bluuebunny/crossref_metadata_2025_split huggingface dataset:
Diversity performance analysis of two parallel dipole antennas mounted on a small metal body
Authors: Tsunekawa Koichi , Kagoshimas Kenichi 
Published: July 2007

AbstractDiversity technology is an effective means to improve the transmission quality in mobile communications. Hence, some portable telephones are equipped with diversity antennas. However no detailed analysis has been carried out. The reason for the low correlation coefficient of such antennas in experiments has not been clarified quantitatively.In this paper, the diversity antenna is assumed to be made of two half‐wave dipole antennas placed in parallel on a small transceiver with a rectangular shape, and its correlation coefficient and efficiency characteristics are analyzed by the method of moments using wire grid models. It is found that the correlation coefficient of 0.23 and the efficiency including the mismatch loss is −2.7 dB even for an antenna element spacing of 0.1 wavelength. Thus a sufficient diversity effect can be obtained on a small transceiver. Specifically, the reason for the low correlation coefficient is studied by separating the mutual coupling between the antenna elements and the effect of the metal body. The relationship between the incoming wave profile and the correlation coefficient is presented. It is shown that the correlation coefficient never exceeds 0.6 in an ordinary operating condition and that the correlation coefficient can be made almost 0 if the load impedance of the parasitic antenna element is chosen appropriately.
A propagation model for mobile radio propagation loss in an urban area at 800 MHz
Authors: Ichitsubo Shinich , Kimuras Masahiro 
Published: July 2007

AbstractTo understand the propagation structure of the microcells with a tall and medium‐height antenna in an urban area, the fundamental propagation parameters are found and the structural model of the propagation loss was constructed. The fundamental propagation parameters were obtained based on the multivariable analysis of the propagation data at 800 MHz measured in the Tokyo Metropolitan area. These parameters are the distance between the transmitter and receiver, the average building height between the transmitter and receiver, and the base‐station height which have high correlation and regression coefficients with the propagation loss.The relationship of parameters obtained from the model is (20 ‐ α) log(h) for the base‐station height characteristics and (α ‐ 20) log (H) for the building height characteristics if the distance characteristics are α log (d). The relationships of coefficients of the conventional estimation equation and the regression equation obtained by the measured data almost agreed with those of the model so that the validity of the model was confirmed.
Performance analysis of slotted aloha over time‐varying channels
Authors: Mukumoto Kaiji , Fukuda Akira 
Published: July 2007

AbstractThis paper considers a slotted ALOHA network which consists of a central base station and many mobile terminals. In classical performance analyses of random access networks, a channel between the station and a terminal is assumed to be always in a good state. However, this is not the case in mobile radio networks since the channel suffers from many factors such as fading, shadowing, and so on. Moreover, the channel condition changes with the terminal location.In this paper, a simple channel model is used to consider the effects of time‐varying channels in a random access network. The channel model assumed in this paper has three states: shadowing, good, and bad. The transitions between the channel states are described by a Markov chain. The dynamic performance of a slotted ALOHA network over such time‐varying channels is evaluated by means of the equilibrium point analysis. Then the influence of the time‐varying channel on the throughput performance of a slotted ALOHA network is studied.
Assigned power level and assigned slot‐based multiple‐access scheme by capture effect
Authors: Shimamoto Shigeru , Onozato Yoshikuni , Teshigawara Yoshimi 
Published: July 2007

AbstractThe TDMA scheme, a typical multiple‐access scheme, can provide secure transmission; but its efficiency is poor under low traffic conditions. By contrast, the random access scheme, represented by the ALOHA scheme, has a small‐delay characteristic under low traffic conditions but a stability problem under heavy traffic conditions.This paper presents a new multiple‐access scheme in which each station is assigned a slot in every frame and stations are assigned to a slot at different power levels to obtain the capture effect. Therefore, the proposed scheme can adapt itself under various traffic conditions with channel status monitoring based control. Different models of capture effect are proposed, and the performance of the models is analyzed both by theory and by computer simulation.
Optimal quantization scheme for orthogonal transform coefficients, allowing for the noise‐masking effect due to the local variation of video signal
Authors: Hamada Takahiro , Matsumoto Shuichi 
Published: July 2007

