bluuebunny/crossref_metadata_2025_split huggingface dataset:
Number of subscribers and system cost in mobile communication systems
Authors: Ogawa Keisuke , Sakamoto Masayuki 
Published: July 2007

AbstractThe rapid growth in mobile communication services has created the serious problem of how to accommodate the expanding demand in metropolitan areas. Also, a large problem is how to provide services at a reasonably low cost for a small number of subscribers in less populated areas.This paper considers both subscriber capacities and system costs per subscriber in large‐demand areas, and numbers of subscribers and system costs per subscriber in small‐demand areas. The following results are obtained.There exists an optimum zone radius to minimize the system cost per subscriber, and the optimum radius is smaller in large‐demand areas than in small‐demand areas.Service quality degradation probability allotments are studied under the condition that the sum of degradation probabilities due to thermal noise and interference is constant. From the viewpoints of both subscriber capacity and system cost per subscriber, it is desirable to assign most of the probability to interference in large‐demand areas and, on the other hand, to thermal noise in small‐demand areas.
A new network configuration with local and global channels for packet radio networks
Authors: Mutsuura Kouichi , Okada Hiromi 
Published: July 2007

AbstractA new configuration for packet radio networks, called local/global (LG) network configuration, is proposed, aiming at total throughput improvement. By using two kinds of channels (local channel and global channel) and geographically partitioning the total area, the spatial reuse of channel capacity is realized. The performance of this LG configuration is analyzed for a fixed radio network by introducing the delay ratio γ between local and global channels. s‐ALOHA protocol is used under heavy overload. By the performance analysis and numerical results, it is concluded that the improvement of the total throughput is attained for a typical network configuration without greatly increasing the mean delay. Also, various schemes for determining the allocation ratio of channel capacity to the local and global channels are presented and studied to apply this LG configuration effectively.
Beam‐scanning characteristics of offset reflector antennas with polarization grids
Authors: Chikara Sakae , Ando Makoto 
Published: July 2007

AbstractWhen a multibeam antenna uses a reflector antenna, the effect of blocking for a large feeder system cannot be neglected. An offset type becomes advantageous for such a case. However, the cross‐polarized waves increase due to asymmetry of the reflector. We considered an antenna in which a grid plate is inserted between the primary radiator and the reflector. We can suppress the components of cross‐polarized waves by choosing the position of the grid plate and by designing strip patterns. In this paper, we performed a full‐wave analysis for such an antenna. We clarified the cross‐polarization suppression effects of grids during beam scanning. It provides guidance in designing a multibeam antenna. We showed a design method using geometric optics for strip patterns according to scanning directions. We confirmed the effectiveness of this design method.
High‐frequency long‐range propagation phenomena in semicylindrical conducting concave boundary
Authors: Ishihara Toyohiko , Shirai Kazuhiro , Goto Keiji , Toda Kohji 
Published: July 2007

AbstractThe electromagnetic field generated in a concave boundary by a magnetic line current source placed on a semicylindrical conducting concave boundary is analyzed by means of three representations. The effectiveness and physical interpretation of these representations are discussed. If the product of the wave number and the radius is sufficiently large, the conventional representation by the geometric optical rays and the integral‐type interference wave cannot be applied well. The representation by means of a combination of the geometric optical rays, lower‐order whispering gallery modes and the error‐correcting term has simple calculations and good accuracy. The mutual relationship between the geometric optical rays and the modes is found and the propagation characteristics within the boundary layer characteristic to the concave boundary are addressed.
An evaluation of systematic errors in VLF direction findings via full‐wave analysis
Authors: Nagano Isamu , Mambo Masayoshi 
Published: July 2007

AbstractThe full‐wave analysis method is described for computing the electromagnetic field on the ground when a beam‐shaped wave is incident from above the ionosphere. By means of this method, the directional error was evaluated in various VLF direction finders which measure the exit point of the natural wave at the lower portion of the ionosphere, under the assumption that the downgoing wave is radiated from a duct. In this method, the directional errors due to multiple reflection, polarization, beam wave of the arriving radio wave and the type of ionospheric models can be found systematically so that a simulation result most resembling the practical situation is provided. The main results are as follows: (1) When the transmission cone is within the trapping cone, the NPF method using orthogonal loop antennas and vertical antennas can indicate an almost correct direction within a radius of about 100 km from the maximum point of the radiowave strength on the ground. The error increases at a distance of more than 150 km. On the other hand, the Poynting method indicates almost correct directions even at a distance of more than 200 km regardless of the polarization. The goniometer method has almost the same accuracy as the Poynting method; (2) if the overlapping of the transmission cone and the trapping cone is smaller, the error is increased in the south direction in all three methods; and (3) no significant frequency dependence is observed in the directional error.
Highly contoured beam antennas for 21 ghz‐band ldr hub stations
Authors: Nomoto Shinichi , Watanabe Fumio 
Published: July 2007

