bluuebunny/crossref_metadata_2025_split huggingface dataset:
Throughput performance of ARQ schemes on a markov bit‐error channel
Authors: Komatsu Masaharu , Okamoto Katsuaki , Kinoshita Kozo 
Published: July 2007

AbstractThe performances of ARQ schemes depend on the error process. This paper evaluates the throughput performances of Stop‐and‐wait ARQ and Go‐back‐N ARQ schemes on an unslotted channel or a slotted channel. In these channels, channel time is divided into fixed size intervals called bit‐time and channel state changes according to a two‐state Markov chain. the two‐state Markov chain has two states, S1 and S2. In state S1, a bit‐error never occurs; while in state S2 a bit‐error occurs with probability one. Also, the property of the process is uniquely determined by two transition probabilities, i.e., the transition probability p1 from S1 to S2 and the transition probability p2 from S2 to S1.From the analysis, it is found that the state changes less frequently for larger decay factor δ( =1 ‐ p1 ‐ p2) and the throughput performances of the ARQs depend strongly on the decay factor for fixed bit‐error rates. Furthermore, the numerical examples show that for a given bit‐error, round‐trip delay, packet length, and overhead length, their throughput and optimum packet length giving the maximum throughput become larger when the decay factor becomes larger.
A coherent demodulator for fast frequency‐hopping spread‐spectrum signal employing an adaptive algorithm
Authors: Takakusaki Keiji , Nakagawa Masao 
Published: July 2007

AbstractIt has been considered impossible to demodulate a fast frequency‐hopping (FFH) spread‐spectrum signal coherently in a frequency selective fading channel as a result of difficulties with making the receiver local oscillator track the phase of a received signal that lacks phase continuity. This paper proposes a coherent demodulator for both FFH‐PSK (phase‐shift keying) and FFH‐FSK (frequency‐shift keying) signal employing a method in which the received signal is noncoherently down‐converted and phase‐adjusted by an adaptive algorithm.Computer‐simulations show that performance is better than in the case of noncoherent demodulators and that the interference‐rejection effect of the adaptive algorithm produces strong protection against interferences from other CDMA users.
Measurement of polarization characteristics of VHF radio waves reflected by the Es layer
Authors: Ichinose Masaru , Kainuma Syoji 
Published: July 2007

AbstractTo investigate the change of the rotation of the polarization plane of the very‐high frequency (VHF) radiowave after reflection by the sporadic E layer, a television wave transmitted from Seoul, Korea, was measured in Tokyo.In this paper, the measurement principle and equipment for the rotation of the polarization plane are described. From the measured results, it is shown that most of the measured values have rotation by a certain angle from the polarization state of the transmission and exhibit fine changes swiftly and randomly within 40 to 90° centered at the rotated angle. Sometimes, there is a case of slow rotation from +90° to ‐90°. Further, the cause of the rotating characteristics of the polarization plane is presented from the Faraday rotation theory.
Coherent hybrid ds‐FFH CDMA‐basic performance in mobile radio environment
Authors: Tomisato Shigeru , Fukawa Kazuhiko , Suzuki Hiroshi 
Published: July 2007

AbstractThis paper proposes a coherent hybrid DS‐FFH CDMA system that combines the coherent frequency‐hopping (FFH) and the direct sequence (DS) techniques. the basic performance in the mobile radio system is analyzed. the proposed method features the following:(i) CDM by the low‐chip‐rate DS using the orthogonal codes;(ii) the frequency‐diversity effect obtained for each symbol by the maximum‐ratio synthesis of the multiple chips spread by the coherent FFH.The system configuration and the operation are described. Assuming a channel where the delayed wave components of the four waves contain respective Rayleigh fadings, a computer simulation is executed and the following transmission characteristics are revealed.(i) When there does not exist an interference wave in the 4‐chip system, the 4‐branch frequency‐diversity effect is verified. the average Eb/No required in order to realize the average BER of 10−2 is 8 dB.(ii) When space diversity is combined, the average Eb/No required to realize the average BER of 10‐2 is 8 dB, even if there exists an interference wave.(iii) In the dynamic fading environment, the maximum Doppler frequency that can realize the average BER of 10‐2 for the average Eb/No =15 dB, is 20 Hz and 80 Hz, respectively, for the cases with and without interference.
Evaluation of speech quality impairment due to burst bit errors
Authors: Kozono Jun‐Ichi , Irii Hiroshi 
Published: July 2007