AbstractIn general, an optimum quantizer which gives the minimum distortion at a given bit‐rate is uniquely determined when the statistical characteristics of the source signal are given. This quantizer, however, is not optimum for the human visual characteristics; and a quantizer which is designed to minimize the estimated distortion (estimated noise) reflecting the human visual characteristics is more likely to be optimum. In the optimum quantization of orthogonal transform schemes, theoretical quantizer design schemes considering only the human visual characteristics of the spatial frequency direction have so far been reported. However, there is another human visual characteristic, that is, the noise‐masking effect which is the difference in the detectability of noise, depending on the local variation of a video signal (activity). For this, only the quantizers which use this effect experimentally have been reported; and they have not been studied theoretically.In this paper, it is proposed, as the first step, that the visual sensitivity to noise be expressed on two axes, i.e., spatial frequency and “activity.” A three‐dimensional (3‐D) structure quantization cube is then proposed which is obtained by minimizing the noise estimated by the visual sensitivity of the noise at the given bit‐rate and the theoretical design scheme of this optimum quantization cube is described. Finally, the effectiveness of the quantization cube designed by this theoretical scheme is compared with that of the conventional quantization schemes by a computer simulation using real picture data.
Signal transmission characteristics of diversity reception with least‐squares combining—relationship between desired signal combining and interference canceling
Authors: Suzuki Hiroshi 
Published: July 2007

AbstractThis paper considers the diversity reception system where the combining coefficients are controlled by the least‐squares method. The CNR characteristics in the presence of the interference wave are derived, and the signal transmission characteristics are analyzed.First, the optimal coefficients are determined by the MMSE criterion. The expression for the optimal CNR is derived in two ways, i.e., from the macroscopic and the microscopic viewpoints. It is shown that the two results agree and the variables are related through the Pythagorean theorem. Then CNR is represented by the projection matrix which is specified by the correlation matrix for the noise and the interference wave. The signal combining/interference canceling characteristics are examined.Next, the eigenvector expansion for the correlation matrix is applied and the representation for CNR under fading condition is derived, using the statistical properties of the eigenvalue, the probability density function and the probability distribution function for CNR are derived in two ways. Then the expression for the average BER is derived for CBPSK and DBPSK. The extension of the idea to the nonlinear interference canceler and the application to the cellular mobile communication also are discussed.
Design of power systems for air conditioners used in telecommunication networks
Authors: Koizumi Yasuyuki , Yotsumoto Katsuichi , Hayama Hirofumi , Furubo Shizuo , Muroyama Seiichi 
Published: July 2007

AbstractThe reliability of air conditioning systems for next‐generation high‐power‐consuming telecommunication equipment is calculated taking into consideration the time delay effect. Also, a method is presented for improving the reliability of the air conditioning system. This method increases power supply reliability by sending the status information signal from the commercial power source to both the control equipment and the switch. Switching occurs only when the switch receives matching signals from both the control equipment and the power source.
Corner reflector antenna with the same beamwidth in two frequency bands
Authors: Suzuki Tamami , Kagoshima Kenichi 
Published: July 2007

AbstractThe demand for expanded mobile communication capacity is increasing rapidly. It is expected that in addition to the currently used 900‐MHz band, the 1.5‐GHz band will have to be utilized. An antenna is designed so that it has the same sector beamwidth in both bands. The antenna is realized by placing a rod‐type parasitic element close to the driven element which is parallel to a corner reflector having a comer angle of 140°. The absolute beamwidth is determined by the corner length.
Application of adaptive array antennas to radio communications
Authors: Mizuno Mitsuhiko , Ohgane Takeo 
Published: July 2007

AbstractIn the area of mobile communications, there has been increasing demand and development for new technologies and services such as digitization and personalization. With this as background, this paper studies the use of adaptive antenna technology for mobile communication.In the area of mobile communications, the adaptive antenna technology has been studied with a view to reducing the fading for reception by the mobile station. In the case of microcells and indoor communication for which an expanded use is anticipated, arrivals of multiple waves from various directions are expected even for the base station so that the application of the adaptive antennas to the base stations is effective.In the case of high‐speed data transmission such as wireless local wireless networks (LAN), further reduction of fading and interference is required. Also, the frequency sharing among different radio services is an area in which the adaptive antenna is useful.Introductions of dynamic control of the systems are expected for mobile communications in time, space, and frequency domains. The adaptive antenna is effective for control in space. The dynamic zone configuration will be a new application area in which, depending on the distributions of the users, the zone shape is varied.
Ferroresonant‐type DC power supply controlled by fully magnetic technique
Authors: Katane Tamotsu , Fuwa Motoki , Sakaki Yo 
Published: July 2007

AbstractAs a method of compensating for the voltage drop on the dc side of ferroresonant dc stabilized power supplies, a magnetic‐only controlled power supply was developed. When a dc magnetic field is applied in the direction of diameter of a saturable ring core, using the saturation flux density, that is, resonant voltage change, by dc load current feedback to an electromagnet positioned in the diametric direction, the resonant voltage is altered and output voltage stabilization is achieved.By increasing the operation frequency of the power supply, miniaturization is achieved and simultaneously, as a feedback control method, is expressed in a block diagram. An investigation was made on the power supply design method and the response to various disturbances. As a result, design criteria were established to make the steady‐state output voltage error zero. The transient response simulation was verified to explain well the experimental result.
Double search self‐healing algorithm and its characteristics
Authors: Fujii Hiroyuki , Yoshikai Noriaki 
Published: July 2007

