1、INTERNATIONAL TELECOMMUNICATION UNION)45G134 1 TELECOMMUNICATIONSTANDARDIZATION SECTOROF ITU05“,)#G0G0,!.$G0G0-/“),%G0G0.%47/2+3%.%2!,G0G0!30%#43G0G0/ in this case the MSCs are the functional interfacesbetween the fixed network and a PLMN for call set-up. In the second case, it can be considered as
2、an assemblage ofspecial logic in existing or future PSTN/ISDN stored program controlled digital local exchanges, conceptually integratedwithin a common numbering and routing plan.Functionally the PLMNs may be regarded as independent telecommunications entities even though differentPLMNs may be inter
3、connected through the PSTN and PDNs for forwarding of calls or network information. A similartype of interconnection may exist for the interaction between the MSCs of one PLMN.The location register system of a PLMN may be centralized, distributed or segmented. So long as we areconcerned with functio
4、ns of a PLMN, such as routing and interworking, the configuration and operation of the locationregister system have no influence on external networks.The use of the concept PLMN is illustrated in Figure 1/Q.1001 where various PLMNs are shown with theirinterfaces to the fixed networks. It should be n
5、oted that a PLMN may have several interfaces with the fixed network (e.g.one for each MSC). Interworking between two PLMNs may be performed via an international gateway.Figure 1/Q.1001 also shows the information paths between a PSTN and a PLMN and between two differentPLMNs. The solid lines indicate
6、 a possible physical path between the PLMNs through the PSTN. The dotted lineindicates that, for some interactions, an end-to-end information path (established through the physical path) may existbetween the two PLMNs.2 Fascicle VI.12 - Rec. Q.10012.1.3 Mobile Services Switching CentreIn an automati
7、c system the Mobile Services Switching Centre (MSC) constitutes the interface between the radiosystem and the public switched telephone network. The MSC performs all necessary signalling functions in order toestablish calls to and from mobile stations.In order to obtain radio coverage of a given geo
8、graphical area a number of base stations (radiotransmitters/receivers) are normally required; i.e. each MSC would thus have to interface several base stations. Inaddition several MSCs may be required in order to cover a country. The definition of the MSC may be prefixed by theterms “land“ or “mariti
9、me“ if that is more suitable in a specific application.2.1.4 base stationThe base station (BS) is the common name for all the radio equipment located at one and the same place usedfor serving one or several cells.2.1.5 mobile stationThe mobile station (MS) is the interface equipment used to terminat
10、e the radio path at the user side. It includesterminal functions required to provide services to the user, e.g. terminal equipment and terminal adaptors.2.1.6 cellThe area covered by a base station, or by a sub-system (sector antenna) of that base station corresponding to aspecific logical identific
11、ation on the radio path, whichever is smaller.Every mobile station in a cell may be reached by the corresponding radio equipment of the base station.2.1.7 base station areaThe area covered by all the cells served by a base station.2.1.8 location areaThe location area is defined as an area in which a
12、 mobile station may move freely without updating the locationregister. A location area may comprise several cells.2.1.9 MSC areaThe part of the network covered by an MSC. An MSC area may consist of several location areas.Fascicle VI.12 - Rec. Q.1001 32.1.10 service areaThe service area is defined as
13、 an area in which a mobile station is obtainable by another PLMN, PSTN or ISDNsubscriber without the subscribers knowledge of the actual location of the mobile station within the area. A service areamay consist of several PLMNs. One service area may consist of one country, be a part of a country or
14、comprise severalcountries. The location registration system associated with each service area must thus contain a list of all mobilestations located within that service area.Figure 2/Q.1001 shows an example of the composition of a service area.Note - This definition does not take into account any co
15、nstraints on routing imposed by the internationaltelephone network.4 Fascicle VI.12 - Rec. Q.10012.1.11 system areaThe system area consists of one or more service areas with fully compatible MS-BS interfaces.Note - The location registers of the individual service areas remain autonomous; updating of
16、 the locationinformation is not performed when a roaming mobile station moves from one service area to another. The overallcomposition of the international land mobile system is shown in Figure 3/Q.1001.2.1.12 Mobile Subscriber International ISDN NumberThe Mobile Subscriber International ISDN Number
17、 is defined as the number which has to be dialled in order toreach a mobile subscriber in a service area. See also Recommendations E.164 and E.213.2.1.13 international mobile station identityThe mobile stations identification uniquely identifies the MS internationally. The identity is composed asdef
