bluuebunny/crossref_metadata_2025 huggingface dataset:
Fuzzy control of telecommunications networks using learning technique
Authors: Tanaka Yoshiaki , Hosaka Shinichiro
Published: July 2007

Communications services and traffic have become varied with the development of communications and progress in telecommunications network control for call acceptance and routing has been desired. In implementing flexible control in communications networks, which are complicated systems, introduction of fuzzy control techniques which is an application of knowledge engineering is considered to be effective.

To realize fuzzy control efficiently, it is necessary to establish appropriately membership functions that are quantitatively homologous with the target of control. However, finding and identifying such membership functions are difficult tasks.

From this viewpoint, this paper proposes a method of tuning a membership function by learning and investigates call acceptance control in detail as an example. By this method, the input values to the fuzzy system and the revenues of the network are measured and optimal values are obtained automatically for various parameters of the membership functions by learning based on these data and the past tuning history. In this study, the efficiency of this tuning method is evaluated by simulation. As a result, it has been shown that by this method membership functions converge to appropriate forms and good control characteristics can be obtained.
Analysis of microstrip antennas on a curved surface using the conformal grids fd‐td method
Authors: Oonishi Teruo , Kashiwa Tatsuya , Fukai Ichiro
Published: July 2007

With the development of mobile communication, active research is being done on the small‐sized antennas such as microstrip antennas (MSAs). Moreover, MSAs normally are placed on spherical or cylindrical surfaces as a conformal antenna.

Conformal MSAs are expected to have different characteristics compared to planar structure. In this case, numerical analysis is needed before the actual experiment.

The method of analysis which has wide applications may be considered as efficient for this purpose. One such method is the conformal grids finite‐different time‐domain method (FD‐TD method).

In this paper, an MSA on a curved surface is analyzed using the conformal grids FD‐TD method. Moreover, comparison with the experimental values also is performed. The experimental results and the analytical results are in close agreement which shows the validity of the method of analysis. As a result, it is confirmed that in the range of this paper, the input impedance and radiation pattern varies from their values for the planar patch when the patch surface is curved.
Radiation properties of microstrip array antennas fed by radial line
Authors: Shibata Osamu , Saito Sakuyoshi , Haneishi Misao
Published: July 2007

This paper proposes a new type of radial line microstrip antenna and studies both the design method and radiation characteristics. The following conclusions are obtained.

(1) The relationship between the basic design parameters of this new type of planar antenna and the radiation characteristics was demonstrated, and the essential design data of this type of antenna were obtained.

(2) A boresight antenna was fabricated based on the design data obtained in the foregoing, and it was shown clearly that such a type of antenna system offers an aperture efficiency of above 90 percent, ranging from the small‐aperture (low‐gain) type to the large‐aperture (high‐gain) type.

(3) A beam‐tilt type antenna also was studied theoretically as well as experimentally, and the relationship of its radiation characteristics with the tilt angle and aperture efficiency was explained. It was demonstrated that such an antenna system may be considered to be effectively applicable as a high‐efficiency circularly polarized planar antenna.
System to measure the chromatic dispersion of optical fibers
Authors: Nagaki Yoshiro , Taniguchi Akira , Tsukamoto Takeshi , Tanimoto Takao
Published: July 2007

Because of the progress in optical communication technology, understanding the propagation characteristic of optical fibers has become very important. In particular, since optical networks have been used widely, the evaluation of optical fibers in the field is essential.

This paper describes the measurement of the chromatic dispersion of optical fibers and a system suitable for the measurement in the field. The approach is based on the baseband phase‐comparison method. First, the conditions required for this measurement system will be clarified. Then the measurement of wavelengths and wavelength separation satisfying the requirements will be obtained by simulation. The source of each wavelength must be modulated.

However, to increase the fiber length and to improve measurement precision, a modulation method based on multiple sinusoidal waves will be proposed, and the upper and lower limit of the optimum modulation frequency will be clarified. The measurement system will be constructed from these results. The technical problems in realizing the system will be shown.

Finally, an example of data measured by the constructed system will be shown, and it will be demonstrated that a resolution of 0.01 ps/nm/km and measurement precision of ± 0.3 ps/nm/km can be achieved at wavelengths of 1.3 and 1.55 μm.
A scattering matrix of a slot set for the aperture illumination design of radial line slot antennas
Authors: Takada Jun‐Ichi , Takahashi Masaharu , Ando Makoto , Goto Naohisa
Published: July 2007

To realize the desired aperture distribution in a radial line slot antenna (RLSA), accurate evaluation of the coupling, guided wavelength and radiation phase of slot sets are required. Moreover, for the slot set similarly to the linearly polarized RLSA whose reflection is essentially large, reflection from one slot set should be reduced sufficiently to realize the desired traveling wave operation; therefore, the reflection coefficient should also be evaluated.