AbstractAlthough there has been some research on the relation between random errors that cause speech quality impairment and mean opinion score (MOS), speech quality impairment factors have not been clarified for the bursty code error noise. A subjective evaluation experiment that uses a free conversational form is conducted and the effect of bursty code error noise on speech quality is studied. Moreover, Q‐value quantification of bursty code error noise and random code error noise and its additivity are studied. MOS and tolerance rate change linearly according to a logarithmic number of bursts during a certain length of conversation. Impairment changes according to the number of error bit rates in a random bit error. A more simplified relationship can be obtained by converting MOSs to Q values. It is confirmed that the additivity law holds between Q values for impairment that is due to random and bursty errors.
Very low latitude whistlers and the effect of earth‐ionosphere waveguide propagation
Authors: Ohta Kenji , Shimizu Akio , Hayakawa Masashi , Shimakura Shin 
Published: July 2007

AbstractWhen a sonogram of the nighttime whistlers observed in Wuchang, China, at a low latitude (at a geomagnetic latitude of 19.4°N) was studied in detail, whisker‐type spectral components were observed, which may be due to the waveguide propagation effect of the second‐ and third‐order modes, in the spectra of intense whistlers accompanied by echo trains. By applying the field analysis direction‐finding method to this part, the propagation characteristics are derived and the results exhibited a tendency identical to that of the characteristics of tweek atmospherics. It was found that the whistlers transmitted through the ionosphere at a very low latitude in Zhanjiang (geomagnetic latitude of 10.0°N) and exhibited an extremely rare waveguide mode propagation after subionospheric propagation of over approximately 1000 km.
Dual‐frequency corner‐reflector antennas fed by elements connected to parallel feed lines
Authors: Maruyama Tamami , Kagoshima Kenichi 
Published: July 2007

AbstractThe dual‐frequency antenna with the same beam‐width is well suited to the mobile communication base station antenna. One candidate is a corner reflector antenna whose elements are connected to a parallel feed line. However, no design equations or analysis have been published. This paper corrects this deficiency through analysis of the characteristics after integration of the two factors, spatial coupling and transmission line, for this antenna. A two dual‐frequency corner reflector antenna is designed. One uses co‐phase feedlines and is a wide band sector‐beam antenna with a 3 dB beamwidth difference of 30° in the field pattern of horizontal plane and a return loss of less than ‐15 dB over a wide frequency range (from 900 MHz to 1.5 GHz). the other uses antiphase feed lines and its beamwidths can be varied by changing the corner angle while the beamwidths are coincident at two frequencies.
A reconfiguration method for fiber optic subscriber loops
Authors: Imanaka Hideo , Iwashita Motoi , Yamamoto Hideo 
Published: July 2007

AbstractA fiber optic subscriber loop provides many services that require high quality for a large number of subscribers. This means that it is necessary to establish a highly reliable, economical subscriber network.A method for high‐reliability network construction has been proposed. In this method, the amount of equipment is reduced by utilizing a fiber access module (FAM), which allows fiber lines between the adjacent loops to be connected in the optical subscriber loop. to realize the function of the FAM inexpensively, manual cross‐connection is indispensable. However, the restoration time in the event of cable failure is quite long for manual crossconnection.This paper proposes a reconfiguration method, the selected node reconfiguration method (SRM), which has a shorter restoration time than the conventional method, assuming a manual cross‐connection FAM. to further shorten the restoration time, a cross‐connection method is proposed in which several fibers are switched at the same time. the efficiency of this method and the functional structure of the FAM will be shown.
Optical digital cross‐connect system using photonic switch matrices and optical amplifiers
Authors: Shiragaki Tatsuya , Fujiwara Masahiko , Suzuki Syuji , Burke Conrad , Shiozawa Takahiro 
Published: July 2007

