WPCL 2BJ|x ( ")x-    6'6' xI  x|@   Fascicle VI.14 Rec. Q.1102 xI x|@  Fascicle VI.14 Rec. Q.1102    Recommendation Q.1102 A INTERWORKING BETWEEN SIGNALLING SYSTEM R2 ă F AND INMARSAT STANDARD A SYSTEM ă 1  Introduction  It is necessary to specify the interworking of Signalling System R2 and the signalling systems used in the INMARSAT Standard A system. This is because:  a)h( it may be desirable that a Maritime Satellite Switching Centre (MSSC) 1) be connected to an international switching centre (ISC) by employing System R2 on the circuits between the MSSC and the ISC;  b)h( the signalling system used in the Maritime MobileSatellite Service will be different from System R2. Therefore it would be necessary to establish rules by which signalling events in one system may be related to corresponding events in the other system.  It is desirable that the interworking be such that the full capability of both System R2 and the maritime satellite signalling system be utilized.  This Recommendation considers only automatic interworking between the MSSC and an ISC utilizing either the analogue or digital versions of System R2 signalling. For description of the INMARSAT Standard A signalling system, see annex A to RecommendationQ.1101.   2  Calls from Signalling System R2 to the maritime satellite system (see figure 1/Q.1102) NFIGURE 1/Q.1102  2.1The ISC sends the seizing signal followed by either of the following sequences of address signals:  2.1.1( Signal I10 or a language digit when the country code 87S is not required for routing in the MSSC. At the MSSC this signal should be acknowledged by the signal A5 in order to obtain the calling subscriber's category (Group II signal). The Group II signal is acknowledged at the MSSC by A1. The ISC then continues to send further address signals which are acknowledged in compelled cycles withA1 at the MSSC.  2.1.2( The country code indicator when the country code 87S is required for routing in the MSSC. One of the following signals can be used as country code indicator: ( Signal I11 when the MSSC has to insert an outgoing halfecho suppressor; ( Signal I14 when an outgoing halfecho suppressor has been inserted.   At the MSSC this signal should be acknowledged by the signal A5 in order to obtain the calling subscriber's category (Group II signal). The Group II signal is acknowledged at the MSSC by A1. The ISC continues to send the country code digits and further address signals which are acknowledged in compelled cycles with A1 at the MSSC.  2.1.3( Any numerical (or address) signal of the above sequences may be acknowledged by the signals A3 or A4: ( A4 if congestion or abnormal release occurs in the MSSC;  ( A3 may, for example, be used in order to indicate to the ISC barring of unauthorized group calls. Such calls are identified from the first digit following the discriminating digit. The appropriate Group B signal would in this case be B2.  X( This use of A3 is only possible if analysis of the discriminating (or language) digit and the first digit of the subscriber number takes place before the whole number has been received by the MSSC. If this is not the case, the procedure of 2.2 should be followed.  2.2When the last address signal has been received at the MSSC, and number analysis has been completed, one of the following events leading to unsuccessful call completion may occur:  ( The called ship earth station is excluded from participating in the system, the number of the called terminal has been changed or the received number is an unauthorized group call number (see also 2.1.3 above). In these cases the MSSC shall send the A3 signal followed by B2 after the Group II signal has been received from the ISC.  ( The NCS/MSSC is out of service. In this case the A4 signal is sent, or the A3 signal followed by B4 after receipt of the Group II signal.  ( The received number does not belong to any ship earth station. In this case the A3 signal is sent followed by B5 after receipt of the Group II signal.  2.3If the received number is valid, the MSSC sends A1 as an acknowledgement to the last digit (or the endofpulsing signal I15) in order to suspend the compelled signalling.  2.4The MSSC sends a wRequestforAssignmentw message to the Network Coordination Station (NCS) in order to obtain a satellite channel (see Annex A to Recommendation Q.1101).  "If no reply to this request is received within 4 seconds (or 8 seconds if the request is repeated by the MSSC) or, if a congestion message is received from the NCS, the MSSC sends the pulsed A4 signal or the A3 signal followed by B4 after receipt of the Group II signal."  If a wShip busyw message is received, the MSSC sends the pulsed A3 signal followed by the B3 signal after recognition of the forward Group II signal.  If an wAssignmentw message is received from the NCS, the MSSC connects the continuity tone on the assigned satellite channel. If a continuity tone is received from the ship earth station within 10 seconds, the MSSC sends the pulsed A3 signal followed by the B6 signal after recognition of the forward Group II signal. The continuity check may fail in two ways:  ( no radio carrier is received from the ship earth station within 10 seconds (e.g. the ship is outside the satellite coverage area), or  ( a radio carrier but no continuity tone is received from the ship earth station within 10seconds.  The MSSC sends the pulsed A3 signal followed by B2 or B8 respectively after recognition of the forward Group II signal.  