bluuebunny/crossref_metadata_2025 huggingface dataset:
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

This 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

This 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.
Diversity performance analysis of two parallel dipole antennas mounted on a small metal body
Authors: Tsunekawa Koichi , Kagoshimas Kenichi
Published: July 2007

Diversity 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

To 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

This 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

The 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

In 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

This 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

The 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

The 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

In 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

As 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

The 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

Various 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

A 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

The 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

In 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

System 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

With 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

Recently, 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

Recently, 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

To 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.
Advanced signaling protocol for broadband ISDN services
Authors: Kuribayashi Shin‐Ichi , Shiraishi Satoshi
Published: July 2007

A signaling functional model (separated model) that assumes the functional separation of call control (CC) and bearer control (BC) must be considered for B‐ISDN because B‐ISDN deals with various levels of service quality, various speeds, and various connection configurations. This paper provides the basic structure of the forementioned separated model and the functions of the CC and BC based on actual B‐ISDN service specifications. Also, system design guidelines are proposed for connection‐type bandwidth selection and interworking between broadband ISDN and narrowband ISDN, which are key issues in the study of B‐ISDN signaling protocol.
Approximate performance evaluation method for TST‐type switching networks employing multislot connections
Authors: Hayashi Zenji
Published: July 2007

This paper describes the method for approximate evaluation of the performance of TST‐type switching networks employing multislot connections. Since the start of ISDN service, traffic has increased in volume and systems need to have large capacity. the TST‐type switching network is the most typical configuration to increase the system capacity. However, conventional methods for evaluating performance with multislot connections are not accurate.

First, a method is proposed for a single traffic stream of multislot connections where iteration is applied to solve the traffic model with loss rates in state transitions. Next, making use of traffic stream distribution probabilities for each single‐class traffic and full availability traffic model and the offered traffic of each traffic stream, the blocking probabilities of each class of traffic for a mixed traffic stream is approximately evaluated. This method well approximates the traffic characteristic of TST switching networks and its computation time is negligible compared to the simulation.
Adaptive predictive image coding using variable block shapes controlled by edge orientation
Authors: Ebitani Kenji , Kitajima Hideo , Shirakawa Tomoaki , Ogawa Yoshihiko
Published: July 2007

This paper proposes adaptive predictive image coding with variable block shapes based on edge orientation, as a highly efficient coding method for low bit rates. the method aims at the improvement of reconstructed image quality in edge areas.

In addition to the conventional method, where the quantizer is switched adaptively, according to the standard deviation of the prediction error signal calculated for each block 8 × 8 pixel, a predictor matched to the edge structure is used. Whenever necessary, the block is segmented into two, according to the orientation of the edge, and vector quantization is applied to the prediction error signal. When the block is segmented, the maximum number of bits assigned to each pixel is doubled if the number of representative vectors in quantization is kept the same.

By this scheme, saturation of the signal‐to‐noise (SN) ratio for the high bit‐rate condition, which is observed in the conventional system, can be avoided. In the proposed system, the forementioned control is executed by table look‐up based on the standard deviation of the prediction error signal. the table is independent of the image and can be constructed beforehand with the advantage of the conventional system being inherited. the proposed method exhibits overall satisfactory coding performances over A‐VQ‐PE and A‐DCT‐VQ, which have high coding efficiency. This verifies the usefulness of the proposed method.
Asymptotic analysis of transient electromagnetic fields in a semicylindrical concave conducting boundary
Authors: Goto Keiji , Yukutake Kazutoshi , Ishihara Toyohiko
Published: July 2007

The propagation of the pulse wave radiated from the pulse source on a concave cylindrical conducting boundary has been studied by using asymptotic representations by: (1) a combination of the geometric optical wave and the integral‐type interference wave; and (2) a combination of the geometric optical wave and the lowest‐order whispering gallery (WG) modes.

The effectiveness of the asymptotic representations is determined by comparison of the numerical results with the reference solution using a combination of the WG modes and the continuous spectrum. Also, the asymptotic method was used for deriving the complex rays on the shadow side of the caustic and the uniform asymptotic solution effective in the transition region near the caustic. It was shown that the pulse wave represented by a complex ray can reach the observation point on the shadow side of the caustic. Further, if both the source and the observation points are on or near the boundary surface, the waves due to the multiple reflection can be represented by the interference wave of an integral type or by the lowest‐order WG mode.

The mutual relationship between the geometrical optics and the WG modes was determined. It was shown that the asymptotic solution in the time domain is more effective than the results in the frequency domain in the detailed analysis of the physical meaning of the wave propagation in a concave boundary.
Beam‐space CMA adaptive array antennas
Authors: Chiba Isamu , Chujo Wataru , Fujise Masayuki
Published: July 2007

In the communication system using a constant modulus signal, a constant modulus algorithm (CMA) adaptive array antenna is effective for elimination of the frequency‐selective fading generated in multiple propagation paths. On the other hand, in the system in which CMA adaptive loops are installed for each antenna element in an array with more than 10 elements used for mobile satellite communication, the computing time and the amount of hardware become excessive.