18、ined in Recommendation E.212.2.1.14 radio traffic pathThe radio communication facility between a mobile station and a base station intended to carry a call anduniquely assigned to the mobile station during that call.2.1.15 radio control pathThe radio communication facility between a mobile station a
19、nd a base station intended to carry all theinformation transfer between the mobile station and the MSC, in which area the mobile station currently is located,during the time that no radio traffic path between that base station and that mobile station is assigned.2.2 Roaming definitions2.2.1 location
20、 registerTo establish a call to a mobile station the network must know where this mobile station is located. ThisFascicle VI.12 - Rec. Q.1001 5information is stored in a function named location register. A mobile station is registered at one location register whichfunctions as its home centre for ch
21、arging and billing purposes and for administering its subscriber parameters.2.2.2 location informationThe location register should as a minimum contain the following information about a mobile station:- international mobile station identity;- actual location of the mobile station (e.g. PLMN, MSC are
22、a, location area, as required).2.2.3 home PLMNThe PLMN in which a mobile station is permanently registered.2.2.4 home location registerThe location register to which a mobile station is assigned for record purposes such as subscriber information.2.2.5 home MSCThe term home MSC (HMSC) may be used in
23、cases where the home location register is implemented in anMSC.2.2.6 equipment Identity RegisterThe register to which an international mobile equipment identity is assigned for record purposes.2.2.7 visited PLMNThe PLMN, other than the home PLMN, in which a roaming subscriber is currently located.2.
24、2.8 visitor location registerThe location register, other than the home location register used by an MSC to retrieve information for, forinstance, handling of calls to or from a roaming mobile station, currently located in its area.2.2.9 visited MSCThe term visited MSC (VMSC) may be used in cases wh
25、ere the visitor location register is implemented in anMSC.2.2.10 gateway PLMNThe PLMN which receives a call from a fixed subscriber, via a public switched network, for extension to amobile station. The gateway PLMN may vary for interconnection with different public networks.The gateway PLMN could be
26、 the home PLMN or the visited PLMN or any other.2.2.11 gateway MSCThe MSC which receives a call from a fixed subscriber, via a public switched network, for extension to amobile station. The gateway MSC may vary for interconnection with different public networks.The gateway MSC may be any MSC of the
27、PLMN, including the HMSC or VMSC if the home and visitedlocation registers are implemented in the MSC.2.2.12 designation methodThe calling subscriber must know the actual location area of any mobile station. The call is establishedaccording to the dialled information only, i.e. the call is not rerou
28、ted by the location register when the mobile stationcurrently is in another location area.6 Fascicle VI.12 - Rec. Q.10012.2.13 non-designation methodThe calling subscriber is not required to know the actual location area of the mobile station. The call is routedaccording to the dialled information a
29、nd, if required, rerouted on additional information given by a location register.2.2.14 mobile station roaming numberThe network internal number used for routing of calls to the mobile station. See Recommendation E.213.2.3 Handover definitions2.3.1 handoverHandover is the action of switching a call
30、in progress from one cell to another (or between radio channels in thesame cell). Handover is used to allow established calls to continue when mobile stations move from one cell to another(or as a method to minimize co-channel interference).2.3.2 MSC-A (Controlling MSC)The MSC which first establishe
31、d the radio connection to or from a mobile station for mobile terminating ororiginating calls respectively. This MSC will be the call controlling MSC for the duration of the call also in cases wherea call is handed over to another MSC.2.3.3 MSC-BThe first MSC to which a call is handed over.2.3.4 MSC
32、-BThe second (or subsequent) MSC to which a call is handed over.Note - After the handover is completed and the circuit between MSC-A and MSC-B has been released. MSC-Bwill look, from the point of view of MSC-A and the network, like MSC-B did before the handover.2.3.5 candidate MSCA Candidate MSC is
33、an MSC which controls cells that could be candidates for receiving a call in case of ahandover.2.3.6 target MSCThe Target MSC is the MSC controlling the cell(s) selected as target(s) for a handover.2.3.7 serving MSCThe Serving MSC is the MSC which handles the call at the moment.2.3.8 old serving MSC
