1、CEPT T/CD*02-04*E 88 2326434 003LhbO BIT Page 1 CD 02-04 E Recommendation T/CD 02-04 (Odense 1986, revised in Edinburgh 1988) ENGINEERING REQUIREhENTS FOR A STNCHRONOL-S DIGITAL 1IULTIPLEXER FOR CSE TITH NON ENVELOPE STRL-CTCRED D.4T.4 Recommendation proposed by LVorliing T WG 10 “Data communication
2、s“ CD) Test of the Recommeticlcrtion (idopted bx the “Te.lec.oiiiniiirlic.cltions“ Coniriiission: “The Conference of European Post and Telecommunications Administrations. considering - that working group CD has studied under the auspices of Question CD 1 the harmonization of Data Circuit Terminating
3、 Equipment. recommends - that the attached specification of engineering requirements for a synchronous digital multiplexer for use tvith non envelope structured data as contained in Annex 1 to this Recommendation should be taken into account b- all CEPT Administrations Lvhen the implementation of a
4、relevant piece of equipment is being planned by Administra- tions.“ Administrations are free to stipulate additional requirements. and also which of the optional requirements. if any. are to be provided. .Vote 1. It should be noted that this Recommendation may be reLised from time to time. :Vote i?.
5、 It is left to each Administration to decide which of the three Recommendations Le. T CD 02-01. T CD 02-02 and T CD 03-04 is to be used in their individual national network. For international intertvorking the question of a-hich multiplexer is to be used is a matter of bilateral or multilateral a= u
6、reement. Edition of October I i. 1988 CEPT T/CD*OS-OY*E AB 23ZbYl1Y OOllbbB 75b T/CD 02-04 E Page 2 Annex 1 SECTION I. PARAMETERS REQUIRED FOR INTERWORKING 1-1. 1-2. 1-3. 1-3.1. 1-3.1.1. 1-3.1.2. 1-3.1.3. 1-3.1.4. 1-3.1.5. GROSS BIT RATE The aggregate bit stream shall have a gross bit rate of 64 khi
7、t!s. TRIBUTARY CHANNEL BITRATES The following tributary channel hitrites arc supported: - 2.4 kbit/s - 4.8 kbitls - 9.6 kbitls - 19.2 kbitjs Other bitrates are not excluded. MULTIPLEX SCHEME The multiplex scheme is shown in Figure 1-1 (TKD 02-04). The frame length is 630 bit. The frame duration is 1
8、0 ms. Tributary channel data is grouped in octets and appears in slots A, through F,. Slots S, contain synchronisation octets. Slots T, contain service octets. 4- 160 bits = 70 octets + - I S4 I B2 I A2 ID2 I CZ I F2 I E3 I A3 I B3 I C3 I D3 I E3 IF3 I B4 I A4 I I34 I C4 1 F4 I E4 I T4 Figure 1-1 Tj
9、CD 02-04). Multiplex scheme. Data Octets One frame contains 72 data octets. Thus the multiplex stream cin support 24 channels of 2.4 kbit/s. or 12 channels of 4.8 kbitla, or 6 channels of 9.6 kbitls. or 3 channels of 19.2 kbit/s. or combinations thereof. The allocation of individual octets to a trib
10、utary channel is detailed below. 2.4 khitls 2.4 kbit/s tributary channels employ 1 out of 24 data octets. A 2.4 kbits channel will thus be allocated to all slots with the same identifier, .e. identification letter and identification digit e.g. Al). 4.8 kbitls 4.8 kbit/s tributary channels employ 1 o
11、ut of 12 data octets. A 4.8 k4it.s channel will thus be allocated to a11 slots with the same identification letter in the range A-F and two different identification digits 1 and 3 or 2 and 4 (e.g. BI and B3). 9.6 kbitls 9.6 kbit/s tributary channels employ 1 out of 6 daPi octets. A 9.6 kbitjs channe
12、l will thus be allocated to all slots with the same identification letter in the rang A-F and four different identification digits 1, 2. 3 and 4 (e.g. D1, D2, D3 and D4). 19.2 khitls 19.2 kbitls tributary channels employ 1 out of 3 data octetr;. A 19.2 kbitis channel will thus be allocated to slots
13、with two different identification letters from the range A-F: A and D or B and E or C and F. and four difterent identification digits 1. 2, 3 and 4 (e.g. C1. Fi. C2. F2. C3. F3. C4 and F41, Other bitrutes For other bitrates no allocution of octets to a tributary channel is specified. From the scheme
14、 in Figure 1-1 (TICD 02-04) it can be derived that any bitrate n times 3.4 khit,% where n is 1 through 24 can be supported. Edition of October IS. 1988 I O CEPT T/CD*02-04*E BB W 2326434 0033662 692 T/CD 02-04 E Page 3 1-3.2. Synchronisation Octets One frame contains 4 synchronisation octets. These
15、contain fixed bit patterns as follow: s1 = 27 = 00100111 S2 = 1B = O0011011 S3 = 05 = O0000101 s4 = 35 = 00110101 .ore. Coding of the synchronisation octets is such that the! do not overlap: Le. when in random data one of the synchronisation octets is simulated. no other simulation -ill occur for 12
16、5 ps being the nominal duration of one octet. 1-3.3. Service octets Use of these octets is to be defined. Possible applications are: - use for exchange of information between the multiplexers concerning tributary channel allocation. - transfer of status information V.74 105-109 signalling or X.33 C-
17、I signalling) per tributary channel: -justification. routing. maintenance etc. : 1-4. FRAME SYKCHRONISATION Frame synchronisation is obtained by the receiving multiplexer during normal operation. No interaction between multiplexers at both ends of the link is required for this purpox Edition of Octo