In this paper, the scattering matrix equivalent circuit of the slot set is presented for the design of the radial line slot antenna. Using this equivalent circuit, the slot set configuration can be optimized for reflection characteristics, and it becomes possible to realize traveling wave operation with arbitrary polarization.

Compared with the conventional analysis assuming uniform slot array, this method has greatly reduced the computation time, and the analysis and design of the antenna has become possible. This analysis has established first the designing of a RLSA with arbitrary polarization.
Measurement of a mesh reflecting surface for large deployable antennas
Authors: Hanayama Eiji , Araki Shinsuke , Takano Tadashi
Published: July 2007

In a satellite‐borne large deployable antenna, a mesh‐reflecting surface is used as a reflector material. Its electrical characteristic is an important factor determining the antenna characteristics.

In this paper, a measurement system and a measurement method are presented for the transmission loss and the reflection loss of the mesh‐reflecting surface, and an error analysis is made. With a planar mesh made of doubly inlaid knitting of gold‐plated molybdenum wires with a diameter of 30 μm, the transmission loss and the reflection loss are measured systematically, and the data are evaluated. The loss characteristics due to the anisotropy of the mesh and to the dependence on the incident angle and the polarization are found.

Further, it is shown experimentally that a loss other than the transmission loss and the reflection loss exists. A quantitative evaluation is made. It is shown that an incident angle dependence exists. A concept of a strip‐aperture model mesh is introduced which simplifies the actual mesh. By comparison with the measured results, the parameters for the strip‐aperture model are determined. Subsequently, the relationship between the actual mesh and the model mesh is discussed.
Comparative evaluation of band management systems considering multichannels in atm networks
Authors: Baba Ken‐Ichi , Saito Toshihiko , Murata Masayuki , Miyahara Hideo
Published: July 2007

Various communications services are provided over asynchronous transfer mode (ATM) networks, and traffic produced by these various services has various characteristics. Thus, in attempting to utilize circuits effectively by statistical multiplexing effects as in ATM networks, band management control reserving bands necessary to ensure communications quality in terms of cell loss probability, etc., is necessary when a call occurs. In addition, since communications quality required by various services differ, band management considering priority processing is effective. In addition, since a number of switching machines exist between transmission and reception nodes and a number of channels exist in links between each ATM switching machine, control to select one of these channels at the time of call setup is important. It is necessary even in this case to sufficiently consider traffic characteristics of calls for each service.

In this paper, channel selection methods for such multichannel links are studied. For this purpose, the multiplicity of traffic establishable for a set of channels is obtained analytically following a step‐modeling technique and the efficiencies of various channel selection methods for a number of channels are studied. The characteristics and efficiency of each method are clarified by analyses and simulation using channel utilization rate and call loss rate as efficiency parameters for designing the efficiency of channel selection systems.
Performance of adaptive equalizer using iterative application of viterbi algorithm
Authors: Murata Hidekazu , Yoshida Susumu , Takeuchi Tsutomu
Published: July 2007

The Viterbi equalizer is effective for frequency selective fading in digital mobile communication, but as the multipath component propagation delay time difference increases, the number of states increases exponentially and the computation amount increases drastically. Combining the Viterbi equalizer and interference reduction operation based on the equalization result, this paper proposes a new type of Viterbi equalizer with iterative equalization. It can expand the equalizable range without increasing the number of states. Computer simulation result shows that its performance is better than that of a conventional one.
A paraboloid antenna fed by the equiangular spiral‐bent slotted waveguide
Authors: Ohtera Isao , Ujiie Hiroshi , Yoneyama Tsukasa
Published: July 2007

With a view to focusing the electromagnetic wave, an “equiangular spiral‐bent slotted rectangular waveguide (SSW)” made of an axially slotted rectangular waveguide, which is one of the leaky wave antennas, was proposed and its focusing characteristics were reported. In this paper, a new diffusion‐type radiator based on the operating principle fundamentally identical to that of the SSW as a focusing radiator is proposed. The radiation pattern of the offset parabolic reflector using this radiator as the feed is investigated. First, its far field is treated by a wave optical approach. Using a cylindrical offset parabolic reflector as an example, the radiation pattern and the frequency scanning characteristics are studied numerically. Further, a reflector antenna was actually constructed and the measured results are compared with the analysis so that the offset parabolic antenna with a proposed diffusion‐type slotted waveguide as a feed and its frequency scanning possibility are reported.
A new ground resistance‐reducing material based on water‐absorbent polymer
Authors: Yamane Hiroshi , Ideguchi Tsuyoshi , Tokuda Masamitsu , Koga Hiroaki
Published: July 2007

