bluuebunny/crossref_metadata_2025 huggingface dataset:
A soft decision viterbi decoding method using received carrier level in fading channel
Authors: Yamaguchi Kazuhiko , Tokita Toshio , Imai Hideki
Published: July 2007

Transmission channels in mobile communication are extremely unstable due to the effect of multipath fading. Therefore the realization of high‐reliability communication necessitates the introduction of error control in the form of error‐correction coding.

This paper considers the decoding of error‐correcting codes that are adapted to digital mobile communication operating under Rayleigh fading conditions. A soft decision Viterbi decoding using the received carrier level is studied for the case of convolutional codes. This soft decision method is based on the level of the received carrier by adaptively determining the metric used in the decoding. In this way a metric is obtained for digital mobile communication.

This paper also presents an estimation method using error exponent which provides effective means to realize such a soft decision method. If the channel can be considered memoryless due for example to interleaving, then this method provides an easy way to estimate: (1) the figure of merit for quantizing thresholds, and (2) the gains of the soft decision.

First, it is shown that using this kind of estimation in the case of channels which can be considered sufficiently memoryless due to interleaving, extremely large gain is obtained by the soft decision method discussed in this paper.

Next, simulations are performed and the efficiency of the estimation method is demonstrated. Finally, the bit error rate characteristics are shown for the case when the channel is not made sufficiently memoryless by interleaving.
Performances of integrated voice/data multiplexing system with controlled arrival
Authors: Fujii Shumji , Hayashida Yukuo , Tezuka Yoshikazu
Published: July 2007

In the integrated voice/data multiplexing system based on a time‐slotted frame format, the expected queue length of data packets increases significantly when the voice calls temporarily occupy all slots, even if the traffic loads of voice and data are light. To reduce such an increase of data queue, the integrated voice/data multiplexing system is investigated in this paper, and the arrival and service rates of voice calls are controlled with the number of slots occupied with voice calls. The system is analyzed exactly as an M/M/X queue by varying the number of servers, and the approximation method is presented for studying the behavior of a large‐number slot system. As a result, in a light data traffic load, it is effective in reducing the increase of data queue that the arrival and service rates of voice calls be controlled when a large number of slots are occupied by voice calls. However, in a heavy data traffic load, it is effective to use the movable boundary scheme in which necessary numbers of slots are reserved for data traffic.
Voice, data and video integrated broadband metropolitan area network
Authors: Kobayashi Hiroshi , Haruyama Hideaki
Published: July 2007

This paper discusses the technical feasibility of the multimedia metropolitan area network based on the tree‐shaped broadband network, employing two‐way CATV technology. In the proposed network, all information can flow on any transmission line through the headend. This leads to the following features, which cannot be realized in the star network as in the telephone network:

Flexible services are provided.

An efficient information communication service can easily be realized.

It is easy to provide the highspeed broadband service at a low cost.

The security of the network can be improved.

The following systems were developed by the authors as examples of the information communication services utilizing those features: TDMA circuit switching service using “time‐slotted bus with control window,” CSMA/CD packet switching service using “beat signal level detection,” and TDMA video switching service, where several video signals are multiplexed as analog signals. Those services can be provided to more than 10,000 subscribers in a service area of diameter 20 km or more. The system is expected to provide the basis for the information communication in local communities, together with the widespread use of urban‐type CATV.
A noncongestion self‐routing control algorithm of generalized benes network
Authors: Sezaki Kaoru , Tanaka Yoshiaki , Akiyama Minoru
Published: July 2007

Recently, to realize broadband ISDN, ATM has been studied vigorously. As the switching network for ATM, the delta network and other switching networks have been investigated by a number of researchers. The delta network performs the self‐routing based on the multistage connection of 2 × 2 sized matrix switches. However, this network has a problem in that the throughput is decreased drastically when the traffic imposed on the switching network is nonuniform.

To avoid such a situation, a method is proposed to make the whole network a Benes network by placing a distribution network preceding the delta network to balance out the traffic. The addition of the distribution network, however, has only been investigated for the case where all matrix switches are of the same size.

With this as the background, this paper discusses the switching network with several sizes of matrix switches. The method of placing the distribution network is discussed together with the characteristics, and application examples are presented.
A study on shared buffer‐type atm switch
Authors: Kitamura Haruo
Published: July 2007

The conventinal shared buffer‐type switch in ATM multiplexes the cells, and a large number of cells is stored in a memory. This produces a problem in that the speed within the switch must be increased, which is limited by the speed of the circuit.

This paper proposes a shared buffer‐type switch in which a number of memories are provided, each storing a cell, and the switching is executed without the cell multiplexing. Several features are realized as follows.

