CEPT T CD 02-01 E-1986 Specification of Engineering Requirements for a Synchronous Digital Multiplexer Operating at 64 KBit s Using an 8 Bit (6+2) Envelope Structure《使用8 Bit(6+2)封套.pdf
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1、. CEPT T/CD*02-03*E 79 = 2326434 0003YbL b W Page E 1 Recommendation T/CD 02-01 E (Ostende 1979, revised at Cannes 1983) Concerning the specification of engineering requirements for a synchronous digital multiplexer operating at 64 kbit/s using an 8-bit (6+2) envelope structure O Recommendation prop
2、osed by Working Group T/WG 10 “Data Communications” (CD) Text of the revised Recommendation adopted by the “Telecoirnitiicntioiis” Commission: “The Conference of European Post and Telecommunications Administrations, Coilsidering - that CCITT Recommendation X.50 describes the standard for a TDM syste
3、m for synchronous data transmission - that GT/CD has studied the harmonization of multiplex equipment for data communication under the auspices at 64 kbit/s using an 8-bit (6+ 12) envelope structure; of Question CD 1. Recommends - that the attached specification of engineering requirements for a syn
4、chronous digital multiplexer operating at 64 kbit/s using an 8-bit (6+ 12) envelope structure, annexed to this Recommendation should be takeninto account by all CEPT Administrations when implementation of such a piece of equipment is being planned by Administra- tions.” O Administrations are free to
5、 stipulate additional requirements, and also which of the optional requirements, if any, are to be provided. Note 1: This specification is the subject of continuing study and possible amendments. Note 2: The Annex is an integtai part of the Recommendation. Edition of March 15, 1986 CEPT T/CD*82-OL*E
6、 79 m 2326414 0003462 8 m . TlCD02-01 E Page 3 Contents SCOPE 5 Section A . Common requirements 5 1 . GENERAL CHARACTERISTICS . 5 1.1. Bitrate . 5 1.2. Timingsignal 5 2 . FRAMESTRUCTURE 5 2.1. 80 8-bit envelope structure . 5 2.2. 20 8-bit envelope structure . 7 2.3. Allocation of channels on interna
7、tional multiplex links at 64 kbit/s 7 3 . ALIGNMENT 9 3.1. Envelope alignment at the tributary interface . 9 3.2. Frame alignment at 64 kbit/s interface 9 4 . FAULT CONDITIONS AND CONSEQUENT ACTIONS . 9 4.1. Fault conditions . 9 4.2. Consequent actions 9 5 . TESTLOOPS 10 6 . PERFORMANCES 11 7 . POWE
8、R SUPPLY 11 8 . MECHANICAL REQUIREMENTS 11 9 . ENVIRONMENTAL REQUIREMENTS 11 Section B . Network dependent requirements 12 1 . INTERFACES . 12 1.1 Tributary interfaces 12 1.2. 64 kbit/s interface definitions 12 2 . CONTROLOFLOOPSIANDK . 13 3 . TELEMAINTENANCE OVER A DATA NETWORK USING X.50 FRAME STR
9、UCTURE 13 O Section C . Optional reqitiretnents 15 1 . INPUT BUFFER REQUIREMENTS 15 2 . EXTERNALCLOCKINTERFACE 15 O Note: Bars at the left hand margin indicate that the wording of this Specification is similar to CCITT Recommendation X.50 for the relevant item . Edition of March 15. 1986 / I CEPT T/
10、CD*02-O1*E 79 m 2326414 0003463 T m F T/CD 02-01 E Page 5 I I I I I D S SCOPE This specification gives the characteristics of a synchronous digital multiplex equipment which combines on an octet by octet basis, n synchronous homogeneous or heterogeneous tributary channels at the net bit rates from 0
11、.6 to 9.6 kbit/s defined in CCITT Recommendation X.l into a digital stream, at the gross bit rate of 64 kbit/s, according to CCITT Recommendation X.50. Section A. Coinmon reqrrireineiits 1. 1.1. 1.2. 2. 2.1. GENERAL CHARACTERISTICS The functional structure and the interfaces of the multiplex equipme
12、nt are shown in Figure 1 (T/CD 02-01). Bit rate The nominal bit rate is 64 kbit/s. The tolerance on this rate is +50 parts per million (ppm). Timing signal It should be possible to synchronise the internal clock in two ways: i) synchronization from the incoming 64 kbit/s signal; ii) synchronization
