bluuebunny/crossref_metadata_2025_split huggingface dataset:
Error performance of two decision schemes for frequency‐detector gaussian minimum shift keying (gmsk) on a frequency‐selective fading channel
Authors: Shibata Koji 
Published: July 2007

AbstractIn high‐speed digital mobile communication systems, one of the most spectrally efficient modulation methods is Gaussian‐filtered minimum shift keying (GMSK). In this paper, two decision schemes of frequency‐detected GMSK under frequency‐selective fading are compared theoretically from the viewpoint of bit error rate (BER) performances.The GMSK signal which is encoded differentially has an eye pattern with three levels; and, by using the characteristic, the offset decision is made. The BER performances of the offset decision method are compared with those of the conventional one which is based on the eye pattern with two levels.Under the frequency‐selective fading, which is characterized by a two‐ray model, the BER performances for BbT = 0.20 with the offset‐type decision are superior to those with the conventional one when normalized rms delay spread (τ/2T for two‐ray model, τ: delay spread) is less than 0.10.By using the post‐detection selection diversity with two diversity branches, we can reduce the degradation of signal energy per bit to noise power spectral density ratio with the offset decision greater than that with the conventional one for τ/2T < 0.20.
Diffraction control and improvement of interference characteristics by beam shaping
Authors: Yonehara Satoshi , Takano Tadashi 
Published: July 2007

AbstractThe diffraction phenomenon usually degrades the extinction and signal‐to‐noise (S/N) ratios of optical devices which utilize the interference of light beams. In this paper, the use of spatial filters to shape the field distribution in the cross section is proposed as the method by which the degradations due to diffraction effects can be reduced. The beam shape and the diffraction characteristics are shown experimentally to be improved due to two types of filters with Gaussian and trapezoidal transmission profiles in radial direction.In fabrication of the filters, due to the difficulties in the control of the deposited film thicknesses, the transmission characteristics are deviated from the designed ones. However, the extinction ratio is shown to be almost doubled using the realized filters.
Optical fiber amplifiers for optical amplitude‐modulated vestigial sideband transmission systems
Authors: Shigematsu Masayuki , Kashiwada Tomonori , Nishimura Masayuki , Kanamori Hiroo , Okitas Toshio 
Published: July 2007

AbstractAn optical fiber amplifier for an optical amplitude‐modulated vestigial sideband (AM‐VSB) transmission system has been developed. Various pumping methods in an Er‐doped optical fiber for a high‐power and low‐noise performance are discussed. The bidirectional pumping method was found to be the best. A high‐performance Er‐doped optical fiber has been fabricated, and an optical amplifier has been made with it. The loss budget of 14 dB was obtained in 40‐channel transmission with 51‐dB carrier‐to‐noise ratio (CNR) by using this prototype optical amplifier, which is 6 dB better than before.
High‐speed lan architecture based on b‐isdn technology
Authors: Takiyasu Yoshihiro , Amada Eiichi , Hatakeyama Yasuhiko 
Published: July 2007

AbstractMultimedia backbone local area networks (LAN) have recently become key components of private networks as fiber distributed data interface (FDDI) backbone LANs. This paper discusses the architecture of loop‐type high‐speed multimedia backbone LANs (MBLANs) based on B‐ISDN technology as the next generation LAN targeting the introduction stage of the B‐ISDN age and its realization.This paper highlights problems to be solved with respect to the adoption of B‐ISDN technologies, such as synchronous digital hierarchy (SDH) and asynchronous transfer mode (ATM) technology, to MBLANs and proposes some solutions. It also presents high‐speed MBLANs with transmission rate of 622 Mbit/s and the basic hardware implementations of the system.
Signal‐detection characteristics in trellis‐coded modulation system under impulsive noise environment and its optimum reception
Authors: Miyamoto Shinichi , Morinaga Norihiko , Katayama Masaaki 
Published: July 2007