The required number of buffers is less than in the output buffer type. The priority control and the broadcasting can be realized. There is a flexibility in that the number of input and output lines are arbitrary. If the proposed switch with a high speed is used in the multistage switching network, a switch with an excellent performance such as low‐loss rate and high throughput can be obtained.
Frequency selective surfaces for radio astronomy–characteristics of 40/80‐ghz fss
Authors: Irimajiri Yoshihisa , Takano Toshiaki , Tokumaru Munetoshi
Published: July 2007

Frequency selective surfaces (FSS) have been developed for applications to the 45‐m telescope of the Nobeyama Radio Observatory (NRO), the National Astronomical Observatory (NAO), Japan, for simultaneous observations of radio astronomical sources at the 40‐ and 80‐GHz bands.

The Jerusalem‐cross array configuration has been used for the conducting array. The designed characteristics satisfy requirements for radio astronomy: small insertion losses and little distortion of polarization. The measured characteristics were in good agreement with the calculated ones. The fabricated FSS has low insertion loss of 0.1 and 0.6 dB at the 40‐ and 80‐GHz bands, respectively.

It was found that the distortion of circular polarization is not significant for polarized radio astronomical sources of polarization degree of more than 5 percent. The characteristics of the developed FSS satisfy solar radio astronomical requirements.
Jitter characteristics of an optical repeater module using dpll
Authors: Takahara Mikio , Noda Kenta
Published: July 2007

Initially, jitter characteristics of the multistage connection of optical repeater modules using the digital phase‐locked loop (DPLL) for the timing extraction are examined. Then some problems to be solved are pointed out from the results. Next, a system using new modules with a nonresponse period to improve the jitter characteristics of the module is proposed. It is shown that the nonresponse period is nearly equal to one divided period (TDO).

The proposed scheme shows much better jitter suppression characteristics than some other systems, e.g., the clock frequency duplication system, the phase correcting‐restriction system and the system using a random walk filter.

Finally, experimental jitter suppression characteristics of multistage connection of new modules with a nonresponse period of 0, 0,5TDO and 1.0TDO, respectively, are shown. These characteristics show a good agreement with simulated results. It is confirmed that the system using DPLL with a 1.0TDO nonresponse period shows the most satisfactory result.
Direct sequence/spread spectrum communication systems using chip interleaving and its applications for high‐speed data transmissions on power lines
Authors: Tachikawa Shin‐Ichi , Toda Kiyoshi , Isikawa Takehiro , Manibayashi Gen
Published: July 2007

This paper presents direct sequence/spread spectrum (DS/SS) systems using chip interleaving and its burst noise suppression effect for data transmissions on power lines. First, to protect from the impulsive or periodic burst noise, a convolutional chip interleaving method for randomizing the time intervals of interleaved chips and synchronizing with PN sequence is applied. Second, to obtain the randomness of chip intervals, multielement M‐sequences and Tausworthe‐Lewis‐Payne (TLP) sequences are adopted, and several properties (generation frequency of each element, autocorrelation function, etc.) are shown. Finally, as an application, experimental results for high‐speed (8.2 kbit/s) data transmissions on power lines are shown.
Clamp spring removal and fitting method for optical multifiber connector with index matching material
Authors: Kobayashi Hideo , Ueno Kouji , Uenoya Takuya
Published: July 2007

In single‐mode multifiber connectors, the ferrule endfaces spacing is filled with index matching material and the contact is pushed by the clamp spring. To perform the transfer splicing, the clamp spring must be removed and fitted before and after the transfer action.

In this paper, first, the relations among the ferrule pushing force, Young's modulus of the ferrule material, radii of curvature of ferrule endfaces, contact length, etc., are investigated elastomechanically to find the conditions under which the ferrule endfaces‐contact remains stable.

Next, the fluidity of index matching material and the applied force, together with loss variations are investigated to clarify the mechanisms responsible for loss generation and the situation in which the losses can be kept small.

Finally, based on the results of these investigations, the removable clamp spring and fitting mechanism is manufactured. By evaluation of its characteristics, it is shown that satisfactorily good performances are confirmed.
Self‐healing techniques utilizing virtual path concept for ATM networks
Authors: Kawamura Ryutaro , Hadama Hisaya , Sato Ken‐Ichi
Published: July 2007

Strong international effort has been made toward the realization of a B‐ISDN based on ATM techniques. This paper proposes self‐healing techniques for enhancing ATM network reliability. Self‐healing is defined here as failed path restoration with distributed control mechanism by using cross‐connects.

