摘要:

AbstractThis paper proposes a two‐stage coding scheme, whereby a reduced image for retrieval is sent at the first stage, as a highly efficient coding scheme for images and other databases. In the first stage, the reduced image is encoded by block adaptive DPCM. In the second stage, the interpolative error component is encoded using adaptive vector quantization. In this scheme the number of quantization levels is easily determined from the standard deviation of the prediction error signals calculated for each subregion and the rate‐distortion characteristic of the scalar or vector quantizers, using the same method for either of the two stages. By designing the quantizers for typical probability distributions of the predictive error signal, a highly versatile coding scheme is realized.The proposed method has a better overall coding performance than a vector quantizer with the same block size (4 × 4 pixels), which has been designed in an optimal way in the original signal space. Compared with adaptive discrete cosine transform vector quantization [16] and adaptive predictive error vector quantization of the prediction error signals [7], which are also highly versatile, the proposed method exhibits a better characteristic when the coding rate exceeds a certain level. There is little degradation due to the two‐stage coding process. It has also been verified that the proposed method is effective for coding color

ISSN:8756-6621    

DOI:10.1002/ecja.4410730701

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

年代:1990

数据来源: WILEY

摘要:

AbstractIn multislot circuit‐switched networks, it is necessary to apply a GOS control method to trunk groups to improve network utilization and to protect services against overload. As a GOS control method for multislot networks, this paper considers a trunk reservation method, split high‐usage group method, split final‐group method and virtual circuit method, which have also been studied for telephone networks. They are compared then by evaluating their blocking performance and peakedness of overflow and carried traffic involved. Based on numerical examples, it is shown that although the trunk reservation method is superior with respect to trunk utilization, there are some cases where the other methods are advantageous with respect to the ability to withstand overload and peakedness of tr

ISSN:8756-6621    

DOI:10.1002/ecja.4410730702

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

年代:1990

数据来源: WILEY

摘要:

AbstractMultiple‐destination telecommunication is one of the new services in circuit switching. The telephone conference service, which is already in practical use in Tokyo 03 area, is an example of such a service. This paper assumes the use of a network control data base, and proposes a routing algorithm which is required in the realization of wide‐area multiple‐destination communication by placing a large number of bifurcations (bridges) in the network. It is required that the algorithm should not only suppress the circuit utilization cost for the determined route but also should determine the route in a sufficiently short time to cope with the immediate call.Five kinds of algorithms are proposed, including the search of the “minimum‐spanning tree,” which generally is considered as the basic connection configuration for the multiple‐destination communication. The two foregoing items are used as the items for evaluation, and a connection algorithm is presented which is the optimal for the given mumber distribution and the bridge placement. It is shown as a result that there exists an algorithm which is better than the “minimum‐spanning‐tre

ISSN:8756-6621    

DOI:10.1002/ecja.4410730703

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

年代:1990

数据来源: WILEY

摘要:

AbstractAs one approach to the realization of post 64 kbit/s ISDN, studies have been made on the optic broadband distribution system, based on the fiber optic transmission by tree (or bus) trunk line and star subscriber line. To realize a more versatile C‐E communication system, however, not only must the service functions such as distribution of multichannel video information, character, still picture and data be provided, but also the information retrieval function with random access such as videotex.This paper discusses theoretically the realizability of the information retrieval service by the optic broadband distribution system from the viewpoint of whether or not a sufficient number of subscribers can be accommodate

ISSN:8756-6621    

DOI:10.1002/ecja.4410730704

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

年代:1990

数据来源: WILEY

摘要:

AbstractThe metal subscriber transmission cable is a cascade connection of cables with different core radius and line length. To realize a digital subscriber transmission equalizer with a high accuracy requires an equalizer which does not produce an equalization error because of differences of core radius or cable length.This paper presents a multiband AGC equalizer to absorb the difference of core radius and line length whereby the filter coefficients are determined so that the equalization is optimized at several frequencies. Also, its construction, control by DFT and the design for parameters based on linear programming are presented. Based on the results of those investigations, an equalizer is constructed. By a transmission experiment using the actual transmission line, the equalization ability was verified.

