摘要:

AbstractProduct codes show improved correcting capability by a comparatively simple method of combining codes and are also effective in correcting bursty errors. In this study, product codes using several kinds of single‐error correcting and double‐error detecting (SEC‐DED) codes, different by rows, are proposed. A method of probabilistically correcting bursty errors by using SEC‐DED codes different by rows and utilizing the differences in these error‐correcting characteristics is proposed. In addition, a decoding method that can correct random errors of the type that could not be corrected by the conventional product codes for this code is

ISSN:8756-6621    

DOI:10.1002/ecja.4410771201

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

年代:1994

数据来源: WILEY

摘要:

AbstractThis paper presents a detailed study of a binary optical direct detection optimum receiver for the use of optical space communication systems, where a long‐distance transmission makes optical received signals extremely week. At such a low‐power operation of the receiver, the quantum discreteness structure of the shot noise process is evident in the optical detector output.A statistical model for optical detection output is derived, considering this quantum discreteness, thermal noise at the receiver circuit system, dark current at optical detector, and random photomultiplication. Moreover, the optical detection system is considered as an ideal integration system, and optical detection output is expressed by using a time‐dependent sample value vector.A logarithmic likelihood function derived from this sample value vector on the basis of maximum likelihood testing is studied, and the optimum receiver structure for weak optical signals is clarified. That is, it is shown that, even under the existence of thermal noise and random photomultiplication, primary photon count plays an essential role in signal detection similar to that in the shot noise limited case and the primary photocount estimator‐maximum likelihood detection receiver is derived theoretically. Then the error rate performance is analyzed theoretically and compared with that of a conventional direct detection receiver. As a result, it is shown that by introducing a wide‐band optical detection system, a significant improvement in error rate performance is observed over conventional

ISSN:8756-6621    

DOI:10.1002/ecja.4410771202

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

年代:1994

数据来源: WILEY

摘要:

AbstractA highly effective video coding method is proposed for application in a wide range of fields that utilize video information and in multimedia systems where data must be easily manipulated. The proposed video coding scheme is a hierarchical system that uses vector quantization and which also incorporates many of the basic coding components of the internationally standardized lowrate MPEG 1 coding system. In addition to providing the special data handling operations of MPEG 1, the new system incorporates a multiresolution hierarchical decomposition that permits the user to select a desired resolution level at the decoder. Source coding is achieved with mean‐separated normalized vector quantization applied to image blocks that contain fundamental image patterns. However, instead of using separate codebooks for each of the different prediction modes of the coding system, this paper shows that it is possible for various prediction modes to share codebooks to achieve a more efficient implementation. The coding efficiency of the new system is estimated and compared with the performance of a DCT based system. Although the signal‐to‐noise ratio of the VQ system falls short by 0.5 to 1.2 dB, subjectively, the two coding systems give about the same performance. Methods for improving the quantitative signal‐to‐noise ratio performance are also c

ISSN:8756-6621    

DOI:10.1002/ecja.4410771203

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

年代:1994

数据来源: WILEY

摘要:

AbstractThis paper discusses issues in the research of B‐ISDN standardization being conducted by the CCITT and other institutions, the results of this research to date, and possible future studies. More specifically, it discusses the technology of deploying high‐speed data communications services for initial servi

ISSN:8756-6621    

DOI:10.1002/ecja.4410771204

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

年代:1994

数据来源: WILEY

摘要:

AbstractThe integrated train access scheme is an access scheme integrating synchronous traffic and asynchronous traffic based on the train concept. It has a feature that an upper limit can be bounded on the train ring rotation time by limiting the number of asynchronous frames that can be connected to the train running on the ring network. Furthermore, it can also have the feature of round‐robin scheduling. An approximating analysis by a polling model is made to clarify the traffic characteristics of this integrated train access scheme under medium and light load. As a result of simulation studies, it has been found that this analysis shows a good approximatio

ISSN:8756-6621    

DOI:10.1002/ecja.4410771205

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

年代:1994

数据来源: WILEY

摘要:

