1、INTERNATIONAL TELECOMMUNICATION UNION)45G134 1 TELECOMMUNICATIONSTANDARDIZATION SECTOROF ITU).4%27/2+).G0G07)4(G0G03!4%,)4%-/“),%G0G03934%-3%.%2!,G0G02%15)2%-%.43G0G0- the continuity of the satellite channel has been verified;- all digits necessary for routing decision by the maritime satellite swit
2、ching centre have been received.5.4 Clear-back conditions5.4.1 The clear-back/re-answer sequence may not apply for shore originated calls, in which case the satellite linkwill be released when a clear-back signal is detected at the maritime satellite switching centre from the satellite link,without
3、waiting for a clear-forward signal from the terrestrial network.Precautions should be taken either at the MSSC or at the ship earth station in order to avoid unintentionalclearing.5.4.2 For ship originated calls the normal clear-back procedures should apply (see Recommendation Q.118).5.5 Clear-forwa
4、rdWhen detecting a clear-forward from the satellite link, the MSSC should immediately pass the clear-forwardsignal into the terrestrial network.When detecting a clear-forward from the terrestrial network, the release guard (and clearing) sequence shouldfollow the procedures defined for the signallin
5、g system used.5.6 Splitting arrangementWhen in-band signalling is used over the satellite link for setting-up and clearing of the link, a splittingarrangement shall be provided in order to avoid that signalling tones are passed into the terrestrial network. Thesplitting time shall be less than 20 ms
6、.4 Fascicle VI.14 - Rec. Q.1101In order to protect the maritime satellite system from line signals used on terrestrial signalling systems, itshould be observed that such signalling tones passing through splitting arrangements in the terrestrial network mayhave a maximum duration of 50 ms.6 Audible t
7、ones sent by the MSSCTones sent by the maritime switching centre (MSSC) should have the following characteristics:Dial tone: 425 Hz (1.5 seconds maximum, minimum is determined by receipt of first dialdigit)Ringing tone: 425 Hz (1 second on, 4 seconds off, immediate ringing)Busy tone: 425 Hz (1/2 sec
8、ond on, 1/2 second off)Congestion tone: 425 Hz (1/4 second on, 1/4 second off)Special information tone: as defined in Recommendation Q.35.Note - The dial tone is given as 1.5 seconds pulse in order to avoid subscribers confusion due to the two-waytransmission delay of 0.5 seconds. If the normal cont
9、inuous tone with interruption after the receipt of the first digit wasused, the delay would cause the tone to stay on after entry of the first digit.7 Control of echo suppressorsSince all calls to and from a ship earth station will include a satellite link, appropriate actions must be taken toinsert
10、 an incoming or outgoing half-echo suppressor at the MSSC or at an international exchange closer to theterrestrial subscriber. The ship earth station will connect to the satellite link on a 4-wire basis or will be provided withthe equivalent of a half-echo suppressor. In order to reduce the analysis
11、 and control requirements at the MSSC it mayprove convenient to carry out all echo suppressor control at one of the international exchanges rather than at the MSSC.This is most easily achieved by fitting permanent half-echo suppressors at the ISC end of each MSSC-ISC circuit. Inany case the overall
12、echo control requirements are the same as specified in Recommendation Q.115.7.1 Terrestrial signalling systems with signals for control of echo suppressors7.1.1 Ship original callsThe MSSC should send an echo suppressor indicator informing transit centres or incoming centres whether ornot an incomin
13、g half-echo suppressor should be included.Insertion of an incoming half-echo suppressor will always be requested if the MSSC does not carry out echosuppressor control.7.1.2 Shore originated callsThe MSSC will decide whether or not to insert an outgoing half-echo suppressor depending on the receivede
14、cho suppressor indicator. If echo control is not performed at the MSSC, the echo suppressor indicator will alwaysinform the MSSC that an outgoing half-echo suppressor has already been included.7.2 Terrestrial signalling systems without signals from control of echo suppressorsWhen signals for the con
15、trol of echo suppressors are not available on the particular terrestrial route, significantadvantage is to be gained by carrying out the echo suppressor control at the international exchange. In any case thefollowing rules should be observed:7.2.1 Ship originated callsa) When the terrestrial connect
16、ion between the outgoing ISC, (or MSSC) and the incoming ISC (or nationalincoming switching centre) does not normally require the use of echo suppressors, the outgoing ISC (orMSSC) should enable (or insert) an incoming half-echo suppressor associated with the satellite link.b) When the terrestrial c
17、onnection between the outgoing ISC (or MSSC) and the incoming ISC (or nationalincoming switching centre) normally requires the use of echo suppressors, the outgoing ISC (or MSSC)should disable (or should not insert) any half-echo suppressors associated with either the satellite link orthe terrestria
