenomenon originates from the nature of toroidal fields of the Poynting vector and the cross Poynting vector.
Fault location in optical lines of passive double star networks by pattern matching of OTDR waveforms
Authors: Takeda Kazutoki , Koga Hiroaki
Published: July 2007

Passive double‐star networks (PDS) in which optical branches are used to connect local offices and subscribers have been intensively studied. If optical time domain reflectometry (OTDR) is used to test optical cables, the return wave will be a complex superposition of many reflected waves from many optical branches. Therefore, the determination of fault locations by conventional analytical methods is difficult. To detect fault locations more accurately, a new method using pattern matching of the reflected waveforms obtained by OTDR with the waveforms calculated by a computer is proposed. The scattering matrix and an algorithm for calculating the waveform are described and the principle used in detecting the fault location is discussed. A theoretical equation for the error due to noise in the optical circuit is formulated and is used to derive an equation relating the measurement error to the location of the fault, the number of branches, the bandpass frequency, and the pulsewidth. An experimental optical cable (about 3 km long) with four branches was fabricated and used in tests of the accuracy of fault location with a pulsewidth of 1 μms. The error was found to be less than 12 m.
A dynamical system model and equivalent steering signal concept in adaptive arrays
Authors: Ueno Motoharu , Kawabata Kazuaki , Moro‐oka Tasuku
Published: July 2007

The versatile and affluent adaptive array antenna (adaptive array) is studied as a linear dynamical system. Also, the concept of the equivalent steering signal is introduced by expanding the concept of the steering signal of a maximum signal‐to‐noise ratio (MSN) array. The adaptive array is considered as a system which is expressed by two equations, i.e., the state equation and the output equation, and its model is proposed. As the input signal to this method, the equivalent steering signal is defined. Based on the correlation coefficient between the equivalent steering signal and the array input signal, the characteristics of adaptive arrays are analyzed.

From this viewpoint, a simple, clear and systematic investigation method for adaptive antennas is proposed for several characteristics of adaptive arrays for which the analysis is cumbersome and the physical meaning is not clear in the conventional methods. Further, it is illustrated that the equivalent steering signal is related closely to the a priori information of the desired signal which is important in the adaptive array. The importance of the a priori information in the adaptive array is emphasized.
A method to estimate normal mode noise voltage induced on indoor telecommunication lines due to adjacent AC supply lines
Authors: Ideguchi Tsuyoshi , Hattori Mitsuo , Ootsuki Fumio
Published: July 2007

When metallic telecommunication lines carrying digital signals are laid adjacent to ac supply lines in an office or a house, then the noise generated by the ac supply lines is induced on the telecommunication lines and the quality of transmission may be degraded. To calculate the induced voltage generated directly between the cores of a telecommunication line requires accurate values of the coupling admittance or coupling impedance between the two lines corresponding to the cable construction and the problem becomes very complicated.

This paper proposes a simple method of estimating the voltage induced between the cores of a telecommunication line when the telecommunication line is laid adjacent to an ac supply line. The amount of coupling from the primary circuit with an open‐circuited terminal and with a short‐circuited terminal to the secondary circuit is measured. Using this value, the characteristics of the induced voltage corresponding to an arbitrary value of terminal impedance of the primary or secondary circuit simply are estimated. The validity of the estimation method was confirmed by experiments.
Improving the sensitivity of electric field sensor with linbo3electrooptic crystals by loading inductance
Authors: Tajima Kimihiro , Amemiya Fujio , Kuwabara Nobuo , Kobayashi Ryuichi
Published: July 2007

Recently, with the diversification of electromagnetic compatibility (EMC) problems, the need for an electric field sensor to measure the electromagnetic pulses and the electric field near the equipment has increased greatly. An electric field sensor using LiNbO3, which has an electrooptical effect, has been used for such measurements; but the sensitivity is not satisfactory. However, the sensitivity can be improved by increasing the sensitivity of the optical modulator or by increasing the output of the optical modulator source.

Here, we describe a method to improve the sensitivity at resonance frequency by loading inductance. First, an equivalent circuit representing the sensor with loading inductance is derived. Second, the frequency characteristics are analyzed theoretically by applying the moment method to this equivalent circuit and the improvement in sensitivity by loading inductance is demonstrated. Moreover, the validity of analysis is confirmed by performing the experiments using the GTEM‐cell.

