ÿWPCL ûÿ2BJ|xÐ ` ÐÐÌÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿH øÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÌÐÐ °°°è ÐÁà1ÁÑ Âx„|ü@Ž ÑÐ Å@8Ø'@8Ø'Å ÐÓÓÃÃContents of Recommendation Q.1032Äă ÁàAÁƒ Áà'ÁSIGNALLING REQUIREMENTS RELATING TO ROUTING OF CALLSƒ Áà7ÁTO MOBILE SUBSCRIBERSƒ ÁàAÁƒ ÁàAÁƒ 1.ÁHÁIntroduction ÁàAÁƒ 2.ÁHÁGeneral routing rules ÁàAÁƒ 3.ÁHÁGeneral requirements for the fixed network ÁàAÁƒ Ð Ð Ð4.ÁHÁSignalling aspects on routing a call to a mobile managed by a home PLMN situated in the same country ÁàHOÁƒ 5.ÁHÁRouting a call to a foreign mobile subscriber ÁàHOÁƒ 6.ÁHÁAlternative solution: re©routing of the call after clearing ÁHÁthe previous connection ÁàHOÁƒ 7.ÁHÁUnsuccessful call set©up ÁàHOÁƒ ÁàHOÁƒ ÁàHOÁ*ƒ ÁàHOÁƒ ÁàHNÁ*     *ƒ ÁàHOÁƒ ÁàHOÁƒ ÃÃRecommendation Q.1032ÄÄ ÁàH5ÁSIGNALLING REQUIREMENTS RELATING TO ROUTING OF CALLSƒ ÁàHEÁTO MOBILE SUBSCRIBERSƒ ÁàHOÁƒ 1.ÁHÁÃÃIntroductionÄÄ ÁHÁWhen a subscriber wants to call a mobile subscriber, the fixed network needs to know the actual location of the MS in order to route the connection to the relevant Mobile Services Switching Centre (see Recommendation Q.1003 on location registration). This contribution tries to present the signalling requirements the fixed network has to comply with for that purpose. The document considers the different assumptions concerning the capabilities of the fixed exchanges to perform some signalling procedures prior to call set©up. ÁHÁThis Recommendation assumes that the routing analysis requirements specified in Recommendation Q.107bis are fulfilled. ÁHÁThis Recommendation assumes that the ISDN number of the mobile contains a specific National Destination Code. The cases where the mobile numbering plan is fully integrated in the fixed numbering plan are for further study. 2.ÁHÁÃÃGeneral routing rulesÄÄ ÁHÁThe number dialled by the calling subscriber contains no indication concerning the actual location of the called MS. Therefore, to set©up the complete connection, it is necessary to know the location of the MS and the routing address to be used, i.e. the Mobile Station Roaming Number. The only equipment able to provide this information is the Home Location Register. Therefore to route the call to the Mobile Services Switching Centre where the MS is located, it is necessary to interrogate the HLR. ÁHÁThe preferred procedure with regard to signalling is the following: ÁHÁ1)Á   ÁWhen a subscriber wants to call a mobile station he dials the ISDN number of that station. ÁHÁ2)Á   ÁThe local exchange (or a transit exchange) analyzes the number dialled and recognizes the mobile service National Destination Code indicating that the call is destined to a mobile subscriber. In general this complete routing analysis can be made for the national calls only: when the outgoing exchange recognizes that the calling subscriber dialled the international prefix, it routes the call directly to the outgoing International Switching Centre (ISC) without any further analysis. This ISC can then recognize the mobile national destination code. ÁHÁ3)Á   ÁIf the result of routing analysis shows that it is necessary to get additional information to set©up the complete connection to the MSC where the called station is located, then this information must be obtained from the HLR in charge of the mobile subscriber. If the interrogation procedure is implemented in an exchange referred to in 2) above, this exchange then performs the interrogation of the Home Location Register. The HLR sends back the roaming number of the called MS. This procedure is supported by the Transaction Capabilities of Signalling System No. 7. ÁHÁ4)Á   ÁThe connection is then set©up in the fixed network to the MSC according to the roaming number of the MS. 3.