1、Page 1 Ts61-20E Recommendation T/S 61-20 (Edinburgh 1988) EXCHANGE INTERFACES TO SUBSCRIBERS Recommendation proposed by Working Group T/WG 11 “Signalling, Protocols and Switching” (SPS) Text of the Recommendation adopted by the “Telecommiiriications” Cominission: “The European Conference of Postal a
2、nd Telecommunications Administrations, recommends to the members of the CEPT that digital local and combined exchanges provide the interfaces to subscribers as specified below.” The reader is referred to CCITT Recommendation 4.512 i to which this Recommendation is identical, except for the addition
3、and modifications indicated below. The section references (indicated $) are to Q.512 i. $3.5.3.: delete the reference to 23 B + 1D channel type at 1.544 kbit/s. O 53.6. : $3.6. 3.6.1. 3.6.2. 3.6.3. replace by the following: Interface V6 Geiieral Interface V6 is a digital interface used to connect di
4、gital customer equipment, via the static multiplexed Basic Rate Access Section. This section may include a 1st order digital link between muldex and V6 interface. Local digital muldex application is considered to be a subset of the remote digital muldex application. Electrical characteristics The el
5、ectrical characteristics of interface V6 are described in CCITT Recornmendation G.703. The basic frame structure at interface V6 should be identical to that of the 1st order multiplexing described in CCITT Recommendations G.704 and G.705. Cfiannel types, channel allocation and signalliiig The V6 int
6、erface is composed by a number of individual ISDN Basic Rate Access Sections, as described in section 3.3. The channel allocation at interface V6 is defined within a 1st order structure using a static multiplexing at 2.048 kbit/s as follows: Twelve basic access channels are multiplexed in a static m
7、anner using fixed allocation of the channels. The Figure 4/Q.512 illustrates the channel allocation for 2.048 kbit/s, where 24 of 32 channel time slots are used by B1 and B2 channels and the other 6 channel time slots are used by each D and CV, channels of the 12 basic accesses. The CV, and D channe
8、ls of two basic accesses are multiplexed into one channel time slot. Five contiguous channel time slots are occupied by two basic accesses each consisting of B1 + B2 + D + CV1 channels. Channel time slot O is used for synchronization including the application of CRC4 according to Recom- mendation G.
9、704. Additionally, the alarm handling facilities of channel time slot O are used for maintenance of the primary link, described in Recommendation 1.605. According to the channel allocation shown in Figure 4/Q.512 the CVI channel is in time slots 5, 10, 15, 21, 26 and 31. Each line represents 8 bits
10、of a D + CV, common to two basic accesses. Since the multiframe alignment is performed individually for two basic accesses each, groups of n x 5 64 kbit/s channels conveying signals of n x 2 subscribers each (n = 1, 2 . . . 6) can be arranged so that basic accesses entering the network on digital mu
11、ldex devices may be connected to a local exchange using one common V6 interface. The D channel signalling procedures are dened in CCITT Q.920- and Q.930-Series Recommendations. Edition of January 15. 1989 V 232b4L4 00090b5 b O TIS 61 -20 E Page 2 3.6.4. Fiinctional description The functional descrip
12、tion is illustrated in Figure 3JQ.512 and the following functional requirements are defined : - m x (2 B + D): to provide the bidirectional transmission capability for the B and D channels from - timing: to provide the necessary timing information for bit transmission, frame synchronization and - m
13、x (CV,): to provide the bidirectional transmission capability for the CV1 channel from each Basic - operations and maintenance: to provide the transmission capability to carry the operation and main- The use of the CRC procedures described in Recommendations G.704-G.706 is recommended between the mu
14、ldex and exchange. The information on the status of the CRC processing shall be passed across the V6 interface in time slot O. each Basic Rate Access Section; subscriber line synchronization; Rate Access Section; tenance signals of the digital link and the basic access muldex as defined in 1.605. m
15、x (2B+D) LT ET Timing m x CVI Operation and maintenance Figure 3/QS 12. Functional description of V6 interface. Q Edition of January 15, IYL. ! = 2326414 0009066 B _ Edition of January 15, 1989 frr-= Channel Time slot No. O 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 2
16、9 30 31 Contents Frame alignment signal/Remote service alarm indication B1,l B2,l B1,2 B2,2 D1, CV1l, D2, CV12 B1,5 B2,5 B1,6 B2,6 D5, CV15, D6, CV16 B1,9 B2,9 B1,lO B2,10 D9, CV19, D10, CVl10 not used B1,3 B2,3 B1,4 B2,4 D3, cv13, D4, cv14 B1,7 B2,7 B1,8 B2,8 D7, CV17, D8, CV18 B1,ll B2,ll B1,12 B2
17、,12 D11, CV1ll, D12, CV112 TIS 61 -20 E Page 3 Bl,i B2,i Di CVli = CONTROL channel of basic access i Figure 4/Q.512. = B1 channel of basic access i = B2 channel of basic access i = D channel of basic access i Channel allocation at the V6 interface for 2.048 kbit/s. = 232b414 00090b7 T M. TIC 61-20 E
