1、Page 1 TJCS42-09E Recommendation T/CS 42-09 (Nice 1985) SIGNALLING AND CIRCUIT SUPERVISION VIA THE EUROPEAN COMMUNICATIONS SATELLm (ECS) Recommendation proposed by Working Group T/WG 11 “Switching and Signalling” (CS) Text of the Recommendation adopted by the “Telecommiiriicatioiu” Commission: “The
2、European Conference of Postal and Telecommunications Administrations, considering - that the ECS system is to be integrated into the European telephone network; - that the use of multidestination and terrestrial multiplex techniques is proposed in order to economise on satellite - that System R2 is
3、recommended for use and conveys per-circuit information concerning the state of the trans- - that for Signalling Systems Nos. 5 and 7, it will be advantageous for ISCs to be informed of the state of the capacity; mission media utilised; transmission media utilised, O recommend that members of the CE
4、PT who use the European Communications Satellite for the telephone service should adopt the procedures specified below.” PREAMBLE This recommendation has no direct equivalent CCITT recommendation although some information is similar to that in red book Recommendation 4.33 3. This recommendation revi
5、ews the ECS system briefly and highlights potential alarm problems which occur because of the optimisation of the satellite path. It further reviews the problems which may be encountered when using systems SS R2, SS No. 5, SS No. 6 and SS No. 7 via ECS if alarm transparency end to end is not provide
6、d. A solution is proposed to provide end to end transmission of alarms, and it is left to the administration/RPOA to decide whether or not to adopt this solution. Edition of November 15, 1986 TICS 42-09 E GENERAL The European Communications Satellite (ECS) employs Time Division Multiplex Access (TDM
7、A) techni- ques with Digital Speech Interpolation (DSI) (see specification ECS/C 11-17 Rev. 1) i. With such application of DSI at earth stations the integrity of primary multiplex systems, either FDM or PCM, used for terrestrial access to the satellite system cannot be maintained within the satellit
8、e system. For example time-slots O and 16 of a 2,048 kbit/s PCM system or the group pilot of an FDM system will not be available between earth stations for the transfer of signalling or transmission alarm information. The provision of equivalent facilities over the satellite section needs special co
9、nsideration. When sections of a transmission link are maintained as separate entities, transmission alarms are not transferred between sections for maintenance purposes (see CCITT Recommendation G.704) 2. However, the transfer of relevant alarni information between sections is necessary for end-to-e
10、nd circuit supervision when this cannot be provided by other means, such as normal circuit signalling. Such transmission failure indications provide the means whereby affected circuits can be automatically removed from, and restored to, service under control of the ISC (see CCITT Recommendation 4.33
11、) 3. Although not necessarily a fault condition, an increase in circuit activity on a TDMA/DSI system may lead to an overload condition, e.g. “bit stealing” in the DSI equipment. Conveyance of overload indicators to the associated ISC may be used to initiate appropriate network management actions to
12、 reduce or eliminate the overload conditions on groups of circuits routed via the TDMA/DSI system. Implementation of this capability is at the discretion of individual administrations. SIGNALLING SYSTEMS In accordance with Recommendation T/CS 14-01 4 and CCIT Recommendation 4.7 5 specified signallin
13、g systems considered to be applicable for ECS operation using TDMA/DSI are: - System R2, provided that the digital version of line signalling is employed (see Recommenda- - System No. 5 7. - System No. 7 SI. 2.1. Signalling System R2 2.1.1 1.1. 1.2. 1.3. tion T/CS 42-03) 6. In the case of System R2,
14、 only the digital version of line signalling is recommended for this use. However, the analogue version of line signalling may still be used at ISCs accessing the satellite system, with signalling conversion being provided, at either the ISC or the earth station, in accordance with Recommenda- tion
15、T/CS 42-04 9. Figure 1 (T/CS 42-09) shows the possible arrangements that Administrations may employ in order to utilise System R2 analogue and digital signalling equipment with FDM and/or PCM terrestrial transmission systems to provide the digital line signalling required on the satellite section. A
16、 satellite Line Signalling Channel (LSC) is provided to convey the System R2 digital line signalling code. Two signalling bits, a and b, are required in the LSC for each System R2 terrestrial circuit accessing the satellite section. Under transmission failure conditions bits a and b are set to state
17、 1, so that the line signalling protocols of System R2 will eventually block the circuit. Fault conditions detected at the earth station and the consequent actions to be taken are given in Tables 1 and 2 (T/CS 42-09) respectively when terrestrial access is via a 2,048 kbit/s PCM system or via a FDM
18、system with signalling conversion at the earth station. The application of actions given in these tables enables appropriate end-to-end supervision to be provided on a per-circuit basis. Table 3 (T/CS 42-09) shows the format and organisation of the LSC for System R2 line signalling. 2.1.2. 2.1.3. 2.