The increase in communications facilities is accompanied by a rapid increase in the number of groundings required. However, it is difficult to achieve the required ground resistance values in areas of high grounding resistance such as volcanic ash, sandy or rocky soils, so that there is a strong need for the use of ground resistance reducing materials. This article proposes a method of reducing ground resistance using water‐absorbent polymers. The use of water‐absorbent polymer materials is expected to provide approximately twice the resistance reducing effect as currently used materials. When selecting such materials for placement in the soil, it is necessary to consider susceptibility to decomposition by microorganisms as well as temperature characteristics. One type of water‐absorbent polymer, anhydrous maleic acid polymers, is found to satisfy both requirements. In addition, the use of such polymers as ground resistance reducing materials requires approximately 1/160 the quantity of currently used bentonite mixtures and causes approximately 1/10 to corrosion of the copper used in grounding electrodes, demonstrating that water‐absorbent polymers are a highly useful method of reducing grounding resistance.
Design of multibeam satellite networks realized by subchannel switched FDMA (SS/FDMA) system
Authors: Shinonaga Hideyuki , Ito Yasuhiko
Published: July 2007

This paper aims at improvement of the interbeam connectivity of the multibeam satellite for fixed satellite communications under frequency division multiple access (FDMA) operation and proposes the subchannel switched FDMA (SS/FDMA) system, which is realized by installing the filter matrix on‐board the satellite. In the proposed system, each transponder is used to realize multiple interbeam connections and the interbeam connectivity is improved greatly compared to the traditional system. A satellite network among multiple beams can be constructed efficiently.

A method is shown in this paper to determine the transmission parameters which maximize the system capacity of the multibeam satellite network and minimize the average transmission equivalent isotopically radiated power (e.i.r.p.) for one carrier. Example calculations are shown for the power‐limited and band‐limited systems. In the band‐limited system, the number of subchannels and the ratio of band widths of the subchannels are important parameters.

From such a viewpoint, a method is shown which determines the number of subchannels when the bandwidth ratio of the subchannels is specified. An example calculation is shown taking into account uniform and nonuniform traffic distribution patterns.
Traffic analysis of a hybrid go‐back‐n arq scheme using repeated transmissions
Authors: Komatsu Masaharu , Kinoshita Kozo , Hayashida Yukuo
Published: July 2007

The transmission delay and throughput performances of a hybrid Go‐Back‐N automatic repeat request (ARQ) scheme are analyzed. In the hybrid scheme, multiple alternate transmissions of the copy and parity block of each data block are repeated continuously by transmitter. The receiver detects or corrects errors in a received block by using Wang and Lin's error control algorithm. It is shown that we can obtain the optimum total number of continuous transmissions of copies and parity blocks, which minimizes the average delay time and maximizes the throughput.
Adaptive KL‐transform coding of images based on variable block shapes
Authors: Matsuda Ichiro , Itoh Susumu , Utsunomiya Toshio
Published: July 2007

Although orthogonal transform coding exhibits superior coding efficiency at low rates, it shows a decreased picture quality of reproduced images as a result of noises unique to transform coding, such as mosquito noise and block distortion.

This paper proposes a new transform coding scheme, which has a high coding efficiency and significantly reduced noises. It is based on applications of the concepts of region‐oriented coding, to orthogonal transform coding, and has been attracting attention in recent years. The proposed scheme expresses all the regions by quadrilateral blocks to reduce the number of bits required for coding a region shape. Block segmentations are realized with stability and certainty by repeatedly transforming the shapes of the blocks with the square block as the initial shape.

The approximating accuracy of an image is improved by the mean values of the blocks by using a smoothing filter. In addition, KL‐transform coding derived from a correlation function model of images is applied to the luminance elements of each block, and bit allocation is optimized on the basis of this model; and the coding efficiency is improved by using an adaptive control method. Simulation results confirm that this method realizes a coding efficiency which surpasses that of the conventional orthogonal transform coding based on square blocks, and gives visually good reproduced images.
Hitless path protection switching techniques for ATM networks
Authors: Tatsuno Hideo , Tokura Nobuyuki
Published: July 2007

This paper describes a hitless path switching technique that utilizes fully the benefits of an ATM. First, hitless path protection switching in ATM networks is discussed. It is shown that for the path configuration of working and preestablished protection paths, the best switching method switches on the transmitting side. Then the proposed switching algorithm is described, along with several examples of its application to mesh and ring networks.

A cell interval compression method suitable for hitless path switching is proposed that empties and disconnects the transmission delay difference absorption buffer. Finally, an approximate formula is proposed that directly determines the multinode queuing delay. This delay is needed to calculate the capacity of the delay difference absorption buffer. The accuracy of the formula is confirmed by simulations.
A common air interface between wide‐area cordless telephone and urban cellular radio: Frequency channel doubly‐reused cellular systems
Authors: Kinoshita Yasuaki , Tsuychiya Toshiki , Ohnuki Sinya
Published: July 2007

This paper proposes a new system [1] in which the frequency channel of the wide‐area cordless telephone is reused doubly by the frequency channel employed in the urban cellular mobile telephone with a weak power. A condition is imposed whereby the two systems can operate with equal telephone qualities when cochannel interferences exist between two systems.

