bluuebunny/crossref_metadata_2025_split huggingface dataset:
Calculation on complex multiple reflection in optical fiber transmission lines
Authors: Tachikura Masao 
Published: July 2007

AbstractCalculation techniques have been developed for the accurate evaluation of the relative intensity noise due to forward reflection in optical transmission lines. Discrete reflections at connection points and Rayleigh backscattering in fibers are taken into account in the calculations. Formulas for simplified models and a numerical calculation algorithm for practical models are investigated.Numerical results for a typical subscriber loops with a total fiber length of 7 km reveal for the first time that Rayleigh backscattering has a strong influence due to its interactions with discrete reflections. Variations in the total amount of forward reflection caused by variations in the reflectance of connection points, the connection loss, and the connection spacing also are analyzed by computer simulation.
Digital phase‐locked loops with a wide locking range using a fractional divider
Authors: Sato Fumiyo , Saba Takahiko , Mori Shinsaku , Park Duk‐Kyu 
Published: July 2007

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

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

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

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

AbstractWhen more than one satellite is operated nominally at the same longitude of the stationary orbit, there is a danger of collision. At present, to avoid the collision, the cooperative station‐keeping is applied so that the spacing of the satellite orbits is maintained as evenly as possible. In this method, however, it is difficult to cope with the situation when a larger number of satellites is operated at the same longitude in the future. From such a viewpoint, it is intended to apply the relative orbit determination by the differential angle tracking to the orbit monitoring of multiple satellites.An experiment for accuracy evaluation is executed using the satellites in operation. The position of the satellite, which is to be used as the reference in the evaluation, is calculated by calibrating the present orbit‐determination system. The orbit is calibrated by observing the close satellites by a large telescope on the same scene and measuring accurately the differential angle between the two satellites. The accuracy of the relative orbit determination is evaluated by the differential angle measurement using the calibrated orbit‐determination system and it is seen that the relative position of the two satellites can be estimated with the accuracy of 1 km. In other words, it is seen that the relative orbit determination by differential angle tracking can be executed practically for monitoring the approach of satellites.
Transmission efficiency of spread ALOHA system using unified spread‐spectrum code
Authors: Sasamori Fumihito , Takahata Fumio 
Published: July 2007

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

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

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

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

AbstractIt is expected that the demand for personal satellite communications will increase and systems providing various services enabling direct communications between automobiles and portable stations will be in demand in the near future. Load transponders and experimental systems are being developed and studied for the advanced mobile satellite communications systems of the Communications and Broadcasting Engineering Test Satellite (COMETS) expected to be launched in 1997 in order to develop and verify multibeam interconnection technologies and regenerative repeater technologies as technologies required to implement such next‐generational mobile satellite communications systems.In this paper, the functions required by COMETS experimental systems have first been clarified, assuming future systems. Next, the payload configuration satisfying the required functions and performance has been designed based on the conditions restricting the load. As a result, a batch‐type regenerator using a digital polyphase‐fast Fourier transform (FFT) filter bank, Ka‐band 20‐W solid‐state power amplifier, and a millimeter‐wave low‐noise amplifier (N.F. = 2.4 dB) has been realized. In addition, experiments have been considered employing the experimental system using the foregoing.
Optimization of antenna aperture distribution with ground reflection
Authors: Tajima Hirohisa 
Published: July 2007

AbstractIn general, the radiation pattern in the vertical plane of an antenna requiring a low elevation angle coverage is made to have sharp cutoff characteristics so that the reduction of the electric field intensity by ground reflection, known as “the lobbing effect,” can be avoided. However, the lobbing effect depends on the installation of height of the antenna, and therefore the determination of the optimal antenna pattern for a certain installation environment is difficult.In this paper, an aperture distribution that takes into consideration the ground reflection is optimized in the case where the height of the top of the DME/P antenna for distance measurement of MLS for aircraft landing is restricted to 3 m. The aperture distribution was evaluated by the minimum values of the electric field intensity at many sampling points around the required coverage area in the presence of ground reflection. The optimization was carried out by maximizing these minimum values using the steepest descent method. As a result, the minimum values of the electric field intensity within the covered region became uniform so that the electric field distribution was improved. In the optimized aperture distribution, the phase center of the antenna is shifted to the upper part of the aperture so that the lowest electric field intensity at the lower coverage edge was improved by 6.5 dB.
A coherent detection system with a suppressed pilot channel for ds/cdma systems
Authors: Abeta Sadayuki , Sampei Seiichi , Morinaga Norihiko 
Published: July 2007

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

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

AbstractThe kinematic global positioning system (GPS) is a system that successively executes the positioning of a mobile user with the accuracy of several centimeters by measuring the phase of the radio wave (carrier) from the GPS satellite while moving. A problem in the kinematic GPS system, however, is that the phase‐shift corresponding to the integer multiple of the wavelength (cycle slip) produced during the phase measurement must be eleminated to realize a highly accurate positioning.For this problem, this paper presents a method that can detect and eliminate the cycle slip with a high accuracy and lobustness by more than four GPS satellite signals which is needed in the positioning. The detection/elimination of the cycle slip based on the update residual error of the Kalman filter and the detection/elimination of the cycle slip based on the redundant GPS signal are integrated and a method to determine the cycle slip with a high accuracy is realized.
A model for a token ring system using jump‐type stochastic differential equations
Authors: Minowa Hiroyuki 
Published: July 2007

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

AbstractThere is increasing demand for a system that supports various multipoint activities such as a conference and education using multimedia information. This paper considers the situation where such a multimedia remote presentation system is to be constructed and discusses the condition for maintaining the synchronization among the media in the information presentation at each node.In this paper, first, the synchronization semantics is defined based on the information presentation timing between the media information taken out from the storage information source and the live media information such as the user's voice. Then a computation procedure is shown for the buffer size needed in each node in order to satisfy the semantics. Based on those reasonings, the design condition is presented for the buffer size and the command response time.
Lightning surge test generator for telecommunication equipment
Authors: Motomitsu Tamio , Kuwabara Nobuo , Ideguchi Tsuyosi , Tokuda Masamitsu 
Published: July 2007

AbstractLightning surge which is induced on a telecommunication cable may damage telecommunication equipment. This paper proposes a design method for a lightning surge generator which can accurately predict reliability for the lightning surges in telecommunication equipment and the quality of the lightning surge generator developed based on this method is described.First, the characteristics of the lightning surge which is fed to the equipment are determined from such factors as the lightning surge inducing mechanism. Next, the testing surge waveform design method is determined in which evaluations of the lightning surge proof of equipment by the peak voltage, steepness (peak voltage/ front time) and energy of the lightning surge can be performed in one surge test. The testing surge waveform then is determined based on this design method.A method is described for realizing the lightning surge characteristics and the testing surge waveform using a basic impulse voltage generator circuit which consists of an LRC circuit with few circuit elements. Experimental results demonstrate that the developed lightning surge generator based on the proposed designing method can predict the malfunction rate accurately.It is shown also that it is highly practical because its size and cost are about one‐tenth that of a conventional testing device.
A packet channel sharing protocol for microcellular mobile communications
Authors: Kayama Hidetoshi , Ichikawa Takeo 
Published: July 2007

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

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