AbstractThis paper investigates the performances of the trellis‐coded modulation (TCM) systems under impulsive noise environment. Conventionally, receivers for a TCM system have been designed based on Euclidean distances between signal sequences assuming their use under Gaussian noise environments. These receivers are not suitable for impulsive noise environments having statistics significantly different from Gaussian noise and thus designs based on the statistics of impulsive noise are needed. The error event probability characteristics of TCM signals received by conventional‐type receivers have been obtained, and it has been clarified that coding gain is obtained even under impulsive noise when the carrier‐to‐noise power ratio (CNR) is sufficiently large, and there is a range of CNR at which the error event probability characteristics of TCM signals become worse than those of uncoded signals.Next, it is shown that the error event probability characteristics of TCM signals are inferior to those of the case in which uncoded signals are received by optimum receivers designed by considering impulsive radio noise. In addition, it has been shown that optimum receivers for TCM systems under impulsive radio noise can simply be constructed by adding a number of circuits to conventional‐type TCM receivers, and their performances exceed those of the case in which uncoded signals are received by optimum receivers at any CNR and great coding gain is obtained.
An er‐doped fiber active switch controlled by coded pump light
Authors: Sato Yoshiaki , Aida Kazuo , Nakagawa Kiyoshi 
Published: July 2007

AbstractIn this paper, a new optical matrix switch using Er‐doped fiber amplifiers is reported. The Er‐doped fiber amplifier acts as an optical gate, depending on the presence or absence of the pump light. The pump light may be a pulsed light whose repetition period is shorter than the fluorescence lifetime. Here the pump light contains interconnection information as a code, and an optical matrix switch where the pump light is distributed through an optical decoder to multiple optical gates is proposed. As a result, an optical matrix switch where the interconnections may be changed by changing the code became possible.In experiments, first, a basic optical gate characteristics were investigated. Using a 20‐mW pump light, the isolation for ON/OFF was 35 dB in the optical gate. In optical gates pumped by pulsed light, it was clarified that there was no influence on the signal light when the repetition rate of the pump light is above 5 kHz. Next, from the above conditions, a 1 × 2 optical switch using an acousto‐optical deflector for the optical decoder was constructed and the switching operation controlled by a coded pump light was demonstrated. The extensibility of matrix size was also investigated; and, by a combination of the proposed switch configuration and Clos‐network construction, it was found that a realization of a 225 × 225 optical matrix switch was possible.
Optimized bandwidth of optical filter in optical preamplifier
Authors: Kinoshita Susumu , Okiyama Tadashi , Kuwahara Hideo 
Published: July 2007

AbstractIt has been demonstrated that the receiving sensitivity in the direct detection scheme is significantly improved by using an optical preamplifier. The bandwidth of an optical filter plays an important role in the characteristics of such an optical preamplifier. Therefore, in this paper, a method to optimize the optical filter bandwidth by taking into account the wavelength tolerance is presented. First, the noise figure is found to increase due to the relative increase of the ASE power compared to the signal optical power on detuning, if we consider the tolerance of the wavelength and the spectrum of the filter. Second, the increase in the noise figure is expressed in terms of the equivalent noise bandwidth of the ASE‐ASE beat noise and is compared with the experimental result obtained for the various detuning values. The optimized bandwidth which keeps the preamplifier noise level low even for the maximum detuning is determined. For example, for a Lorentzian‐type optical filter spectrum, the full‐width at half‐maximum (FWHM) is 3.46 times larger as compared to that at the maximum detuning. Also, a preliminary study on the intersymbol interference due to the detuning in a 2.4 Gbit/s intensity modulation‐direct detection system was conducted; it was found that the intersymbol interference can be neglected for a Lorentzian‐type filter spectrum with FWHM 1 nm.
A mathematical model for evaluation of overload traffic in communication networks
Authors: Ohta Masataka 
Published: July 2007

