1、 ETSI TR 123 924 V15.0.0 (2018-06) 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 15.0.0 Release 15) TECHNICAL REPORT ETSI ETSI TR 12
2、3 924 V15.0.0 (2018-06)13GPP TR 23.924 version 15.0.0 Release 15Reference RTR/TSGS-0223924vf00 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
4、t shall not be modified without the prior written authorization of ETSI. In case of any existing or perceived difference in contents between such versions and/or in print, the only prevailing document is the print of the Portable Document Format (PDF) version kept on a specific network drive within
5、ETSI Secretariat. Users of the present document should be aware that the document may be subject to revision or change of status. Information on the current status of this and other ETSI documents is available at https:/portal.etsi.org/TB/ETSIDeliverableStatus.aspx If you find errors in the present
6、document, please send your comment to one of the following services: https:/portal.etsi.org/People/CommiteeSupportStaff.aspx Copyright Notification No part may be reproduced or utilized in any form or by any means, electronic or mechanical, including photocopying and microfilm except as authorized b
7、y written permission of ETSI. The content of the PDF version shall not be modified without the written authorization of ETSI. The copyright and the foregoing restriction extend to reproduction in all media. ETSI 2018. All rights reserved. DECTTM, PLUGTESTSTM, UMTSTMand the ETSI logo are trademarks o
8、f ETSI registered for the benefit of its Members. 3GPPTM and LTETMare trademarks of ETSI registered for the benefit of its Members and of the 3GPP Organizational Partners. oneM2M logo is protected for the benefit of its Members. GSMand the GSM logo are trademarks registered and owned by the GSM Asso
9、ciation. ETSI ETSI TR 123 924 V15.0.0 (2018-06)23GPP TR 23.924 version 15.0.0 Release 15Intellectual Property Rights Essential patents IPRs essential or potentially essential to normative deliverables may have been declared to ETSI. The information pertaining to these essential IPRs, if any, is publ
10、icly available for ETSI members and non-members, and can be found in ETSI SR 000 314: “Intellectual Property Rights (IPRs); Essential, or potentially Essential, IPRs notified to ETSI in respect of ETSI standards“, which is available from the ETSI Secretariat. Latest updates are available on the ETSI
11、 Web server (https:/ipr.etsi.org/). Pursuant to the ETSI IPR Policy, no investigation, including IPR searches, has been carried out by ETSI. No guarantee can be given as to the existence of other IPRs not referenced in ETSI SR 000 314 (or the updates on the ETSI Web server) which are, or may be, or
12、may become, essential to the present document. Trademarks The present document may include trademarks and/or tradenames which are asserted and/or registered by their owners. ETSI claims no ownership of these except for any which are indicated as being the property of ETSI, and conveys no right to us
13、e or reproduce any trademark and/or tradename. Mention of those trademarks in the present document does not constitute an endorsement by ETSI of products, services or organizations associated with those trademarks. Foreword This Technical Report (TR) has been produced by ETSI 3rd Generation Partners
14、hip Project (3GPP). The present document may refer to technical specifications or reports using their 3GPP identities, UMTS identities or GSM identities. These should be interpreted as being references to the corresponding ETSI deliverables. The cross reference between GSM, UMTS, 3GPP and ETSI ident
15、ities can be found under http:/webapp.etsi.org/key/queryform.asp. Modal verbs terminology In the present document “should“, “should not“, “may“, “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 expres
16、sion of provisions). “must“ and “must not“ are NOT allowed in ETSI deliverables except when used in direct citation. ETSI ETSI TR 123 924 V15.0.0 (2018-06)33GPP TR 23.924 version 15.0.0 Release 15Contents Intellectual Property Rights 2g3Foreword . 2g3Modal verbs terminology 2g3Foreword . 5g3Introduc
17、tion 5g31 Scope 6g32 References 6g33 Definitions, symbols and abbreviations . 6g33.1 Definitions 6g33.2 Abbreviations . 6g34 General Description 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
18、 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 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 substa
19、nce, i.e. technical enhancements, corrections, updates, etc. z the third digit is incremented when editorial only changes have been incorporated 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 23.2
20、36 2 has some issues for MSC Pool with existing deployments and implementations, e.g. upgrade of existing nodes. This TR studies whether these 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
21、23.236 2. ETSI ETSI TR 123 924 V15.0.0 (2018-06)63GPP TR 23.924 version 15.0.0 Release 151 Scope This Technical Report evaluates the feasibility 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. Thi
22、s Technical Report also identifies the impacts on specifications. 2 References The following documents contain provisions which, through reference in this text, constitute provisions of the present document. - References are either specific (identified by date of publication, edition number, version