ÁHÁÃÃGeneral requirements for the fixed networkÄÄ ÁHÁTo route a call up to a mobile subscriber, an interrogation of the HLR must be performed in order to get the roaming number allocated to that MS. This interrogation procedure is supported by the Transaction Capabilities of Signalling System No. 7. The preferred solution is that the local exchanges be adapted to TC, and able to perform this interrogation: then they can route the call directly to the called mobile according to the roaming number they obtain from their interrogation of the HLR. The following section of this document shows possible solutions if this assumption is not fulfilled. ÁHÁAs it is described below, in the case where there are no interrogation facilities in the fixed network, on recognition that a call is destined to a mobile subscriber, the routing is first performed to a Gateway MSC. The interrogation of the HLR is then performed by the MSC and the call proceeds according to the Roaming Number received. ÁHÁSection 5 deals with the routing of calls to foreign mobile stations: usually, in this case, the local exchange does not analyze the national part of the called address and routes directly to the outgoing International Switching Centre which then performs the correct routing of the call. 4.ÂXHÂÃÃSignalling aspects on routing a call to a mobile managed by a home PLMNÄÄ ÃÃsituated in the same countryÄÄÆÆ 4.1ÂàHÂÃÃThe originating exchange is adapted to the interrogation procedureÄÄ ÃÃ(Figure 1/Q.1032)ÄÄÆÆ ÁHÁIf the originating local exchange is able to perform the interrogation procedure, the call set©up occurs as it is specified in section 2 of this document. 4.2ÁHÁÃÃThe originating exchange is not adapted to the interrogation procedureÄÄ Ô w.ÔŒÁHÁIf the originating exchange is unable to use TCAP, the following cases can be considered: ÁHÁ©Âà  Âthe interrogation procedure is performed by a transit exchange;ÆÆ ÁHÁ©Âà  Âthe call is re©routed by a Gateway MSC.ÆÆ 4.2.1ÁHÁÃÃThe interrogation is performed by a transit exchange (Figure 2/Q.1032)ÄÄ ÁHÁIf the originating exchange is unable to perform the interrogation of the HLR, the connection is set©up to a transit exchange. This exchange analyzes the address received (the ISDN number of the subscriber) and notices that the call is destined to a mobile subscriber. It then performs the interrogation of the HLR and routes the call as it is described in section 2. 4.2.2ÁHÁÃÃThe call is re©routed by a Gateway MSC (Figure 3/Q.1032)ÄÄ ÁHÁIf the fixed network is unable to interrogate the HLR in order to route the call to the actual location of the MS, the connection is set©up to a Gateway MSC. ÁHÁThe Gateway MSC interrogates the HLR of the called MS (using MAP in general cases). It receives back the roaming number of the subscriber. With this address, the GMSC set©up a connection via the telephone (or ISDN) network to the MSC where the mobile is located. If the called subscriber is abroad, the connection is normally set©up via the international network. 5.ÁHÁÃÃRouting a call to a foreign mobile subscriberÄÄ ÁHÁAs for a normal telephone call, the calling subscriber, when he wants to join a foreign mobile subscriber, dials the international access prefix first. His local exchange, according to this prefix, routes the call directly to the outgoing International Switching Centre without any further analysis of the number dialled. ÁHÁThe routing of the call is then performed by the outgoing international Switching Centre. Two assumptions can be envisaged: ÁHÁ©Âà  Âthe outgoing International Switching Centre recognizes that the called party is a mobile subscriber and can perform the interrogation of the HLR;ÆÆ ÁHÁ©Âà  Âthe outgoing International Switching Centre is unable to perform the interrogation of the HLR.