18、ber 15. 1988 CPT T/CD*02=04*E 88 W 232bliL4 001iLbb3 529 m T/CD 02-04 E Page 4 SECTION II. EQUIPMENT SPECIFICATION 11-1. SYSTEM LAYOUT The basic multiplexer consists of two dilrerent units. tributary channel units (TCUs) and multiplexing units (MUS). See Figure 11-1 (TICD 03-04). Several units of ea
19、ch type constitute a physical multiplexer configura- tion. The minimum configuration is one MU and one TCU. Specilk configurations may he tailored by Administrations depending un the application and can be changed when so required. NOW. Other units may bc specificid in future. All units are connecte
20、d via ;I bus in accordance with the CEPT BUS SPECIFICATION T!CD 02-05. Structure 2 of this spccilicatin is recommended. The bmic functirm of each unit is to receive data from the external interface (tributary channcl or aggregate channel). arrange these data into octets. apply these octets together
21、with adeyuatc address information to the bus and vice versa. There shall be no limitation to the possibility to transmit datu via thc bus to any other unit. The internal address option of the structure 2 bus is used to identify physical channels in TCUs or logical channels in MUS. Address informatio
22、n is derived from instructions received from the maintenance system as described in chapter 11-5. BUS BUS BUS 11-2. TRIBUTARY CHANNEL UNIT The tributary channel unit (TCU) may suppurt cinc or more tributary channels. If the unit supports more than one tributary channel. the channel data rates may be
23、: identical - independent within the set 24-19.? kbitjs - independent within a subset The TCU will collect datu from the tributary channel interfaces, arrange these data into octets and apply these octets together with address information (destination address. consisting of unit address and internal
24、 address) to the bus with minimal delay. Data octets received from the bus will iw buffered prior to hing transferred to the tributary channel interface in order to allow for the correction of system jitter. A maximum dclay of K octets is recommended for rates until 9.6 kbit/s. BufTer si/e for 19.7
25、kbit,s is for further study. For 2.4 kbit.s a smaller buffer may be advisable. Channels (= bus internal addresses) are numbered with even numbers starting with 2. Internal address O is reserved for maintenance purposes (ref. chapter 11-51. Maintenance functions of the TCU arc described in chapter 11
26、-5. CEPT T/CD*02-04*E 88 = 2326414 0013664 465 = TICD 02-04 E Page 5 11-3. MULTIPLEXIKG L3-U 11-3.1. General The multiplexing unit (MU) will support one 64 kbit s channel. The MU will collect data octets from the incoming 64 kbit s line. Snchronisation octets ill be used for framing purposes as desc
27、ribed in chapter II-3.3. Service octets will be used for maintenance purposes as described in chapter 11-5. Data octets will be applied to the bus with minimal delay together with address information (destination address. consisting of unit address and internal address). Data octets received from th
28、e bus will be buffered prior to being transferred to the 64 kbit s channel interface in order to allow for the correction of system jitter. Buffering may be employed on a per channel basis or via a common buffer for all channels. Recommended delay is between 5 and 15 ms. Logical channels (= bus inte
29、rnal addresses) are numbered with even numbers starting nith 7. Internal address O is reserved for maintenance purposes (ref. chapter 11-5.). Allocations of time slots to logical channels is described in chapter 11-5. Maintenance functions of the MC are described in chapter 11-5. Timing functions of
30、 the -MU are described in chapter 11-6. 11-32 Frame alignment 11-3.2.1. General reqiiiremrnts - The frame synchronisation method should be insensitke as far as possible to bit errors. error bursts. and -When a slip occurs in the transmission equipment. a fast frame alignment recoLery must be possibl
31、e. - The frame alignment recovery time after a slip. in the absence of bit errors and aith random data in - A random error ratio of 1 in 10 - When the unit loses synchronisation. e.g. due to the synchronisation pattern no longer being present in the incoming bit stream. the unit +ill enter the loss
32、of synchronisation state after 50 ms (minimum) to 100 ms (maximum). short bursts of AIS generated by transmission equipment. 11-3.2.2. Framing nzethod performancr all channels. should be less than 160 octets (3 frames) sith 95% probability. shall not cause any frame alignment recaler) action. 11-3.3
33、. Consequent action in case of loss of synchronisation When the MU is in the loss of snchronisation state it should transmit to the bus at least 74 octets containing all logical ones in all logical channels that are active. After that. the hC nil1 continue to send these octets or cease sending octet