18、 Page 4 3.6.5. Conveyance of maintenance and operation functional elements of each individual basic access across the V6 inteiface The functional elements for the operations and maintenance of the digital section of the basic rate access are conveyed in the CV1 channel and can be classified as shown
19、 in Table 1 (T/S 61-20). TYPES MAINTENANCE AND OPERATION FUNCTIONAL ELEMENTS Alarm Reporting Status Reporting Loop Control “L” -TYPE FUNCTIONAL ELEMENTS Operations “O” -TYPE FUNCTIONAL ELEMENTS “A” -TYPE FUNCTIONAL ELEMENTS “S” -TYPE FUNCTIONAL ELEMENTS performance Monitoring “M” -TYPE FUNCTIONAL EL
20、EMENTS Table 1 (T/S 61-20). Functional elements in CVI, crossing the V6 interface. This is shown in figure 5 (T/S 61-20) where the direction of information flow is given. Alarm Reporting Status Reporting Performance Monitoring Requests Performance Monitoring Responses Loop Control Operations DIGITAL
21、 b SECTION b OF THE 4 ET BASIC b RATE 4 ACCESS b Figure 5 (T/S 61-20). Functions in CV1, crossing the V6 interface. 3.6.5.1 Operations (O-TYPE functional elements) The following operational controls must be conveyed across the V6 interface per basic access from the ET to the digital section of the b
22、asic rate access: - activation request for the line and S/T interface - deactivation request for the line and S/T interface - request for the activation of line only and deactivation of the - switch off/on of power to line, its use is optional *Note. Optional. 3.6.5.2. Alarm reporting (A-TYPE functi
23、onal elements) The following alarm reports must be conveyed across the V6 interface to the ET, per basic access: - loss of synchronization or signal on the line, detected by the LT - multiple alarm indication (for further study) - general fault condition, not related to an individual basic access 3.
24、6.5.3. Status reporting (S-TYPE functional elements) The following status information must be conveyed across the V6 interface per basic access to the ET: - loss of synchronization at T interface - line and S/T interface activation indication - line and S/T interface deactivation indication - line s
25、ystem activation/T interface deactivation indication - power switched off indication, its use is optional Note. The setting of a loop is confirmed by the functional element S2 and is described in the Draft Recommendation IAA For the digital transmission section for ISDN basic rate access. *Note. Opt
26、ional. (“01” functional element) (“02” functional element) S/T interface (“03” functional element) (“04” functional element) I* (“Al” functional element) (“A2” functional element) (“A3” functional element) (see Table 2 (T/S 61-20) (“Sl” functional element) 7 * (“ST functional element) (“S3” function
27、al element) (“S4” functional element) 7 * (“S5” functional element) Edition of January 15, 1989 m 2326414 0009068 L = TIS 61 -20 E Page 5 3.6.5.4. Loop control (L-TYPE functional elements) The following commands must be conveyed across the V6 interface per basic access from the ET to the access: - a
28、ctivation/deactivation NT1 loop - activation/deactivation LT loop - activation/deactivation regenerator loop 3.6.5.5. Performance monitoring (M-TYPE functional elements) When the line system in the basic access is in an active state, performance monitoring functions in the NT1 and LT will provide in
29、formation on the performance of the transmission system. Two types of performance monitoring over the V6 interface can be envisaged: 1. System dependent counter values (“Ll” functional element) (“L2” functional element) (“L3” functional element) In this situation the ET receives system dependent cou
30、nter values and has to take into account some properties and parameters related to the system used (e.g. scrambling and coding method, error multiplication factor) in order to process error performance parameter values. In this situation adaption taking into account the above-mentioned system depend
31、ent parameters is performed in the digital section and the ET receives system independent counter values, representing the number of detected errors for a given period T, related to a 144 kbit/s datastream, from which error performance parameter values directly can be derived. Performance informatio
32、n must be conveyed across V6 to the ET for each basic access. Two alternatives exist: The rst one combines the bit/code errors detected in both directions, while the second one reports the errors of each direction of transmission separately. Upon a request from the exchange, error counters in the di
33、gital section are read and the value is sent to the ET. After readout, the counter is set to zero. It is left to the ET to request the readout of the counters in defined time periods. The G.821 parameters can be derived from this error performance information. The choice of mechanism is for further