AbstractWith the advent of the information age, congestion of communication networks due to natural and social phenomena occurs more easily, and coping with this overload traffic is necessary.In this paper, a mathematical model for evaluating overload traffic is presented, and methods for using this model to evaluate overload traffic are shown. Since the state of a congested network varies with time, the transient behavior of the traffic needs to be analyzed. However, it is impossible to conduct the analysis by means of existing methods because of the enormous amount of computations required. Therefore, by regarding the traffic in a congested network as deterministic, an approximate solution, by means of deterministic equations, is proposed in this paper.The transient analysis of the throughput and overflow rate of networks with finite resources can be evaluated by means of this approximate solution. In accordance with the proposed model, the methods to compute the call blocking probability, which is used to evaluate the network robustness against temporary overload, and the throughput in circuit‐switched networks are shown. It is possible to compute the number of resources (i.e., buffers) which is appropriate for a given blocking probability considering the robustness of the network against congestion. The maximum throughput of the network can also be evaluated with transient analysis of the throughput.
Transient response of resistively loaded dipole antennas for pulse radar
Authors: Kominami Masanobu , Takagi Tohru , Sawa Shinnosuke , Kikuta Takashi 
Published: July 2007

AbstractTo improve the coverage and the resolution of the baseband pulse radar system, it is important to predict accurately the characteristics of the transmitting and receiving antennas due to a pulse and the electromagnetic transient field scattered by a target.In this paper, a moment method and Fourier transform are presented to solve the problem of transient coupling between two orthogonally and resistively loaded dipole antennas and a thin‐wire target, both placed in free space.Numerical results show that if resistances with optimum values are loaded in both arms of the dipoles, the multiple reflections arising between their ends and their feeder can greatly be suppressed. Based on these results, the coverage method for such a pulse radar system using resistively loaded dipoles as well as the near field patterns at the first resonant frequency are examined.
A radial line slot antenna without a slow wave structure
Authors: Member Katsuei Ichikawa , Takada Jun‐Ichi , Ando Makoto , Goto Naohisa 
Published: July 2007

AbstractThe radial line slot antenna is a thin circularly polarized antenna intended for satellite broadcast reception, and is expected to be highly efficient in principle. To improve the efficiency, it is necessary to suppress the grating lobe in the 90‐deg direction by means of a slow‐wave structure in the antenna. To this end, styrofoam is mainly used. However, it is more appealing to find a structure without any dielectric material from the viewpoint of heat resistance, fluctuation of the permittivity, and fabrication cost.This paper proposes a radial line slot antenna without a slow‐wave structure in which the wavelength reduction phenomena due to slot coupling analyzed quantitatively are used intentionally. From the analysis, the antenna gain is derived as a function of the antenna thickness (waveguide height), which is the principal parameter for the wavelength reduction effect. It is demonstrated that the grating lobe can be suppressed. Also, by means of an experiment, the antenna efficiency of 61 percent is attained in a hollow configuration so that the viability of this approach is proven.
Throughput analyses of packet radio communications systems
Authors: Hara Shinsuke , Morinaga Norihiko 
Published: July 2007

AbstractCollision of packets is inevitable and is a problem in contention‐type random access systems. In radio systems, however, the throughput of the systems is improved as a result of the capture effect on power differences between colliding packets caused by propagation characteristics of channels such as fading, shadowing, and distance problems.In this paper, analyses are made of the capture effect by considering channel characteristics of radio channels and modulating and demodulating schemes. First, a theoretical equation for the packet reception success probability of the ALOHA system under frequency nonselective slow Ray‐leigh fading has been derived, and the validity of this equation has been proven by computer simulation. Thus, throughput characteristics of slotted ALOHA and pure ALOHA system have been analyzed by means of this theoretical formula. In addition, it has been proven theoretically that the channel capacity of the ALOHA system is improved two times by the capture effect for the case of a large number of mobile stations and high mean power versus noise power ratios.
Improvement of traffic bias characteristics and acknowledgement method for MULTISTAR LAN
Authors: Saito Tadao , Aida Hitoshi , Ooi Eng‐Theam , Tomiyama Tadahiro 
Published: July 2007