AbstractThe requirements of today's communication networks are changing rapidly with the introduction of highcapacity transmission links and the increased amount of data traffic, thus fast restoration from failures is of increasing importance. To meet this requirement, self‐healing algorithms, which are distributed algorithms based on autonomous control at each node, are discussed.The conventional self‐healing algorithms called single‐search self‐healing algorithms have the following problems: (1) the self‐healing process for bidirectional path failure has not been investigated; and (2) a large search area is affected by restoration messages.To solve these problems, this paper proposes and evaluates the restoration characteristics of a new self‐healing algorithm called the “double‐search self‐healing algorithm.” The results indicate that the proposed algorithm can restore foiled bidirectional paths faster and find alternate paths more effectively man conventional self‐healing algorithms. To evaluate the restoration characteristics, an SDH network model based on existing telephone network data in Japan also is constructed.
Performance evaluation of file transfer under multimedia environment in atm networks
Authors: Baba Ken‐Ichi , Saito Toshihiko , Murata Masayuki , Miyahara Hideo 
Published: July 2007

AbstractVarious communications services are being provided over ATM networks, and among them, file transfer is considered to be an important service. In file transfer, cases in which immediacy with respect to the connection request of a call is not as strong as in voice and picture may also be considered. In addition, in band allocation necessary during the call setup time, the transmission rate may be established freely to a certain extent by a terminal.In view of the foregoing, in this article, performance of file transfer multiplexed with other traffic in ATM networks is evaluated considering the forementioned characteristics.First, the effects of the file transmission rate and the performance of the system maintaining the file transfer over a single channel are studied and then the performance over multichannels is evaluated. As a measure of these performances, the throughput, which is important in file transfer, also is evaluated using the call loss probability considered to be important from the viewpoint of the user.
Idle‐signal casting multiple access with partial echo (icma‐pe) for mobile packet communications
Authors: Umeda Narumi , Onoe Seizo 
Published: July 2007

AbstractA highly efficient random access scheme ICMA‐PE (Idle‐Signal Casting Multiple Access with Partial Echo) is proposed for digital mobile communications. In this scheme, partial echo (PE) bits are broadcast with idle busy bite and receive nonreceive indicating bits as collision control bits to control mobile transmission, thus improving the random access efficiency.First, frame formats, behavior of mobile and base stations, and the transmission procedure are explained.Next, the packet failure rate and throughput are evaluated with both theoretical analysis and computer simulations. As a result it is clarified that about 20 percent improvement in maximum throughput is achieved compared to conventional schemes. The improvements achieved with transmissions also are mentioned and the transmission characteristic when various message length signals coexist is clarified. Finally, the effect of the coincidence of a PE with one from another station is evaluated, and it is shown that the PE bit length of about 7 bit is necessary to maintain the characteristic.
Multidimensional coding schemes in combined satellite and terrestrial channels
Authors: Tsujioka Tetsuo , Oka Ikuo , Fujiwara Chikato , Okumoto Takaaki 
Published: July 2007

AbstractThe sudden deterioration in transmission quality due to rain or snow attenuations is a problem in VSAT communications using the 14/12‐GHz band‐link, and a system that can cope with such a problem has been developed and studied.This paper proposes a method for improving the bit error rate (BER) of an overall system for satellite channels showing a decreased carrier‐to‐noise (CNR) by using a terrestrial channel of low error rates in addition to satellite channels and by coding both channels simultaneously. The effectiveness of the proposed scheme has been clarified by deriving the theoretical upper bounds of the BER and evaluating its performance by computer simulations for the case of multidimensional coding based on QPSK signals.
Usage parameter control employing a tagging method
Authors: Sakamoto Nobuo , Murata Masayuki , Miyahara Hideo , Ohba Yoshihiro 
Published: July 2007

AbstractIn asynchronous transfer mode (ATM) networks, each user requests a call setup with the traffic descriptor which describes its own traffic characteristics. Since network resource control is carried out by this traffic descriptor, it would be necessary that the traffic generation is monitored by the network, which is the so‐called usage parameter control (UPC).In this paper, three methods are evaluated analytically for implementing the UPC function: a discarding method, a tagging method, and a hybrid method. The last method is proposed anew in the paper and the comparative results for the three methods are offered from a viewpoint of performance of the cell multiplexer when the output traffic from UPC is superposed.
A method to evaluate effective use of transmitting power in bandlimited psk channels
Authors: Miyauchi Kazuhiro , Ito Mikio , Okada Takahiro 
Published: July 2007