AbstractAn optical digital cross‐connect system (DCS) comprised of both photonic switching networks and electric DCSs is proposed for applications in network‐failure restorations. Optical DCSs exhibit excellent characteristics in restorations of multiple failures and when compared against their electrical counterparts, size‐reduced apparatus can be expected. the design of DCSs for applications in metropolitanarea networks are investigated and it is shown that such DCSs can be realized using LiNbO3photonic switch matrices together with traveling wave optical amplifiers (TWA).With respect to the problem arising from the polarization dependency of TWA gain, it was solved using the output power controller (APC) which is shown theoretically to cause no difficulty in the noise characteristics. the optical DCS is designed and manufactured using LiNbO3switch matrices and TWA, by which its basic operation properties are verified. Using this trial system, it is confirmed that the network failures can be restored by changing the optical routes.
A spread spectrum communication system without a reference signal for a frequency‐selective fading channel
Authors: Miyatani Tetsuhiko , Akaiwa Yoshihiko 
Published: July 2007

AbstractIn a spread spectrum communication system (SS), RAKE reception is effective as a measure against frequency‐selective fading. Channel impulse response should be known for RAKE reception. In a conventional system where a reference signal is added to a transmission signal to obtain an impulse response, a decrease in transmission efficiency occurs under fast fading.This paper proposes a scheme that does not use the reference signal by allocating different codes to information signals. In addition, a channel‐estimation scheme that alleviates effects of undesired autocorrelation values or cross‐correlation values of spreading codes is proposed. This scheme subtracts cross‐correlation values or excess autocorrelation values from a matched filter (MF) in measuring a channel impulse response and eliminates responses lower than a given threshold. Computer simulations under two‐path fading were performed. the error characteristics were improved with the proposed channel‐estimation scheme. It is shown that the proposed scheme is better than the scheme using a reference signal.
Performance of DS/FH‐CDMA over fading channels with near‐far problem
Authors: Shinkaji Yasuhiko , Yamazato Takaya , Katayama Masaaki , Ogawa Akira 
Published: July 2007

AbstractThe performance of a hybrid direct‐sequence/frequency‐hopping code‐division multiple‐access (DS/FHMA) system is investigated in the presence of both the near‐far problem and multipath fading. It is confirmed that the error‐correcting technique is essential lessening the effect of the near‐far problem and that the coded DS/FH system employing the Reed‐Solomon forward error‐correcting code preforms better than the coded DS system. It is shown also that the path‐diversity technique is effective in reducing the degradation caused by multipath fading.As a result of this study, it is concluded that the DS/FH‐CDMA with the error‐control code and the path‐diversity technique is better suited to solve both near‐far problem and multipath fading than DS‐CDMA in which an accurate power control is difficult to achieve in such an environment.
Evaluation of handover performance in DS/CDMA systems
Authors: Kudoh Eisuke 
Published: July 2007

AbstractThis paper considers the performance of traffic capacity and handover frequency in a DS/CDMA system under imperfect handover. the effect experienced when the number of base stations observed by the personal station is restricted is estimated. Furthermore, the effect of handover hysteresis also is considered. Simulation models are presented which can evaluate the traffic capacity and the handover frequency under these imperfections. System performance is evaluated by computer simulations using these models.It is found that if the number of observed base stations is 3 and the standard deviation of short‐distance medium value variance is 6 dB, the reverse‐link traffic capacity is reduced to about 90 percent and the forward‐link traffic capacity is reduced to about 85 percent, while the handover frequency is about 90 percent of the frequency of the short‐distance medium value variance.It is found also that if the handover hysteresis is 4 dB and is 6 dB, the reverse‐link traffic capacity is reduced by about 10 percent while the handover frequency is about 60 percent of the frequency of the shortdistance medium value variance.
Throughput evaluation of multicast error control schemes with maximum distance separable codes
Authors: Salcakibara Katsumi , Kasahara Masao 
Published: July 2007

