外文翻译----30MHz-3000MHz 地面数字音频广播系统技术规范.docx

附录一、英文原文Specification of 30-3000MHz Terrestrial Digital Audio Broadcasting SystemThe principal method of user access to the service components carried in the Multiplex is by selecting a service. Several services may be accessible within one ensemble, and each service contains one or more service components. However, dedicated DAB data terminals may search for and select the User Application(s) they are able to process automatically or after user selection. The essential service component of a service is called the primary service component. Normally this would carry the audio (programme service component), but data service components can be primary as well. All other service components are optional and are called secondary service components.The sub-channel organization defines the position and size of the sub-channels in the CIF and the error protection employed. It is coded in Extensions 1 and 14 of FIG type 0. Up to 64 sub-channels may be addressed in a multiplex using a sub-channel Identifier which takes values 0 to 63. The values are not related to the sub-channel position in the MSC.The service organization defines the services and service components carried in the ensemble. It is coded in the Extensions 2, 3, 4 and 8 of FIG type 0. Each service shall be identified by a Service Identifier which, when used in conjunction with an Extended Country Code, is unique world-wide. Each service component shall be uniquely identified within the ensemble. When a service component is transported in the MSC in Stream mode, the basic service organization information is coded in FIG 0/2 . Service components, carried in the Packet mode, require additional signalling of the sub-channel and packet address. Extension 3 is used for this purpose . Also, when service components are scrambled , the Conditional Access Organization field is signalled in Extension 3, for data in packet mode, and in Extension 4 for data carried in the stream mode or in the FIC. The Extension 8 provides