1、 ETSI TR 123 924 V14.0.0 (2017-05) Universal Mobile Telecommunications System (UMTS); Feasibility study on Non-Access Stratum (NAS) node selection function above Base Station Controller (BSC) / Radio Network Controller (RNC) (3GPP TR 23.924 version 14.0.0 Release 14) TECHNICAL REPORT ETSI ETSI TR 12
2、3 924 V14.0.0 (2017-05)13GPP TR 23.924 version 14.0.0 Release 14Reference RTR/TSGS-0223924ve00 Keywords UMTS ETSI 650 Route des Lucioles F-06921 Sophia Antipolis Cedex - FRANCE Tel.: +33 4 92 94 42 00 Fax: +33 4 93 65 47 16 Siret N 348 623 562 00017 - NAF 742 C Association but non lucratif enregistr
3、e la Sous-Prfecture de Grasse (06) N 7803/88 Important notice The present document can be downloaded from: http:/www.etsi.org/standards-search The present document may be made available in electronic versions and/or in print. The content of any electronic and/or print versions of the present documen
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12、which are, or may be, or may become, essential to the present document. Foreword This Technical Report (TR) has been produced by ETSI 3rd Generation Partnership Project (3GPP). The present document may refer to technical specifications or reports using their 3GPP identities, UMTS identities or GSM i
13、dentities. These should be interpreted as being references to the corresponding ETSI deliverables. The cross reference between GSM, UMTS, 3GPP and ETSI identities can be found under http:/webapp.etsi.org/key/queryform.asp. Modal verbs terminology In the present document “should“, “should not“, “may“
14、, “need not“, “will“, “will not“, “can“ and “cannot“ are to be interpreted as described in clause 3.2 of the ETSI Drafting Rules (Verbal forms for the expression of provisions). “must“ and “must not“ are NOT allowed in ETSI deliverables except when used in direct citation. ETSI ETSI TR 123 924 V14.0
15、.0 (2017-05)33GPP TR 23.924 version 14.0.0 Release 14Contents Intellectual Property Rights 2g3Foreword . 2g3Modal verbs terminology 2g3Foreword . 5g3Introduction 5g31 Scope 6g32 References 6g33 Definitions, symbols and abbreviations . 6g33.1 Definitions 6g33.2 Abbreviations . 6g34 General Descriptio
16、n 7g34.1 Architecture Assumptions 7g34.2 Overview 7g34.2.1 Issues with deploying NNSF in BSC nodes for MSC pool. 7g34.2.1.1 In certain networks some existing BSC/RNC nodes do not support the feature . 7g34.2.1.2 Mesh TDM circuit connection between BSCs with MSCs is required . 8g34.2.1.3 Complex O 2
17、presented to TSG for approval; 3 or greater indicates TSG approved document under change control. y the second digit is incremented for all changes of substance, i.e. technical enhancements, corrections, updates, etc. z the third digit is incremented when editorial only changes have been incorporate
18、d in the document. Introduction The solution for support of the Intra Domain Connection of RAN Nodes to Multiple CN Nodes for GSM and UMTS systems in TS 23.236 2 has some issues for MSC Pool with existing deployments and implementations, e.g. upgrade of existing nodes. This TR studies whether these
19、issues can be resolved by deploying a function above the BSC/RNC nodes which provides similar functions as the NNSF in BSC/RNC nodes that is specified in TS 23.236 2. ETSI ETSI TR 123 924 V14.0.0 (2017-05)63GPP TR 23.924 version 14.0.0 Release 141 Scope This Technical Report evaluates the feasibilit
20、y of implementing a function above the BSC/RNC nodes to provide similar functions as the NNSF function in BSC/RNC nodes that is specified in TS 23.236 2. This Technical Report also identifies the impacts on specifications. 2 References The following documents contain provisions which, through refere
21、nce in this text, constitute provisions of the present document. - References are either specific (identified by date of publication, edition number, version number, etc.) or non specific. - For a specific reference, subsequent revisions do not apply. - For a non-specific reference, the latest versi
22、on applies. In the case of a reference to a 3GPP document (including a GSM document), a non-specific reference implicitly refers to the latest version of that document in the same Release as the present document. 1 3GPP TR 21.905: “Vocabulary for 3GPP Specifications“. 2 3GPP TS 23.236: “Intra-domain