AbstractOne of the important issues in the multicast error control scheme is how to suppress the deterioration of the throughput due to the increase of the number of receivers. This paper proposes two multicast error control schemes, where the deterioration of the performance is ameliorated by generating the retransmission frame based on the maximum distance separable (MDS) code. One is the scheme which uses the MDS code with the fixed code length, and the other is the scheme to use the MDS code with the fixed minimum distance.The throughput performance of the proposed scheme is derived analytically, and the result is compared with that of the conventional multicast error control scheme using the MDS code with the fixed number of information symbols. It is shown as a result that the throughput performance is better in the order of the scheme with fixed code length, the scheme with fixed number of information symbols, and the scheme with fixed minimum distance.
Orthogonal multicarrier frequency hopping‐code division multiple access scheme for frequency‐selective fading
Authors: Ohkawa Mitsugu , Kohno Ryuji , Imai Hideki 
Published: July 2007

AbstractTo improve frequency efficiency or user capacity in land mobile communication systems, orthogonal multi‐carrier frequency hopping‐code division multiple access (FH‐CDMA) is introduced and investigated. Such improvement is achieved by combining orthogonal frequency division multiplexing (OFDM) with FH‐CDMA. the theoretical analysis includes bit error rate (BER), required S/N, and maximum bit rate.A modified scheme allowing transmission power to be controlled according to the number of simultaneously accessing users also is discussed. This scheme improves BER performance for frequency‐selective fading when the number of simultaneously accessing users in a cellular zone is small.
A method for observing the three‐dimensional patterns of electromagnetic power absorbed by the human body‐the gel phantom of the human body used to study the electromagnetic environmental problem
Authors: Miyakawa Michio , Takahashi Naoki , Hoshina Shinichiroh 
Published: July 2007

AbstractBy adding salt to highly molecular materials such as polyacrylamide and gellan gum, it is possible to construct a physical model for the biological system called “phantom,” which has nearly the same conductivity and relative dielectric constant close to that of biological tissue and is highly transparent at room temperature. If the nonionic surface active agent is added to such a gel, the following property is realized. When the phantom is heated and a small region reaches the temperature called a clouding point, the surface active agent is segregated, making the phantom white and opaque. When the phan tom is irradiated by the electromagnetic wave, the white and opaque region is produced according to the absorbed energy, making the three‐dimensional distribution of the absorbed power visible from the outside. Since the material is high molecular gel, there is no convection. It is also possible to construct a biological model without a container. This paper reports on the method for fabrication of such a phantom and a typical example is applied to the electromagnetic environmental problem.
Number of wavelengths required for constructing large‐scale optical path networks
Authors: Nagatsu Naohide , Hamazumi Yoshiyuki , Sato Ken‐Ichi 
Published: July 2007

AbstractPhotonic networks that exploit the abundant optical bandwidth capability are needed to realize a truly effective B‐ISDN. We have proposed two optical path schemes, the wavelength path (WP) scheme and the virtual wavelength path (VWP) scheme, wherein wave length division multiplexing/frequency division multiplexing (WDM/FDM) technologies are employed in the path layer of the transport networks. Although wave lengths are precious resources in photonic networks, the number of wavelengths required for any network has never been evaluated because of the NP‐completeness of the wavelength assignment problem. In this paper, we propose heuristic optical path accommodation design algorithms that can minimize the wavelength requirements in the network. We also evaluate the wavelength requirements for large‐scale and irregularly structured physical network topologies utilizing the proposed algorithms. Accordingly, we elucidate, for the first time, that the wavelength requirements for the WP and VWP schemes are almost the same regardless of physical network topologies and path demand distribution patterns.
A method of applying message sequence chart specifications for services with variant process structure
Authors: Moriyasu Kenji , Hirakawa Yutaka 
Published: July 2007

