摘要:

AbstractThis paper proposes a self‐routing Benes network controlled distributively by dynamic load balancing. This Benes network consists of a distribution network and a routing network. The distribution network is controlled by a proposed method called “Dynamic Load Balance,” where load information is fed back to the input side via each unit switch so that loads at intermediate unit switches are equalized.The routing network is self‐routed by an output tag. The computer simulation results show that mean time delay vs. throughput characteristic of the proposed dynamic load balance Benes network is superior to those of conventional n

ISSN:8756-6621    

DOI:10.1002/ecja.4410730901

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1990

数据来源: WILEY

摘要:

AbstractThis paper describes a robust error control scheme used for propagation paths especially involving a long time‐frame burst error as in mobile radio communication and its effect on actual data communication channels. This is an adaptive error control scheme based on forward error correction code and composed adaptively of plural coding modes.Here, the BCH code is used as a block code, the diffused code is used as a convolutional code, and 3–5 majority logic is used as a majority voting code. The optimum coding mode is selected automatically according to the status of data transmission channels composed of a radio transmission span and telephone cable transmission lines. Cyclic code is used as an error detection method to evaluate channel status.Under practical transmission circumstances, extremely high throughput efficiency of more than 70 percent is realized for 4800 bit/s data for transmission over the cellular network in Britain. This scheme has been presented at CCITT SG XVII as a standard scheme candid

ISSN:8756-6621    

DOI:10.1002/ecja.4410730902

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1990

数据来源: WILEY

摘要:

AbstractIn the digital transmission system using a symmetrical pair cable, the following problems arise in the application to the communication network.(1) The transmission distance and the system accommodation rate in the symmetrical pair cable are limited by the crosstalk noise. Consequently, it is necessary to evaluate the crosstalk noise in pulse transmission with synchronized clock frequency and to provide system design based on the evaluation.(2) In the application of digital transmission systems to city links and subscriber loops, a highly efficient system accommodation in the existing cable is required. Then the signal‐to‐noise ratio (SNR) of the system in the multiple crosstalk environment must be evaluated accurately.For the first problem, it is noted that the crosstalk noise is a cyclostationary stochastic process. It is shown that the peak value of the instantaneous noise power, which is an ensemble average over multipairs, gives the worst evaluation of the crosstalk interference to the systems with synchronous clock operation. A new method for noise evaluation is proposed based on the result.For the second problem, a general case is considered. In this case, the crosstalk noise of the cable in SNR evaluation of multiple crosstalk is composed of more than one subpopulation. The principle of SNR distribution is analyzed, and a method of calculation for SNR is proposed based on the average and variance. It is shown that the proposed method of SNR valuation can be used in the design of digital transmission system in a crosstalk environm

ISSN:8756-6621    

DOI:10.1002/ecja.4410730903

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1990

数据来源: WILEY

摘要:

AbstractThe time slot interchanger (TSI) is employed widely in practice as the switch fabric of digital cross‐connect systems or exchange systems in the digital synchronized network. With the increasing need for ISDN with the fundamental rate of 64 kbit/s as the background, it is desired to realize a large‐capacity TSI. This paper discusses the optimum design of the pipelined TSI which has been proposed in the past, aiming at the realization of a large‐capacity TSI.First, the TSI configuration is proposed which realizes the time slot integrity in multislot connection, which has been a problem in the traditional pipelined TSI. The proposed method corresponds to the traditional TSI using RAM, where the time slot sequence integrity is realized by employing the double‐buffer structure.Then the optimum design method for the proposed pipelined TSI is presented, where the evaluation measure is the performance index, defined as the product of memory capacity and the operation speed. For comparison based on the defined performance index, the pipelined TSI optimized by the proposed method has several tens to several hundred times better performance than the conventional TSI using RAM or shift registers. Thus, it is demonstrated that the proposed construction is effective in realizing a large‐cap

ISSN:8756-6621    

DOI:10.1002/ecja.4410730904

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1990

数据来源: WILEY

摘要:

AbstractIn the stutter go‐back‐N ARQ scheme proposed by Towsley, a packet is transmitted by sending its copies in idle slots. Thus, it can achieve very small packet delay at light‐offered traffic load, but the maximum throughput is small.The stutter go‐back‐N scheme is improved by sending a multiple copy of a negatively acknowledged packet at retransmission time. The improved scheme is analyzed, and average packet delay, maximum throughput, and so on, are derived. Furthermore, from numerical examples, it is shown that the improved scheme can achieve higher throughput and smaller average packet delay than the basic go‐back‐N and the original stutter go