23、 connection of Radio Access Network (RAN) nodes to multiple Core Network (CN) nodes“. 3 3GPP TS 25.413: “UTRAN Iu interface Radio Access Network Application Part (RANAP) signalling“. 4 3GPP TS 23.251: “Network sharing; Architecture and functional description“. 5 3GPP TS 48.008: “3GPP TS 48.008: “Mob
24、ile Switching Centre - Base Station System (MSC BSS) interface; Layer 3 specification“. 6 ITU-T Recommendation Q.714: “Specifications of Signalling System No. 7 - Signalling connection control part (SCCP): Signalling connection control part procedures“. 3 Definitions, symbols and abbreviations 3.1 D
25、efinitions For the purposes of the present document, the terms and definitions given in TR 21.905 1 and the following apply. A term defined in the present document takes precedence over the definition of the same term, if any, in TR 21.905 1. Serving Node Selection Function: A logical function above
26、 the BSC/RNC nodes used to assign an MSC Server to serve a mobile station and subsequently route the traffic to the assigned network resource. 3.2 Abbreviations For the purposes of the present document, the terms and definitions given in TR 21.905 1 and TS 23.236 2 and the following apply. A term de
27、fined in the present document takes precedence over the definition of the same term, if any, in TR 21.905 1 and TS 23.236 2. SNRI SCCP Network Resource Identifier SNSF Serving Node Selection Function ETSI ETSI TR 123 924 V14.0.0 (2017-05)73GPP TR 23.924 version 14.0.0 Release 144 General Description
28、 4.1 Architecture Assumptions Figure 4.1-1 illustrates the set of network elements related to deploying the SNSF node for MSC Pool. Figure 4.1-1: Network Architecture of deploying SNSF node for MSC Pool Serving Node Selection Function is a newly introduced function which is between the BSC/RNC nodes
29、 with the MSC Servers for control plane. As implementation options, SNSF node is a logical function; it may be standalone or co-located with existing nodes. See clause 5.6 for the detail of the SNSF processing. To resolve the issues identified from deploying NNSF within the BSC/RNC nodes for MSC poo
30、l illustrated in clause 4.2 and to avoid any potential update requirement on existing BSC/RNC equipments, the A/Iu-CS interface is used between BSC/RNC with SNSF. 4.2 Overview 4.2.1 Issues with deploying NNSF in BSC nodes for MSC pool In certain networks and with certain implementations, some deploy
31、ment issues have been identified relative to the deployment of the MSC Pool feature as specified in TS 23.236 2. Such issues associated with deploying NNSF in BSC/RNC for MSC pool are described in the following clauses. 4.2.1.1 In certain networks some existing BSC/RNC nodes do not support the featu
32、re In certain networks, most of the existing BSC/RNC nodes do not support the feature, and it is not easy to update them to support the feature and to be maintained in the future. New BSC/RNC nodes can be required to support the function, but some of the existing BSC/RNC can not be upgraded. Therefo
33、re the advantage of deploying MSC Pool can not be fully exploited within certain networks. ETSI ETSI TR 123 924 V14.0.0 (2017-05)83GPP TR 23.924 version 14.0.0 Release 14MSSMSSMSSBSC/RNCBSC/RNCBSC/RNCBSC/RNCBSC/RNCBSC/RNCBSC/RNCBSC/RNCBSC/RNCBSC/RNCBSC/RNCMSC Pool feature is supported by the BSC/RNC
34、 equipmentMSC Pool feature is not supported by the BSC/RNC equipmentFigure 4.2.1.1.1: Part of BSC/RNC nodes support connecting to multiple MSS In the real-world example provided in Figure 4.2.1.1.1, nine BSC/RNC nodes do not support MSC Pool feature while two other ones support it. Only for mobile s
35、tations moving with the coverage of the 2 BSC/RNC nodes, which support NNSF and where the NNSF function is enabled, the interaction between MSC servers and HLR and inter-MSC handover are reduced, while moving to the coverage of any other BSC/RNC nodes, the interaction and the handover will still be
36、required as if no MSC Pool feature is deployed. And when MS is in the coverage of one of the other 9 BSC/RNC nodes that do not support NNSF, only one MSC server that the BSC/RNC node connects to can serve for the subscriber, thus the resources of the MSC servers in this pool area cannot be shared. V