AbstractMessage sequence charts have recently been the focus of considerable attention as formal specification descriptions and become standardized. However, At is difficult to use them for specifying services with variant process structure, such as interrupt services.This paper proposes a method that allows the number of processes in a service to change by selecting a suitable message sequence chart and switching the operation of each process over from the previous message sequence chart according to a specific procedure. Using this method, conventional synthesizing and verification techniques that deal with services with constant process structure can be applied to services with variant process structure.
A structure and control method of the fast re‐arrangeable nonbiocking (FAN) switch
Authors: Kim Dongwhee , Take Keijiro , Tominaga Hideyoshi 
Published: July 2007

AbstractWe propose a new self‐routing switch network, the fast rearrangeable nonbiocking (FAN) switch, and its control algorithm. the FAN switch is a rearrangeable switch network and is applicable to asynchronous transfer mode (ATM) switching because rearranging and routing are performed by hardware on the same time. the FAN switch has a modular structure that is constructed by connecting 4 × 4 elementary switches that consists of 2 × 4, 2 × 2, and 4 × 2 elements. We prove that the FAN switch with its characteristic control algorithm is a nonblocking network and compare it to other self‐routing switch networks.
Wideband phase‐locked loop synthesizer using linear frequency variation direct digital synthesizer as reference oscillator
Authors: Itoh Kenji , Lida Akio , Kanagawa Yousuke 
Published: July 2007

AbstractA wideband phase‐locked loop (PLL) synthesizer is proposed in which a linear frequency variation direct digital synthesizer (LFDDS) is used as a reference oscillator and a frequency variation band can be widened up to the full tunable range of voltage controlled oscillator (VCO) by frequency hopping within the lock‐in range of PLL. A. theoretical study is made and experimental results are explained. At first, assuming continuous frequency variation of LFDDS, transient behavior of frequency difference between two input signals of phase comparator of PLL is determined. Next, the condition for frequency variation speed of LFDDS is derived so that phase locking can be obtained using the maximum value of this frequency difference. Then the quantized frequency variation of LFDDS is assumed, transient behavior of the frequency difference is determined, and its difference from the continuous variation is clarified. A 6‐GHz band PLL synthesizer is fabricated, and the theory's validity is confirmed through experiments. Using LFDDS, a frequency setting time for a PLL synthesizer increases less than 10 percent for five times wider operation bandwidth. Performing experiments in 79 6‐GHz band. we obtained an operation bandwidth of 23 percent and so frequency hopping can be performed. Moreover, a frequency setting time of 50 μs and spurious level of ‐55 dBc were obtained.
Tracking ability of decision feedback equalizer for time‐varying channel characteristics
Authors: Serizawa Mutsumu , Namekata Minoru , Murakami Junzo 
Published: July 2007

AbstractThe magnitude of the delay difference due to multihop wave propagation is such that it cannot be ignored compared to the inverse of the transmission speed, and it is capable of degrading transmission characteristics in TDMA digital mobile communications. It is known that adaptive equalizers are effective in preventing this problem; however, the tracking characteristics of such equalizers with respect to high‐speed variations of mobile communications transmission paths are not adequate.This paper is an attempt to clarify the factors that degrade the tracking ability of such equalizers and to develop counter measures to protect against them. Specifically, the fact that the equalizer cannot track a time varying channel and evaporates when a decrease in the received signal level occurs due to the effects of wave propagation, etc., is a major contributor to the deterioration of equalization characteristics. This assertion is demonstrated analytically by simulations using the two‐ wave Rayleigh model and the one‐wave model in which the amplitude changes linearly with respect to time. In addition, to decrease the level of deterioration, a symbol‐ selective double‐directional equalizing system has been proposed; the efficacy of this system is demonstrated by simulation.
Parameter design of dynamic connection admission control in asynchronous transfer mode networks
Authors: Kawamura Yosbinori , Saito Hiroshi , Chaki Shinichiro 
Published: July 2007

AbstractDynamic connection admission control (dynamic CAC) has been proposed as one of the connection admission controls for asynchronous transfer mode (ATM) networks. Dynamic CAC uses the distributions of the number of cells arriving during a fixed interval. This distribution is renewed by exponential forecasting with smoothing parameter α This paper proposes a parameter design method that will enable this control to provide high utilization while suppressing VP GOS deterioration due to excess VC connections.