ISSN:8756-6621    

DOI:10.1002/ecja.4410730905

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1990

数据来源: WILEY

摘要:

AbstractDigital signal transmission will be used widely in the future mobile satellite communication system to realize an efficient operation of the system and to provide diversified service. In the global mobile satellite communication system, such as maritime and aeronautical communications where a wide service area is required, the influence of the multipath fading due to sea surface reflection at low elevation angle on the digital signal transmission characteristics is a particular problem.This paper deals with the application of the digital transmission system to the INMARSAT (International Maritime Satellite Organization), which provides the international maritime satellite communication service. The configuration of the digital maritime satellite communication system, which was developed for experimental purpose, as well as the result of analysis of the digital signal transmission characteristics in the low‐elevation maritime communication experiment, are presented.Based on the result of field experiment, the required power margin for low elevation operation is evaluated, and a means to secure a high‐quality communication is discussed. Thus, a guideline is presented for the digital transmission system design in mobile satellite communication, affected by the sea surface multipath fad

ISSN:8756-6621    

DOI:10.1002/ecja.4410730906

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1990

数据来源: WILEY

摘要:

AbstractIn high‐speed digital transmission in mobile satellite and land mobile communications, one of the serious problems is the effect of waveform distortion due to the frequency‐selective fading. This paper considers the GMSK modulation system, which is considered as useful as the modulation scheme for digital mobile communication.The effect of the waveform distortion produced by the time‐delay spread of the scattered interfering waves in the Nakagami‐Rice fading channel is considered and the bit error rate is calculated theoretically. Numerical examples of bit error rate performance are illustrated. It is shown that the bit error rate is improved when there is an average delay time or a time‐delay spread in the scattered interfering wave, compared with the case without a delay. However, the effect is relativ

ISSN:8756-6621    

DOI:10.1002/ecja.4410730907

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1990

数据来源: WILEY

摘要:

AbstractThe adaptive transmitter power control (ATPC) which controls the transmitter power in accordance with the propagation loss between the base station and a mobile station in the land mobile communication is effective in reducing the interference within a channel and that between the adjacent channels of the base station. Also, the portable mobile station which must be small and lightweight is required to reduce the average power consumption. One of the ATPC methods is the ATPC feedback control in which the up‐ and downlinks can be controlled independently.In this paper, the receiving level probability density function is derived theoretically as the basic characteristics in the case of an ATPC feedback. Finally, the effects on the receiving level profile from the control parameters such as the controlled delay time, maximum amount of control, control step width and control level setting are investigated theoretically and experimentall

ISSN:8756-6621    

DOI:10.1002/ecja.4410730908

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1990

数据来源: WILEY

摘要:

AbstractSome means to cope with frequency‐selective fading is indispensable to the realization of a wideband digital mobile communication, and various investigations have been made to this end. For example, the decision feedback equalizer (DFE) is considered promising, since it requires smaller‐scale equipment and is versatile in applications.The application of DFE to mobile communication requires tracking to the time‐varying channel as well as the fast initial adaptation. Thus, comprehensive investigations, including the construction of the equalizer and tap‐updating algorithm are needed.The Kalman algorithm is employed as the tap‐updating algorithm. By introducing the memory factor into the algorithm, the tracking performance to the time‐varying channel is improved as well as the speed of the initial adaptation.A computer simulation is made for the proposed method based on the model of 256 kbit/s TDMA system with QPSK modulation. It is verified that DFE is useful in compensating for the frequency‐selective fading in mobile

ISSN:8756-6621    

DOI:10.1002/ecja.4410730909

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1990

数据来源: WILEY

摘要:

AbstractA V dipole antenna with multiple stub loading is proposed as a traveling wave antenna with a wide bandwidth in both the gain and input impedance. It is considered that the present antenna is essentially a tapered transmission line loaded with open stubs. Then the operating principle is studied by reducing the structure to an equivalent nonuniform transmission line. It is found from the relationship between the equivalent distributed parameters and the stub that the dipole‐type stub array with its stub length reduced gradually from a half wavelength to a quarter wavelength is a basic structure for the broadband nature by the decaying traveling wave. Based on this concept, an actual stub‐loaded V dipole antenna was characterized numerically.It is demonstrated that uniform characteristics of an input admittance of 5 mS, a gain of 8 dB and a front‐to‐back ratio of 10 dB are obtained over ±30 percent around the center frequency in the case of a V dipole with an included angle of 30°. This antenna was fabricated and the validity of the present theory was confirmed because the theoretical and experimental results ag

ISSN:8756-6621    

DOI:10.1002/ecja.4410730910

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1990

数据来源: WILEY