AbstractWith the recent development of the digital electrical communication network and the advent of low‐cost large‐capacity digital storage media, an effort is made toward the digitization of the TV signal. Along with this, the image coding technique is becoming more important, where the research emphasis is shifting from the low bitrate pseudodynamic image representation, to high‐resolution, high‐quality images. Among various image coding methods, the feature of the entropy coding based on Huffman coding [1–3] is that a large amount of image data can be compressed efficiently by combining discrete‐cosine transform (DCT) and the motion‐compensated interframe coding, and is used presently as the indispensable element of the algorithm.To apply the method to the future digital dynamic image with a high image quality requirement and to realize the real‐time processing, it is necessary to develop a fast processing architecture for the Huffman coding, together with its VLSI implementation. With this as background, this paper describes the fast processing architecture for the Huffman coding developed by the authors, together with its VLSI

ISSN:8756-6621    

DOI:10.1002/ecja.4410771206

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

年代:1994

数据来源: WILEY

摘要:

AbstractThe spatial tracking system controlling the directivity of the optical antenna determines the quality of communication in the ultradistance intersatellite optical communication system. The spatial tracking system using optical heterodyne detection has a high receiver sensitivity, being less susceptible to background light. This is the dominating factor for noise in cosmic space. In recent years, intensive studies have been made on this system hoping for the tracking performance with a higher accuracy than that obtained by the direct detection system.This paper presents a principle of angular error detection which is different from the conventional system and proposes a new optical heterodyne/spatial tracking system based on that principle. The principle on which the proposed system is based is that the incoming angle of the signal light is tracked by utilizing the variation of the spatial matching to the local light due to the variation of the incoming angle of the signal light. Its feature is that the angle error can be detected using a single ordinary optical detector, not the quadrant optical detector.A theoretical analysis of the noise equivalent angle (NEA) is presented. The optimal local light diffraction pattern is shown for the rectangular antenna aperture. The performance of the system is analyzed from the viewpoint of NEA, and the result is compared to the performance of the optical heterodyne detection/spatial tracking system using the quadrant optical detector.

ISSN:8756-6621    

DOI:10.1002/ecja.4410771207

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

年代:1994

数据来源: WILEY

摘要:

AbstractRecently, the differential detection scheme has attracted considerable attention as a demodulated scheme for digital mobile communications because of its robustness in the frequency nonselective fading channel. A problem of the differential detection scheme is that its bit error rate (BER) performance in the additive white Gaussian noise (AWGN) channel is inferior to that of the coherent detection scheme. To solve this problem, many methods to improve BER performance of the differential detection in the AWGN channel have been proposed. However, those methods require complex signal processings.This paper proposes a novel differential detection scheme as a simpler improvement method which estimates the differential phase of the transmitted signal by a sequence estimation scheme using the Viterbi algorithm. The proposed scheme is simplified in a manner such that its signal processing is composed of only additions and subtractions on the phase information of the received signal. Results of computer simulation show that BER performance of the proposed scheme is close to that of the ideal coherent detection in the AWGN channel. In addition, the trellis diagram of the Viterbi algorithm can be reduced without performance degradation introducing the signal processing similar to the Scarece State Transition (SST) type Viterbi decoding. The proposed scheme also is useful in the case of the fast Rician fading channel and the slow Rayleigh fading channel.

ISSN:8756-6621    

DOI:10.1002/ecja.4410771208

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

年代:1994

数据来源: WILEY

摘要:

AbstractTo resolve the problem of electromagnetic interference generated at the actual configuration of electronic equipment by a radiated interference wave, it is desirable to establish a technique to estimate the radiated interference of electronic equipment. This paper discusses a method for estimating the radiated interference in actual configuration from the measured radiated interference at the test site of the electronic equipment. In the proposed estimation method, a simulated source of the electronic equipment is used for deriving the deviation (conversion coefficient) of the wave propagation characteristics of the test site and the actual configuration. By means of this conversion coefficient, the radiated interference in actual configuration is estimated from the radiated interference at the test site. An estimation method is shown in the case where a spherical dipole antenna is used as a simulation source of the electronic equipment. When the effectiveness of the estimation method was verified experimentally with actual electronic equipment, it was found that the radiated interference in the actual configuration can be estimated with accuracy of 4 to 5 dB at the frequencies of 30 to 300 MHz.

ISSN:8756-6621    

DOI:10.1002/ecja.4410771209

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

年代:1994

数据来源: WILEY