First, the characteristics of virtual paths (VPs) are compared with those of digital paths in STM networks. It is clarified that VP benefits can be exploited for network restoration upon failure. Two high‐speed self‐healing algorithms that make the best use of VP characteristics are then proposed for restoring single‐link failures. A technique for multiple‐link failure restoration also is proposed. Finally, restoration performance is evaluated by computer simulation. It is confirmed that the proposed algorithm enables faster restoration than that possible using the existing algorithm for STM networks.
A multiplexing method of multimedia signal in ATM networks
Authors: Kajiyama Yoshio , Tokura Nobuyuki
Published: July 2007

In the ATM network, which handles such multimedia services as voice, video, and data, a traffic control technique must be established to cope with various requirements of the media for transmission quality. From such a viewpoint, this paper discusses the multiplexing control method which can control the quality. Through the discussion, a control method is proposed which multiplexes the multimedia with various quality requirements and the details of the method are presented.

The proposed multimedia multiplexing method contains two control schemes: the polling control for the number of queueing cells with an offset; and the control by monitoring the queue length. The two control methods are switched according to the number of waiting cells of the medium in the severest condition so that the cell delay and the cell loss are controlled.

Using the proposed design, the optimal hardware configuration can be derived from the input model and the requirements. Based on the designed optimal hardware configuration, the multiplexing performance of the proposed control method is evaluated by a simulation. It is verified that the multiplexing performance meeting the requirement of each medium is obtained, and a higher throughput is obtained than the polling control without an offset or the queue length monitoring control, indicating that the proposed method is an excellent multiplexing control method.
Photonic lattice‐type self‐routing switching network
Authors: Ogino Nagao
Published: July 2007

The asynchronous transfer mode (ATM) is considered as a fundamental technique in constructing the broadband ISDN. High‐speed switching is required in the ATM switching equipment, which forms the core of the ATM network. Then it is desirable to apply the self‐routing switching network. Various self‐routing switching networks have been proposed including the Banyan network, as well as its improvements. This network is composed of the multistage connection of 2 × 2 switches. However, problems remain in such switching networks, for example, the hardware scale in the large network and the hardware reliability.

This paper proposes anew a photonic lattice‐type self‐routing network with the following features: (1) the system has essentially a bus structure and excellent expandability; (2) by its structure, the hardware scale increases only slowly in proportion to the number of accommodated circuits. This is an advantage in the large‐scale network; (3) again by its structure, it is possible to deroute the cells thereby avoiding the point of failure which improves the reliability; (4) by restricting the number of cell transfer paths to a certain number, a relatively simple routing control circuit can be employed based on the optical switching circuit; and (5) by the application of the optical switch, the transfer delay of the cell is reduced greatly.
Integrated train access protocol with synchronous and asynchronous traffic
Authors: Hayashida Yukuo , Uchikoshi Tadashi
Published: July 2007

Integrated train access protocol for a high‐speed ring network is proposed in this paper. Using the concept of the train, synchronous and asynchronous traffic is integrated. To consider the fundamental performance, the periodicity of the channel activity is found in the steady state, and the cycle length is derived. On the basis of this cycle length, the train length, channel utilization, and access interval of each traffic are derived.

To characterize the proposed protocol more clearly, it is compared with fiber distributed data interface (FDDI), which uses the timed token scheme. As a result, it is shown that the proposed protocol and FDDI have the same high channel utilization.

On the mean access interval of the asynchronous traffic, FDDI shows the increase character with the target token rotation time (TTRT), while the proposed protocol shows the decrease character with the number of asynchronous frames contained in the train γ.
Analysis of a coil‐loaded wire antenna
Authors: Taguchi Mitsuo , Yamashita Kiyomi , Tanaka Kazumasa , Tanakas Toshiyuki
Published: July 2007

An analysis method using Pocklington's integral equation is presented for wire antennas with lumped inductive loading along its arm. In the formulation of the integral equation, using the equivalence principle, the equivalent electric and magnetic currents on the coil surface are expressed instead of the current flowing on the coil and the electric field. The boundary condition that the axial component of the total electric field vanishes is applied on the antenna axis including the coil. Piecewise‐sinusoidal functions are used for the current expansion functions and the weighting functions.

The numerical calculation is made for the different numbers of turns, pitch, and radius of the coil loaded at the midpoint or the top of a dipole antenna. The good agreement between calculated and measured values for the current distribution and input impedance are obtained. The analysis method proposed in this paper is applicable to antennas with resistive or capacitive loading by changing the expressions for the equivalent currents on the surface of loads.
An interference cancellation method for small earth stations
Authors: Minamisono Kenichi , Satohs Gunkichi
Published: July 2007

This paper proposes an interference cancellation method called the in‐band power minimizing method (IPMM), and describes the use of the method in satellite communication earth stations. In this method, an interfering signal arriving from an earth station antenna is combined by a cancellation circuit with an interfering signal received by an auxiliary antenna and the two interfering signals are arranged to have equal amplitudes but opposite phase. To achieve this condition, the amplitude and phase are adjusted so that the signal power of the output signal from the cancellation circuit contained in the desired signal frequency band is to be a minimum. This method is characterized by the fact that a simple circuit can be used to detect interference rapidly and accurately even at low C/N ratios.