As a result, it is found that the measured results show good agreement with the calculated results and the sensitivity can be improved by inductance loading. It has been confirmed that the sensitivity of the electric field sensor with element length of 150 mm could be improved by about 40 dB at 200 MHz by using the loading inductance of 600 nH.
Observation of k‐distributed sea clutter via an x‐band radar
Authors: Ishikawa Yoshihiro , Sekine Matsuo , Musha Toshimitsu
Published: July 2007

In radar signal processing, it is important to eliminate unwanted noise called clutter and to detect the desired target so that the degree of discrimination is improved. To this end, the statistical characteristics of the clutter have been investigated. In such instances, it is necessary to have a process which obtains a constant false alarm rate (CFAR).

In this paper, the amplitude intensity distribution of the sea clutter measured by an X‐band radar is studied quantitatively by means of the Akaike Information Criterion (AIC) under an assumption that the intensity distribution is Weibull, log‐normal and K‐distributions. It is confirmed that, for a high sea state with wave height of 6 to 9 m and wind velocity of 25 m/s, the sea clutter follows a log‐normal distribution as a whole and a K‐distribution within the antenna beamwidth.

With regard to the CFAR circuit by normalization of the standard deviation which is considered effective for suppression of the clutter following a Weibull and a log‐normal distribution, a CFAR processing was carried out with both Monte Carlo simulation and raw data. From the results of computer simulation, it was confirmed that the CFAR circuit is effective for suppression of clutters following a K‐distribution. Also, by processing the raw data by this circuit, it was successful in correctly detecting targeted ships while the clutter was suppressed.
A subband‐dpcm codec for HDTV and its performance
Authors: Irie Kazunari , Okumura Yasuyuki , Sakurai Naoya , Kishimoto Ryozou
Published: July 2007

Transmitting high definition television (HDTV) signals over digital networks requires bit‐reduction coding techniques if cost‐effective services are to be provided. This paper describes a high‐quality HDTV codec that can encode original 1.2 Gbit/s HDTV signals into 60 and 300 Mbit/s. These bit rates are selectable and are compatible with the transmission rate used in B‐ISDN based on the synchronous digital hierarchy (SDH). A subband DPCM (differential pulse‐code modulation) coding algorithm capable of distortion‐free encoding is used. A new type of perfect reconstructive short‐kernel subband filter that reduces subband signal entropy is introduced. the performance of the codec is evaluated using actual video signals. Experimental results show that a very high percentage of the component signals can be transmitted distortion‐free at 600 Mbit/s. High‐quality images can be regenerated from the 300 Mbit/s signal.
Computer experiments for excitation mechanism of upshifted electromagnetic emission observed in ionospheric heating experiments
Authors: Ueda Hiroko , Goodman Simon , Matsumoto Hiroshi , Omura Yoshiharu , Okuzawa Takashi
Published: July 2007

The component wave called the BUM (broad upshifted maximum) excited at the time of electromagnetic heating experiment of the ionosphere is seen on the higher‐frequency side band of the pump wave or its harmonics. Therefore, its excitation mechanism cannot be explained by a simple parametric instability. There fore, the mode instability theory based on the nonuniform density plasma has been proposed.

In the present research, in reference to the theoretical prediction as a starting point of analysis of the excitation mechanism, computer experiments are carried out by means of the electromagnetic particle code. It was confirmed that the density nonuniformity of the plasma is important for the excitation of the BUM. Also, an excitation mechanism of the BUM conceivable from the computer experiment results is proposed.
Virtual path restoration techniques based on centralized control functions
Authors: Hadama Hisaya , Kawamura Ryutaro , Sato Ken‐Ichi
Published: July 2007

To create a highly reliable ATM transport network, one of the most important issues for network providers is to identify the most efficient restoration technique against network failure. This paper determines which virtual path route alteration techniques can restore virtual paths against single‐link failure in a nationwide ATM transport network within a few seconds.