AbstractSystem models and evaluation parameters are proposed for comparing the efficiency of transmitting power utilization of various kinds of PSK transmission systems and bandlimiting and spectrum‐shaping schemes by the peak output power of the transmitting amplifier and the signal‐to‐noise ratio (SNR) at the decision instant. Applying this method to the transmitter‐side Nyquist shaping model and the Butterworth reference equalization model, the characteristics of the BPSK, QPSK, and offset and π/4 shifted QPSK for power amplification before and after filtering are calculated and discussed.
Earth satellite communication systems with low orbits, and effects of the doppler shift
Authors: Katayama Masaaki , Ogawa Akira , Morinaga Norihiko 
Published: July 2007

AbstractWith the increase in the need for versatility in satellite communication, improvements in satellite launching technology and development of small satellites with higher capabilities, there is tremendous research activity in satellite communications using nongeostationary satellites. However, most of these satellites are meant for the polar regions and the application to general communication between widely scattered areas or the marine and airborne in which traditional communication systems are difficult to use.This paper shows first the possibility of a low‐orbital satellite system for an area such as Japan where population density is high and where a geostationary satellite or a terrestrial communication system may easily be employed, and the performance of such a system is investigated.Next, we investigate the Doppler shift in the low orbit. It is shown that complete correction on the transmitting station is not possible, which is different from a long elliptical‐orbit satellite. Moreover, phase‐locked loop (PLL) and block demodulation techniques are considered for carrier recovery in the presence of Doppler shift. A comparative study of the Doppler shift on the spectral efficiencies of multiple access techniques is performed, and the superiority of CDMA over FDMA is shown.
Bit interleaving technique as a radar interference canceller
Authors: Aikawa Satoru , Ohmoto Ryutarou , Okuno Takao 
Published: July 2007

AbstractRecently, degradation due to radar interference has been reported in high‐frequency efficiency microwave radio systems. However, there has been no solution to this problem. This paper proposes a bit interleaving technique as a radar interference canceller and presents a designing method and its performance in digital microwave radio systems. First, the characteristics of radar interference are described. Next, the bit interleaving technique is proposed as an interference canceller for maritime radar, whose source is difficult to determine. Next, the method of designing the bit interleaving on a channel with burst errors and random errors is described. Finally, the effectiveness of the canceller is shown by the experimental results obtained using a prototype. The results show that bit interleaves can correct errors due to radar interference.
Differential detection scheme for DPSK using phase sequence estimation
Authors: Kojima Toshiharu , Miyake Makoto , Fujino Tadashi 
Published: July 2007

AbstractRecently, the differential detection scheme has attracted considerable attention as a demodulated scheme for digital mobile communications because of its robustness in the frequency nonselective fading channel. A problem of the differential detection scheme is that its bit error rate (BER) performance in the additive white Gaussian noise (AWGN) channel is inferior to that of the coherent detection scheme. To solve this problem, many methods to improve BER performance of the differential detection in the AWGN channel have been proposed. However, those methods require complex signal processings.This paper proposes a novel differential detection scheme as a simpler improvement method which estimates the differential phase of the transmitted signal by a sequence estimation scheme using the Viterbi algorithm. The proposed scheme is simplified in a manner such that its signal processing is composed of only additions and subtractions on the phase information of the received signal. Results of computer simulation show that BER performance of the proposed scheme is close to that of the ideal coherent detection in the AWGN channel. In addition, the trellis diagram of the Viterbi algorithm can be reduced without performance degradation introducing the signal processing similar to the Scarece State Transition (SST) type Viterbi decoding. The proposed scheme also is useful in the case of the fast Rician fading channel and the slow Rayleigh fading channel.
Techniques of estimating radiated interference field in actual configurations
Authors: Murakawa Kazuo , Masuda Hidetoshi , Masugi Masao , Tokuda Masamitsu 
Published: July 2007

AbstractTo resolve the problem of electromagnetic interference generated at the actual configuration of electronic equipment by a radiated interference wave, it is desirable to establish a technique to estimate the radiated interference of electronic equipment. This paper discusses a method for estimating the radiated interference in actual configuration from the measured radiated interference at the test site of the electronic equipment. In the proposed estimation method, a simulated source of the electronic equipment is used for deriving the deviation (conversion coefficient) of the wave propagation characteristics of the test site and the actual configuration. By means of this conversion coefficient, the radiated interference in actual configuration is estimated from the radiated interference at the test site. An estimation method is shown in the case where a spherical dipole antenna is used as a simulation source of the electronic equipment. When the effectiveness of the estimation method was verified experimentally with actual electronic equipment, it was found that the radiated interference in the actual configuration can be estimated with accuracy of 4 to 5 dB at the frequencies of 30 to 300 MHz.