This paper also discusses the principle of IPMM and examines the results obtained when it is applied to small earth stations. It was found that IPMM is quite effective in this application.
Computer experiments on electromagnetic disturbance produced by a spacecraft in a fast plasma flow
Authors: Okada Masaki , Omuras Yoshiharu , Matsumoto Hiroshi
Published: July 2007

When the electromagnetic environment of the space plasma is observed by a spacecraft in space, it is often difficult to distinguish the disturbance due to the satellite itself and natural phenomena. In such cases, it is effective to use a numerical experiment in which the phenomena arising around a spacecraft are reconstructed on a computer. Since the plasma filling the space is extremely dilute, the particles are in a collisionless condition. To treat such a collisionless plasma, the electrons and ions comprising the plasma are treated as individual particles. In such cases, it is a good approach to use the electromagnetic particle code in which the electric field and the magnetic field are solved progressively in time according to Maxwell's equations.

To reconstruct on the computer, the environment around the spacecraft flying in space as closely as possible, the authors are developing the electromagnetic particle code in which the spacecraft is included as an internal boundary. This paper reports the numerical experimental results on the electromagnetic environment around the satellite which is formed when the spacecraft is exposed to a high‐speed plasma flow in a space plasma. A plasma flow is given from one end of the free boundary, and a spacecraft is placed in such a flow. By changing the parameters of the plasma, the physical quantities controlling the generation of the disturbance are found. In regard to the mechanism of the disturbance generation and the two‐dimensional configuration of the disturbance, several characteristics different from those predicted are obtained.
A method of designing communication service specifications using message sequence charts
Authors: Mizuno Osamu , Niitsu Yoshihiro
Published: July 2007

A new specification design method for describing communication services is developed. This method describes service specifications in sequence charts and provides a user‐friendly man‐machine interface and specification conversion function. Applying this method to actual specification design showed that: (1) services such as call waiting or teleconference, normally impossible to represent with sequence charts, can now be described; and (2) the amount of specification description (the number of elements in sequence characters plus data required for specification conversion) for services frequently repeating the same signal elements is less than 30 percent of the number of steps in the corresponding service software. For services in which signal elements are not greatly repeated, this amount is still less than 40 percent of the number of steps if 20 percent of the signals can be shared between services.
A bit error and cell loss compensation method for atm transport systems
Authors: Iwase Ryoichi , Obara Hitoshi
Published: July 2007

A bit error correction and cell loss recovery method is proposed to provide high‐quality virtual paths in an asynchronous transfer mode (ATM) transport system. This method arranges the cells into a two‐dimensional array and performs error correction coding along both dimensions of the array. The error correction code applied in the horizontal direction corrects bit errors and detects lost cell positions. The error correction code applied in the vertical direction restores lost cells. This compensation method requires no processing at the intermediate nodes of the transport system but can be performed after reception of the coded array at the virtual path terminating nodes. Performance estimates are given for this compensation method. It is shown that when a BCH code is used for the horizontal code and a (15, 14) parity code is used for the vertical code on one‐tenth of the virtual paths, then improvements of approximately seven and ten orders of magnitude are achieved in cell loss and bit error rates, respectively. In this case, the communication efficiency is reduced by 10 percent on those paths that employ error correction coding.
A method of protecting high‐priority packets in video packet transmission
Authors: Sakai Yoshinori , Yamamoto Satoru
Published: July 2007

A method for protecting priority packets is proposed, and its effectiveness is confirmed. This method can be used with video packet transmission schemes for packetized video image signals that have been encoded using redundancy compression encoding. In general, during video packet transmission, the significant parts are transmitted as high‐priority packets. Between each originating and terminating node in the proposed method, a number of copy paths exist together with the main path. A copy packet of the high‐priority packet is generated by the originating node, and this copy packet is transmitted with low priority over a copy path. As a result, even when a sudden increase of packet information causes congestion on the main path, the copy packet arrives correctly at the terminating node. Since the copy packets have a low priority level, these packets also have little effect on the data on other paths. The results of analysis and computer simulation of this method clearly show a decrease in the transmission delay and in the probability of packet loss due to sudden increases in data.
Communication status analysis method
Authors: Watanabe Ichiro
Published: July 2007

To eliminate the effect to the line in the transfer of the optical fiber cable when the line is not used, i.e., when the communication is not conducted. To achieve the transfer during the noncommunication state, there must be a system that can discriminate the communication status of the line. To realize such a system, a principle must be established for discrimination as well as a design based on the characteristics of the transmission equipment.