18、l link.Fascicle VI.14 - Rec. Q.1101 57.2.2 Shore originated callsa) When the international connection between the outgoing ISC and the incoming ISC (or MSSC) does notnormally require the use of echo suppressors, the incoming ISC (or MSSC) should enable (or insert) anoutgoing half-echo suppressor ass
19、ociated with the satellite link.b) When the international connection between the outgoing ISC and the incoming ISC (or MSSC) normallyrequires the use of echo suppressors, the incoming ISC (or MSSC) should disable (or should not insert)any half-echo suppressors associated with either the satellite or
20、 terrestrial link.8 Handling of group calls8.1 GeneralA group call is a simultaneous call to a given group of ships. Such calls are identified by the followinginternational number:87S0X2X3. Xkwhere the first digit of the ship station number has the fixed value 0. The remaining digits determine which
21、group of ships is being addressed.Facilities for originating group calls from operators either in the MSSC country or another country may bereadily made available by permitting such calls only when the Z digit is a language digit. Group calls originating fromordinary telephone subscribers should not
22、 be permitted so long as calling line identification is not available.8.2 Barring at the ISC of originIn order to avoid setting up of the international chain for unauthorized group calls from ordinary subscribers,barring of such calls should, as a general rule, be done at the ISC of origin.8.3 Barri
23、ng at the MSSCBarring should also be provided at the MSSC in order to reject group call attempts from ships or fromsubscribers in countries where barring at the outgoing ISC is not possible.9 Avoiding two or more satellite links in tandem9.1 Shore originated callsThe country code 87S should be analy
24、sed at all transit centres where the call may either be routed on a circuitcontaining a satellite link or on a circuit not containing a satellite link. The latter circuit should always be chosen (seeRecommendation Q.14).9.2 Ship originated callsIf the signalling system provided between the MSSC and
25、the terrestrial network contains signals which may beused to indicate that one satellite link is included, such signals should be used.If the signalling system does not contain such signals, the outgoing ISC should avoid forwarding the call on anoutgoing circuit which includes a satellite link. If,
26、however, the signalling system employed between the outgoing ISCand the next ISC in the connection contains such signals, the outgoing ISC should insert the required information. Theoutgoing ISC could base its procedure upon incoming route identification.10 Operator assistance for semi-automatic sho
27、re originated callsIf code 11/12 assistance facilities are not provided at the MSSC, then arrangements should be made tointercept such calls at the preceding ISC and route them to an appropriate operator.It may be advantageous for Administrations to provide a publicized number (e.g. C12XXXX) for spe
28、cializedassistance on calls to the maritime network.6 Fascicle VI.14 - Rec. Q.1101ANNEX A(to Recommendation Q.1101)Brief description of the INMARSATStandard A systemA.1 IntroductionThis annex describes the signalling in the INMARSAT Standard A system in a multiple Maritime SatelliteSwitching Centre
29、(MSSC) configuration, i.e., there is more than one MSSC serving an ocean region. Automatic callset-up and clearing are illustrated below. For calls which cannot be completed, the subscriber will receive from theMSSC or the terrestrial network the proper audible tone which describes the call status (
30、i.e., busy tone, congestiontone).A.2 System configurationThe INMARSAT system is composed as shown in Figure A-1/Q.1101. Only the components required forinterfacing the telephone network are shown. There are additional interfaces similar to the MSSC for interfacing thetelex network and the internatio
31、nal public data network.The purpose of the MSSC is defined in 2 of the Recommendation.There is one operating Network Coordination Station (NCS) in each ocean area (there may in addition be oneor more standby NCSs per ocean area). The main functions of the NCS are as follows.The ship earth stations c
32、an only monitor one calling channel in the shore-to-ship direction. This callingchannel, denoted as the common assignment channel, is transmitted by the NCS. Each coast earth station transmits itsown calling channel which is monitored by the NCS for relaying signalling messages from a coast earth st
33、ation to aship.The NCS also performs all assignment of telephone channels on a call-by-call basis and monitors the actualuse of the channels for maintenance purposes. The NCS keeps an up-dated list of all busy ships in the ocean area. If acoast earth station calls a busy ship, the NCS may thus retur
