1、CCIR VOLUME*IX-IJ 90 LI855232 0510b7b 20 Rec. 556-1 RECOMMENDATION 556-1 HYPOTHETICAL REFERENCE DIGITAL PATH FOR RADIO-RELAY SYSTEMS WHICH MAY FORM PART OF AN INTEGRATED SERVICES DIGITAL NETWORK WITH A CAPACITY ABOVE THE SECOND HIERARCHICAL LEVEL (Question 33/9) (1978-1986) The CCIR, I CONSIDERING .
2、 (a) guidance to the designers of equipment and systems for use in international telecommunication networks; (b) agreement with the 2500 km hypothetical reference digital paths as specified by the CCIlT; (c) . or an integral multiple of it, that it is desirable to define a hypothetical reference dig
3、ital path for digital radio-relay systems, t afford that the hypothetical reference digital path for digital radio-relay systems should, as far as possible, be in . that the capacity of digital radio-relay systems should be that of a CCIlT recommended hierarchical level . UNANIMOUSLY RECOMMENDS 1. t
4、hat a hypothetical reference digital path for digital radio-relay systems, meeting the requirements of “high-grade performance” specified in CCIT Recommendation G.821 and with a capacity above the second hierarchical level, should be 2500 km long (see Note 1); 2. that this digital path should includ
5、e, for each direction of transmission, nine sets of digital multiplexing equipment at the CCIIT recommended hierarchical levels, it being understood that a set of digital multiplexing equipment comprises a number of associated multiplexers and demultiplexers; 3. Note 2); that this digital .path shou
6、ld include nine consecutive identical digital radio sections of equal length (see 4. Note 1. - In conformity with considering (c) this hypothetical reference digital path also applies to systems with a capacity which is an integral multiple of the second or higher hierarchical level. Note 2. - A dig
7、ital radio section consists of two consecutive radio terminal equipments and their interconnecting transmission medium which together provide the whole of the means of transmitting and receiving between two consecutive digital distribution frames (or equivalents), a digital signal of specified rate
8、see CCIlT Recommenda- tion G.702). The characteristics of some radio-relay systems (for instance code conversion, insertion of justification bits, parity bits and service bits) may cause the bit rate within the digital radio section to be different from the CCIT recommended hierarchical level or an
9、 integral multiple of it. that this hypothetical reference digital path should be as represented in Fig. 1. COPYRIGHT International Telecommunications Union/ITU RadiocommunicationsLicensed by Information Handling ServicesCCIR VOLUME*IX-1 90 4855212 0510b97 T Rec. 556-1 c Y 21 COPYRIGHT International Telecommunications Union/ITU RadiocommunicationsLicensed by Information Handling Services