This paper discusses the method of discriminating the communication and noncommunication status, using the most general coded mark inversion (CMI) code as the code to be propagated in the optical subscriber line. First, properties of the code that are generated in the communication and noncommunication states are discussed. It is shown to be most effective to use the ratio of the average powers of the line spectrum at 1/THz and the signal light as the discrimination data, whereT[s] is the period of the transmitted information. Then the design method is shown based on the actual transmission equipment.

Finally, the result of evaluation is presented for the experimentally constructed communication/noncommunication discrimination equipment. It is shown that the correct discrimination is achieved down to the minimum ‐41 dBm of the average signal optical power, propagating in the optical fiber; and the proposed method is well applied to the actual transmission equipment.
Picture degradation caused by motion detection disagreement on MUSE encoder/decoder
Authors: Gohshi Seiichi , Izumi Yoshinori , Ninomiya Yuichi
Published: July 2007

In the multiple sub‐Nyquist sampling encoding (MUSE) system, stationary areas and moving areas of an image are processed differently from each other. These two processings are switched in accordance with the motion detection pixel by pixel. Since this motion detection is carried out independently on the encoder and the decoder, motion detection disagreement may occur between them [“motion detection disagreement”] due to transmission channel noise or particular image patterns.

In this paper, the degradation of picture quality caused by the forementioned motion detection disagreement is analyzed. The analysis has made it clear that decoding an image which was encoded as a static image would generate picture degradation accompanied by flicker. However, when a static input image which was encoded as a moving image is decoded as a static image, the decoded image would only generate resolution degradation in its stationary areas but it would not produce any picture degradation through aliasing.

This analysis conforms with the results of tests using the MUSE encoder and decoder. Thus, a prototype of a simplified encoder equipped with only a moving image processing was made. This prototype was combined with a MUSE decoder and images of good quality were obtained. The simplified encoder resolution in the stationary areas is somewhat inferior to that of conventional encoders. However, since it helps to reduce the machinery size by a third, or even smaller than that of conventional MUSE encoder, it may be used in consumer Hi‐Vision cameras if most of its devices are replaced with LSIs.
Optimum design of yagi‐uda antenna for millimeter‐wave imaging
Authors: Uehara Kazuhiro , Nishimura Hiroshi , Yonekura Takeshi , Natsume Ken‐Ichiro , Mizuno Koji
Published: July 2007

A millimeter‐wave imaging array is proposed in which many Yagi‐Uda antennas are placed on a dielectric lens. By changing the dimensions of these antennas, the impedance matching with the detector is optimized. At the same time, a radiation pattern matched to the incident beam from the focusing optics is realized. The crosstalk between the adjacent detectors on the array is measured. An optimum spacing is derived and a good imaging property is realized. The present imaging array is suitable for MMIC and is applied in practice for plasma measurement for nuclear fusion research.
Jitter reduction for asynchronous network application of synchronous digital hierarchy
Authors: Rokugo Yoshinori , Yoshida Norio
Published: July 2007

The synchronous digital hierarchy (SDH) architecture has been recommended by C.C.I.T.T. to establish a synchronous digital network. Although the network is inherently synchronous, it must also accommodate conventional asynchronous mode applications. In the asynchronous mode applications, tributary signals are transported using the frame transfer technique which is performed by AU or TU pointer adjustment at each network entity. At the final network entity stage, however, these tributary signals are regenerated with strong low‐frequency phase jitter, which might cause substantial transmission quality degradation.

This paper describes the operation of the AU frame transport system employing pointer adjustment. Next, jitter caused by pointer adjustment and subsequent signal degradation are analyzed. Then a new method of suppressing the jitter to an allowable level is proposed. This jitter is caused by a frequency difference in reference clocks used in pointer generating and pointer adjustment operations. Therefore, this jitter can be suppressed theoretically by carrying out the demapping at the identical reference clock frequency used during the mapping process. The proposed method uses a frequency analyzer that directly calculates the moving average of the positive/negative justifications to regenerate the mapping frequency.
Long‐distance propagation in a stratified atmosphere with an even power n profile
Authors: Kawaguchi Yoshinari
Published: July 2007

The propagation characteristics of the radio wave were analyzed in a nonuniform atmosphere in which there exist an inverted layer with an even power profile of a height under a standard atmosphere and the lowest layer with a linear profile. If the modified index of refraction obtained by introduction of the earth‐flattening approximation has a 2n power profile of the height, the solution of the wave equation cannot be given by a closed form function. Hence, the rigorous solution was obtained by a series representation in accordance with the method by Frobenius. This series solution is found effective even if the wave equation has two turning points close to each other. The function value can be obtained within a time shorter than the one required for the numerical solution such as the one by the Runge‐Kutta method.