34、n a ship busy indication to the calling coast earth station onthe common assignment channel.The procedures are further described below.A.3 Ship earth station originated callsThe normal call set-up procedure for automatic call processing from a ship earth station is shown inFigure A-2/Q.1101. The shi
35、p earth station transmits an out-of-band request message which includes the type of calldesired, the identify of the MSSC through which the terminal wishes to communicate and the identification number ofthe ship earth station.Fascicle VI.14 - Rec. Q.1101 7The MSSC upon reacting to the received reque
36、st message, sends a Request for Assignment message to theNetwork Coordination Station (NCS). The NCS receiving the request for assignment message assigns a channel(frequency) and transmits this information in an assignment message to both the MSSC and the ship earth station. Boththe MSSC and ship ea
37、rth station receive the assignment message, automatically select the correct frequency, andinitiate a continuity by transmitting a 2600 Hz tone.When continuity has been established, the MSSC sends a dial tone pulse to the ship earth station. The shipearth station subscriber then dials in the desired
38、 prefix, country code and national significant number followed by anend-of-selection signal. The signals are transferred as in band push button signals on the satellite link.The MSSC proceeds to select a terrestrial trunk and follows the standard signalling sequences of the signallingsystem used tow
39、ards the ISC (Figure A-2/Q.1101). The ringing tone from the terrestrial network is allowed to passdirectly to the ship earth station subscriber. When the terrestrial party answers the call, the ISC passes the answer signalto the MSSC and the international connection is established. The answer signal
40、, if implemented, may then be passed tothe ship earth station1).A.4 Terrestrial originated callsThe normal call set-up procedure for automatic call processing from the terrestrial network to a ship earthstation is shown in Figure A-3/Q.1101. The ISC selects a circuit and sends the seizing signal and
41、 the mobile terminalidentification digits to the MSSC in accordance with the procedures used in the terrestrial signalling system. TheMSSC then sends a request-for-assignment message to the NCS containing the ship earth station identity. The NCSresponds by sending an assignment message to both the M
42、SSC and the ship earth station. The MSSC and the ship earthstation activate their carriers and send a 2600 Hz tone. Upon receipt of the 2600 Hz tone from the ship earth station theMSSC interprets this as an address complete condition, sends the ringing tone to the terrestrial network and stopssendin
43、g 2600 Hz to the ship earth station. When the operator or subscriber at the ship earth station answers, the shipearth station discontinues sending its 2600 Hz tone.The MSSC recognizes the cutting of the 2600 Hz tone as an answer signal from the ship earth station andbegins the answer sequence toward
44、 the ISC as shown in Figure A-3/Q.1101._1)This is currently under study by INMARSAT.8 Fascicle VI.14 - Rec. Q.1101 Fascicle VI.14 - Rec. Q.1101 9A.5 Automatic clearing of callsWhether a telephone call originated from a ship earth station or from the terrestrial network, the MSSC, uponreceiving a cle
45、ar-forward signal, will begin to clear the call independently in each direction.The MSSC, receiving a 2600 Hz clearing tone from a ship earth station will initiate clearing toward theterrestrial network in accordance with procedures defined for the signalling system used between the MSSC and theISC.
46、 This applies to both clear-forward and clear-back from the ship earth station. Clearing will also be continued inthe maritime satellite system independent of the terrestrial network.Clearing initiated in the terrestrial network would be recognized by the MSSC receiving the appropriate clear-back or
47、 clear-forward signal. For clear-forward, the MSSC would continue clearing with normal terrestrial proceduresand begin clearing the maritime satellite circuit. For clear-back from the terrestrial network, normal time-outsupervision will take place and clear-forward will commence either after expiry
48、of time-out or after receipt of a clear-forward from the ship, whichever happens first.As examples of clearing sequences, Figure A-4/Q.1101 illustrates the clearing of a ship earth stationoriginated call and Figure A-5/Q.1101 illustrates the clearing of a call originated in the terrestrial network.
49、For aterrestrial originated call which has clearing initiated by the ship earth station, the satellite circuit is cleared after theMSSC recognizes the stopping of the ship earth station carrier. The terrestrial circuit is held until the end of releaseguard sequence as shown in Figure A-5/Q.1101.10 Fascicle VI.14 - Rec. Q.1101ANNEX B(to Recommendation Q. 1101)Logic procedures for incoming INMARSAT Standard Asignalling system (ship originated call)This annex only includes those elements of the St