First, centralized restoration techniques are classified and the relative benefits of the techniques are clarified. Then the evaluate restoration time, necessary spare capacity, size of data storage and necessary time for data distribution from the control center to cross connect systems for restoration are evaluated. This study shows that virtual path grouping and predetermined route alteration scenarios are extremely effective in restoring damaged virtual paths rapidly. High‐speed data distribution links or predistributed route alteration data also are important for rapid restoration from failure.
SN improvement ratio by time delay and integration for high‐resolution earth observation system
Authors: Nagura Riichi
Published: July 2007

The improvement of the signal‐to‐noise (SN) ratio is one of the most important issues for the high resolution earth observation system. A time delay and integration (TDI) method combining plural CCD output signals should provide the solution for acquiring high SN ratio without increasing the optical diameter. However, for an actual satellite, there are various fluctuations in the satellite attitude or jitters from other equipment, which degrade the SN improvement ratio achieved by the time delay and integration method. This paper analyzes SN improvement ratio characteristics under the above fluctuations. the paper reveals optimum integration times and the maximum SN improvement ratio and also the requirement on satellite attitude variation and jitters from other equipment. the paper also discusses the methods to obtain the maximum SN improvement ratio using correlation detection between adjacent CCD for the time delay and integration method even under the presence of the above fluctuations.
Characteristics of a slot‐couped microstrip antenna using high‐permittivity feed substrate
Authors: Takeuchi Kazunori , Chujo Wataru , Fujise Masayuki
Published: July 2007

The slot‐coupled microstrip antenna can be used for constructing a thin and lightweight active antenna without a feed loss by electromagnetic coupling of such active circuits as MIC and MMIC on the back side directly with the radiating element via the slot. Hence, this structure is promising as a highly functional mobile communication antenna. In this case, the feed substrate has a high dielectric constant as MIC and MMIC and are used while the antenna substrate has a low dielectric constant so that a large bandwidth and a high radiation efficiency can be obtained. It is important for the design of active devices to understand various characteristics of the present antenna constructed from substrates with different dielectric constants.

In this paper, the effect of the dielectric constant of the feed substrate on various antenna characteristics is derived both by measurement and by computation using the spatial network method. It is found that the resonant frequency changes if a high dielectric consant material is used, although the amount of change is less than the relative bandwidth and that the relative bandwidth of the antenna does not depend on the dielectric constant of the feed substsrate. When an MIC or an MMIC is attached to the back side, the radiation from the feed line including the slot to the back side is coupled directly with the active device and causes intermodulation. the effect of the dielectric constant of the feed substrate on the back‐side radiation is an indispensable item of investigation for development of active antennas. This investigation also is carried out in this paper which deals with the effect of the dielectric constant on the backside radiation.
Approximate analysis of a bidirectional looped dual‐bus network
Authors: Shi Guizeng , Fukuda Akira
Published: July 2007

The characteristics of a system consisting of a number of terminals (queues) connected to two buses with slots in opposite directions are analyzed here. Cells arrive independently at each terminal and are sent to a gateway station on an empty slot. In addition, cells to be emptied at terminals may be loaded on the slots transmitted from the gateway station. Such a slot can be utilized by a destination terminal and its downstream terminals. A bidirectional bus structure is used to alleviate unfairness among terminals and to improve system reliability. A rigorous solution of a basic model consisting of only one queue is first obtained in analyzing this system. Next, an approximate analysis is performed on the target model utilizing the foregoing result. Since rigorous analysis of the characteristics of the target model is difficult, two approximate analyses are proposed here. the validity of these approximate analyses is evaluated by making comparisons with simulation results. the results indicate that the analyses presented in this paper are useful and are sufficiently accurate for the case without cell unloading.
SDH line‐error detection method using reduced BIP
Authors: Tokizawa Ikuo , Ueda Hiromi , Uematsu Hitoshi
Published: July 2007

For STM‐N transmission lines in a synchronous digital hierarchy (SDH), a 24N bits interleaved parity (BIP) detection code is established in order to monitor transmission line errors. the hardware required for BIP code calculation increases in proportion to the speed of the transmission line. For example, with STM‐16 (2.48832 Gbit/s), the BIP code uses 384 bits, and the line‐error detection function occupies a large portion of the SDH interface hardware.

This paper proposes a method to solve the foregoing problem, which implements line‐error detection by using a shorter BIP code obtained by conversion of the received BIP code, at the receiving end. At the transmitting end, BIP code conforming with the ITU‐T (formerly CCITT) standard is generated. This method allows integration with international standards, without degrading performance. That is, with an STM‐16, the hardware size is reduced by about 3000 gates, which is approximately a 20 percent reduction in the total gate count of an SDH processor.
Number of wavelengths required for constructing optical path network considering restoration
Authors: Hamazumi Yoshiyuki , Nagatsu Naohide , Okamoto Satoru , Sato Ken‐Ichi
Published: July 2007

Optical networks that support high‐speed, low‐cost communication services are required. an optical path is proposed that utilizes wavelength multiplexing technology at the path layer of transport network layers. Optical path schemes, wavelength path (WP)/virtual wavelength path (VWP) that can realize optical path networks are also proposed. Although wavelengths are a resource in optical networks, the number of wavelengths required to construct an optical path network has not been evaluated.