The radius of the microcell and the weak power are analyzed and completed. According to the analysis, the theoretical limit of the spectrum efficiency of the new system is doubled compared to the system where the frequency bands of the two systems are placed independently in adjacent bands (AB) [2, 3]. To realize the cooperation between the wide‐area cordless telephone and the urban cellular mobile telephone on the equally coexistent condition, an autonomous spectrum distributed management system is proposed in principle [3] which can maintain in a simple way the cochannel interference sharing.
Channel coding performance of an adaptive DCT image coding in combination with m‐transform
Authors: Yamane Nobumoto , Morikawa Yoshitaka , Hamada Hiroshi , Fukuda Hideki
Published: July 2007

In the conventional adaptive discrete cosine transform (ADCT) using the fixed length code, it is known that the source coding performance can be improved greatly by the combined use of the M‐transform (MT). This method is called ADCT‐MT. The purpose of this paper is to evaluate the effect of the combined use of MT from the viewpoint of the channel coding performance. In the conventional ADCT, as well as in the scene adaptive coding (SAC) using the variable length code, the damage in the reconstructed image due to the channel error often is manifested as the local block distortion. In ADCT‐MT, the damage is diffused and distributed uniformly by the inverse MT over a large number of blocks, making the damage less noticeable.

A subjective evaluation experiment is conducted (five‐step score) assuming the binary symmetrical channel. A simple error‐correcting code is applied to the coding data of the additional information and DCT dc component. When the bit‐error rate is 10−3, the average score is approximately 3.5 for ADCT and 1.2 for SAC, while it is above 4.5 in ADCT‐MT. Thus, in ADCT‐MT, the damage is little noticeable.
A method of reconstructing front‐looking radar using long‐wavelength holography
Authors: Sakamoto Yuji , Aoki Yoshinao
Published: July 2007

When the synthetic aperture method is applied to the imaging of objects in the front direction of a moving vehicle, a problem arises in that, if the objects are at positions symmetrical to the direction of movement, the Doppler frequencies change in the same way. Consequently, ghosts symmetrical to the axis are produced in the reconstructed image. From another viewpoint, when an object exists in the direction perpendicular to the direction of movement, the change of the Doppler frequency depends on the position of the object. Then the rate of change is not kept constant and the processing based on the FFT algorithm, as in the general cases of synthetic aperture radar and long‐wavelength holography, cannot be employed.

This paper proposes an imaging method for the front‐looking radar based on the principle of long‐wave‐length holography. The proposed method can solve the ghost problem for the objects symmetrical to the direction of movement using a small number of antennas in the azimuth direction. An algorithm also is proposed for high‐speed image reconstruction from the data acquired by the system. The theoretical resolution and the range of maximum possible imaging are discussed. Furthermore, the validity of the proposed method is verified by a computer simulation and an experiment using microwaves.
Characteristics of grid ferrite electromagnetic wave absorber
Authors: Naito Yoshiyuki , Anzai Hiroki , Mizumoto Tetsuya , Takahashi Michiharu
Published: July 2007

A novel ferrite grid electromagnetic wave absorber composed of sintered ferrite is proposed. Based on the condition that the return loss should be above 20 dB at 30 MHz, its wideband characteristics for suppressing reflections compared to a single‐layer absorber are demonstrated by computer simulation.

Calculating the return loss by varying the geometrical parameters of the ferrite grid, an optimum structure is determined which gives the maximum frequency band. In addition, it is found that the return loss of the grid absorber is impaired by an air gap between the ferrite and conductor. Moreover, the operating characteristics of the grid absorber are demonstrated by experimental models.
Full wave calculation method of VLF wave radiated from a dipole antenna in the ionosphere‐analysis of joint experiment by HIPAS and akebono satellite
Authors: Nagano Isamu , Miyamura Kazutoshi , Yagitani Satoshi , Kimura Iwane , Okada Toshimi , Hashimoto Kozo , Wong Alfred Y.
Published: July 2007

A method has been developed for numerically calculating, by means of the full‐wave method, the electromagnetic field intensity distribution on the ground and at the satellite altitude (∼2000 km) using the electromagnetic wave radiated by an infinitesimal dipole placed in a lower ionosphere. The amplitude and polarization are analyzed for the simultaneous observation data on the ground and the Akebono satellite for the VLF wave radiated in the ionosphere heating experiment by a high‐power HF wave. The values computed by the full‐wave method agreed well with the observed data if the VLF sources by the heating experiment are at an altitude of 66 km along the east‐west direction and the current moment is 4.3 × 104 Am.
Hierarchical video coding scheme using mean‐separated normalized vector quantization
Authors: Hanamura Tsuyoshi , Sekiguchi Shunichi , Tominaga Hideyoshi
Published: July 2007