In this paper, a beam‐space CMA adaptive array antenna (BSCMA) is proposed in which a portion of the multibeam output is selected to form a CMA adaptive array. In the BSCMA, first, a multibeam is formed by means of a fast Fourier transform (FFT) and only the beams whose output power exceeds a threshold level are selected. an adaptive process is carried out with the CMA as a guiding principle only for the selected beam outputs. the BSCMA has an advantage of carrying out the capture of the desired wave and the elimination of the interference wave effectively with degrees of freedom corresponding to the number of arriving waves. the method is effective for an adaptive antenna system applied to an array antenna constructed with many antenna elements. In this paper, the configuration of the BSCMA is shown and its characteristics are investigated by the numerical simulation.
Expansion of lightwave network rooknet: TDMA RookNet
Authors: Kato Manabu , Uchino Takeo , Oie Yuji , Miyahara Hideo
Published: July 2007

Lightwave networks based on optical wavelength division multiplexing (WDM) have been considered promising for high‐speed communication. Such lightwave networks are divided mainly into two groups according to the number of hops required for packets to arrive at their destinations: single‐hop networks and multihop networks. the authors have already proposed a lightwave mesh network RookNet, which allows packets to arrive at any node at most in two hops, by taking advantage of both single‐hop and multihop networks, and analyzed its performance. This paper proposes a scheme to enlarge the RookNet without increasing the number of receivers per node and analyzes its performance. Specifically, the TDMA scheme is used in which a pair of nodes share a channel and employed sequentially. As a result, the proposed RookNet, referred to as the TDMA RookNet, accommodates about three to four times as many nodes as the original one.
An optically controlled array antenna with a beam‐forming network (BFN) using two laser sources
Authors: Konishi Yoshihiko , Chujo Wataru , Fujise Masayuki
Published: July 2007

With respect to the optically controlled array antenna in which the optical Fourier transform and the O/E conversion are used for generation and control of the microwave excitation distribution in the optical region, the excitation amplitude and phase distribution and the radiation characteristics are studied theoretically and experimentally for a two‐laser system in which two laser sources with their oscillation frequency difference set at the desired microwave frequency are used.

First, the excitation distribution and the radiation pattern are expressed theoretically in the case where a circular aperture image mask is used and the relationship between the image mask aperture diameter and the element antenna spacing is derived.

Next, a two‐laser experimental system is shown which uses LD pumped Nd: YAG lasers as the laser sources. an excitation distribution experiment was carried out at 1.54 GHz. From the experimental results, it is found that a stable excitation distribution corresponding to the theoretical value can be obtained in the experimental system in the two‐laser system as in the one‐laser system. Further, by using the measured excitation distribution, the array radiation pattern is computed. In this way, it is confirmed that the radiation pattern in a beam shape corresponding to the image mask aperture diameter can be obtained.
Throughput analysis of a transport protocol in an FDDI network
Authors: Ishibashi Yutaka , Maruyama Mitsuru , Sakamoto Hideki
Published: July 2007

This paper analyzes the throughput of a transport protocol, such as the ISO transport protocol class 4 (TP4) and the transmission control protocol (TCP), in a fiber distributed data interface (FDDI) network. It also studies the influence of the target token rotation time (TTRT), ring latency, window size, and frame length on the throughput performance in cases of both symmetric traffic and asymmetric traffic. Furthermore, the throughput is compared with that of FDDI without transport protocol in order to quantify the overhead of the transport protocol. Numerical results indicate that the influence of window size and frame length on the throughput is larger than that of ITRT.
Mode‐field‐diameter measurement method using a field mask
Authors: Kuwaki Nobuo , Seino Minoru , Yoshida Koji
Published: July 2007

In the mask method, which is one of the measurement procedures of estimation of the mode field size of single mode optical fibers, measurement setup can easily be devised. the advantage is that the overall system is small in size. However, there are few investigations with only a few reports on the physical properties of the field mask required in realization of the measurement method or the details of applications to the dispersion shifted optical fibers used in trunk lines. the present paper investigates the required physical characteristics of the mask and it is found that in order to keep the error in the measurement of the mode field radius below, the mask attenuation must be larger than 45 dB. Further, when the required attenuation is not satisfied by the mask, the equation under which there is still the possibility of field measurement is derived. Using the derived equation, it became clear that it is possible to measure the mode field radius of the 1.3 μm band and the dispersion shifted fibers by the far field method with deviations below 1 percent. Further, when such a method is devised to fit into the far end of the fiber cables, their mode field radius can be measured when the maximum cable loss is 45 dB.
Shared output buffer‐type switching architecture with fair output port contention
Authors: Tode Hideki , Yamamoto Miki , Okada Hiromi
Published: July 2007

This paper considers the shared output buffertype switching system as an architecture suited to the large‐scale ATM switching system. an architecture is proposed, which can solve the fair throughput assignment problem among the ports belonging to the same shared memory, which is a problem in sharing the output buffer. the proposed architecture realizes fair access to the destination port contained in the specified shared buffer, by sort processing and the address attachment, without using the random access contention unit to the buffer in the knockout switch.

