摘要:

AbstractIn the conventional header‐driven storageless LAN (HDSL), the simultaneous multiple transmission, in general, is impossible, which made it difficult to cope with the increase of the traffic due to the system expansion and other situations. This study proposes a star‐type LAN (multistar LAN) which realizes multiple simultaneous transmission by providing the center node with the multiple simultaneous switching function. In the multistar LAN, HDSL‐type communication is realized by the switching function of the center node. The assignment of the usage of the switching function is determined through the contention and arbitration among the data units sent from the grouped end node.This paper first outlines the structure and operation of the multistar LAN, and presents the theoretical and experimental evaluation of the traffic‐delay characteristics. The features of the multistar LAN features are that the delay for low traffic is small, the performance is less deteriorated for high traffic, and there is a flexibility in accommodating the increase of the

ISSN:8756-6621    

DOI:10.1002/ecja.4410740301

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

年代:1991

数据来源: WILEY

摘要:

AbstractThe wide zone AVI system is an automatic vehicle identification system that can cope with more than one vehicle in the detection zone. Such a system includes a possibility of identification failure by the collision of ID packets, in addition to the ordinary transmission failure. A method to remedy this is to transmit the ID packet several times. This paper considers two methods of transmitting the ID packet from each vehicle. In the first, the packet transmission interval follows an exponential distribution, and in the second, a specified number of transmissions are made at random points which are distributed uniformly during the zone pass period.Using approximate analyses of the identification failure probability, the effects of the design parameters on the system performance are examined for each method. As a result, it is shown that the constant number transmission method has a better performance than the exponential transmission interval method, in terms of the probability of identification success, the number of ID packet transmissions, and other aspects.

ISSN:8756-6621    

DOI:10.1002/ecja.4410740302

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

年代:1991

数据来源: WILEY

摘要:

AbstractThis paper derives a transform coding method for offset‐sampled image data. The method is based on the idea that the usual discrete‐cosine transform (DCT) as well as the symmetrical cosine transform (SCT) are regarded as discrete Fourier transforms for the signal sequences obtained by forming mirror images of the given signal sequence. The derived transform is composed of DCT and SCT, which have one‐half transform length of the ordinary square lattice DCT.Using the proposed method which corresponds to the DCT with the block size of 8 lines × 8 pixels, the number of multiplications required in the transform is reduced drastically to approximately one‐fourth. The coding efficiency between the proposed method and the DCT is compared by a computer simulation, and it is shown that the proposed method has a higher coding efficiency. Especially, the following advantage should be noted.The slope of the proposed method in the linear part of the rate‐SNR characteristic is steeper than the DCT (the slope of the proposed method is 1/0.64 of DCT) for the forementioned block size, resulting in a more remarkable improvement of the coding efficiency for higher rate coding. This improvement is the result of the gain due to sample reduction of a factor 2 per image area, and the loss due to the duplicate block pa

ISSN:8756-6621    

DOI:10.1002/ecja.4410740303

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

年代:1991

数据来源: WILEY

摘要:

AbstractThe capacity assignment problem of the packet‐switched network is to determine each link capacity (channel rate and number of channels) to minimize the total cost of the network, based on the given network topology and the link traffic, and under the constraint for service quality. Most past designs have discussed the simple network model in which the cost and the channel rate are in linear relation, and the channel rate can be set as an arbitrary value.Recently, several studies have been made considering the discreteness of the channel rate, but most of them consider only a single kind of channel. This paper proposes a link design method for the packet‐switched network which considers different kinds of channels, with the average delay of the packet for each destination in the network as the constraint. More precisely, the design procedure is divided into three parts and modified into the general nonlinear optimization problem to optimize the network. Through numerical examples, the accuracy and the effectiveness of the proposed method are demonstra

ISSN:8756-6621    

DOI:10.1002/ecja.4410740304

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

年代:1991

数据来源: WILEY

摘要:

AbstractIn multimedia communication, where media data with various requirements for the delay quality are transmitted through the multinode network, it is desirable to apply a priority control method according to the nature of the media. This paper proposes a new priority control method whereby the delay quality of each medium is evaluated by the fuzzy satisfaction, and the priority is adjusted through the feedback of the delay quality. The performance of the system is examined by a simulation.In the proposed system, the delay time is observed for each origination/destination pair at the destination node, and the fuzzy satisfaction of the delay quality is determined. The average satisfaction of the whole system is determined. Then the priority is renewed according to the difference between the satisfaction for each origination/destination pair and the average satisfaction of the system. It is shown that by the proposed method, the delay quality of the whole system is made almost uniform.