ISSN:8756-6621    

DOI:10.1002/ecja.4410730705

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

年代:1990

数据来源: WILEY

摘要:

AbstractIn multimedia communication, the quality requirement from each medium to the network is not a definitive measure but usually contains a fuzziness. This paper represents, by a fuzzy set, the propagation delay of the network that can be tolerated by each medium and discusses the optimal burst multiplexing method for the required quality.First, various kinds of fuzzy quality requirements are examined, and it is shown that the quasi‐optimal quality measure is obtained in common with the control at the network node.Then based on the quasi‐optimal quality measure, two control methods at the network node are proposed: the variable priority and fuzzy priority methods. The performances of these methods are examined by numerical analysis and computer simulation, and the results are compared with those of the traditional control methods.Finally, it is shown that the variable priority method is better when the packet delay at each node can be measured, and the fuzzy priority method is better when it cannot be measu

ISSN:8756-6621    

DOI:10.1002/ecja.4410730706

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

年代:1990

数据来源: WILEY

摘要:

AbstractIn mobile satellite communications with a wide service area, the largest problems in composing the system are the Rician fading, where the direct wave component and the random time‐varying scattered wave component interfere with each other, as well as the low received power due to the propagation for a long distance.This paper considers diversity as a means to overcome these problems. The four‐phase DPSK system is considered, and a theoretical analysis is made on the error rate improvement by the post‐detection combining diversity. The characteristic functions of two orthogonal delayed detection outputs of the branches are used in the derivation of the error rate. Three communication systems of satellite/aircraft, satellite/land mobile and satellite/ship are considered as the models. Theoretical expressions are derived to evaluate the improvements. The error rate is also evaluated for the selective diversity. The result is compared with the case of combining diversity, together with the discussion for the difference between the two sc

ISSN:8756-6621    

DOI:10.1002/ecja.4410730707

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

年代:1990

数据来源: WILEY

摘要:

AbstractAs an applicator for heating deep‐seated tumors in the human body in a non‐invasive manner, a multiapplicator system radiating TE wave is proposed. In addition, it is shown that a hot zone can be formed deeply inside the human body if a method for good adjustment of the amplitude and phase of each applicator element is used. As an actual example, a homogeneous two‐layered cylindrical human body model is used for the cross section of the adrenal‐kidney level. Numerical calculations are carried out for the case where several line sources are placed around this model. It is confirmed that a hot zone is formed near the center. It is also demonstrated that the FD‐TD method is effective for the analysis of the electromagnetic scattering of a TE wave by an inhomogeneous cylindrical model which is the most important in the algorithm in the prese

ISSN:8756-6621    

DOI:10.1002/ecja.4410730708

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

年代:1990

数据来源: WILEY

摘要:

AbstractThis paper describes the characteristics of reflection and transmission when a three‐dimensional Gaussian beam of fundamental mode is launched into a uniaxially anisotropic dielectric slab in which the optical axis has an arbitrary direction. The Fourier transform and solutions are obtained in integral form. Amplitudes of reflected and transmitted beams are calculated numerically by using FFT. To check the theory, experiment is performed by using laser and calcite. The numerical results are in nearly good agreement with the experimental one

ISSN:8756-6621    

DOI:10.1002/ecja.4410730709

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

年代:1990

数据来源: WILEY

摘要:

AbstractIn the detailed time domain analysis of high‐speed transient phenomena in connection with discharge of an electric contract viewed as a noise source, an experimental circuit for observation of the phenomena was investigated. It was found that the effect of wiring cannot be neglected and the investigation becomes more difficult in the experiment with a lumped element system if the sampling rate of the waveform observer is high. For this reason, a distributed experimental circuit system suitable for observation of a high‐speed phenomenon was set up and an experiment was carried out with this circuit.From the results of observation of transient voltage variation in connection with the discharge, it was found that the transient waveform agrees well with the theoretical waveform and a detailed observation is possible even if the sampling rate is 1 GS/s. In this experimental circuit, there is no effect of the interior of the power supply, of the load and of the reactance and interference of wiring and devices. Since the charge is stored in the distributed circuit, it is possible to generate discharge with a supply of a homogeneous electric energy for a given time. Therefore, detailed observations of various phenomena are possi

ISSN:8756-6621    

DOI:10.1002/ecja.4410730710

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

年代:1990

数据来源: WILEY