23、 number, etc.) or non specific. - For a specific reference, subsequent revisions do not apply. - For a non-specific reference, the latest version 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 tha
24、t 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 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
25、Part (RANAP) signalling“. 4 3GPP TS 23.251: “Network sharing; Architecture and functional description“. 5 3GPP TS 48.008: “3GPP TS 48.008: “Mobile Switching Centre - Base Station System (MSC BSS) interface; Layer 3 specification“. 6 ITU-T Recommendation Q.714: “Specifications of Signalling System No
26、. 7 - Signalling connection control part (SCCP): Signalling connection control part procedures“. 3 Definitions, symbols and abbreviations 3.1 Definitions 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 do
27、cument takes precedence over the definition of the same term, if any, in TR 21.905 1. Serving Node Selection Function: A logical function above 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 Abbreviati
28、ons 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 defined 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 Ident
29、ifier SNSF Serving Node Selection Function ETSI ETSI TR 123 924 V15.0.0 (2018-06)73GPP TR 23.924 version 15.0.0 Release 154 General Description 4.1 Architecture Assumptions Figure 4.1-1 illustrates the set of network elements related to deploying the SNSF node for MSC Pool. uni0049uni0075uni002Duni0
30、043uni0053Figure 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 with the MSC Servers for control plane. As implementation options, SNSF node is a logical function; it may be standalone
31、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 pool illustrated in clause 4.2 and to avoid any potential update requirement on existing BSC/RNC equipments, the A/Iu-CS inte
32、rface 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 deployment issues have been identified relative to the deployment of the MSC Pool feature as specified in TS 23.236 2. Such issu
33、es 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 feature In certain networks, most of the existing BSC/RNC nodes do not support the feature, and it is not easy to update them t
34、o 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. Therefore the advantage of deploying MSC Pool can not be fully exploited within certain networks. ETSI ETSI TR 123 924 V15.0.0 (2
35、018-06)83GPP TR 23.924 version 15.0.0 Release 15Figure 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 stations moving with
36、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 required as if no MS
37、C 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. Very little advantage
38、s 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 supported by the existi
39、ng 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 feature enabled BSC wil
40、l 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. uni0050uni006Funi006Funi006Cuni0020uni0041uni0072uni0065uni0061uni004Duni0053uni0053 uni0031uni004Duni0053uni0053 uni0032uni004Duni
41、0053uni0053 uni0033uni0042uni0053uni0043uni0020uni0031uni0042uni0053uni0043uni0020uni0033uni0042uni0053uni0043uni0020uni0032Figure 4.2.1.2.1: BSC/RNC connects to each MSS in the pool area That is, the mesh TDM circuit connections between BSC with MSC Servers will be required because each BSC is need
42、ed to be able to connect to each MSC server in the pool area, and it will be extremely hard to implement as the ETSI ETSI TR 123 924 V15.0.0 (2018-06)93GPP TR 23.924 version 15.0.0 Release 15POOL scale increases. When adding a new MSC into the pool area, the TDM circuit connection between all the BS
43、Cs 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 MGWs between BSCs and MSC servers, but the TDM circuit configura
44、tion 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-used for the pair BSC 1 and MSC 2. Thus, the usage of the TDM circu
45、its (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 to be re-installed (either by re-planing the TDM circuit configur
46、ation 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). uni0050uni006Funi006Funi006Cuni0020uni0041uni0072uni0065uni0061uni004Duni0053uni0053uni0020uni0031uni004Duni0053uni0053uni0020uni0032uni004
47、2uni0053uni0043uni0020uni0031Virtual MGW 1 Virtual MGW 2uni0042uni0053uni0043uni0020uni0032McFigure 4.2.1.2.2: MGW between BSCs and MSC servers used as intermediary node But if each BSC/RNC only connects with one or two intermediary nodes, thus keeping the number of intermediary nodes small, it will
48、 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 intermediate nodes for the control plane. Figure 4.2.1.2.3: BSC and MSS connect to a single intermediary node Furthermore, if the TDM c
49、ircuits 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 intermediary node and BSC nodes as normal resources and managed by the intermediary node itself. ETSI ETSI TR 123 924 V15.0.0 (2018-06)103GPP TR 23.924 version 15.0.0 Release 154.2.1.3 Complex O as such, SGSN Pool is considered as being out of the scope of this feasibility study. 4.3 Load Balancing The Serving Node Selection Function balances the signalling load between the av
