1、CCIR RECflN*827 92 4855212 0520234 199 0 Rec. 827 219 RECOMMENDATION 827 HYPOTHETICAL REFERENCE DIGITAL PATH FOR SYSTEMS IN THE MOBILESATELLITE SERVICE USING FEEDER LINKS (Question 8218) (1992j The CCIR, considering a) afford guidance to designers of equipment and systems for use in networks employi
2、ng digital transmission techniques; that it is desirable to establish hypothetical reference digital paths (HRDP) for mobile satellite systems to b) that satellite-to-satellite links in the intersatellite service may be used in mobile-satellite systems; c) significance in a plesiochronous (Note I) n
3、etwork and facilities to compensate for it may be located at earth stations; that the transmission delay variation introduced by satellite movement relative to the Earth is of particular d) that a number of modulation and access techniques may be used in digital satellite links; e) that single chann
4、el and multiplexed digitai signals may be transmitted on satellite links; f) hypothetical reference connection (HRX) as defined by the CCITT; that a mobile-satellite service HRDP may form part of an integrated services digital network (ISDN) g) Le. maritime, aeronautical, or land mobile-satellite se
5、rvices; that the cbannel bit rate required at the terrestrial network interface may vary depending on the application: b) feeder links should be included in the HRDP; that communications may be effected between mobiles and land earth stations in which case the associated j) that communications may a
6、lso be effected between mobiles and this may need a separate HRDP, re commends 1. that an HRDP for mobile-satellite service transmissions between land earth stations and mobiles should consist in one direction of one land earth station to satellite to mobile earth station link, and in the reverse di
7、rection of one mobile earth station to satellite to land earth station link; for either direction the space portions may comprise one multi-satellite link; 2. that the HRDP for land earth stations to mobile earth stations should include the equipment indicated in Fig. 1; and that the HRDP should int
8、erface with the terrestrial network on the land earth station side, and if needed then with other relevant network on the mobile earth station side, at a suitable digital distribution frame (DDF) at the lowest bit rate appropriate to that HRDP; 3. Note I - The term “plesiochronous” is used according
9、 to the definition given in CCITT Recommendation G.701 as follows: Two signals having the same nominal digit rate but not stemming from the same clock or homochronous. Note 2 -Further study should be made on an HRDP for mobile-to-mobile communications. Note 3 - The term feeder link refers to the lin
10、k between the LES and satellite and the term service link refers to the link between the satellite and mobile. Note 4 - For the mobile earth station it may not be possible to subdivide the component paths due to the integrated nature of the equipment. that the following Notes be considered as part o
11、f this Recommendation. COPYRIGHT International Telecommunications Union/ITU RadiocommunicationsLicensed by Information Handling ServicesCCIR 220 Digital distribution frame RECMN*27 Rec. 827 FIGURE 1 Hypothetical reference digital path I P=-=tl I Satciiite link Digital distribution frame I i/l DM M R
12、 (Note 2) a M DM I I Mobile earth station I I I I Land earth station S: DM digital multiplex equipment M modem equipment R: space stations in the mobile-satcliite service W/RF equipment including multiplexcr if required COPYRIGHT International Telecommunications Union/ITU RadiocommunicationsLicensed by Information Handling Services