19、1.4. Edition of November 15, 1986 2.2. 2.2.1, 2.2.2. 2.2.3. 2.2.4. 2.3. 2.3.1. 2.3.2. 2.3.3. 2.3.4. TICS 42-09 E Page 3 Signalling System No. 5 Note: On circuits employing System No. 5 signalling, some administrations utilize a repeat forward clear procedure as a means of achieving clear down under
20、failure conditions. This procedure, which may involve periodic sending of fonvard clear signals synchronously on a number of circuits, can result in severe periodic overloading of DSI channels. In order to avoid this possible overloading of DSI channels, it is preferable to send the periodic forward
21、 clear signals cyclically on the circuits involved. The in-band signalling of System No. 5 does not require information to be conveyed in a separate signalling channel, so a satellite LSC would not normally be required for this signalling system. However, the LSC used for System R2, shown in Table 3
22、 (T/CS 42-09) may be utiiised to provide end-to-end supervision on a per-circuit basis for circuits employing System No. 5. In this case the a and b signalling bits in the LSC corresponding to the Terrestrial Channels (Tcs) for which supervision is applied shall assume the following meaning: Under n
23、ormal conditions: b = O indicates that the relevant TC is in a normal condition. The a signalling bit contained in the same slot shall be set, as convenient, either to zero or 1. Under abnormal conditions: a = b = 1 indicates that the relevant TC is in an abnormal condition. Thus, for effective appl
24、ication, the failure of a distant terrestrial transmission system (FDM or PCM) in either direction between an earth station and its associated ISC should result in the sending of a = b = 1 for each affected circuit backward over the satellite section. The alarm information passed via the LSC is tran
25、sferred from the receiving earth station to its associated ISC as follows: - when digital access circuits are provided, bits a and b in Time Slot 16 corresponding to the faulty circuits, are set to “1”; - when analogue access circuits are employed receipt by the earth station of bits a = b = 1 for 6
26、 or more circuits in an analogue group should result in the removal of the group pilot towards the ISC, depending on the requirements of individual Administrations. Administrations may then utilise this information at their ISC to block or busy affected circuits, or for example, to inhibit the sendi
27、ng of repeat forward clear signals. Where appropriate to the use of System No. 5, the fault conditions and consequent actions given in Tables 1 and 2 (T/CS 42-09) are also applicable. Signalling System No. 7 This signalling System employs a common signalling channel which may be conveyed via the sat
28、ellite system (for example, via a 64 kbit/s signalling channel) or via an associated terrestrial transmission path. The provision of transmission alarm information for circuit supervision purposes is necessary because: - Although a speech path continuity check (when provided) will remove faulty circ
29、uits from service, a faster method is required if severe operational problems at the ISC are to be avoided when a large number of circuits are affected by a transmission system failure. - It is not mandatory for an ISC recognising a transmission system failure to send a blocking signal for each affe
30、cted circuit. If the common signalling channel and associated speech circuits are routed via ECS, methods of conveying circuit supervision information via the LSC are similar to those described for System No. 5. This will require a satellite channel to carry circuit supervision information in additi
31、on to the common signalling channel. Digital terrestrial access systems will also require a time slot for circuit supervision purposes beside that required for common channel signaling. Methods of utilising the common signalling channel for the purpose of conveying information on the status of the t
32、ransmission path of the speech circuits require further study. .- y Edition of November 15, 1986 CEPT T/CS*42-09*E 85 = 2326434 0004805 b = TICS 42-09 Page 4 b DIGITAL LINK DIGITAL R2 SIGNALLING TERMINAL - ISC ES 1 Ir . ANALOGUE R2 SIGNALLING TERMINAL ANALOGUE R2 SIGNALLING TERMINAL c + / - 0 ANALOG
33、UE LINK ISC ES A - TSC I SIGNALLING CONVERSION EQUIPMENT Figure 1 (T/CS 42-09). System R2 - ECS access configurations. Edition of November 15, 1986 CEPT T/CS*42-09*E 5 W 2326414 0004O6 W I TICS 42-09 E Page 5 Terrestrial link to own ISC Satellite link E 2 -z 8 B E e Yes Note 1 Yes Note 1 m U .- c 2
34、a - - - - Yes - Yes - YeS 2 .- Digital earth station c equipment B Fault conditions Yes Yes Loss of frame alignment BER exceeded or loss of incoming signal Loss of multiframe alignment Alarm indication from ISC (Bit 3, TS O. Even Frame. Bit 6, TS 16. Frame O) Power supply failure - TDMA/DSI Yes Yes