A highly effective video coding method is proposed for application in a wide range of fields that utilize video information and in multimedia systems where data must be easily manipulated. The proposed video coding scheme is a hierarchical system that uses vector quantization and which also incorporates many of the basic coding components of the internationally standardized lowrate MPEG 1 coding system. In addition to providing the special data handling operations of MPEG 1, the new system incorporates a multiresolution hierarchical decomposition that permits the user to select a desired resolution level at the decoder. Source coding is achieved with mean‐separated normalized vector quantization applied to image blocks that contain fundamental image patterns. However, instead of using separate codebooks for each of the different prediction modes of the coding system, this paper shows that it is possible for various prediction modes to share codebooks to achieve a more efficient implementation. The coding efficiency of the new system is estimated and compared with the performance of a DCT based system. Although the signal‐to‐noise ratio of the VQ system falls short by 0.5 to 1.2 dB, subjectively, the two coding systems give about the same performance. Methods for improving the quantitative signal‐to‐noise ratio performance are also considered.
Development of VLSI of entropy coding for digital video
Authors: Fujiwara Hiroshi , Sakaguchi Toshifumi , Saito Ryuji , Maruyama Masanori
Published: July 2007

With the recent development of the digital electrical communication network and the advent of low‐cost large‐capacity digital storage media, an effort is made toward the digitization of the TV signal. Along with this, the image coding technique is becoming more important, where the research emphasis is shifting from the low bitrate pseudodynamic image representation, to high‐resolution, high‐quality images. Among various image coding methods, the feature of the entropy coding based on Huffman coding [1–3] is that a large amount of image data can be compressed efficiently by combining discrete‐cosine transform (DCT) and the motion‐compensated interframe coding, and is used presently as the indispensable element of the algorithm.

To apply the method to the future digital dynamic image with a high image quality requirement and to realize the real‐time processing, it is necessary to develop a fast processing architecture for the Huffman coding, together with its VLSI implementation. With this as background, this paper describes the fast processing architecture for the Huffman coding developed by the authors, together with its VLSI implementation.
Proposal and evaluation of time critical communication protocol on LAN
Authors: Koui Yuuji , Seno Shoichiro , Takada Yoshinori , Ishizaka Michihiro , Ideguchi Tetsuo
Published: July 2007

In the field of control and communication using LAN, such as plant control, there exists a requirement for the time critical property that the data transfer should be completed in the specified time (time window), in addition to the requirement for the high speed. In the timed token protocol (TTP) that has been used in FDDI and other systems, however, the transfer time increases when the input traffic exceeds the system specification, making it impossible to maintain the time‐critical property.

This paper proposes an extension of TTP where only the data that can be transferred within the time window are allowed to transverse by applying dynamic distributed management to the data transmission queue in each node. to demonstrate the performance of the proposed protocol, simulations are executed under various conditions; and it is verified that the protocol is effective when applied to the time‐critical communication.
Multicast routing scheme adequate for virtual path environment
Authors: Tode Hideki , Yamamoto Miki , Okada Hiromi , Sakai Yasuharu
Published: July 2007

The problem of accommodating multicast traffic in a virtual path (VP) environment under asynchronous transfer mode (ATM) conditions is examined. A network structure scheme suitable for all possible multicast communications is proposed. the expected result, statistical multiplexing effects during the accommodation of multiple multicast traffic over a VP should reduce hardware costs associated with the accommodation of multicast traffic. Multicast routing algorithms (the carrier‐to‐noise ratio (CNR) algorithm and the improved CNR algorithm) for an ATM network environment are proposed here. the efficiency of these algorithms is tested using their basic characteristics in computer simulations.
An error‐correction method of FM multiplex broadcasting for mobile reception
Authors: Kuroda Toru , Takada Masayuki , Yamada Osamu
Published: July 2007

FM multiplex broadcasting for mobile reception can provide new services such as traffic information, graphics, and characters by multiplexing new digital signals with a frequency band higher than the baseband signal for existing FM stereo sound broadcasting. From the standpoint of efficient frequency use and simplicity of broadcasting equipment, the transmission path for traffic information service should be such that it may be established quickly.

As a method of digital detection of FM multiplex broadcasting for mobile reception, level controlled minimum shift keying (LMSK) has been reported [1], where the amplitude of the digital signal has been controlled by the level of difference signal (L‐R signal) of the stereo sound.

In this paper, comparison between the (272, 190) shortened difference‐set cyclic code [4] which is used for television character multiplex broadcasting [2] or for FM multiplex broadcasting for fixed reception [3] and the one‐half convolutional code which has high error‐correction capability is performed, and an error‐correction method of FM multiplex broadcasting for mobile reception is proposed. As a result, the product code of the (272, 190) code has shown better performance as an error‐correction method of FM multiplex broadcasting for mobile reception. Moreover, laboratory transmission and field transmission experiments have been performed using this method, and it is confirmed that the mobile reception is possible within the service area of FM stereo sound broadcasting by repeating the reception three times.
System unavailability and quality degradation during available time for mobile satellite systems in the mobile ISDN era
Authors: Karasawa Yoshio , Matsudo Takashi , Minamisono Kenichi , Shiokawa Takayasu
Published: July 2007

It is expected that mobile‐radio systems will play an important role in realizing general personal communication networks through ISDN. In the near future, the so‐called mobile ISDN era, it is necessary to have common performance objectives between mobile radio links and fixed (or fiber) links and have a common assessment method for data transmission quality.