For the proposed architecture and the conventional shared output buffer‐type knockout switching system, the performances are compared by deriving the cell loss probability due to the output contention for each port. As a result, it is verified that the proposed architecture is better in terms of the realized cell loss probability.

The performance of the switching system is evaluated by a computer stimulation when various buffering schemes are applied to the shared output buffer. Then it is shown that the fair throughput assignment among the considered output ports can be realized by combining the proposed architecture with an adequate buffering scheme.
Performance analysis of a wireless local area network with a TDD channel taking into consideration capacity allocation between uplink and downlink channels
Authors: Suzuki Takahiro , Tasaka Shuji
Published: July 2007

This paper deals with a wireless LAN of microcells. We focus on a single microcell, which consists of a base station and wireless terminals. We consider here a problem of the channel capacity allocation between the uplink (terminal‐to‐base) and downlink (base‐to‐terminal) communications for a wireless LAN with a TDD (time division duplex) channel. the ALOHA‐Reservation protocol is selected as a MAC protocol for the uplink communication. the performance of the ALOHA‐Reservation protocol with a TDD channel is analyzed in terms of throughput, average message delay, and average response time. Then, the effect of the uplink and downlink channel capacities on the performance is examined under various traffic conditions.
An approach to optical parallel data transmission using optical symbolic substitution
Authors: Takahashi Hideya , Shimizu Eiji , Kajiki Yoshinori
Published: July 2007

This paper proposes a flexible parallel optical data transmission system as follows. the data transmission itself is executed in parallel by utilizing the super‐parallelism of the light. In addition, the address information which is necessary for the transmission is super‐posed on the transmitted data. By those schemes, the capacity of the individual transmission channel as well as the number of transmission channels in the system are made variable.

This paper describes first the principle of parallel optical data transmission. It is shown that the symbolic substitution (SS) is useful in the superposition and separation of the address information, which are the basic operations of the system. SS is a parallel and positioninvariant logical operation. an experimental system is constructed by the SS technique using the computer‐generated Fourier hologram (CGFH). A result of experiment is shown for the single‐channel parallel transmission of two‐dimensional data. Thus, it is shown that the flexible transmission system, where the capacity of the individual transmission channel as well as the number of transmission channels are variable, can be realized by the proposed transmission scheme.
Receiver design using the dependence between quadrature components of impulsive radio Noise
Authors: Miyamoto Shinichi , Morinaga Norihiko , Katayama Masaaki
Published: July 2007

In this paper, the statistical characteristics of Middleton class A impulsive noise are investigated to obtain a receiver that is robust against impulsive radio noise. It is shown that the in‐phase and quadrature phase components of class A impulsive noise are not statistically independent though they are uncorrelated. Then a new receiver design based on the dependence between these components is proposed for class A impulsive noise. Numerical results show that the proposed receiver is quasioptimum and its performance is much better than that of a conventional receiver.
Fast frequency hopping transmitter and receiver based on digital signal processing and its performance
Authors: Sawahashi Mamoru , Adachi Fumiyuki
Published: July 2007

Frequency hopping is an effective technique in which error correction is performed by randomizing the bust error due to fading. In this paper, frequency translation based on digital signal processing is applied and the structure of fast frequency hopping transmitter and receiver is proposed. the principles of frequency hopping modulator and frequency translating filter for hopped‐signal reception are first described. Then an experimental 1.5 GHz transmitter and receiver (128 kbps, differentially encoded /4‐shifted quadriphase‐shift keyed (QPSK), differential detection) that can hop among 96 frequencies (12.288 MHz bandwidth) are developed. It is confirmed that a frequency switching time of 2(32) s is realized at the transmitter (receiver) and that the receiver successfully frequency translates and demodulates the hopped signal within approximately 75 s. Finally, the combined effect of frequency hopping in a fading environment and with forward error correction is experimentally evaluated. the proposed structure replaces the conventional frequency synthesizers consisting of frequency divider and phase‐locked loop by fixed frequency oscillators so that fast frequency switching can be realized. Moreover, the proposed system uses very little power and is small, making it suitable for miniaturization of LSI.
Circularly polarized conical beam antennas
Authors: Kawakami Haruo , Sato Gentei , Watanabe Takeshi , Wakabayashi Ryoji
Published: July 2007

A small and lightweight antenna was developed which generates a circularly polarized conical beam in the desired direction by changing the incline angle of the linear antenna elements and the spacing between the antenna elements without phase shifters. the experiment for directivity of the circularly polarized conical beam antenna was carried out by using four monopole antennas, and the effectiveness of the theoretical analysis was confirmed.