35、If Poss Yes If Poss - - - - - Yes If Poss - - - Power supply failure - satellite signalling equipment Yes If Poss Yes Yes Yes Yes Yes Yes Yes YeS If Poss YeS If Poss Loss of reference timing Yes BER exceeded in satellite path Yes Yes Yes Note 2 - Backward alarm indication from remotees concerning BE
36、R in satellite path Loss of data unique word Yes Yes Yes Note 2 - - Yes Vote 3 Backward alarm indication from remotees concerning data unique word Yes Yes Note 2 - Yes Loss of alignment or BER exceeded in satellite signalling channel Backward alarm indication from remotees concerning satellite signa
37、lling channel Power supply failure - TDMA/DSI - Yes If Poss - - - Yes If Poss Yes If Poss - Yes - Yes - Power supply failure - satellite signalling equipment Table 1 (T/CS 42-09). Fault conditions and consequent actions at eakh stations with 2,048 kbit/s digital acte; links. Note 1: Prompt maintenan
38、ce alarm is inhibited if AIS is present. Note 2: Prompt maintenance alarm shall be inhibited if the backward alarm is received from only one origin if the interface concerned is working to more than one destination. It is not inhibited when working to a single destination. Note 3: If prompt maintena
39、nce alarm according to Note 2 is not inhibited. O Edition of November 15, 1986 CEPT T/CS*42-09*E 85 m 2326434 0004807 T m TICS 42-09 Page 6 ?errestria1 link to own CT Satellite link Digital earth station equipment Fault conditions Loss of forward signal (group pilot failure) YeS Yes Power supply fai
40、lure FDM trans. equip. Yes f Pos: YeS Failure of line signal converter Yes YeS Yes f Pos: Yes f Pos: - YeS - YeS Power supply failure - TDMA/DSI Power supply failure - satellite signalling equipment Note 6 - Yes Loss of reference timing Note I . 6 Yes YeS BER exceeded in satellite path Yes Yes YeS N
41、ote 2 - Backward alarm indicating from remotees concerning BER in satellite path Yes Yes - Yes YeS Yes Note 2 - Loss of data unique word - YeS Note 3 Backward alarm indication from remotees concerning data unique word Loss of alignment or BER exceeded in satellite signalling channel YeS Yes Yes Note
42、 2 - Backward alarm indication from remotees concerning satellite signalling channel Yes Yes f Pos: YeS f Poss - - Power supply failure - TDMA/DSI Power supply failure - satellite signalling equipment Table 2 (T/CS 42-09). Fault conditions and consequent actions at earth stations with analogue acces
43、s links and signalling conversion at the earth station. Note 1: The “relevant blocking signal” is that signal which the recommendation for analogue R2 line signalling calls for in the event of interruption control or it may be the defined blocking condition resulting from busying equipment. Note 2:
44、Prompt maintenance alarm shall be inhibited if the backward alarm is received from only one origin if the interface concerned is working to more than one destination. It is not inhibited when working to a single destination. Note 3: If prompt maintenance alarm according to Note 2 is not inhibited. N
45、ote 4: In this case the line signalling converter shall apply this condition. It is assumed that power supply failure on FDM transmission equipment will result in a group pilot failure. Note 5: The line signalling converter should comply with the principles described in Recommendation T/CS 42-03, Se
46、ction 3. Note 6: A relevant blocking signal will be generated by the converter in the analogue part. 7 Edition of November 15, 1986 CEPT T/CS*42-0*E 5 2326414 0004O 1 = Symbol N 1 2 3 4 5 P channel O 1 y, y3 %+I Q channel 1 O y2 y4 bx+, TICS 42-09 E Page 7 6 7 63 64 ax., ax+3 ax+, axcm bX+, bx+3 bx.
47、59 bx+m Table 3 (T/CS 42-09). Format of each 64 kbit/s unit forming a satellite line signalling channel (LSC) for system R2 line signalling. (See specification ECS/C 11-17 Rev. 1). - Symbols 1 and 2 carry the fixed pattern shown. - Symbols 3 and 4 carry Backward Alarm Indications related to the sate
48、llite system. - a, and b, are the signalling bits relating to the International Circuit number n indicated by the subscript, where : x = x = 60 in the second 64 kbit/s unit, x = 120 in the third 64 kbit/s unit, x = 180 in the fourth 64 kbit/s unit. O in the rst 64 kbit/s unit, References Specificati
49、on ECS/C 11-17 Rev. 1. Time Division Multiplex Access techniques with Digital Speech Interpolation. CCITT Recommendation G.704. Functional characteristics of interfaces associated with network nodals. CCITT Recommendation Q.33. Protection against the eflects of faulty transmission on groups of circuits. CEPT Recommendation T/CS 14-01. Use of Signalling System R2 in European telephone networks. CCITT Recommendation 4.7. Signalling systems to be used for international ai$omatic and semi-automatic telephone working. CEPT Rec