34、study. 2. System independent counter values 3.6.6. 3.6.6. Characteristics of the signalling capabilities . Signalling capabilities for the maintenance of the basic access multiplexer The signalling capabilities for the functions related to the maintenance of the basic access multiplexer, as identifi
35、ed in 3.4. are given in Table 2 (T/S 61-20). Failure Idle Loss of signal from the ET Loss of synchronization AIS received CRC error Reaction in time slot O G.704 towards the ET A=O Sn3=0000 A=l Sn3=1110 A=l Sn3=1110 A=l Sn3=1111 A=O Si=O Information in the control channel of the individual access to
36、wards the ET (“A37 NO YES YES YES NO Information in the control channel of the individual access towards the individual access (,O,) NO YES YES YES NO Note. This application of the Sn3 bit does not restrict a future standardization on the use of Sn bits in a global concept. Table 2 (T/S 61-20). Faul
37、t conditions detected in the basic access multiplexer and consequent actions. Detection of power alarm of the basic access multiplexer should be based on additional signalling capabities. Edition of January IS. 1989 - - W 232b4L4 OOOOb 3 W TIS 61-20 E Page 6 3.6.6.2. The CVl channel The maintenance
38、and operation functions as far as the basic access is concerned and which are identified in paragraph 3.6.5. are conveyed in the CV1 channel across the V6 interface. In Recommendation Q.512 i this CV, channel is defined and the frame structure on the V6 interface, containing this CV, channel, is giv
39、en. (See Figure 4/Q.512) 3.6.6.3. CVl signal/message allocation to the identified operation and maintenance functions for the digital section of the basic access 3.6.6.3.1. The frame structure The frame structure in the D+CV1 channel is given in Figure 6 (T/S 61-20) containing: - A-bits words Al-A4,
40、 for the control of the activation/deactivation of the U and T interfaces, the set up - M-bits octets for the transfer of the monitor channel data. - E-bit to indicate the validity of the following M-bit. - T-bit for the transmission of transparent data to be conveyed across the U interface. The use
41、 of the T-bit - R-bits, representing a multiframe alignment word. of loops and the signalling of fault indications. is for further study. Edition of January 15, la89 TIS 61-20 E Page 7 -* Channel time slot No. of frames SYN B1,l B2, B1,2 B2,2 D + CV1 O 1 2 3 4 5 D D D D D D D D RO Al A3 E R1 Al A3 E
42、 4 ms I L 0.5 ms D D D D D D D D - MO A2 A4 T MI A2 A4 T - - - M7 A2 A4 T Basic access 1 - D D D D D D D D - - D D D D - D D D D D D D D - D D D D - RO Al A3 E R1 Al A2 E R7 Al A3 E - MO A2 A4 T M1 A2 A4 T - M7 A2 A4 T - cv12 Basic access 2 Al . A4: Activation/deactivation, loop aiid line feed contr
43、ol. T: Transparent channel. E: Indication of information in the M-channeI. M: Monitor channel. R-bit multiframe alignment word for every basic access: Figure 6 (T/S 61-20). Multiframe structure of the V6 interface. TIS 61 -20 E Page 8 3.6.6.3.2. Coding for the A-bits The coding for the A-bits is giv
44、en in Tables 3 (T/S 61-20) and 4 (T/S 61-20). Bits 41 A2 A3 A4 O000 O001 O010 O011 O100 O101 O110 o111 1000 1001 1010 1011 1100 1101 1110 1111 Command Exchange-B AMX Idle Not used National use Not used Req. REG loop Req. NT loop Req. LT loop PH-AR PH-AU/DT * National use National use Not used Disabl
45、e req. Not used Not used MPH-DR Description ?00? Power down state - - - ?L3? Hold loop in repeater ?Ll? Hold loop in NT ?L2? Hold loop in LT ?01? ?03? Activate U/Deactivate T (Notes 1, 2) Activate layer 1 U and T - - - ?04? Switch off power +U transmit Sig. - - ?02? Deactivate layer 1 U and T interf
46、aces Table 3 (T/S 61-20). Note 1. This code is allocated for additional mode of operation as explained in 4.512 93.3.4. Note 2. This function is optional. *Note 3. Provisional. Bits $1 A2 A3 AA O000 O001 O010 O011 O100 0101 O110 o111 1000 1001 1010 1011 1100 1101 1110 1111 Note 1. This coi Indicatio
47、ns B AMX-Exchange PH-DI Not used Not used Not used MAI Not used National use PH-Al PH-AU1 Not used Sync loss U Disable ind. Not used National use MPH-EI PH-EI Description ?S3? Confirmation deactivation T+U - - ?S2? Configuration layer 1 activation ?A2? study) Potentially ?Awake-indication? (Start Ti
48、mer TI*) ?S4? Confirmation T deact. U activ. (Notes I, 2) ?Sl? ?Al? Synchronization loss on U interface ?S5? Power/Transmitter/Wake up disabl. - Multiple alarm indication (for further - - LOS/Sync loss on T interface (Note 2) ?A3? to an individual basic access (see Table 2 (T/S 61-20) General fault
49、condition not related Table 4 (T/S 61-20). is allocated for additional mode of operation as explained in 4.512 93.3.4. Note 2. Optional. *Note 3. Timer TI is defined in the Draft Recommendation IAA on the digital section and the transmission system for the ISDN basic access. e Edition of January 15, 19891- m 232b414 0009072 3 W MAI-data: (for further study) TIS 61-20 E Page 9 e.g. 1 octet, linear coding 3.6.6.3.3. M-bit coding The M-bit coding is given in Tables 5 (T/S 61-20) and 6 (T/S 61-20). MO M1 M2 M3 M4 M5 M6 M7 Exchange-BAMX/description O O O O O O O O Idle