This paper describes a method of network protection using the optical path technique that enhances network reliability and proposes a method for establishing a restoration path that restores failed active paths in both WP and VWP schemes. Proposed herein is an optical path accommodation design to establish WPs or VWPs in a physical network considering the proposed restoration method. Furthermore, optical path networks are constructed by establishing WPs or VWPs on a physical network that has a regular structure and the number of wavelengths required in the network are evaluated. This evaluation makes it clear that the VWP scheme requires fewer wavelengths than the WP scheme.
NTSC interframe direct coding scheme by composite motion compensation on hadamard transform
Authors: Hamada Takahiro , Matsumoto Shuichi
Published: July 2007

As a highly efficient coding scheme for the TV signal, the component coding based on the motion‐compensation DCT is employed widely because of its high coding efficiency. On the other hand, the TV signals in the studio in the broadcast station, etc., are based mostly on the composite TV signal configuration including NTSC. In the composite TV signal, the subcarriers modulated by the chrominance signal are superposed on the luminance signal. Consequently, the algorithm for the component coding cannot be apolied directly.

With such a situation as the background, this paper proposes an NTSC direct interframe coding scheme in which the motion compensation can be applied directly to the composite TV signal. the direct coding is realired in the proposed scheme using the composite motion compensation that compensates the phase errors of the color subcarrier component and the chrominance component on the Hadamard transform.

It is shown as a result of computer simulation that the motion compensation, with the same efficiency as that of the original luminance/chrominance separated motion compensation DCT, can be realized by directly applying the proposed scheme to the composite TV signal. It is shown also that the generated information content, when there is no distortion, is reduced by approximately 30 percent compared to the original scheme.
Tentative reduction of analog cellular facsimile communication time
Authors: Uchiyama Hiroki , Kokaji Harumi , Kasuga Masao , Kagawa Tetsuya
Published: July 2007

Various studies have been done, mainly from the viewpoint of improving image deterioration on G3 facsimile transmission using analog cellular channels. This paper discusses communication time with analog cellular facsimile transmission using ITU‐T's error correction mode (ECM). the communication state graph proposed shows its transmission state. Then the protocol of standard ITU‐T's ECM is studied and an effective fall‐back method is proposed. the goal is to use a 9600 bps modem rate, which is not used in analog cellular facsimile transmission, and then an effective fall‐back, e.g., from 9600 bps to 7200 bps, is performed in the case of poor line conditions. This method allows the communication time in analog cellular facsimile transmission to be shortened. Results of field experiments have revealed that a shorter communication time can be achieved with the proposed method than with the conventional transmission method.
Technique for estimating electromagnetic field distributions in and around buildings using wire‐grid approximation
Authors: Maeda Yuji , Murakawa Kazuo , Yamane Hiroshi , Tokuda Masamitsu
Published: July 2007

The technology to derive analytically the electromagnetic field distribution inside and outside a building by the electromagnetic interference caused by electronic equipment and from external illegal CB has been an important subject of study for establishment of the protection of damages to equipment.

In this paper, the building as a complex configuration is approximated by a wire‐grid model considering its steel frame construction. the electromagnetic field distribution inside and outside the model is analyzed numerically by the moment method so that the distribution of the electromagnetic interference around the building is derived.

First, for a model of a simple building, the calculated and measured electric field intensity values are compared. They agree within a maximum deviation of 3 dB in the frequency range of 30 MHz to 1 GHz. the effectiveness of the calculation method and the resonance characteristics of the building model have become clear.