AbstractMULTISTAR was proposed as a system to improve header‐driven storageless (HDSL) local area network (LAN) to transmit simultaneously more than one frame, but it has a problem in that the throughput is deteriorated for the high or biased load.This paper presents two improvements for MULTISTAR LAN: One is that the tournament switch is devised as a means to realize the multiinput arbiter and is used instead of the input arbiter; and the other is that a system is devised where the central node can notify the passage of a packet to the originating side. The performances of those two new MULTISTAR configurations are evaluated by simulation. It is then demonstrated that the system implementing those new ideas exhibits a drastic improvement in the efficiency, compared to the original MULTISTAR LAN.
Coding of motion compensation prediction error signal
Authors: Shishikui Yoshiaki 
Published: July 2007

AbstractThis paper discusses the properties of the motion‐compensating prediction error signal and the appropriate coding scheme. For a high‐efficiency coding of the moving picture, generally, a method combining the motion‐compensating prediction and the spatial coding such as discrete cosine transform (DCT) is used. It is shown that the spatial coding used here is effective for the input picture signal. On the other hand, the motion‐compensating prediction error signal has spatial properties which are considerably different from those of the input picture signal. For example, the correlation between pixels is small, especially in the vertical direction, or the magnitude of the correlation locally fluctuates greatly. Consequently, such signal transformations as the orthogonal transform and subband partition are not effective in the motion‐compensating prediction error signal.This paper analyzes the correlation between pixels to reevaluate the traditional coding schemes and to propose the adaptive coding scheme with and without signal transformation. It is shown that the proposed scheme can prevent the deterioration of the picture quality found in the traditional schemes while retaining equal or better rate‐distortion performance than that of the traditional scheme.
A method of image reconstruction for snow search radar using an estimated permittivity of snow
Authors: Mitsuhashi Ryuichi , Aoki Yoshinao 
Published: July 2007

AbstractFor the image reconstruction of the snow search radar based on the principle of multifrequency holography method, the values of the relative permittivity of snow to be interrogated are needed. Since the relative permittivity of snow changes by various factors, it was necessary to measure it by some means at the same time as the search. The relative permittivity of the snow with low water content which is the medium of the snow search radar has a strong correlation with the density of the snow. Hence, the relative permittivity was estimated by measurement of the density in the past.To eliminate such a procedure, it is necessary to estimate the relative permittivity of the snow from the multifrequency hologram which comprises the data obtained by the snow search radar. In the multifrequency hologram, the information along the frequency axis and that on the azimuth axis are recorded independently. In addition, the distance information in each axis varies in the direction opposite to that of the change of relative permittivity. This property was used for automatically estimating the relative permittivity of snow by discriminating the focusing of the reconstructed image.In this paper, a method is presented for estimating the relative permittivity of snow from the data of the snow search radar. The results are given for processing of actual data.
An atm connecting network—the batcher‐cyclic bus network
Authors: Choi Myung‐Hun , Asano Shoichiro , Ji Yusheng 
Published: July 2007

AbstractThere have been many studies on switching networks using ATM switching machines. With regard to cell loss, methods of reducing the rate of loss of cells within the connecting network, methods of reducing loss of cells by accumulating cells of the same route in buffers introduced to the output circuit line, etc., are being studied. As an example of the latter, knockout networks characterized by buffer control using bus‐type switching networks have been proposed and considered as one of the useful systems. Such knockout networks, however, are known to have the disadvantage of an increased number of switches. In this paper, a new ATM switching network having a smaller number of switches than knockout networks is proposed and its traffic characteristics are clarified.
Adaptive recursive least‐squares maximum‐likelihood sequence estimation with higher‐order state variable model of radio channels—adaptive performance improvement of rls‐mlse
Authors: Fukawa Kazuhiko , Suzuki Hiroshi 
Published: July 2007