AbstractWith a view to applications of the 21‐GHz LDR (local distribution radio) system to point‐to‐multipoint systems, a hub station antenna was developed which produces an improved cosecant square beam in the vertical plane and the fan beam in the horizontal plane. The antenna is made of an offset‐shaped reflector fed by a corrugated conical horn with a rotationally symmetric beam. As a shaped reflector synthesis, an efficient and accurate method is proposed, which is a combination of the geometrical optics method and the physical optics method. To produce the high gain part of the shaped beam (beam nose), the method of a doubly curved reflector is extended so that the main part of the reflector surface is obtained in the geometrical optic process. Next, to form the low gain part (beam skirt), the physical optics shaped reflector design method is applied to an upper portion of the reflector. By defining the boundary shape of the reflector on the cone with a horn as the vertex and the flare angle from the horn axis constant, the control of the illumination level over the entire reflector edge is low and uniform regardless of the polarization, thereby improving the sidelobe characteristics. The measured radiation characteristics of the test antenna are extremely good so that the validity and effectiveness of the present antenna design are proven. The measured values include the simulated experimental results in the case where rain drops are attached to the radome.
Spherical array antenna using digital beamforming techniques for mobile satellite communications
Authors: Chujo Wataru , Kashiki Kanshiro 
Published: July 2007

AbstractProblems arise in providing excitation phases and amplitudes to individual antenna elements for wide‐angle scanning by applying spherical array antennas for mobile satellite communications for ships, automobiles, and aircraft. These antennas do not have many antenna elements. Thus, emphasis is on obtaining the maximum gain rather than realizing the characteristics of low sidelobe levels.This paper considers the application of spherical arrays for antennas of mobile satellite communications. An adoption of a control method is assumed which regulates the phases and amplitudes freely and accurately for individual antenna elements for the beamforming circuits of digital beamforming antennas. A beamforming method is examined for spherical arrays.First, a selection of necessary antenna elements is proposed utilizing the received signals and an adjustment of their phases and amplitudes. This method is applied to a 16‐element spherical array which had circular micro‐strip antennas. Their radiation characteristics are calculated. As a result, it was clarified that the maximum directive gain could be obtained almost without being influenced by the properties of individual antenna elements.Next, circuits are designed for the reception of binary PSK signals of constant envelope modulated waves. Carrier recovery circuits are established for individual antenna elements for spherical arrays, and a method is used to detect their phases and amplitudes. The method shows the effectiveness in obtaining the amount of gain reduction due to the detected phase and amplitude errors.
Abstraction and control of transport network resources for intelligent networks
Authors: Esaki Shuji , Omiya Tomoki , Shigematsus Naoki 
Published: July 2007

AbstractThe intelligent network (IN) is expected to play an important role in rapidly and efficiently introducing new telecommunication services. This, paper discusses the abstraction and control methods for constructing a service control environment in the intelligent network which does not depend on specific service. By using this method, a real network configuration is abstracted into several patterns, considering the control points required by each service specification and each pattern can be described as a combination of functional virtualized resources.It is made possible to handle the diversified service specifications in a unified way which is independent of detailed conditions of the transport network. It is made possible also to ensure the service independency of the control interface specifying the interface by control of each virtualized resources. Moreover, a model for the call control is proposed and the function assignment in introducing IN into existing network is discussed.
Analysis of common‐channel signaling network congestion in the presence of considering various kinds of delay
Authors: Ohta Masataka 
Published: July 2007

AbstractCommon channel signaling networks play an important role in providing advanced switching services. With the increase in the degree of the reliability of such switching services on common channel signaling networks, the common channel signaling networks are easily congested, and controlling congestion on these networks has become increasingly important. On the other hand, the network scale has been increasing with the development of the information society. With the increase in the network scale, signal transmission delay and control signal delay have increased, giving adverse effects on congestion control. In this article, the congestion control on common channel signaling networks recommended by CCITT has been analyzed considering the above‐said transmission delay and control signal delay. As a result of this analysis, the above‐said adverse effects could be evaluated quantitatively. A rigorous solution of this model could not be obtained. Thus, a method of analysis by fluid approximation is proposed. In addition, this approximating analytical method is shown to have sufficient practical accuracy in comparison with simulation results. By this analytical method, the rates of blocking of congested resources (signal links, circuits), mean delays, etc., can be easily obtained. As a result of the analysis, it is shown that these delays greatly influence the efficiency of congestion control. Especially, it is shown that the call loss rate shows a great effect; and control parameters must be determined considering these delays in order to satisfy certain standard values by congestion control.
FD‐TD analysis of power loss distribution in a human body model heated by a waveguide applicator
Authors: Araki Noriyuki , Morita Nagayoshi 
Published: July 2007