Next, an actual building (Telecommunication Center Building) was modeled and the calculated and measured values of the electric field intensity in the model were compared. the calculated and measured results agreed within a maximum deviation of 5 dB in the frequency range of 30 to 200 MHz so that the validity of the present estimation method was confirmed. Also, the frequency characteristics of an actual building have become clear.
Even harmonic resonant class E tuned power amplifier without RF choke
Authors: Iwadare Minoru , Mori Shinsaku , Ikeda Kazunaga
Published: July 2007

A method for designing an amplifier that does not need an RF choke coil is proposed. This is accomplished by adding a shunt capacitor to a class E amplifier with a shunt inductor; this creates class E switching where higher harmonics are induced in the inductor‐fed input waveform. A design method is derived by performing an analysis of the circuit assuming load current is sinusoidal. Because the switch current is smaller than that of conventional class E amplifiers (with the same output power), the losses due to the series saturation resistance of the switch device are greatly reduced for the proposed amplifier. A 96‐percent RF conversion efficiency for 2 W of output power was obtained in experiments using a 2‐MHz switch using the proposed design.
Configuration and characteristics of an interference cancellation system using a pilot signal for radio channel estimation
Authors: Fukasawa Atsushi , Sato Takuro , Kawabe Manabu , Sato Sinichi , Sugimoto Hiroki
Published: July 2007

This paper proposes a new configuration for an interference cancellation system for spread‐spectrum communications and will verify its performance. In the proposed system, a pilot signal with a known code is spread modulated without altering the data and sent to the common reverse link. Blind deconvolution is avoided because the characteristics of the radio channel are determined from the received pilot signal. The new configuration is simpler and offers improved interference cancellation.

A filtering system is proposed for the estimated and the correlated signals using a time‐variant model to alter the characteristics of the radio channel along with the operation of the personal station. A sequential configuration system is proposed for interference cancellation (simply called cancellation). This is considered to be equivalent to the basic configuration that has been previously proposed, yet it further simplifies the configuration. The cancellation system is based on the system stated above. The path‐diversity combination of the delay wave and the data and the amount of interference on the destination and interfering channels are estimated, and interference from other channels is removed.

This paper discusses, first, the estimation system for time‐variant multipath radio channels and, second, the configuration of sequential cancellation and its management. Based on the above, a cancellation system is proposed and the effectiveness of the proposed system is verified.
A differential positioning scheme with a single satellite to be incorporated into mobile communications
Authors: Yabumoto Yasuyuki , Katayama Masaaki , Yamazato Takaya , Ogawa Akira
Published: July 2007

The case in which the radio determination capability is integrated into a mobile satellite communication system is investigated and a positioning scheme is proposed which operates with a single satellite. In the proposed scheme, each mobile terminal is designed to be equipped with the minimum additional function for positioning, aiming at the integration of communication functions with low cost. It is not necessary to transmit the correction signal for range error although a differential technique is applied to improve positioning accuracy. To evaluate the feasibility of the proposed scheme, we calculate the horizontal dilution of precision (HDOP) and available area taking account of the time period required for positioning and satellite altitude.
Design and evaluation for the mobile packet communication system using continuously allocated small zones
Authors: Takaba Sadao , Sakai Sei‐Ichirou , Sekine Tomiyoshi , Hamabe Kojiro
Published: July 2007

A new land‐mobile packet communication system is proposed in which continuously allocated small zones are used. This system is an expansion of a spot‐covered digital communication system, the application of which to mobile navigation is currently being advanced.

In this system, data for driving guidance and general‐purpose data are assumed to be transmitted. The communication control of this system is designed and a hierarchical system configuration and efficient communication protocol are proposed. Also, the effectiveness is confirmed through system evaluation by an experimental model which consists of two pieces of mobile equipment and two roadside stations and by computer simulation.
Surface error measurements of large reflector antennas by phase retrieval holography—an application of extrapolation algorithm
Authors: Nishibori Toshiyuki , Hirabayashi Hisashi , Kobayashi Hideyuki , Murata Yasuhiro , Shimawaki Yutaka , Nomura Takuya
Published: July 2007

This paper investigates the phase retrieval holography (PRH) method using the Misell algorithm for measuring the surface error of a large reflector antenna. PRH is a technique that does not require phase measurement. The algorithm is investigated experimentally and the estimation errors are evaluated quantitatively using measurement simulation. First, it is shown that estimation errors can be reduced using an initial aperture distribution calculated by ray‐tracing. The measurement resolution is improved by applying an extrapolation algorithm to the Misell algorithm. Finally, the surface error of a Cassegrain antenna with an aperture of 64 m to resolution of about 4.1 m in the aperture plane was measured by receiving a test signal from a geostationary satellite (frequency: 1.545 GHz). As a result of the experiment, the surface error of 1.57 mm RMS and measurement reproducibility of 0.54 mm RMS were obtained and it was confirmed that this method is effective as a simple surface measurement method.
Stimulated brillouin scattering threshold representing bit‐error ratio degradation in single‐mode optical fiber transmission
Authors: Hayashi Yoshihiro , Ohkawa Norio , Ito Takeshi
Published: July 2007