By continuation of the analytic solutions for each atmospheric model layer, the wave function was derived and the received electric field at a far distance was obtained by the mode theory. It was found that the received electric field depends strongly on the order n of the 2n‐th power N profile as the atmospheric layer near the zero of the index of refraction slope is increased.
Multiple‐feedback‐loop synchronization control scheme for SS‐TDMA
Authors: Okada Kazuyasu , Kawai Makoto
Published: July 2007

Satellite‐switched time‐division multiple access (SS‐TDMA) is investigated as a multiple‐connection scheme to be applied to the multibeam satellite communication system, aiming at a large‐capacity satellite link and small‐sized earth station equipment. When the traditional single‐feedback loop scheme controlling the frame/burst synchronization of traffic stations by a single reference earth station is applied to SS‐TDMA, however, problems arise when the number of traffic stations in the system is increased. In other words, the transmission capacity of the beam, including the reference station, is decreased drastically and a data burst region is produced where the access to a particular beam cannot be achieved even if there is an idle channel.

To remedy this problem, this paper proposes the multiple‐feedback‐loop scheme, where the receive timing at the traffic station is synchronized to the reference station; but the burst synchronization is controlled by the synchronization control stations provided for each beam. The proposed scheme has the following advantages.

(1) The transmission capacity of the beam including the reference station, which decreases drastically in the single‐feedback loop scheme, is maintained as the same as that of other beams.

(2) Even if the number of beams is increased, the usage efficiency of the reference station beam is kept constant and the same frame structure can be applicable.

(3) The data burst region in which the access becomes impossible between particular beams is not produced.

(4) The frame/burst synchronization accuracy is the same as that of the traditional scheme.
A burst mode all‐digital high‐speed clock recovery circuit and block clock recovery scheme
Authors: Matsumoto Yoichi , Morikura Masahiro , Kato Shuzo
Published: July 2007

This paper is focused on an all‐digital implementation of the high‐speed burst mode demodulator for time‐division multiple access (TDMA) satellite communication. A clock recovery scheme in a preamble‐less burst recovery demodulator is considered which is an item of research and development in recent years.

A burst clock recovery scheme is proposed which can be operated at a speed twice higher than the symbol rate. The deterioration due to the error in the clock phase estimation in the burst clock recovery scheme is regarded as a stochastic process, and the effect of the burst signal on the bit error rate is evaluated by the computer simulation.

It is shown, as an example, that when the burst clock recovery scheme is applied to the TDMA satellite communication with a burst length of 800 symbols and transmission filter roll‐off factor of 0.4, the burst probability is 1 ± 10‐6 times/burst for the degradation of 0.2 dB of Eb/N0. In other words, the proposed system affects only slightly the burst loss probability required in the TDMA system.
Circularly polarized energy flux densities
Authors: Tokumaru Shinobu , Tanaka Rie
Published: July 2007

As one of the methods to understand electromagnetic wave propagation and radiation mechanism of antennas, it is useful to use streamlines of electromagnetic energy flux densities. However, the Poynting vector, as an electromagnetic energy flux density, does not include any information about polarization.

In this paper, the circularly polarized energy flow is explained in light of the circularly polarized electromagnetic energy flux densities proposed recently. As the most fundamental example, fields of circularly polarized cross dipoles are drawn by using the circularly polarized electromagnetic energy flux densities. Then, radiation characteristics of circularly polarized antennas are explained by newly defined circularly polarized radiation efficiency and directivity. Moreover, the conventional delta source excitation model for linear antennas is unable to explain the circularly polarized wave radiation from a conical spiral antenna composed of thin conductor.
Overview of the theory of adaptive antennas
Authors: Takao Kazuaki
Published: July 2007

The problem of control methods as the basics of the adaptive antenna is discussed. First, the general concept of the guiding principle and control algorithm is introduced. Next, the relationships between the guiding principles and corresponding control algorithms are explained for the LMS method, H‐A method, DCMP method, and CMA method. With respect to the first three methods, the control characteristics of the optimization systems by the feedback based on the steepest descent method are analyzed. Several factors governing the convergence speed are pointed out. The use of several algorithms intended to improve the convergence characteristics, where they came from and where they will develop are discussed.
Noise theory of distributed optical amplifiers and its application to fiber amplifiers
Authors: Yamashita Shinji , Okoshi Takanori
Published: July 2007

Usually, noise characteristics of optical amplifiers are described by the theory of Shimoda, Takahashi, and Towns (STT theory). This theory deals only with lumped amplifiers whose noise parameters are spatially uniform. However, it is not the case with fiber amplifiers.