34、The old serving MSC is the MSC which was the serving MSC before a handover, other than MSC-A.Fascicle VI.12 - Rec. Q.1001 73 Architecture of the Public Land Mobile Network3.1 Configuration of a Public Land Mobile Network3.1.1 GeneralFigure 4/Q.1001 presents PLMN entities and the associated signallin
35、g interfaces. The specific implementationin each country (or PLMN, if more than one in each country) may be different; some of the functional entities may becombined in the same equipment and this may result in some interfaces becoming internal. The configuration of aPLMN must in any case have no im
36、pact on the relationship with other PLMNs. Example: PLMN entities and associatedsignalling interfaces are shown in Figure 5/Q.1001. To illustrate some implementation possibilities three examples ofconfigurations are presented in Figures 6/Q.1001, 7/Q.1001 and 8/Q.1001. In addition, it can be mention
37、ed that HLRand VLR can be physically implemented in the same equipment, as an integrated Location Register.3.1.2 Configuration example No. 1 (No co-location of functional entities)This configuration is presented in Figure 6/Q.1001. All functions are implemented in dedicated equipment. Theinterfaces
38、within the PLMN are equipment external and therefore need the support of the Mobile Application Part(MAP) of Signalling System No. 7 to exchange the data necessary to provide the mobile service. All PLMNconfigurations can be deducted from this basic configuration. In instances where some functions a
39、re contained in thesame equipment, the relevant interfaces become equipment internal to that equipment and the use of the MAP is notnecessary. Some examples are given in 3.1.3 and 3.1.4.3.1.3 Configuration example No. 2 (VLR co-located with VMSC)This configuration is presented in Figure 7/Q.1001. Th
40、e Visited Location Register is co-located with orimplemented in the VMSC for the following reasons. The main type of data stored in the VLR is the practical locationinformation (i.e. location area) which has to be updated by the VMSC when the mobile station moves from one locationarea to another. Th
41、e VMSC also has to interrogate the VLR at call set-up in order to know the relevant subscriber data(e.g. restrictions and supplementary services).3.1.4 Configuration example No. 3 (HLR and VLR co-located with a MSC)This configuration is presented in Figure 8/Q.1001. In cases where the HLR is impleme
42、nted in the MSC, thisMSC will become the HMSC for the subscribers managed by the Location Register. The two functions HLR and MSCare not of the same type: the HLR is a pure network data base function, interrogated when needed and the MSC ismainly in charge of call handling. The HMSC performs the cal
43、l handling function for all its subscribers, as defined bytheir allocation to the HLR, when they are located in the HMSC area. Call set-up to mobile stations handled by theHMSC uses only the international mobile subscriber ISDN/PSTN number and no roaming number is allocated to thesemobile stations.3
44、.2 Interconnection between PLMNsAs the configuration of a PLMN does not have any impact on other PLMNs, the specified signalling interfacescan be implemented between entities within a PLMN or between PLMNs, with or without intermediate interfaceequipment providing a gateway function at the applicati
45、on level.A difference in the interface can be found at lower levels (SCCP), since different signalling networks can beinvolved in the exchange of messages and they are at least independent with respect to the signalling network addressingplan.A specific interconnection with a PLMN gateway may be nee
46、ded in cases where the organization andconfiguration of a PLMN does not meet the international specifications. The specific interconnection is used in this caseto mask, from other PLMNs, a national configuration which is not in line with the international specifications.8 Fascicle VI.12 - Rec. Q.100
47、1 Fascicle VI.12 - Rec. Q.1001 9 10 Fascicle VI.12 - Rec. Q.10013.3 PLMN interfaces3.3.1 GeneralThe implementation of the public land mobile service with international roaming and handover implies theexchange of mobile specific signalling information between the equipment involved in the service. Th
48、e introduction ofSignalling System No. 7 and its signalling network will be an opportunity to transfer the data needed to support thePublic Land Mobile Service. Signalling System No. 7 should be used to convey the information, where applicable. Inaddition some parts of the equipment will have signal
49、ling interworking with the fixed network. The descriptions givenbelow are limited to the mobile application. The Mobile Application Part will be supported by the TransactionCapabilities.3.3.2 Interface between MSC and base station (A interface)The exact definition of the interface between a base station and its MSC depends on the division of functionsbetween BS and MSC. Call handling as well as mobile station management may be s
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