Achieving maximum repeater spacing in optical fiber transmission systems is compromised by the input power limit due to stimulated Brillouin scattering (SBS). In digital transmission, SBS causes bit‐error rate degradation. The calculation method for the SBS equation under steady state in a single‐mode optical fiber has been established here; boundary conditions and actual environment are both considered. A new SBS threshold has been proposed as the input optical power at which the backscattered SBS power equals the Rayleigh backscattering power at the fiber input end. Based on a detailed comparison with experimental results, it has been confirmed that the proposed threshold expresses accurately the bit‐error rate degradation due to the SBS; it is approximately 2.5 dB lower than the conventional threshold. Use of the proposed threshold makes accurate system design possible.
Loss probability in distributed‐type communication networks through semishortest routing–for connectionless services
Authors: Takase Juhro
Published: July 2007

A number of logical networks with differing traffic characteristics need to be generated over a distributed physical network in order to deal effectively with future call types and service configurations that involve a range of basic situations. Also, each call must examine one connectionless‐type logical network by selecting the logical network that conforms to fundamental conditions based on the connection stipulations. The shortest route is selected through each switching node for each of the individual header data blocks (HB) of the call. The semishortest routing scheme that permits an increase in the number of relay stages is chosen, notably when a block occurs. Using this scheme, the HB loss probability between the originating and destination nodes is maintained reliably at about Nminld2 where the HB discard rates for each node are d equally and each originating and destination node is sufficiently distant from each other. Nmin is the minimum number of relay stages between the originating and destination nodes, l equals 2 in grid‐type networks, and l equals 3 in honeycomb‐type networks. The number of relays on the route between the originating and destination nodes can be a maximum of 2Nmin. The loss probability can increase by controlling the maximum number of relay stages. If the number of relays is limited to Nmin + 2, the reliable maximum value of the loss probability is approximately Nmind. The minimum reliable value of the loss probability is maintained at a level Nminld2.
Interruption characteristics of distributed dynamic channel allocation with reuse partitioning and power control
Authors: Serizawa Mutsumu , Asakawa Shigeru
Published: July 2007

Distributed dynamic channel allocation (DDCA) schemes are important because they allow flexible handling of variations in traffic. It has been clarified by simulation that better call‐loss and interference characteristics are obtained by combining reuse partitioning and transmission power control schemes. Channel allocation and interference in DDCA are formalized in this article. It is also shown that a lower limit can be established in the signal‐to‐interference ratio (SIR) degradation caused by interference accompanying calls to other stations when channel allocation is performed such that reuse partitioning is ideally realized simultaneously. It is shown that this lower limit is described by the SIR margin and reuse partitioning characteristics and power control schemes. In addition, it is shown that the degrees of degradation in SIR of the mobile station and the base station in conversation can be predicted in advance, including the case in which reuse partitioning may not be performed ideally.
Multicast routing method in optical switching networks
Authors: Harai Hiroaki , Murata Masayuki , Miyahara Hideo
Published: July 2007

In realization of high‐speed and broadband networks of the next century, expectations are toward optical switching and a linear lightwave network (LLN) is proposed as one of the possibilities. Using LLNs, this paper proposes a multicast routing system in which a tree structure is formed with no loop inside the network. In this way, the waste of bandwidth caused by transmission of signals to unintended destinations is avoided. The scheme in which the tree is settled dynamically in case of generation of a call is proposed and its function is evaluated through simulations. As the results, the possibility of the efficient use of the unused links and realization of call setup control of equitable terminals are shown. Further, because of inherent LLN characteristics, the generated call blockings are small and superior performance is achieved in comparison to the previously proposed methods.
Basic characteristics of timing synchronization with recursive least‐squares for digital mobile radio
Authors: Fukawa Kazuhiko , Suzuki Hiroshi
Published: July 2007