In this paper, based on the ITU‐T definition, unavailability statistics are examined in mobile‐satellite systems which are characterized by low margin systems. the characteristics of signal degradation due to propagation impairments in maritime, aeronautical, and land mobile satellite services are examined. Through this analysis, the importance of differentiation between “unavailability” and “signal degradation in available time” is emphasized when the digital signal transmission quality is evaluated.
Variable bit‐rate video transmission under usage parameter control
Authors: Kawashima Masahisa , Inoue Masahiro , Tominaga Hideyoshi
Published: July 2007

This paper proposes a method of video bit‐rate control for the case where the average transmission bitrate is constrained, considering the usage parameter control in an ATM network. By a simulation, the video quality and the network congestion probability of the variable bit‐rate (VBR) transmission system, with the constrained average bit‐rate, are compared to those of the conventional constant bit‐rate (CBR) transmission system or the VBR transmission system without the rate control. the relations among the length of the sliding window (SW) to monitor the average bit‐rate, the video quality, and the network congestion probability are analyzed.

With respect to the video quality, it is shown that the VBR transmission with the average bit‐rate control exhibits a stable image quality when SW is long and exhibits a better image quality than the CBR transmission for the cases of scene change and the panning scene. When the scene changes, the image quality changes and the VBR transmission with the bit‐rate control.

With respect to the network congestion probability, it is shown that the probability is decreased greatly by constraining the average bit‐rate and the probability becomes less when SW is made shorter.

Finally, it is shown that SW should desirably be long to stabilize the video quality but the permissible length of SW depends on how many video signlas can be multiplexed in the network.
Construction of operation platform for optical subscriber cable network using object‐oriented design
Authors: Kashima Norio , Kokubun Toshinao , Yamamoto Yoshikazu
Published: July 2007

It is anticipated that additions of wideband services and automated operation modules, as well as modification of optical cable networks, will be made in optical subscriber systems. For this purpose, the flexibility to add or modify new tasks and automated operation modules is required for future optical subscriber operation systems. A discussion follows on the development of an operation platform for the subscriber loop that is used to establish the flexible operation system by referring to the operation platform concept proposed for advanced network operation. Especially, it is precisely discussed in the field of optical subscriber cable networks; additionally, the necessary functions for flexibility and integration have been derived. Based on these discussions, an operation platform of optical subscriber cable network is designed and its prototype has been constructed. Constructed system flexibility and priority access control efficiency are confirmed through an evaluation of the constructed prototype system.
A method for estimating end‐to‐end blocking probability and traffic flow based on information on links
Authors: Matsumoto Kimihide , Yokoi Tadahiro
Published: July 2007

In circuit‐switched networks (e.g., telephone networks and ISDN), it is important to manage both the quality of the network elements and the end‐to‐end quality. This paper proposes a method of estimating endto‐end blocking probability based on traffic data measured on the links (e.g., the amount of traffic volume or the number of calls). an end‐to‐end blocking probability is an important measure for telecommunications quality management. In circuit‐switched networks, generally, there are many end‐to‐end routes used to connect any two customers. For efficient network management, statistics on the utilization of these routes are also important (this is called end‐to‐end traffic flow). an estimation method for this end‐to‐end traffic flow also is proposed.

The proposed estimation method combines link‐blocking probabilities in accordance with the network configuration and the routing policy of the network considered. the method can be applied to a wide class of networks. Computer simulations of some network models show the properties and the accuracy of the proposed method.
Performance of complexity reduced DFE with improved bidirectional equalization and inverse interpolation
Authors: Kamio Yukiyoshi , Sasaoka Hideichi , Sampei Seiichi
Published: July 2007

In land mobile communications, a frequencyselective fading due to multipath propagation greatly deteriorates the transmission characteristics, especially in high‐speed transmission. As a means to cope with such a frequency‐selective fading, the decision feedback equalizer (DFE) is studied. In the QPSK/TDMA system, a simplified DFE is already proposed for interpolating the preamble and postamble tap coefficients.

This paper discusses the application of the DFE to 16 QAM/TDMA, which has a high spectral efficiency. In this case, the error rate performance is deteriorated due to the decrease of the distance between signals, as well as the error propagation of the decision error.