In this paper, first, a novel noise theory of three‐dimensionally distributed amplifiers based on the STT theory is presented and the fundamental equations for calculations of the gain and noise characteristics of a fiber amplifier and systems with fiber amplifiers are obtained. Next, this noise theory is applied to a practical fiber amplifier and an example of the gain and noise characteristics is shown. The backward propagated spontaneous emission is shown to degrade the noise characteristics severely, and the total noise characteristics are shown to be better at 1.553 μm than at 1.530 μm.

Finally, a low erbium‐doped fiber system whose gain is balanced with the background loss of the system fiber is analyzed as the system optimizing the signal‐to‐noise ratio. Nearly ideal characteristics are shown to be realized in this system with the bi‐directional pumping.
Evaluation of end‐to‐end performance for data traffic in ATM networks
Authors: Baba Ken‐Ichi , Murata Masayuki , Miyahara Hideo
Published: July 2007

When data traffic communications are serviced in ATM networks, a packet from the transmission source is divided into cells to be transmitted. Therefore, the assumption of the Poisson arrival of data packets used widely in the past is unreasonable and the bursty nature of data traffic must be considered. Furthermore, the end‐to‐end packet loss rate rather than the cell loss rate becomes more important in data traffic and retransmission due to packet loss must be considered in evaluating the packet transmission delay.

In this paper, communications of data traffic in an ATM environment are considered by analyzing transmission of data traffic over a number of switching machines using a queueing network model allowing performance characteristics such as the end‐to‐end packet loss rate and the average delay of data traffic.
Adaptive carrier tracking (ACT) demodulation for QPSK mobile radio transmission
Authors: Saito Shigeki , Takami Tadao , Yamamoto Haruo
Published: July 2007

A new QPSK demodulating scheme (adaptive carrier tracking (ACT)) enabling high‐speed carrier tracking has been developed for application to digital mobile communications demodulators. The ACT demodulating scheme, unlike the conventional detection tracking which extracts the carrier by averaging the phases, establishes the phase synchronization and frequency synchronization independently, without using phase‐averaging techniques. This method enables high‐speed tracking of the carrier phase, thereby improving demodulation characteristics of burst signals and demodulation characteristics under Rayleigh fading to the same degree as those of differential detection. In addition, by adopting the digital oscillator of the new scheme, frequency synchronization of a higher speed than coherent detection that allows avoidance of the false lock has been achieved.

A new phase likelihood comparison (PLC) diversity comparing the accuracy of the data obtained from the signal reception phase has been developed, thereby improving the sensitivity and characteristics of detection with respect to co‐channel interference over those of conventional coherent detection and differential detection using the reception level comparison diversity. The ACT demodulation LSI with the diversity implemented by an entirely digital circuit yields good demodulating characteristics and a low power consumption of less than 9 mW, which corresponds to about 1/20 of the conventional differential detection circuit. The foregoing results confirm the practicability of the ACT demodulation method.
Region segmentation coding of color images based on uniform hvc color space
Authors: Horita Yuukou , Miyahara Makoto
Published: July 2007

There are two aspects to the region segmentation coding and the model‐based coding which extract and encode the structure and features from image information. They are the “technique for compression of image information” and the “technique for structural description of image information.” If the image information is described structurally, not only is the highly efficient coding realized but also a new image can be constructed by a local manipulation of the original image.

This paper combines the region segmentation of the image based on Munsell color space and the region merge based on the hue difference between the regions. Then a new region segmentation coding based on the result of the forementioned region segmentation is proposed. It is assumed that an object consisting of the color image corresponds to a region of almost the same hue. The hue information within the region is coarse‐quantized based on the memory colors, and the shape information is coded using the chain code.

For the value information which contains the information for the shape, shade, etc., of the object, the adaptive cosine transform coding is applied. For the chrome information, the region is approximated by a polynomial function and its coefficients are encoded. The proposed coding method is applied to several standard images which are portraits of relatively simple structures with different face sizes.

The color information is transmitted with a relatively high efficiency, occupying approximately one‐fourth of all the transmitted information; and the usefulness of the region segmentation proposed in this paper is demonstrated. Compared to the traditional waveform coding, the method has the advantage that the local manipulation of the image is easier, although the total transmitted information is slightly larger.
An ultrahigh‐speed optical waveform measurement method based on optical sampling with sum‐frequency generation
Authors: Takara Hidehiko , Kawanishi Satoki , Yamabayashi Yoshiaki , Saruwataris Masatoshi
Published: July 2007

To realize a future high‐speed and ultralarge‐capacity optical transmission, it is indispensable to analyze the ultrahigh‐speed transmission characteristics of the entire system as well as functional circuits, devices and materials comprising the system. Evaluation of such a transmission characteristic requires ultrahigh‐speed optical waveform measurement method.

