摘要:

AbstractThis paper studies several aspects relevant to the design of phase synchronization circuits for land mobile satellite systems (LMSS). First, the results of a propagation experiment are presented, with special focus on the effects of vehicle mobility on the signal phase. It is found that the changes of speed and direction cause frequency variations that can be modelled as linear. Bounds for the frequency derivative are given for different percentages of time. The use of third‐order PLLs is considered, as they are optimum for tracking a frequency ramp embedded in white Gaussian noise. The model of third‐order PLL employed is presented, as it is an original model, developed by the authors. Then the performances of second‐ and third‐order PLLs are compared. Theoretical, as well as simulation, results are given. It is shown that third‐order loops give better performance in the presence of frequency variations of the kind observed in this link, but they suffer from a higher sensitivity to oscillators' phase noise. Several conclusions regarding the use of third‐order loops in future systems ar

ISSN:0737-2884    

DOI:10.1002/sat.4600130102

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

年代:1995

数据来源: WILEY

摘要:

AbstractThe scope of this paper is to present the status and the preliminary results of the research activities that Telespazio is carrying out with the aim at identifying the role of the VSAT systems in the advanced telecommunications services, which will be dominant in the second half of nineties and beyond. The first part of the paper is devoted to an overview of the evolution trend of the terrestrial networks. The main body of the paper presents the results of our investigations on the application of VSAT systems in two fields: broadband networks and intelligent networks. Background information has been intentionally added for the easier comprehension of the topics presented in the paper. A list of acronyms appears as an Appendix.

ISSN:0737-2884    

DOI:10.1002/sat.4600130103

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

年代:1995

数据来源: WILEY

摘要:

AbstractWe consider the satellite cluster scheduling problem, which is one of the most interesting problems in the satellite communication scheduling area. This problem is known to be NP‐complete, and a couple of heuristic algorithms have been developed. In this paper, we suggest another algorithm for this problem which has the same computational complexity as the best existing one and provides much better solution quality. Extensive computational simulation results are reporte

ISSN:0737-2884    

DOI:10.1002/sat.4600130104

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

年代:1995

数据来源: WILEY

摘要:

AbstractDeveloped originally to meet increased demand forecast forC‐band capacity in the Pacific Ocean Region (POR), this latest generation of INTELSAT satellites is planned to be operated in a number of traditional and new roles. To date INTELSAT has bought four INTELSAT VIII spacecraft for Pacific, Indian and Atlantic Ocean regions and two modified VIII‐A to meet the specific Landmass requirements for the rapidly expanding Asia‐Pacific and pan‐American market. The VIII spacecraft, using Martin Marietta Astro Space's GS7000 bus has sufficient power and payload carrying capability that it can accommodate a wide variety of services. A new feature for INTELSAT is the inclusion of arcjet propulsion which has the potential for long lifetime while needing only half of the fuel requirement of conventional thrusters. This new high power satellite will form a key part of the INTELSAT global network through to the year 2010 and complement the INTELSAT VII and VIIA

ISSN:0737-2884    

DOI:10.1002/sat.4600130105

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

年代:1995

数据来源: WILEY

摘要:

AbstractIn 1995 the second flight unit of ITALSAT telecommunication satellite will be ary orbit, making operative the ITALSAT telecommunication system after the experimental and preoperational phase performed by ITALSAT F1, which was launched in January 1991 by the Italian Space Agency.A general view of the ITALSAT system is presented with emphasis on the satellite design, the telecommunication mission, the new technologies and the prospects.

ISSN:0737-2884    

DOI:10.1002/sat.4600130106

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

年代:1995

数据来源: WILEY

ISSN:0737-2884    

DOI:10.1002/sat.4600130107

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

年代:1995

数据来源: WILEY

ISSN:0737-2884    

DOI:10.1002/sat.4600130101

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

年代:1995

数据来源: WILEY