From such a viewpoint, a system is proposed which contains the bidirectional equalization and the inverse interpolation based on the timing detection function for the delayed wave in the backward equalization. By this scheme, the number of taps is reduced and the irreducible error rate is improved for the case where there does not exist a delayed wave or there is the effect of a delayed wave.

The proposed system is examined by a computer simulation. the computational complexity of the proposed method is compared to the conventional method. As a result, it is seen that the proposed method can achieve a satisfactory equalization performance with onetenth the computational complexity of the conventional method.
A PSK transmission system employing transmitting and receiving butterworth filters with optimized noise performance
Authors: Okada Takahiro , Miyauchi Kazuhiro , Hangai Seiichiro
Published: July 2007

A band‐limited phase‐shift keyed (PSK) transmission system satisfying Nyquist's first criterion by an equalizer using Butterworth filters for transmitting and receiving filters is discussed. Minimum noise equalization that minimizes the receiver equivalent noise band width is proposed and the characteristics of such a system are calculated. In addition, minimum noise equalization is compared with reference equalization and roll‐off equalization and it is clarified that minimum noise equalization is better than these equalization method in frequency and power efficiency. It is shown also that the frequency efficiency and the efficiency of transmitting power have a trade‐off relationship in a bandwidth‐limiting and then power‐amplifying scheme and the frequency efficiency is increased without decreasing the transmission power by decreasing the heat loss of a high‐order transmitting filter in a power‐amplifying and then band‐width‐limiting scheme.
Prediction of urban propagation characteristics for low base‐station antennas
Authors: Iwama Tsukasa , Mizuno Mitsuhiko
Published: July 2007

Effective use of frequency is extremely important for land mobile communication where the number of users is steadily increasing. One means of achieving frequency efficiency is to employ the microcell in which the service area is subdivided into a minimum unit to increase geographical frequency reuse. One implementation of the microcell system is to position the base‐station antenna at a level below the tops of surrounding build ings. Estimation of the radio wave propagation characteristics is indispensable for implementing such a microcell system.

In this paper, a method of estimating the wave propagation characteristics between arbitrary transmission and reception points based on a building database is modeled theoretically on a computer using geometrical optical methods such as the geometrical theory of diffraction (GTD). Up to two reflections and diffractions are considered. Comparison of theoretical and measured results of the estimated propagation loss show that the estimated average error was less than about 10 dB for distances of less than 500 m from the transmitter to the receiver for streets on which the transmitting antenna is visible from the receiving antenna. By contrast, the error was about +20 dB to ‐10 dB within 600 m on a street crossing one where the transmitting antenna is visible.
Bit error rate and power penalty in MSK coherent optical communication systems with a single interfering echo
Authors: Yamaguchi Yoshiaki
Published: July 2007

If an echo is generated during transmission, then along with the principal wave (directly transmitted wave), an echo with a certain time delay arrives at the receiver, which causes degradation of receiver performance.

In this paper, the bit error rate for optical MSK communication systems with a limiter‐discriminator‐integrator‐type receiver is analyzed and the influence of echo is evaluated qualitatively as well as quantitatively.

In general, there exists a floor value on the error rate curve due to the phase fluctuation of laser light in the coherent optical communication systems, which is not reduced upon increasing the received optical power. It is shown that this floor value increases due to the presence of echo and its value is a maximum when the delay time of echo with respect to the principal wave is an integral multiple of the bit duration. Moreover, when the spectral linewidth of the light with high bit rate is narrow, then the effect of echo becomes even stronger.

A relationship between the received optical power and bit error rate is derived, and the power penalty is determined for given echo amplitude, delay time, and linewidth‐bit duration product. the conditions under which the effect of echo cannot be neglected are clarified. Moreover, the optical MSK system is compared with the optical DPSK system and it is shown that the MSK signal is degraded by echo greater than the DPSK‐signal.

The special feature of this paper is an exact analysis of the case when some phase correlation exists between the principal wave and echo due to coding considerations.
A multiaccess coherent optical communication system using common optical carrier with star configuration
Authors: Tsukamoto Katsutoshi , Fujii Takashi , Morinaga Norihiko
Published: July 2007

A variety of multiaccess optical communication systems with common carrier have been reported recently. This paper proposes a new type of multiaccess coherent optical communication system with star configuration in which a common optical carrier from a single source is distributed by a star coupler. In this system, the carrier is phase‐modulated at each user by an external modulator through a subcarrier signal and the signal is received by an optical heterodyne receiver. A feature of the system is that the distributed optical carrier and the modulated light are directional‐division multiplexed.