This paper describes high precision accurate estimation methods for phase and frame timing frequency by a least‐squares adaptive algorithm for high‐precision master‐slave mobile radio synchronization systems. First, the measurement process of the received timing signal edge in the forward link is described. Next, an estimation algorithm applying least‐squares is presented and its estimation error is obtained. Furthermore, it is shown that the third‐order estimation is superior to the second‐order estimation if the reference oscillator frequency in the slave changes linearly. Computer simulations and experiments numerically verified the theoretical results on the convergence state. A synchronization using a synchronization word transmitted every 20 ms is assumed. It is shown that frequency estimation can be estimated with a precision of 10−8in several ten seconds.
An airspace design and evaluation of enroute sector by air traffic control simulation experiments
Authors: Tofukuji Noriyasu
Published: July 2007

In the enroute air traffic control which controls the aircraft flying between airports, the broad area of airspace is divided into units called sectors. This paper describes the air traffic control simulation experiments considering the function expansion project of the Tokyo International Airport and discusses the evaluation of the airspace design for the enroute air traffic control sectors.

First, the traffic volume after the function expansion is estimated. The result is compared to the already obtained result of experiments for the sector traffic capacity estimation in the present airspace. The sector for which the airspace redesign is needed is pointed out.

Next, based on the evaluation criteria considering the control process, three trial plans (A, B, and C) for the airspace design are presented and examined by experiments. Based on the results of evaluation, the fourth trial plan (D) is presented, including a new control technique. It is shown that, by using that technique, the average traffic volume in the busiest hours anticipated after the function expansion can be controlled smoothly.
A performance evaluation method that uses simple network management protocol for radio local area networks
Authors: Ujiie Keiichi
Published: July 2007

Local area network (LAN) is used widely at present, and the radio LAN also is utilized worldwide in practice. This paper focuses on the performance evaluation of the radio LAN in actual operation. It is shown that the method based on simple network management protocol (SNMP) is useful.
Protocol and network control technology for personal mobile data communication
Authors: Nakakuki Kazuo , Kuribayashi Shin‐Ichi
Published: July 2007

In tandem with a growing information society, personal communication service expansion is expected. Commercial service using a personal handy phone system (PHS) for speech communication started in July 1995. Because the demand for data communication service is on the rise, the need for a realization method is imperative. This paper studies protocol and network control technology with an eye on offering economical personal radio data communication service and clarifies the following.

(1) To share equipment with a personal radio speech service, it is desirable for the interface between a radio base station and a network to be based on I interface. Authentication processing by an out‐channel is better, and sharing the equipment with personal radio speech communication will greatly reduce future costs.

(2) After introduction of personal radio packet communication service, it is suitable for location registration, including that of speech terminals, to be done by packet.

(3) To achieve both economy and wide applicability, a scheme in which service control node accessing at terminating exchange nodes is unnecessary is employed for basic call.

(4) With the introduction of personal radio packet communication service, terminal information, such as transfer mode, is managed at service control nodes and useless connection processing is avoided.
Jitter transmission model and jitter power estimation in pointer processing for synchronous digital hierarchy
Authors: Ohtake Kohhei , Kasai Hiroyuki , Tsuboi Toshinori
Published: July 2007

In the synchronous digital hierarchy (SDH) pointer processing system, jitter is produced in the asynchronous interface operation. Especially, it is difficult to suppress the stuffing jitter since it contains a large amplitude ultra‐low‐frequency component. This kind of jitter deteriorates especially the quality of the image transmission. Thus, it is important to evaluate the jitter in the design of the pointer processing synchronous hierarchy.

This paper considers, as the first stage, the general case where the jitters are included in the input signal as well as in the transmission/reception distribution clocks. The phase tracking condition in the SDH pointer processing synchronization system with the ternary phase control function by positive/negative stuffing is examined and the expressions for the generated jitters are formulated.