13、from an external clock (optional). Moreover an independent operation mode should be possible. FRAME STRUCTURE The signal elements of each individual channel should be assembled in 8-bit envelopes. In an %bit envelope, bit 1 is reserved for framing purposes, bits 2-7 are the information bits of the c
14、hannel, and bit 8 is a status bit, as follows: 12345678 The addition of the framing and the status bits results in 33% increase in bit rate, so that beares channel rates are: 12.8 kbit/s for the 9.6 kbit/s data signalling rate; 6.4 kbit/s for the 4.8 kbit/s data signalling rate; 3.2 kbit/s for the 2
15、.4 kbit/s data signalling rate; 800 bit/s for the 600 bit/s data signalling rate; The status bit is associated with each envelope and, in conjunction with the information bit, conveys call control information. For the multiplexing of channels, an 8-bit envelope interleaved structure should be used w
16、ith a distributed framing pattern employing the framing bits of consecutive 8-bit envelopes. The multiplexing structure will comprise 80 envelopes as described in 2.1. below; as an alternative the multiplexing structure described in 2.2. can be used. 80 8-bit envelope structure In the case of homoge
17、neous multiplexing the envelopes will appear on the 64 kbit/s bearer as follows: - 12.8 kbit/s channels will repeat every 5th - 6.4 kbit/s channels will repeat every 10th 8-bit envelope; - 3.2 kbit/s channels will repeat every 20th 8-bit envelope; - 0.8 kbit/s channels will repeat every 80th 8-bit e
18、nvelope; Where a heterogeneous multiplexing is used, within each 12.8 kbit/s channel only a homogeneous misture of sub-rate channels will be allowed. A 72-bit long framing pattern is recommended. This pattern is part of the 80-bit pattern which is generated according to the primitive polynomial: 1 +
19、 x4 + x7 of the Z7 Galois field with the forcing configuration 1001101 and which is reproduced in Table 1 (T/CD 02-01) showing 8 bits (,A to “H) reserved for housekeeping. The frst F bit, indicsted as “A” in Table 1 (T/CD 02-01) is used to convey to the distant end alarm indications detected at the
20、local end (see paragraph 4.). Edition of March 15, 1986 _= T/CD 02-01 Page 6 CEPT T/CD*OZ-OL*E 2326434 0003464 L o do O on C .- .d - E P .d 3 * 5 Figure 1 (T/CD 02-01). Functional structure and interfaces of 64 kbit/s data multiplexors. Edition of March 15, 1986 CEPT T/CD*02-01*E 79 2326414 OO3465 3
21、 _ I/CD 02-01 E Page 7 The ?A? bit shall be assigned such that: ?A? equals 1 means no alarm ?A? equals O means alarm. The other F bits indicated as ?B?, ?C?, ?D?, ?E?, ?F?, ?G?, and ?H? in Table 1 (T/CD 02-01) could be reserved to convey further international house-keeping information. Pending the r
22、esolution of the house- keeping requirements, these bits are provisionally fixed to : ?B? equals 1, ?C? equals 1, ?D? equals O, ?E? equals O, ?F? equals 1, ?G? equals 1, ?H? equals O. The use of these bits is under study. 1st bit AlOOO11111 B 100001110 C 111001011 D 010010000 E 010001001 F 000101110
23、 G 011011000 H O11001101 Forcing configuration Table 1 (T/DC 02-01). 2.2. 20 8-bit envelope structure In - the case of homogeneous multiplexing, the envelopes will appear on the 64 kbit/s bearer as follows: 12.8 kbit/s channels will repeat every 5th envelope; 6.4 kbit/s channels will repeat every 10
24、th envelope; 3.2 kbit/s channels will repeat every 20th envelope; Where a heterogeneous multiplexing is used, within each 12.8 kbit/s channel, only a homogeneous mixture of sub-rate channels will be allowed. A 19-bit long framing pattern is recommended. The pattern is part of the 20-bit pattern whic
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