Theoretical analysis of the carrier‐to‐noise power ratio (CNR) of the system is carried out in this paper taking into account the effect of interference light caused by reflections, backscattering, or insufficient isolation of a circulator used in the system, followed by discussions on the allowable value of the signal‐to‐interference light power ratio and on the relation between transmitter power and maximum user numbers.
Throughput performance of ARQ schemes on a markov bit‐error channel
Authors: Komatsu Masaharu , Okamoto Katsuaki , Kinoshita Kozo
Published: July 2007

The performances of ARQ schemes depend on the error process. This paper evaluates the throughput performances of Stop‐and‐wait ARQ and Go‐back‐N ARQ schemes on an unslotted channel or a slotted channel. In these channels, channel time is divided into fixed size intervals called bit‐time and channel state changes according to a two‐state Markov chain. the two‐state Markov chain has two states, S1 and S2. In state S1, a bit‐error never occurs; while in state S2 a bit‐error occurs with probability one. Also, the property of the process is uniquely determined by two transition probabilities, i.e., the transition probability p1 from S1 to S2 and the transition probability p2 from S2 to S1.

From the analysis, it is found that the state changes less frequently for larger decay factor δ( =1 ‐ p1 ‐ p2) and the throughput performances of the ARQs depend strongly on the decay factor for fixed bit‐error rates. Furthermore, the numerical examples show that for a given bit‐error, round‐trip delay, packet length, and overhead length, their throughput and optimum packet length giving the maximum throughput become larger when the decay factor becomes larger.
A coherent demodulator for fast frequency‐hopping spread‐spectrum signal employing an adaptive algorithm
Authors: Takakusaki Keiji , Nakagawa Masao
Published: July 2007

It has been considered impossible to demodulate a fast frequency‐hopping (FFH) spread‐spectrum signal coherently in a frequency selective fading channel as a result of difficulties with making the receiver local oscillator track the phase of a received signal that lacks phase continuity. This paper proposes a coherent demodulator for both FFH‐PSK (phase‐shift keying) and FFH‐FSK (frequency‐shift keying) signal employing a method in which the received signal is noncoherently down‐converted and phase‐adjusted by an adaptive algorithm.

Computer‐simulations show that performance is better than in the case of noncoherent demodulators and that the interference‐rejection effect of the adaptive algorithm produces strong protection against interferences from other CDMA users.
Measurement of polarization characteristics of VHF radio waves reflected by the Es layer
Authors: Ichinose Masaru , Kainuma Syoji
Published: July 2007

To investigate the change of the rotation of the polarization plane of the very‐high frequency (VHF) radiowave after reflection by the sporadic E layer, a television wave transmitted from Seoul, Korea, was measured in Tokyo.

In this paper, the measurement principle and equipment for the rotation of the polarization plane are described. From the measured results, it is shown that most of the measured values have rotation by a certain angle from the polarization state of the transmission and exhibit fine changes swiftly and randomly within 40 to 90° centered at the rotated angle. Sometimes, there is a case of slow rotation from +90° to ‐90°. Further, the cause of the rotating characteristics of the polarization plane is presented from the Faraday rotation theory.
Coherent hybrid ds‐FFH CDMA‐basic performance in mobile radio environment
Authors: Tomisato Shigeru , Fukawa Kazuhiko , Suzuki Hiroshi
Published: July 2007

This paper proposes a coherent hybrid DS‐FFH CDMA system that combines the coherent frequency‐hopping (FFH) and the direct sequence (DS) techniques. the basic performance in the mobile radio system is analyzed. the proposed method features the following:

(i) CDM by the low‐chip‐rate DS using the orthogonal codes;

(ii) the frequency‐diversity effect obtained for each symbol by the maximum‐ratio synthesis of the multiple chips spread by the coherent FFH.

The system configuration and the operation are described. Assuming a channel where the delayed wave components of the four waves contain respective Rayleigh fadings, a computer simulation is executed and the following transmission characteristics are revealed.

(i) When there does not exist an interference wave in the 4‐chip system, the 4‐branch frequency‐diversity effect is verified. the average Eb/No required in order to realize the average BER of 10−2 is 8 dB.

(ii) When space diversity is combined, the average Eb/No required to realize the average BER of 10‐2 is 8 dB, even if there exists an interference wave.

(iii) In the dynamic fading environment, the maximum Doppler frequency that can realize the average BER of 10‐2 for the average Eb/No =15 dB, is 20 Hz and 80 Hz, respectively, for the cases with and without interference.
Evaluation of speech quality impairment due to burst bit errors
Authors: Kozono Jun‐Ichi , Irii Hiroshi
Published: July 2007

Although there has been some research on the relation between random errors that cause speech quality impairment and mean opinion score (MOS), speech quality impairment factors have not been clarified for the bursty code error noise. A subjective evaluation experiment that uses a free conversational form is conducted and the effect of bursty code error noise on speech quality is studied. Moreover, Q‐value quantification of bursty code error noise and random code error noise and its additivity are studied. MOS and tolerance rate change linearly according to a logarithmic number of bursts during a certain length of conversation. Impairment changes according to the number of error bit rates in a random bit error. A more simplified relationship can be obtained by converting MOSs to Q values. It is confirmed that the additivity law holds between Q values for impairment that is due to random and bursty errors.