AbstractThree‐dimensional power loss distributions generated inside the human body by the electromagnetic irradiation from a waveguide‐type applicator are analyzed using the finite‐difference time‐domain (FD‐TD) method. To execute the three‐dimensional FD‐TD analysis with a small amount of computation, only a limited small muscular region representing a part of the human body near the waveguide aperture is employed in the analysis region. In this case, the external boundaries of the analysis region are located in the human body which is composed mostly of lossy media. Thus, the conventional absorbing boundary conditions often are not applied effectively.In this paper, new absorbing boundary conditions are proposed so that the FD‐TD analysis can be executed as accurately as possible even if the external boundaries of the analysis region are located in lossy media. The waveguide‐type applicator, with which the human body is heated, is assumed to be filled with water and the radiated electromagnetic wave is assumed to be excited by the electric current on a post. To represent the electric current source on the post, the following two types of formulation method also are presented: 1) a method representing the electric current as the electric field source; and 2) the magnetic field source. Both methods are proved numerically to be valid.
Direction‐finding measurements of magnetospheric vlf chorus emissions and analysis of their generation and propagation mechanism
Authors: Hattori Katsumi , Hayakawa Masashi 
Published: July 2007

AbstractChorus is one of the most important VLF/ELF emissions in the magnetosphere, but several points are still unsolved concerning their generation and propagation mechanisms.In this paper, the near‐equatorial direction‐finding measurements made on board a satellite are studied first and it is confirmed that the rising tone chorus (frequency of the chorus increases with time) is generated at θ (the angle between the wave normal and earth's magnetic field) ˜ 0° by the cyclotron resonance interaction with the energetic electrons.These results support the previous theory of Helliwell. Moreover, the direction‐finding measurements of the rising tone chorus are carried out aboard the GEOS 1 satellite in the off‐equatorial regions. Their generation and propagation mechanism are studied with the help of three‐dimensional ray‐tracing computations and these results are compared with the corresponding results of OGO 5 direction‐finding measurements by Burton et al.As a result, the observations by OGO 5 indicate that after the generation of chorus at the equator with wave‐normal direction θ0 ˜ 0°, it reaches the satellite in ducted propagation along the magnetic field line, whereas the results of GEOS 1 suggest that the waves are generated in a wider region near the equator with comparatively smaller θ0 (30° ˜ 40°, at the most 50°) and that the subsequent propagation is nonducted in the magnetosphere.Finally, the direction finding measurements and the ray‐tracing computation are suggested to be very important in the study of generation and propagation of various emissions generated in the magnetosphere.
Prediction of mobile radio delay spread from frequency correlations
Authors: Member Shinichi Ichitsubo , Fujii Teruya 
Published: July 2007

AbstractA simple method is studied for estimating the delay spread needed for understanding the transmission quality of land mobile communication by means of a narrow frequency band. There exists a certain relationship between the delay spread and the receiving level correlations of multiple waves. There is a method for estimating the delay spread by measuring the receiving level correlation of multiple waves in a relatively narrow frequency band based on the forementioned relationship. However, since the previous method is based on the relationship between the delay spread and the receiving level in the case where the delay profile is of an exponential function, there is an error in the delay spread estimated if a profile is other than the one with an exponential function.In this paper, this error is obtained first quantitatively. Next, a new estimation method which can reduce the error is proposed. Specifically, a profile selecting‐type estimation method is proposed in which a delay profile function considered optimum is selected from the measured receiving level correlation function and the delay spread function is found based on such a delay profile function. In addition to carrying out a computer simulation of the error evaluation of the proposed method, the estimation accuracy is confirmed from the measured data of the delay spread and the receiving level in an actual propagation path. As a result, the estimation error of the average delay spread in a 50‐m section is reduced to 40 percent in the proposed method which is an improvement of about 10 percent over the previous method.
Analysis on statistical multiplexing characteristics of atm cells with voice and video inputs
Authors: Komine Takahiro , Yamada Hiroshi 
Published: July 2007

AbstractIn ATM networks, it is necessary to control the quality of service because a large number of traffic classes with different statistical characteristics and required quality of service is handled uniformly in these networks.This paper evaluates the characteristics of the statistical multiplexing gain among the heterogeneous cell streams from voice and video media. It is considered that the information of picture elements that change between adjacent video frames are packetized and then transmitted into ATM networks. Therefore, when one scene finishes, all the information for the new scene appears as a sudden burst at the first frame of the next scene. This is an important characteristic of video traffic which is called scene change here.By considering scene change, the superposed arrival process is modeled on the heterogeneous cell stream from voice and video media using the phase‐type Markov renewal process. By analyzing the queueing model with this process, the characteristics of the statistical multiplexing gain are obtained. In particular, by using numerical computation, the effect of scene change on the statistical multiplexing gain is evaluated.
A feeding technique for broadbanding and dual‐banding microstrip antenna
Authors: Sakaguchi Koichi , Hasebe Nozomu 
Published: July 2007