37、ery little advantages could be seen from the feature in such a network configuration. 4.2.1.2 Mesh TDM circuit connection between BSCs with MSCs is required While deployment of AoIP (A interface bearer over IP) removes the mesh TDM connection of BSC nodes with MSC nodes, only TDM connections are sup
38、ported by the existing BSC, and not all the existing BSC nodes can be updated to IP mode. The mesh TDM circuit connection between BSC nodes with MSC nodes is still a deployment issue in the absence of AoIP, and is described in this clause. If the MSC Pool feature is deployed per TS 23.236 2, the fea
39、ture enabled BSC will be required to have signaling and bearer connection with all the MSCs in the pool area. Figure 4.2.1.2.1 shows the mesh connection between 3 BSC/RNC nodes and 3 MSCs. Figure 4.2.1.2.1: BSC/RNC connects to each MSS in the pool area ETSI ETSI TR 123 924 V14.0.0 (2017-05)93GPP TR
40、23.924 version 14.0.0 Release 14That is, the mesh TDM circuit connections between BSC with MSC Servers will be required because each BSC is needed to be able to connect to each MSC server in the pool area, and it will be extremely hard to implement as the POOL scale increases. When adding a new MSC
41、into the pool area, the TDM circuit connection between all the BSCs with the new MSC must be installed (either by re-planing the TDM circuits between the BSCs with the MSCs or installing new circuits between the BSCs with the new MSC). A physical mesh connection can be avoided by introducing virtual
42、 MGWs between BSCs and MSC servers, but the TDM circuit configuration between each pair of BSC and MSC is still required as shown in Figure 4.2.1.2.2. The TDM circuits between each pair of BSC and MSC can not be used by any other pair, e.g. circuits used for the pair BSC 1 and MSC 1 can not be re-us
43、ed for the pair BSC 1 and MSC 2. Thus, the usage of the TDM circuits (specifically, the circuits in each BSC virtual MGW pair) is limited by configuration. Any changes in the core network (e.g. adding a new MSC into the pool area) will require the TDM circuits between the BSCs with the virtual MGWs
44、to be re-installed (either by re-planing the TDM circuit configuration between the BSCs with the virtual MGWs or by installing new TDM circuits, i.e. adding new TDM circuits between BSCs with the virtual MGW for the new MSC). Figure 4.2.1.2.2: MGW between BSCs and MSC servers used as intermediary no
45、de But if each BSC/RNC only connects with one or two intermediary nodes, thus keeping the number of intermediary nodes small, it will mitigate the abovementioned need as shown in figure 4.2.1.2.3 that illustrates just a single intermediary node See clause 4.9.1 for BSC/RNC is connected to several in
46、termediate nodes for the control plane. Figure 4.2.1.2.3: BSC and MSS connect to a single intermediary node Furthermore, if the TDM circuits are reused between each pair of BSC and MSC, the likelihood of circuit exhaust will be much less, for example by means of managing the TDM circuits between the
47、 intermediary node and BSC nodes as normal resources and managed by the intermediary node itself. ETSI ETSI TR 123 924 V14.0.0 (2017-05)103GPP TR 23.924 version 14.0.0 Release 144.2.1.3 Complex O as such, SGSN Pool is considered as being out of the scope of this feasibility study. 4.3 Load Balancing
48、 The Serving Node Selection Function balances the signalling load between the available MSC Servers same as specified in clause 4.5 of TS 23.236 2. The load-balancing algorithm is implementation specific. 4.4 Load Re-Distribution Signalling load re-distribution shall be performed as the procedures d
49、efined in clause 4.5a.1 of TS 23.236 2 that the Serving Node Selection Function performs the same as the NAS Node Selection Function. 4.5 Mobility Management No impacts upon mobility management result from the deployment of SNSF. See clause 4.6 of TS 23.236 2. 4.6 Default CN node No impacts to the default CN node concept result from the deployment of SNSF. See clause 4.7 of TS 23.236 2. 4.7 Support of combined mobility management procedures No impacts to the support of combined mobility management procedures result from the deployme
