| Satellite television broadcasting systems mainly consist ofbroadcasting satellite, satellite earth station applied to sendtelevision programs contained in radio-frequency signals, and receivingstation.From the view of satellite, the satellite TV broadcasting systems aremainly classified into two categories: one is the unification ofcommunication and TV broadcasting, that is one or more transponders ofsatellite, or some parts of frequency bands of one transponder are appliedto TV broadcasting, and other resources are applied to communication; theother may employ specialized live broadcasting satellite.Satellite digital broadcasting has the following advantages such asmore cover areas, large volume transmission programs, high qualitytransmission programs, the low power of satellite, suitable for largescale integrated circuit, suitable for communication links and computenetworks, providing new applications and easy to encryption.With the rapid development of satellite communication, satellites TVlive broadcasting is becoming leading services. More and more marketfactors have given rise to the popularity and development of HD digitalTV. MPEG-4 may be the important standard of compression for thetransmission of TV programs. This technique may effectively employ thebandwidth of satellite communication, improve the efficiency of programstransmission and descend the cost of transmission for HD TV programs.Satellite data broadcasting is an important form of data broadcasting. The main distinction between satellite TV broadcasting and it lies in theformer employs computers to receive and the latter employ TV to receive.Generally, computers have more flexible functions than TV and have theability of processing and storing data.In China, satellite data broadcasting has just started, while it mayhave broad developing space. In future, the developing trends of networkare the integration of various broadband technique and multimedianetworks based on IP. Considering the practical conditions of China,satellite data broadcasting may be widely applied to remote educationfields.DVB standard is the general standard for digital TV broadcastingsystems, and embraces the various aspects of digital TV broadcasting. Fromthe view of application, it may consist of eleven kinds of standards suchas transmission standards, multiplexing standards, signal resourceencoding standards, subtitle standards, various interaction standards,middle ware standards, content protection and copyright managementstandards, various interface standards, Internet protocol, conditionreceiving standards and measurement standards. DVB-S system defines thedevice functional modules form MPEG-2 multiplexer to satellite radio–frequency channels and satellite channels adaptors.The satellite providing system of Xinhua News Agency is based on thesatellite communication platform of Xinhua News Agency. The satellitecommunication platform is the satellite IP communication network withsatellite communication devices, and consists of uplink satellite masterstation, satellite transponder and satellite slave station.The client of satellite news providing system is mainly composed offour modules:1. satellite receiving module:the main functions includes receive and forward satellite data; transform picture manuscripts into old 8 line format based onoptions; set up mark file based on options, applied to other third partyapplications; transform old 8 line manuscripts into pure text format; prompt for insufficient disk space; receive streaming media; maintain manuscripts according to date;The performance needs of module are as follows: the time of processing commands from sender in LAN is no morethan 1 second; the start time for receiving program is no more than 2 second; the transformation time is no more than 1 second; The transformation between Cnml picture manuscripts and old8 line is no more than 1 second; the receiving software process authorized information in realtime when the authorization changes; support remote automatic upgrading;2. Manuscripts input module:It is mainly applied to inputting the news manuscripts form satelliteXML format into the corresponding database.3. Disk copy moduleIt is mainly applied to synchronization forwarding data, which is tocopy received manuscripts from satellite to specialized disk.4. FTP forwarding moduleIt is mainly applied to synchronization forwarding data, which is tocopy received manuscripts from satellite to specialized FTP servers.In this paper, we develop forwarding and receiving software based on satellite communication platform based on Xinhua News Agency to set upsatellite news providing system, which may improve the utilization ratioof satellite resources, forwarding efficiency and timeliness ofmanuscripts. The designed and implementation of the client comply toservice standard, and may fulfill the seamless cohesion between front endand back end. It may assure the timeliness and time effectiveness.In future, more efforts may be made on this client to improve itsfunctions, especially B/S mode may be applied, and the application systemthat supports to directly browse and process manuscripts on client. |
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