A jitter transmission model is proposed based on the formulation. Then, under the assumption that the difference input jitter has the spectrum with the first‐order cutoff and exhibits the Gaussian distribution, estimation formulas are shown for the jitter power spectrum and the jitter power. Using the expression for the jitter power, the case of the single‐stage pointer processing synchronization system is estimated. The effect of the power and the bandwidth of the difference input jitter on the stuffing jitter power, which is the major factor for the transmission quality deterioration, is analyzed.
Geo2concentration dependence of nonlinear refractive index coefficients of silica‐based optical fibers
Authors: Wada Akira , Okude Satoshi , Sakai Tetsuya , Yamauchi Ryozo
Published: July 2007

The nonlinear refractive index coefficientn2dependence on the GeO2concentration in optical fibers is quantitatively shown for SiO2core fibers and GeO2‐SiO2core/SiO2clad fibers with Δ = 0.35–2.2% using an XPM measurement method where the phase change in the fiber of a probe signal caused by a pump signal is found from the delay self‐heterodyne spectrum. The GeO2concentration distribution which determines then2distribution in the fiber is not uniform, and the measuredn2is the average of the product of the localn2and the fourth power of the electric field in the fiber. In this work, this relationship of the measuredn2, the cross sectional distribution ofn2, and the electric field distribution in the fiber is used to define an effective GeO2concentration, ηeff. This effective GeO2concentration level is used to evaluaten2. The measuredn2increases proportionally to ηeffby the relationshipn2[x 10–20 m2/W] = 0.0552°eff[mol%] + 2.44. Furthermore, the measuredn2in the fiber agrees well with then2of bulk glass obtained a semiempirically for the nonlinear refractive index coefficient derived from linear refractive index data.
Design and performance of the fsa submarine optical amplifier system
Authors: Murakami Makoto , Takahashi Tetsuo , Aoyama Masaharu , Imai Takamasa , Sumida Masatoyo , Amemiya Masaki
Published: July 2007

The FSA submarine optical amplifier system (submarine fiber using optical amplifiers) has been developed. It can transmit signals up to 10 Gbit/s with a repeater spacing of 100 km. The submarine repeaters contain optical amplifiers for six line pairs to yield a maximum capacity of 60 Gbit/s. This paper describes its system configuration, the repeater configuration, and the fiber dispersion management scheme used to realize bit‐rate flexible transmission and in‐service monitoring.

In long‐haul optical amplifier systems, since the amplified spontaneous emission noise from the optical amplifier is the main impairment limiting the transmission distance, an SNR design technique that takes this noise into account is developed. Finally, the results obtained after the commercial installation of this system in the Kagoshima‐Okinawa route (total length 905 km) are reported, including chromatic dispersion characteristics and SNR values at both 2.5 Gbit/s and 10 Gbit/s transmission. The effectiveness of the system design is verified through the demonstration of good transmission performance and the feasibility of in‐service monitoring.
Development of 128 optical distribution system of 150 chs am/qam hybrid signals
Authors: Fuse Masaru , Kudo Yoshiharu , Maeda Kazuki , Ohya Jun , Ishino Masato , Fujito Katsuyuki
Published: July 2007

An optical distribution system for providing CATV services to approximately 30,000 subscribers using a fiber‐to‐the‐curb (FTTC) system has been developed. This system distributes the optical signal to 128 paths for 90 carriers with a hybrid 150 channel signal which accommodates 60 AM signals and 90 16 QAM signals to provide both conventional service and future services. The development of low distortion and low chirp MQW 1.55 mm DFB‐LD is discussed and the zero distortion conditions for optical fiber amplifiers are verified in the investigation of the main parameters in the design of the system. To satisfy the system specifications, the signal wavelength is chosen to be 1561 nm, the input optical power is set to 6 dBm, and a two‐stage optical fiber amplifier structure is used. The results of transmission tests are shown to verify the performance of the system. Lastly, the potential for expansion of the optical distribution system is discussed.
Application of planar multibeam array antennas to diversity reception
Authors: Mano Shuji , Kimata Masayuki , Inagaki Naoki , Kikuma Nobuyoshi
Published: July 2007

A method is proposed for constructing a diversity branch with each beam of a planar multibeam array antenna (MBAA), and its diversity reception characteristics are evaluated. The proposed method is a kind of directional diversity. If the beam‐forming network of the MBAA is lossless, each beam is orthogonal to the other so that a branch configuration with its correlation coefficient close to zero can be expected.

With respect to a three‐element planar MBAA that has an easy hardware implementation, computer simulations assuming a Rayleigh distribution environment and an indoor diversity reception measurement with test antennas were carried out.

The effectiveness of the method is confirmed as well as good agreement between the numerical results and the measurement results in the Rayleigh distribution environment. The diversity gain at the 1 percent value of the cumulative distribution by computer simulation is about 10, 13 and 14.5 dB for 2, 3 and 4 branches. Improvement of slightly less than 1 dB is expected for the addition of one extra branch.