摘要:

AbstractThe article reports on the characteristics of an algorithm that implements generalized minimum distance (GMD) decoding of Reed‐Solomon codes. The algorithm uses the novel Welch‐Berlekamp (WB) algorithm, as modified by Tze‐Hua, in order to minimize the complexity of the decoder. Both the WB algorithm and the GMD extension of the WB algorithm are described in outline. The performance of the GMD algorithm was simulated on AWGN channels and fading channels. Results are presented both for RS and concatenated RS codes. The gains over conventional decoding are larger for fading channels than for AWGN conditions but seem useful in all cases. The complexities of the GMD algorithm and the WB algorithm are analysed and compared to that of conventional RS decoding algor

ISSN:0737-2884    

DOI:10.1002/sat.4600120402

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

年代:1994

数据来源: WILEY

摘要:

AbstractRecently, a number of commercial digital mobile satellite communications systems have become operational, and the introduction of more systems is imminent. The voice transmission quality of the Inmarsat‐aeronautical, Inmarsat‐M and Inmarsat‐B systems was evaluated and compared with the quality of the Inmarsat‐A analogue communication system on the basis of subjective listener opinion assessments. From this evaluation it can be concluded that, under nominal operating conditions, the current generation of digital mobile systems may offer a perceived performance that surpasses that of the older Inmarsat‐A analogue system, at least when measured in terms of transmissio

ISSN:0737-2884    

DOI:10.1002/sat.4600120403

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

年代:1994

数据来源: WILEY

摘要:

AbstractThe burst mode link analyser with least squares algorithm (BMLA/LS) is a real‐time impulse or frequency response extraction (IRE/FRE) technique of a satellite communication channel, originated and explored by the author. This paper summarizes some key technical points of the BMLA/LS and presents its novel simulation results and applications in a land‐mobile DBPSK/DQPSK satellite channel atKa‐band, including the channel additive white Gaussian noise (AWGN) effect on IRE/FRE by BMLA/LS, and the instantaneous IRE/FRE in a Rician channel with multi‐path reflection, in a shadowed channel by trees and in a combinational fading channel, and their comparisons and conc

ISSN:0737-2884    

DOI:10.1002/sat.4600120404

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

年代:1994

数据来源: WILEY

摘要:

AbstractThe theory of offset Fresnel zone plate antennas is presented. Explicit formulae for the design of the zone boundaries for the offset Fresnel zone plate are given. Theorectical equations and numerical results for the far‐field analysis are presented. It is found that when the offset angle increases, the zone boundaries become more elliptic and the plate becomes more asymmetric in theE‐plane. With the number of full wave zones and the plate width in theW‐plane fixed, the plate width in theE‐plane increases with the offset angle, which keeps the projected aperture area constant. Within a limited range of offset angles, the offset configuration can be employed without degrading the radiation performance much. For large offset angles, however, the asymmetry of the configuration may lead to increased sidelobes and decreased antenna directivity. An experiment with one particular phase reversal zone plate antenna with 30° offset angle shows good agreement between the measured antenna pattern and the theoretical pr

ISSN:0737-2884    

DOI:10.1002/sat.4600120405

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

年代:1994

数据来源: WILEY

摘要:

AbstractA model for the statistical prediction of fade durations, applicable both to scintillation and rain‐induced effects, is presented in this paper. It assumes that durations longer than about 1 minute are lognormally distributed whereas shorter durations follow a power‐law distribution. The model is assessed using data contained in the CCIR data bank and from measurements performed with the SIRIO and Olympus satellites. The model is tested using the same data, and the results give multiplicative errors in the range from 0.6 to 1.8 (averages) and from 0.3 to 3.0 (r.m.s.) in the estimation of the fade durations exceeded for fixed probabil

ISSN:0737-2884    

DOI:10.1002/sat.4600120406

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

年代:1994

数据来源: WILEY

摘要:

AbstractAs a result of recent advances in signal processing technology and standards for video compression systems there has been a dramatic increase in interest in commercial applications. This paper reviews the current broadcasting situation from a number of viewpoints relevant to the future development of the available technologies.After a review of the context, which includes alternative new broadcasting technologies as well as alternative media capable of competing with satellite, digital technology is given a wide ranging assessment with particular attention paid to the direct broadcasting to the home by satellite application currently receiving considerable attention world‐wide. The possible system architectures and subsystem design features are highlighted with the European Baseline Satellite Broadcasting specification developed by the European Digital Video Broadcasting Project gaining special attention. For completeness a brief review of the digital audio broadcasting system (DAB) is also given.In addition to the applications for direct broadcasting, applications in the professional domain for distributing television signals from studios to terrestrial transmitters, satellite up‐link sites or cable heads or for satellite news gathering (SNG) are examined. Features of existing commercially available hardware to support these services are described brie

ISSN:0737-2884    

DOI:10.1002/sat.4600120407

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

年代:1994

数据来源: WILEY

ISSN:0737-2884    

DOI:10.1002/sat.4600120401

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

年代:1994

数据来源: WILEY