34、s in logical channels completely. Indication of this state to the maintenance system is described in chapter 11-5. 11-4. INTERFACES Three different interfaces may be identified in the multiplexer. i.e. the tributar) channel interface. the 64 kbit s channel interface and the bus interface. 11-4.1. Tr
35、ibutary channel interface Three different types of interface are envisaged. II-4.1.1. If the tributary channel modem is integrated in the TCL. the interface will comply with the respective modem recommendation. 11-4.1.2. If the tributary channel modem is not integrated in the TCU. the interface towa
36、rds the modem is a “normal“ DTE-DCE interface. Edition of October 15. 1988 CEPT T/CD*O2=04*E 8 H 232b454 0055bbC 3T5 T/CD 02-04 E Page 6 The following circuits are considered to be es%ntial: 102 ii, b, c) 103 Transmit Data to DCE 104 Receive Data from DCE 1 o9 Received Line Signill Dctcctor from DCE
37、 113 Transmitter Signal Element Timing (DTE source) to DCE 115 Receiver Signal Element Timing DCE source) from DCE Electrical characteristics niay be V.28 or other. depending on the nature of the modem. simulates i DCE. Betiiils of this interface are under study. Signal Groundb) 141 Local Loopback t
38、o DCE 11-4.1.3. If the DTE is interfaced directly to the multiplexer. a V.23:V.iX interFace is required in which the rriultiplexer 11-4.2. 11-4.3. 11-5. 11-5.1. 11-5.2. The 64 kbit/s channel interface The intcrfxe towards the 64 kbit:s chiinnel will Ikl in accordance tbith CC1T- Recommendation G.703
39、 paragraph 1. Additiciniilly interfaces according to CCITT Rwommendations V.35 and or V.36 may be required. The bus interface The bus interfiace is in iiccordiince with the CEPT BUS SPECIFICATION TCD 03-05. structure 2 with some limitations: - The Central Controller will issue BUS REQUEST STROBES wh
40、ile polling all units present or poten- tially present in the system. When the pollcd unit responds via the BUS SEIZED line, the Central Controller will issue an ADDRESS STROBE. followed by an INTERNAL ADDRESS STROBE. followed by a DATA STROBE. followed by u bus release action. - Only write actions
41、Lire envisiiged. Thus the Central Controller will keep the WRITE line permanently in the active state. The duration of a complete poll is equal to or greater than 1 ps. The following additional circuits are used: Name Abbreviation Di rect ion UNIT ADDRESS UA7-UA0 to unit 256 kHz CLOCK S6 kIIL tri un
42、it 19.2 kiIz CLOCK 19.2 kH/ to unit CLOCK SYNCHRONISATION CS from unit (MU only) The UNIT ADDRESS lines contiiin the h bit address of the unit (we chapter 11-9.). The 256 kHz CLOCK line contains a 256 kI1c clock signal (we chapter 11-6.). The 19.2 kH7 CLOCK line contains u 19.2 kH1 clock signal (see
43、 chapter 11-6.). The CLOCK SYNCHRONISATION line contains a signal derived from thc incoming 64 kbit;s signal. Trtinsitions in this signal occur at time intervals which arc muliiplcs of 1256 ms. MAINTENANCE General The maintenance of the multiplexer is performed under control of a maintenance system.
44、 This system is not described in this specification. which is limited to maintenance functions tcr be performed by multiplexers and multiplexer components. Information transfer The maintenance system issues instructions to units anywhere in the network. Units answer these instruc- tions with respons
45、es. Thc niiiintenance system can enter the multiplexer network at one or variou5 locations via a dedicated channel in ;I TCU. which operates at a fixed data rate of 2.400 bit+. Messages containing instructions or responses flow via buses (internal address fi) and M kbit s multiplexer channels (servi
46、ce octets) from maintenance system entrance to units and vice versa. Details on the protocol between the niiiintenance system and the TCU :it its entrance point and between MUS (link layer protocol). the routing of messages through the network (network layer protocol) and the coding of instructions
47、and responses are described in Appendix I. Ediiiiin of Cktokr 15. 1955 CEPT T/CD*02-04*E 88 2326434 0033bbh 238 TfCD 02-04 E Page 7 11-5.3. Configuration Control Each unit is provided by the maintenance system with information concerning the configuration. In the case of MUS. for each logical channe
48、l the following information is provided: - whether or not the channel is active. - number of first time slot. - data rate. destination address (unit address + internal address). In the case of TCCs. for each physical channel the following information is provided: whether or not the channel is active
49、. - data rate. - destination address (unit address + internal address). 11-5.4. Alarms Units may detect alarm situations in the unit itself or in associated equipment. This information is transferred to the maintenance system in responses. In the case of MCs. alarms comprise: - loss of synchronisation. loss of incoming signal. In the case of TCCs alarms comprise: - loss of incoming carrier (for each channel separately). 11-55 Testing Units can be instructed to establish test loops in the lines they control. Loop control may be -ia ci
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