摘要:

AbstractRapid self‐healing under link failure in high‐capacity optical fiber is a basic issue in broadband networks. Failure restoration schemes are being studied which reroute failed paths using the control of path reconfiguration function of the Digital Cross Connect System (DCS). Distributed control schemes based on a flooding algorithm have been proposed to meet real‐time requirements for large‐scale transmission networks, but problems arise, such as message congestion at nodes and internode synchronization.The performance of the self‐healing algorithm depends not only on the algorithm itself but also on physical network topology and spare capacity. In this paper, we propose a distributed restoration algorithm using a flooding technique and a centralized spare‐capacity assignment algorithm minimizing total spare capacity in a network while meeting a given survivability objective.The failure restoration time, restoration ratio, and spare capacity cost of these algorithms will be evaluated by computer

ISSN:8756-6621    

DOI:10.1002/ecja.4410740701

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

年代:1991

数据来源: WILEY

摘要:

AbstractIn the ATM network, information is transmitted by the continuous transmission from node to node of a fixed‐length packet called a “cell.” The requirements of the cell on the traffic characteristics and the network depend on the kind of information source. The information from a video terminal arriving at a node, for example, is bursty, and a severe condition is imposed on the delay. When cells from more than one medium arrive in a mixed way at the network, a certain control mechanism will be needed to satisfy the respective requirements from the cells. On the other hand, this control mechanism should be realized by as simple a structure as possible.This paper discusses the necessity of the quality control at the cell level and the basic concept in the control for the node handling different kinds of calls. First, the characteristics for the case of a single kind of call source (such as voice, video or data) are analyzed. Then the necessity and usefulness of the control methods when various kinds of calls are mixed and arrive at the node are discussed for different control methods using numerical exa

ISSN:8756-6621    

DOI:10.1002/ecja.4410740702

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

年代:1991

数据来源: WILEY

摘要:

AbstractThis paper proposes a control method for the retransmission rate in the continuous‐time 1‐persistent CSMA/CD system with a finite number of stations so that the throughput is maximized. It is shown first that there exists an optimal load that maximizes the throughput. Assuming that the system always operates for the optimal load, the maximum throughput that can be achieved in the 1‐persistent CSMA/CD system is derived. Then an adaptive CSMA/CD system is proposed in which each station monitors the number of collisions and other parameters to estimate the present load and determines the retransmission rate so that the optimum load is realized.As a result of simulation, it is shown that the adaptive CSMA/CD system exhibits a considerably better performance than the Ether‐type CSMA/CD system employing the binary exponential back‐off algorithm based on the 1‐persistent scheme. It is shown that the proposed system can realize the throughput which is almost close to the forementioned maximum in the highly loade

ISSN:8756-6621    

DOI:10.1002/ecja.4410740703

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

年代:1991

数据来源: WILEY

摘要:

AbstractIn optical‐fiber‐cable networks of Japan, usually dry air is compressed into the cable and joints and gas‐pressure sensors are used for remote‐supervision of pressure maintenance. However, optical fibers are different from metallic lines and penetrating water is not a direct obstacle. Further, the manufacture of gas dams is not as easy as that of the metallic cables, and the gas dams become very large in size so that it becomes difficult to put them in the line. Therefore, the nonpressurized cables with reliabilities as high as those of the pressurized ones have been investigated.This paper discusses first the main factors responsible for the reliability deterioration of nonpressurized optical fiber cables and joints, which are the important elements of an optical system. Then, as the nonpressurized line structure, the waterproof optical fiber cables and the remote supervision of joints are discussed. Using a simple remote‐supervisory structure which consisted of the water sensors and OTDR, it is shown that the realization of reliabilities as high as those of the pressurized cables is

ISSN:8756-6621    

DOI:10.1002/ecja.4410740704

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

年代:1991

数据来源: WILEY

摘要:

AbstractRapid acquisition is an important problem in the direct sequence spread spectrum communication system, especially when code length is long. This paper proposes a novel code construction method of making rapid acquisition, in which majority logic combination sequences constructed from M‐sequences mutually of prime length (hereafter M‐MAJ sequences) are used. By tacking cross‐correlation of incoming M‐MAJ sequence with component M‐sequences at the receiver, acquisition time can be reduced considerably. Calculated results of the average acquisition time and comparisons with conventional code construction methods (JPL sequence, concatenated sequence)

ISSN:8756-6621    

DOI:10.1002/ecja.4410740705

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

年代:1991

数据来源: WILEY

摘要:

AbstractMost of the past studies concerning the decoding performance of trellis coded modulation (TCM) in a fading channel have been based on time diversity using interleaving/deinterleaving. One problem with time diversity is that a large decoding delay is produced due to the interleaving/deinterleaving which depends on the fading interval. This paper considers TCM signals using space diversity which can drastically improve the decoding delay and analyzes the decoding characteristics in Rice fading channels. An analysis is also made of the effect of the Euclidean distance (ED) and the Hamming distance (HD) of the trellis code on the average bit error rate (BER), and it is shown that a code design considering those two distance structures is needed in a channel with severe fading.This paper considers the major application of the proposed method to be digital voice transmission in mobile communication via satellite. Consequently, a simulation is made for the second‐order space diversity decoding performance for the trellis coded 8‐PSK signal. The optimal trellis coding at the transmitter is discussed for BER = 1

ISSN:8756-6621    

DOI:10.1002/ecja.4410740706

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

年代:1991

数据来源: WILEY

摘要:

AbstractIn‐the aeronautical satellite system for the air traffic control in the oceanic area, it is important to know the position of aircraft at the ground earth station. This paper describes the ranging and positioning system using two geostationary satellites (real satellite and a pseudosatellite on the ground).This system is designed to allow ranging and positioning of each aircraft every 0.6 s within the ranging and positioning accuracy of 100 m and 1 km, respectively. Experiments to estimate this system were performed using a real aircraft. Results gave better accuracy than those mentioned in the foregoin

ISSN:8756-6621    

DOI:10.1002/ecja.4410740707

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

年代:1991

数据来源: WILEY

摘要:

AbstractAs an adaptive equalization method for multipath fading in a high‐speed mobile communication at 100 kbit/s or more, a decision feedback equalization method with a Kalman filter is proposed based on the time‐variant model of the impulse response variation of the transmission path. In this paper, by means of this equalization method, the autoregressive (AR) model of the variation is derived from the measured values of the impulse response variations. The result of simulation of the equalization is described.First, a method is explained to derive an AR model to be set in the equalizer from a set of measured data of the impulse response. Next, the results of simulation are presented for the case in which the variation characteristics of the transmission path and the equalizer model correspond to each other. It is shown that the results have the error rate almost equal to the case of uniform fading without a delayed wave and are better than those from the LMS method. Further, since the variation of the transmission path is slower than the transmission speed, a model is introduced in which the pole of the AR model is approximated by 1. It is shown that the variation of the transmission path in a wide region can be equalized without significant degradation even if the equalizer model is fi

ISSN:8756-6621    

DOI:10.1002/ecja.4410740708

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

年代:1991

数据来源: WILEY

摘要:

AbstractIn mobile communication, fading due to multipath is a major factor in the deterioration of communication quality. One strategy for this problem is the adaptive array which eliminates the effect of the delayed waves by beam‐forming or controlling the radiation pattern adaptively. However, in the conventional method, the delayed waves simply are eliminated but are not utilized. It has been pointed out also that the directional diversity reception is effective in reducing the fading effect. In the conventional directional diversity reception method, the radiation pattern of the antenna is fixed.In this paper, it is pointed out that the information identical to that in the direct wave is contained in the delayed wave. A directional diversity method is proposed in which, by means of the radiation pattern of the adaptive array antenna, the direct wave and the delayed waves are separated adaptively or combined.In this system, two sets of antenna weights are included for unknown or time‐varying waves and the radiation patterns of the antenna can be controlled adaptively so that the directions of arrival can be estimated individually. By adaptively combining the direct and delayed waves, the SN ratio can be improved. The basic evaluation of this system is carried out to indicate that the error rate can be improved over that for the conventional adaptive array antenna which does not make use of the delayed wave. A possibility of using the proposed system in mobile communication is discus

ISSN:8756-6621    

DOI:10.1002/ecja.4410740709

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

年代:1991

数据来源: WILEY

摘要:

AbstractIn digital mobile communication, the directional diversity method is useful against fading. In this method, the antennas are switched successively to the antenna directed toward the arrival of the desired signal.In this paper, a four‐directional switching antenna is proposed for the directional diversity. The proposed planar antenna consists of a sectoral patch antenna and 3‐dB hybrids. By means of the cavity model, the eigenvalue, radiation pattern and mutual coupling between the elements are calculated for this antenna.It is shown theoretically that this antenna has the necessary characteristics of a four‐direction antenna. The radiation pattern and the mutual coupling between the elements were measured for the antenna fabricated on a dielectric substrate to confirm the validity of the comput

ISSN:8756-6621    

DOI:10.1002/ecja.4410740710

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

年代:1991

数据来源: WILEY