AbstractA method for broadbanding and dual banding of the microstrip antennas (MSA) is proposed and discussed. The effect of errors at the time of fabrication of the MSA also is studied. The method described in this paper combines a transformer made of a distributed circuit with the MSA. The design consists of three steps. Since the radiating element and the transformer are separated completely by the ground plane in the present method, the technique can be applied to an MSA with an arbitrary shape without applying any fabrication on the radiating element. Broadbanding can be accomplished rather easily, and the dual‐banding can be accomplished with a slight modification in the design. The prototype stub‐loaded MSA demonstrated with a bandwidth of 1.3 percent with a VSWR ≤ 2 can be increased to 3.4 percent (2.6 times). For the dual‐banding, the separation rate of two frequencies with respect to the fundamental resonant frequency can be controlled by about 2 to 5 percent.
Time spread modulation system for digital land mobile radio communication
Authors: Sasaoka Hideichi , Kato Eiji 
Published: July 2007

AbstractThis paper proposes an improvement of the time‐spread modulation/demodulation system in land mobile radio communications. The following elaborations are employed in the proposed system. The quadrature modulation with fading compensation is employed to improve the spectral efficiency. The interleaving is employed to enhance the time‐spreading effect. The maximum‐likelihood estimation is employed to improve the error rate.To demonstrate the usefulness of the proposed method, the bit‐error rate is examined by computer simulation. It is seen as a result for the four‐symbol time‐spread that Eb/N0 is approximately 12 dB and 18 dB for the bit‐error rate (BER) of 10‐2 and 10‐3, respectively. The foregoing performance is better compared to the theoretical performance for the absolute phase coherent detection QSK, with Eb/N0 being better by 2.5 dB for BER = 10‐2. It is seen also that the performance is improved by increasing the number of time‐spread symbols to 6 and 8. The proposed system also is compared to the case of the Reed‐Solomon code applied to the multivalued QAM modulation system. The difference of performances is discussed from the theoretical viewpoint.
Selective repeat type‐II hybrid fec/arq systems using concatenated codes
Authors: Miyagi Masayoshi , Niinomi Tadafusa , Sasase Iwao , Mori Shinsaku 
Published: July 2007

AbstractHybrid forward error correction/automatic‐repeat request (FEC/ARQ) systems achieve greater throughput than ARQ systems by combining forward error correction with automatic‐repeat requests. A type‐II hybrid FEC/ARQ system is capable of adapting error‐correction capacity according to varying channel conditions. Although a high throughput can be achieved in such systems by using conventional convolutional or rate compatible punctured convolutional (RCPC) codes, when the channel signal‐to‐noise ratio (SNR) Es/N0 is low, resulting throughput efficiency and mean block delay performances are unsatisfactory.In this paper, selective repeat type‐II hybrid FEC/ARQ systems using concatenated codes are proposed to improve the throughput efficiency and mean block delay performances on channels with low SNRs. Systems using concatenated Reed‐Solomon outer codes and either rate one‐half convolutional or rate compatible convolutional (RCPC) inner codes are evaluated. The throughput efficiency and mean packet waiting and block delay times of these two types of concatenated coding systems are evaluated. A theoretical analysis and computer simulation of throughput efficiency of the proposed systems show increased performance for a wide range of Es/N0 over previous systems that use either stand‐alone rate one‐half convolutional or RCPC codes. It is also shown that the transmitter mean packet queueing delay and mean block delay times are reduced. In particular, by computer simulation, it is shown that when the traffic density is high, mean block delay times are greatly reduced by the use of RCPC inner codes.
High‐speed optical transmission systems using optical fiber amplifiers
Authors: Hagimoto Kazuo , Aoyama Koh‐Ichi 
Published: July 2007

AbstractHigh‐speed transmission technology is accomplishing dramatic reforms due to the application of optical fiber amplifiers.This paper reviews the high‐speed and long‐span repeater transmission which has become possible because of the application of wide‐band and low‐noise optical fiber amplifiers. Also, the device structure together with several other topics and their significance are discussed.
Redundant systems for multibeam transponder
Authors: Kondo Kimio 
Published: July 2007

AbstractThe multibeam transponder allows one to use a smaller ground station in satellite reception system and to make good use of the frequency band. The redundant system is important for the higher reliability of transponder, especially as the number of the beams increases.This paper considers a redundant system for a multibeam transponder. The concept of the expected system value herein introduced takes the reliability and the transponder weight into account simultaneously. Comparing the performance of eight typical redundant configurations, the importance of the common and active redundancy is shown.