In this paper, a new optical waveform measurement method called the sum frequency generation (SFG) optical sampling method is proposed. In this method, the SFG which is a second‐order nonlinear optical effect is used for all‐optically sampling the optical waveform to be measured (at the optical stage) by means of an ultrashort optical gate pulse. Hence, the bandwidth limitation of the optical receivers and the electronics can be eliminated.

By means of this technique, accurate measurement without waveform distortions can be realized while high time resolution and high S/N ratios are maintained. In this paper, the theoretical performance of the present measurement technique is discussed and the measured results by the present method are presented.
Adaptively controlled 4.8 kbit/s speech coders with low distortion
Authors: Hayashi Seiji , Suguimoto Masahiro , Kishis Genya
Published: July 2007

As a low bit‐rate speech coding method to realize a satisfactory quality of reconstructed speech, this paper proposes a 4.8 kbit/s pitch‐controlled multipulse coding method, which adaptively controls the speech pitch prediction interval and represents the multipulse positions for the excitation signals with a small number of bits. As a method to control the pitch adaptively, an algorithm is derived and proposed where the pitch prediction interval is adjusted adaptively for each frame so that the pulse position is determined to minimize the perceptual error power representing subjectively important difference.

In addition to the forementioned method, another method also is proposed to improve the speech quality, where the pitch‐controlled multipulse coding is proposed to control adaptively the coefficients of the synthesis filter. An algorithm is proposed for the adaptive control of the coefficients of the synthesis filter, to calculate anew the optimal filter coefficients for excitation pulses derived from the adaptive control of the pitch.

A simulation is executed for the two methods, and the following results are obtained as an evaluation of SNRseg. It is 7.5 dB in the conventional MPC algorithm, 8.6 dB in the proposed pitch‐controlled MPC algorithm, and 9.8 dB in the pitch‐controlled MPC algorithm including the adaptive control of the synthesis filter coefficients. In other words, the improvement in the latter two is 1.1 and 2.3 dB, respectively. The performance is satisfactory also from the viewpoint of the cepstral distance. The improvement in the reconstructed speech quality also is verified for the proposed methods by the subjective evaluation.
Measurement and analysis of electromagnetic pulses due to indirect ESD
Authors: Masugi Masao , Murakawa Kazuo , Kuwabaras Nobuo , Amemiya Fujio
Published: July 2007

Electrostatic discharge (ESD) usually is accompanied by two phenomena: the injection of discharge current, and the radiation of electromagnetic pulses. The discharge phenomenon can cause transient electrical interference of electronic equipment and the time‐domain measurement of radiated fields associated with ESD is a difficult task because of the very fast and wide‐band waves involved.

This paper describes measurement and analytical results of ESD pulses. ESD pulses were measured by three EMI‐type antennas (a loop antenna, a biconical antenna, and a double‐ridged guide antenna) in the time domain. It is shown that the electromagnetic pulses can be evaluated by the energy spectrum without using the phase information of antenna factors.

Based on the measurement of waveforms of the known electromagnetic pulses, it is shown that the waveform can be evaluated with an accuracy of 2 to 6 dB. As a result, it was found that radiated ESD energy does not always increase in proportion to discharge voltage and that ESD pulses produced by low‐voltage ESD can cause strong electromagnetic interference.
Two‐wire AGC amplifiers with echo cancellers for two‐way voice signals
Authors: Yasukawa Hiroshi
Published: July 2007

A two‐wire voice‐band automatic gain control (AGC) with echo cancellers is studied and applied to an automatic call‐transfer repeater. A four‐wire circuit model of the amplifier and its stability are discussed. Fast tracking and/or stabilizing AGC using variable‐rate control is proposed. Also, a singing protection control method in which the dominant path is selected depending on voice signal powers of the two speech paths is proposed and investigated. The amplifier gain of the inferior path is computed using the measured echo return loss (ERL) values of the echo cancellers. Furthermore, an automatic call‐transfer repeater prototype that is based on the new AGC amplifier and its characteristics is introduced.

The maximum amplifier gain of the proposed methods is about 10 dB higher than that of a conventional two‐wire amplifier with a voice switch. The configuration and algorithms proposed in the paper are proven to be effective for two‐wire amplifiers.
Performance of a transversal equalizer for self‐interference passing adjacent channels
Authors: Kagami Osamu , Watanabe Kazuji , Ohtsuka Hiroyuki
Published: July 2007

Nonregenerative repeating systems on digital microwave radio have the advantage of network flexibility and low‐cost transmission. This paper describes a means of compensating self‐interference passing adjacent channels (S‐IPAC), which degrades the transmission performance. This interference is specific to nonregenerative repeating systems. A transversal equalizer with multitaps is discussed as a countermeasure against S‐IPAC. Bit error rates (BER) and signatures are presented theoretically and experimentally as a parameter of hop numbers.