AbstractSuperior tracking performance for fast fading mobile radio channels is obtained by extending channel models used in the adaptive recursive least squares maximum likelihood sequence estimation (RLS‐MLSE) derived from the theory of maximum likelihood signal estimation. Conventional adaptive maximum likelihood sequence estimators used the simple Markov model or random walk model to describe fluctuations of the impulse response of a frequency‐selective fading channel.In this paper, a second‐order Markov model that incorporates the first‐order time derivative of the impulse response is used. This higher‐order state variable approach improves the adaptability of the channel estimation algorithm and gives a significant improvement in signal transmission performance. Computer simulations show that the RLS‐MLSE based on this higher‐order state variable model yields good performance of 40 kbit/s QPSK with the maximum Doppler frequency up to 160 Hz.
Effect of reduction of mobile communications co‐channel interference by transmission power control considering received signal level correlations
Authors: Fujii Teruya 
Published: July 2007

AbstractIn a small‐zone mobile communications system that reuses the same frequencies in geographically different places, the margin for interference required to obtain a required call quality (CIR margin) can be reduced when there are correlations between geographic variations of the desired and interfering waves in comparison to when there are no correlations.In a sector zone configuration allowing the arrival directions of desired and interfering waves to be the same direction, correlational relationships can be expected in the downlink circuit, while such relationships cannot be expected in the uplink circuit since the topographical and geological factors affecting the mobile stations are clearly different.In this paper, it has been clarified analytically that when there are correlations between geographic variations of desired and interfering waves of the downlink circuit, the CIR margin can be reduced even in the uplink circuit as well as in the downlink circuit by using adaptive transmission power control (ATPC). Next, the direction connecting the base station and the reception point is defined as the direction of arrival of the electric current and the correlational relationships between the arrival angle difference and the received signal level were studied on the basis of propagation test results, considering the differences in angles of the directions of arrival of desired and interfering waves in the downlink circuit (referred to as the arrival angle differences). In addition, the relationships between the spatial frequency utilization rate (spectrum efficiency) and the sector zone divisions of a wireless zone, closely related to the arrival angle differences, in a six‐wave interfering system having six interfering zones have been clarified.
Performance comparison of high‐speed ring networks with nodes of finite buffer capacity
Authors: Fuwa Yasushi , Tasaka Shuji 
Published: July 2007

AbstractThis paper analyzes the performance of a number of MAC protocols in high‐speed ring‐type networks and determines the suitable region for each protocol. The authors previously have evaluated the slotted rings, register‐insertion rings and register‐insertion‐type slotted rings, and begin with the analysis of the token ring in this report. To compare the results of the various analyses, the models of each MAC protocol are constructed under the same set of conditions and evaluated with the same method (EPA). Since the nodes of each model are assumed to have buffers to finite capacity, the discussion of buffer overflow is made possible. The results obtained from analysis matched closely with simulation results verifying the accuracy of the analysis. The MAC protocols also are analyzed under high‐speed network conditions, and a comparison of the results reveals the most suitable protocols for various environments keeping in mind the issue of buffer overflow.
A technique for signal processing of moving areas in the muse system
Authors: Gohshi Seiichi , Naemura Masahide , Izumis Yoshinori , Yamaguchi Kohichi , Ninomiyas Yuichi 
Published: July 2007

AbstractThis paper discusses a new signal processing method which helps improve the quality of moving area images in the MUSE system. The essential point of this method is the application of an interfield signal processing technique to moving areas. Moving images are used to conduct computer simulation tests on the method and this has proved efficient. In addition, the method offers good compatibility with conventional MUSE encoders and decoders.
Queuing network modeling for performance analysis of hdlc based protocols
Authors: Ikegawa Takashi 
Published: July 2007

AbstractThis paper presents a BCMP‐type closed queuing network which models the error recovery defined as HDLC based protocols such as LAPB, LAPD, and LLC type II. Throughput and average end‐to‐end delay against the I‐frame loss probability owing to bit errors are obtained by using the queuing network. With the I‐frame length independence assumption, agreement between analytical and simulation results is shown to be fairly good.