ÆÆ 5.1ÂàHÂÃÃThe outgoing ISC can perform the interrogation of the HLRÄÄ ÃÃ(Figure 4/Q.1032)ÄÄÆÆ ÁHÁWhen the outgoing International Switching Centre receives the call, for routing purposes it analyzes the digits of the country code and the first digits of the national significant number of the called party address. It can then notice that the call is destined to a mobile subscriber and needs a preliminary interrogation transaction prior to setting up the connection. ÁHÁWith the roaming number, the ISC then routes the call to the MSC where the mobile is actually located. The connection is set©up via the international network if the MS is not in the same country as the calling subscriber. 5.2ÂàHÂÃÃThe outgoing International Switching Centre is unable to perform theÄÄ ÃÃinterrogation of the HLR (Figure 5/Q.1032)ÄÄÆÆ ÁHÁIf the outgoing International Switching Centre is unable to perform the interrogation procedure, it routes the call to the incoming ISC of the country where the Home PLMN of the called mobile is situated according to the telephone (or the ISDN) number dialled by the calling subscriber. ÁHÁThe incoming ISC receiving the call notices that it is destined to a mobile. The following assumptions can be envisaged: ÁHÁ©Âà  Âthis ISC can perform the interrogation;ÆÆ ÁHÁ©Âà  Âthis ISC is unable to perform the interrogation: therefore the interrogation has to be made either by a national transit exchange or by a Gateway MSC.ÆÆ ÁHÁIn this assumption where the actual routing has to be made in the home country of the mobile, the connection may comprise two international links in tandem if the subscriber is roaming abroad. Therefore it would be better that the interrogation is performed in the outgoing country; this method would limit the length of the complete connection. The worst case will appear when the called mobile is roaming in the country of the calling subscriber: the complete connection comprises two international links in tandem instead of a simple national routing. 5.3ÂàHÂÃÃThe International Switching Centre recognizes that it is a call to anÄÄ ÃÃMS but cannot perform the interrogationÄÄÆÆ ÁHÁIn this case, the International Switching Centre routes the call to a Gateway MSC which performs the interrogation: ÁHÁ©Âà  Âif the GMSC is accessed by the outgoing ISC, see Figure 6/Q.1032.ÆÆ ÁHÁ©Âà  Âif the GMSC is accessed by the Incoming ISC, see Figure 7/Q.1032.ÆÆ 6.ÂXHÂÃÃAlternative solution: re©routing of the call after clearing theÄÄ ÃÃprevious connection (Figure 8/Q.1032)ÄÄÆÆ ÁHÁThe ISUP provides a backward message to indicate that the call should be re©routed and containing the new address. This facility may be used in the case where a foreign MS is called and no interrogation functions are available in the fixed network to get the Roaming Number from the HLR. A long international connection may be established before the location of the MS is determined but this facility could allow the call to be "dropped back" to the suitable MSC. 7.ÁHÁÃÃUnsuccessful call set©upÄÄ 7.1ÁHÁÃÃRoaming not allowedÄÄ ÁHÁIf the MS is roaming in an area where it is not allowed to have calls, the location is not stored in the HLR and an indication is set. When a call is set©up to this subscriber, the HLR will return an unsuccessful indication to the originating exchange. 7.2ÁHÁÃÃRestart of the HLRÄÄ ÁHÁAfter a restart, the HLR considers that the information coming from the back up is still valid. If an interrogation is related to a subscriber whose information is not yet restored, the HLR gives back the Roaming Number it has in its tables. If there is a mistake, the restoration procedure specified in Recommendation Q.1004 will re©establish the correct information. 7.3ÁHÁÃÃMobile station roaming number unallocatedÄÄ ÁHÁIf the incoming MSC receives a call which roaming number is declaredÔ w.Ô unallocated by the VLR, it sends back an unsuccessful call set©up indication to the outgoing exchange. This situation may occur after a restart of the HLR or of the VLR (see Recommendation Q.1004).