ISSN:8756-6621    

DOI:10.1002/ecja.4410740305

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

年代:1991

数据来源: WILEY

摘要:

AbstractThe go‐back‐N scheme is one of the error control methods in the satellite link. Various improvements have been made on this scheme, and the resulting throughput characteristics and packet delay characteristics have been described. However, in those methods, the priority of the class of the packet to be transmitted is not considered.This paper discusses the go‐back‐N scheme where priority rules are useful when several packets with different priority classes are to be transmitted on the satellite link are introduced. Two priority rules are introduced: nonpreemptive priority queueing and preemptive priority queueing. The go‐back‐N ARQ scheme with those priority rules can easily be realized by adding the packet sort function to the transmitter buffer in the conventional basic go‐back‐N ARQ scheme. The traffic analysis is made of the go‐back‐N ARQ scheme with those two priority rules for an arbitrary number of priority classes, and the packet delay expression is derived for each class. Then by numerical calculation examples, the average packet transmission delay characteristics in the two m

ISSN:8756-6621    

DOI:10.1002/ecja.4410740306

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

年代:1991

数据来源: WILEY

摘要:

AbstractOne method to expand a network is to employ repeaters operating at layer 1. When networks using the optical passive star coupler are connected through repeaters with only a relaying function, there arises the problem of “self‐collision.” This problem occurs when the packet returned from the optical star coupler connected to the destination network is relayed unconditionally by the repeater to the originating network.As a means to avoid the self‐collision, the authors have proposed a repeater with wavelength‐division multiplex technique and gate control [1]. Through the design of the wavelength filter, it is shown that a satisfactory performance is obtained [3]. This paper shows further the results of studies, from the functional viewpoint, for the transmission design of the repeater, the control method for the gate, and the relaying method for the code rule violation. The repeater is built into a system constructed experimentally for the star configured optical transmission system with the transmission rate of 32 Mbit/s. The result of measurement of the transmission performance and the functional operation are described. The design for the repeater, which is applicable to the connection of the passive star network, is now describe

ISSN:8756-6621    

DOI:10.1002/ecja.4410740307

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

年代:1991

数据来源: WILEY

摘要:

AbstractIn land mobile data transmission, the error control by FEC and ARQ generally is employed to improve the reliability of transmission. In the control signal transmission for the radio link control in the mobile communication system, the error usually is detected by FEC, and the reliability is improved by ARQ. Under the condition of motion velocity of 40 to 50 km/h and the tolerable transmission delay of several seconds, the transmission characteristics of ARQ depend greatly on the short‐term median variation of the received level of the retransmitted signal, together with the packet signal transmission characteristics under the instantaneous received level variation due to fading. No evaluation has been presented for the transmission characteristics of ARQ considering such a median variation.This paper considers the stop‐and‐wait (SAW) ARQ where the number of retransmissions is limited to a finite value, and presents an evaluation of the transmission characteristics considering the correlation of the short‐term median variation of the retransmitted signal. Numerical examples are presented. Assuming that SAW‐ARQ is applied to the transmission protocol of the common control channel, the blocking probability is examined, together with numerical

ISSN:8756-6621    

DOI:10.1002/ecja.4410740308

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

年代:1991

数据来源: WILEY

摘要:

AbstractA tracking system consists of an observation part such as a radar and a filter part such as a Kalman filter. To date, numerous adaptive filters have been studied for improving the tracking accuracy. However, the parameters related to the observed data have been fixed. If, on the other hand, one uses a digital beamforming (DBF) radar as the observation part so that the coherent integration number has a degree of freedom, these observation parameters can be adjusted according to the situation to improve the accuracy of the tracking system.From the viewpoint of requirement on the filter, the observation period and the observation accuracy, both of which are functions of the coherent integration number, are opposite to each other, and hence the optimization of the integration number is a problem. In this paper, a DBF radar is used for observation and a Kalman filter as the filter, and a study is made to determine how the angular position prediction accuracy in such a tracking system varies by the coherent integration number. It is shown that there exists an optimum coherent integration number for the entire tracking system.

ISSN:8756-6621    

DOI:10.1002/ecja.4410740309

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

年代:1991

数据来源: WILEY

摘要:

AbstractIn this paper, a millimeter‐wave antenna is constructed with layered magnetic thin films with different saturation magnetizations placed on a grounded conductor and with a periodic structure on the upper layer interfacing with air. Under the condition in which a dc magnetic field is applied externally, the scanning characteristics and the radiation efficiency of the antenna are analyzed with a perturbation method. In the analysis, the multiple scale method also is applied.From the primary field, the coupling characteristics of the radiation field with the guided field and the incident field are derived while the amplitude transport equation is derived from the secondary field. By means of these results, the expressions for the radiation efficiency and the radiation angle of the antenna are obtained. Numerical calculations are carried out in the millimeter‐wave frequency range so that the magnetic field dependence of the beam scanning angle and the radiation efficiency are investigated.From the numerical results obtained, it is found possible to construct a magnetically tuned millimeter‐wave antenna with a large radiation efficiency and a large beam scanning angle by adjusting the structural parameters of the antenna consisting of two layers of magnetic slabs with different saturation magnetiza

ISSN:8756-6621    

DOI:10.1002/ecja.4410740310

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

年代:1991

数据来源: WILEY