Next, experiments were carried out for the impedance and directivity with representative dimensions. the gain in the maximum direction was 4.5 dBi with an axial ratio of less than 2 dB and a standing wave ratio of less than 1.2.
622 Mbit/s‐sixteen‐channel FDM coherent optical transmission system using two‐section MQW DFB‐LDs
Authors: Mizuochi Takashi , Shimizu Katsuhiro , Shimomura Kenkichi , Kitayama Tadayoshi , Ito Katsuyoshi , Ishimura Eitaro
Published: July 2007

A light source and optical frequency control technique needed for realizing the optical frequency division multiplexing transmission (Optical FDM) is developed and experiments of a 622 Mbit/s‐sixteen‐channel FDM coherent optical transmission based on the heterodyne detection are conducted. the transmission is configured such that sixteen 1.55 μm wavelength two‐section MQW DFB‐laser diode (LD) are multiplexed by a star coupler. the wavelength of each LD was spaced at 10 GHz intervals with the frequency fluctuation kept under + 100 MHz by the optical frequency control circuit that uses a scanning Fabry‐Perot interferometer. the receiver configuration has a delay‐line demodulator, polarization diversity, and a frequency discriminator with no dead bands. For the station light source, the two‐section MQW DFB‐LD was tuned, which is the same as the transmitter, using current and temperature control. Random channels could selectively be received with a receiver sensitivity of ‐39.3 dBm. It was verified that 16 channels of 622 Mbit/s high‐vision (Japanese standard HDTV) signal could be transmitted through 110 km of 1.3 μm zero dispersion fiber without signal degradation.
A virtual STM transmission method based on ATM network
Authors: Kamiyama Noriaki , Ohta Chikara , Tode Hideki , Yamamoto Miki , Okada Hiromi
Published: July 2007

This paper considers a new transmission method (quasisynchronous transfer mode, Q‐STM), as a means to eliminate both the cell loss and the network delay fluctuation in an ATM network. the concept of time‐switch in circuit switching is introduced into the ATM switching framework. A switching structure and the call establishment procedure are proposed. In the proposed method, the time‐switch is introduced, which eliminates in principle the output port contention in the ATM switching fabric. By preparing a buffer with a certain capacity, cell loss due to buffer overflow in the output port of the ATM switch can be completely eliminated.
Asynchronous transfer mode call admission control scheme with plural quality classes
Authors: Ogino Nagao
Published: July 2007

In an asynchronous transfer mode (ATM) network, various calls with different trans‐mission quality requirements ranging from low bit‐rate data signals to high bit‐rate motion picture signals are applied. Therefore, it is important to determine how to allocate network resources to those calls and to judge whether those calls can be accepted. This paper proposes a call admission control scheme based upon a data table that holds the relationship between average bit‐rate and needed bandwidth for aggregated signals in each quality class obtained beforehand by simulation. This proposed scheme assumes broadband services where the aver‐age bit rate and burstiness of aggregated signals can be estimated clearly with predictable value ranges. This proposed scheme uses a conventional scheme for service quality class control. the following charac‐terizes this proposed scheme: (1) it is suitable for real time call processing because it has small table search processing and a simple table search algo‐rithm; (2) it realizes more accurate control due to a decreased data volume requirement and more precise data preparation than is the case for some of the conventional schemes; (3) it can be expanded easily to handle increases in the number of quality classes; and (4) it provides control in terms of statistic multiplexing effects between each quality class (also found in some of the conventional schemes).
Pointer conversion method for synchronous digital hierarchy
Authors: Takatori Masahiro , Nakano Yukio , Ishida Keiichi , Ashi Yoshihiro , Kanno Tadayuki , Mori Takashi
Published: July 2007

Synchronous digital hierarchy (SDH) standardized in International Telecommunication Union‐Telecommunication Standard Sector (ITU‐T) applies a new multiplexing method using a pointer that indicates a tributary location in the SDH frame. the location of the SDH frame heads received from several lines is adjusted at interface circuits to facilitate the multiplexing process in the SDH equipment. Since the frame head locations of input signal differ from the output signal, pointer values are attached to the output signals. the pointer conversion of each tributary is performed independently of each other. Therefore the pointer values of tributaries transported on the same line might be different from each other after the conversion even if these values are the same. Hence large amounts of buffer memory would be required at the destination point to provide a transport service utilizing multiple virtual containers (VCs). This paper proposes a new pointer conversion method that keeps the pointer value differences unchanged between tributaries multiplexed in an SDH frame. This method allows multiple VC transport service to be provided.