2.5When the MSSC detects the answer signal from the ship earth station, the MSSC must send the answer signal as soon as possible to the ISC.  2.6When the MSSC detects the clear forward from the terrestrial network, the terrestrial circuit and the satellite link will clear down according to their respective specifications. If, however,  switching at the MSSC is achieved by direct frequency selection then it will be necessary to delay the releaseguard on the terrestrial link until the satellite link is idle.  2.7The MSSC should send the clearback signal into the terrestrial network when clearback is detected on the satellite link. The satellite link will be released so that the provisions of Recommendation Q.118 do not apply for this part of the connection.  2.8For the SDL description of incoming Signalling System R2, see RecommendationQ.616 [1].  2.9For the SDL description of interworking between incoming Signalling System R2 and the outgoing INMARSAT signalling system see Annex A. 2.10For SDL description of outgoing INMARSAT signalling system, see Annex C to RecommendationQ.1101.    3  Calls from the maritime satellite system to Signalling System R2 (see figure 2/Q.1102) MFIGURE 2/Q.1102)  3.1The MSSC should not seize a terrestrial circuit before each of the following conditions have been met: ( the satellite channel has been assigned; ( the continuity of the satellite channel has been verified; ( all digits necessary for routing decisions by the MSSC have been received. 3.2The first register signal to be sent by the MSSC is:  ( the discriminating digit I10 if the call is destined for a country whose ISC has direct connections to the MSSC;  ( the country code indicator I14 if the call is destined for another country and the incoming halfecho suppressor is to be inserted at a later ISC;  ( the country code indicator I12 if the call is destined for another country and the incoming halfecho suppressor can only be inserted at the MSSC.  3.3The MSSC must respond to Group A or Group B signals in accordance with current Signalling System R2 specifications. The following special requirements should however be taken into account:   ( If the signal A14 is received from the ISC, the MSSC must either forward I14 in order to indicate that an incoming halfecho suppressor is required, or forward the next address signal where the MSSC has already inserted an incoming halfЩecho suppressor.  ( If the signal A3 or A5 is received from the ISC, the MSSC should send the II7 signal (for the time being no other category signal would be required).  The signals A3, A5 and A14 may be received at any time during interregister signalling sequence. If the signal A11 is received from the ISC, the MSSC should send:  ( I14 to indicate that an incoming halfecho suppressor is required, or ( I12 where the MSSC has already inserted an incoming halfecho suppressor.  If the signal A12 is received, the next signal shall be the discriminating digit (I10).  The MSSC should be capable of responding to signal A13 with the signal A14 in order to indicate that a satellite link is included (see Recommendation Q.480 [2]).  3.4The end of pulsing signal I15 should be sent by the MSSC, if required and requested, if the equivalent endofpulsing signal is received from the ship earth station.  3.5The tones sent by the MSSC to the ship earth station in response to Group B signals received from the terrestrial network should comply with Recommendation Q.474 [3]. The characteristics of the tones are given in Recommendation Q.1101.  3.6Timeout supervision on the answer signal at the MSSC should comply with the provisions given in Recommendation Q.118, 4.3.1.  3.7If the MSSC receives a clearback signal from the terrestrial network, the timeout of Recommendation Q.118, 4.3.2 shall be started. The satellite and terrestrial links will be cleared either by the ship earth station or by expiry of the 12 minute timeout.  3.8When the MSSC detects a release condition on the satellite link, the terrestrial connection should be cleared forward as soon as possible. 3.9For the SDL description of outgoing System R2, see Recommendation Q.626 [4].  3.10The SDL description of the interworking between incoming INMARSAT Standard A signalling system and outgoing System R2 is given in Annex B.  3.11For the SDL description of incoming INMARSAT Standard A signalling system, see Annex B to Recommendation Q.1101. RANNEX A H(to Recommendation Q.1102) 9 Logic procedures for interworking of Signalling System R2 ă ? to the INMARSAT Standard A signalling system ă ("&)x- ( ")x- MFIGURE A1/Q.1102 6 State overview diagram for interworking of Signalling System R2 ă ? to the INMARSAT Standard A signalling system ă MFIGURE A2/Q.1102 H(Reserved for future notes)   MFIGURE A3/Q.1102 C Interworking of Signalling System R2 ă ? to the INMARSAT Standard A signalling system ă RANNEX B H(to Recommendation Q.1102) 7 Logic procedures for interworking of the INMARSAT Standard A ă A signalling system to Signalling System R2 ă (0%')x- ( ")x- MFIGURE B1/Q.1102 : State overview diagram for interworking of the INMARSAT ă ; Standard A signalling system to Signalling system R2 ă MFIGURE B2/Q.1102 = Notes to interworking of the INMARSAT Standard A ă A signalling system to Signalling System R2 ă EFIGURE B3/Q.1102 (sheet 1 of 2) 9 Interworking of the INMARSAT Standard A signalling system ă J to Signalling System R2 ă EFIGURE B3/Q.1102 (Sheet 2 of 2) 9 Interworking of the INMARSAT Standard A signalling system ă J to Signalling System R2 ă  References  [1]hCCITT Recommendation wLogic procedures for incoming Signalling System R2,w Vol. VI, Rec.Q.616. [2]CCITT Recommendation wMiscellaneous procedures,w Vol. VI, Rec.Q.480. [3]CCITT Recommendation wUse of group B signals,w Vol. VI, Rec.Q.474.  [4]hCCITT Recommendation wLogic procedures for outgoing Signalling System R2,w Vol. VI, Rec.Q.626.  X8"% x|@ ) For definition, see Recommendation Q.1101.