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기술보고서
TTA Technical Report
TTAR-xx.xxxx
개정일: 20xx년 xx월 xx일
3GPP 이종망 연동 기술 표준
분석(기술보고서)
3GPP Standardization Status for Interoperability with other RATs(Technical
Report)
기술보고서
TTAR-xx.xxxx
개정일: 201x년 xx월 xx일
3GPP 이종망 연동 기술 표준 기술
분석(기술보고서)
3GPP Standardization Status for Inter-operability
with other RATs (Technical Report)
본 문서에 대한 저작권은 TTA 에 있으며, TTA 와 사전 협의 없이 이 문서의 전체 또는 일부를
상업적 목적으로 복제 또는 배포해서는 안 됩니다.
Copyrightⓒ Telecommunications Technology Association YYYY. All Rights Reserved.
기술보고서
서 문
1. 기술보고서의 목적
무선
데이터
수요
증가에
따라
WLAN
기술을
이용한
데이터
분석
기술과
heterogeneous network 운용을 위한 3GPP 내 이종망 연동에 대한 표준 논의가 활발히
진행되고 있는 바, 본 기술보고서는 이에 대한 기술 및 표준 동향을 분석하여 제시한다.
본 기술보고서는 앞으로의 3GPP LTE/LTE-A 망과 WLAN 등의 이종망 간 연동의 국제
표준 및 시장 동향을 예측하고 대응하기 위한 참고 문서로 활용될 것이다.
2. 주요 내용 요약
본 기술보고서는 3GPP TSG SA, RAN 등에서 Release 6 이후 현재까지 논의되고 있는
3GPP 망과 WLAN 등의 이종망과의 연동에 관한 표준 진행 상황을 검토하고, 3GPP이종망간 심리스 핸드오버, 트래픽 스티어링 기술에 관한 표준과 표준안을 분석한다.
3. 기술보고서 적용 산업 분야 및 산업에 미치는 영향
LTE 네트워크와 WLAN 등의 네트워크들 간의 심리스 핸드오버 서비스를 제공
가능하게
함으로써
이용자들에게는
사용자
경험
환경의
품질을
높이고
네트워크
사업자에게는 무선 네트워크 자원을 효율적으로 관리 운용하여 경쟁력을 높일 수 있다.
4. 참조 표준(권고)
4.1. 국외 표준(권고)
- 해당 사항 없음.
4.2. 국내 표준
- 해당 사항 없음.
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5. 참조 표준(권고)과의 비교
5.1. 참조 표준(권고)과의 관련성
- 해당 사항 없음.
5.2. 참조한 표준(권고)과 본 표준의 비교표
- 해당 사항 없음.
6. 지식 재산권 관련 사항
본 기술보고서의 ‘지식 재산권 확약서’ 제출 현황은 TTA 웹사이트에서 확인할 수 있다.
※ 본 기술보고서를 이용하는 자는 이용함에 있어 지식 재산권이 포함되어 있을 수
있으므로, 확인 후 이용한다.
※ 본 기술보고서와 관련하여 접수된 확약서 이외에도 지식 재산권이 존재할 수 있다.
7. 시험 인증 관련 사항
7.1. 시험 인증 대상 여부
- 해당 사항 없음.
7.2. 시험 표준 제정 현황
- 해당 사항 없음.
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기술보고서
8. 기술보고서의 이력 정보
8.1. 기술보고서의 이력
판수
제정개정일
제1판
20014.xx.xx.
제정개정내역
제정
TTAR.xx-xx.xxxx
8.2. 주요 개정 사항
- 해당 사항 없음.
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기술보고서
Preface
1. Purpose of Technical Report
The purpose of this Technical Report provides the technologies and standardization
status considering the active discussions in 3GPP for the interworking with WLAN for
better resource utilization between 3GPP and WLAN access. This report is expected to
be a reference for forecasting the trends of global standards and markets on the
interworking between 3GPP LTE/LTE-A and WLAN.
2. Summary of Contents
This Technical Report introduces the standardization status of 3GPP TSGs (SA and
RAN) on the 3GPP-WLAN interworking. This report also analyzes the technologies of
seamless handover and traffic steering between 3GPP and WLAN access networks
based on the standards and draft documents.
3. Applicable Fields of Industry and its Effect
This technical report will provide mobile subscribers with the seamless handover
between the 4th generation mobile network like LTE/LTE-A and WLAN to enhance the
performance experience. This will also provide mobile network operators with the
efficient network resource utilization to increase the competiveness in the market.
4. Reference Standards(Recommendations)
4.1. International Standards(Recommendations)
- None
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기술보고서
4.2. Domestic Standards
- None
5. Relationship to Reference Standards(Recommendations)
5.1. Relationship of Reference Standards
- None
5.2. Differences between Reference Standard(Recommendation) and this Technical
Report
- None
6. Statement of Intellectual Property Rights
IPRs related to the present document may have been declared to TTA. The
information pertaining to these IPRs, if any, is available on the TTA Website.
No guarantee can be given as to the existence of other IPRs not referenced on the
TTA website.
And, please make sure to check before applying the technical report.
7. Statement of Testing and Certification
7.1. Object of Testing and Certification
- None
7.2. Standards of Testing and Certification
- None
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8. History of Technical Report
8.1. Change History
Edition
Issued date
The 1st edition
2014.xx.xx
Outline
Established
TTAx.xx-xx.xxxx
8.2. Revisions
- None
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기술보고서
목 차
1. 개 요 ........................................................................................................... 1
2. 기술보고서의 구성 및 범위 ............................................................................. 1
3. 참조 표준(권고) ............................................................................................. 1
4. 용어 정의 및 약어 ......................................................................................... 2
5. 3GPP 이종망 연동 표준 기술 .......................................................................... 3
5.1. Release 6 ............................................................................................. 3
5.2. Release 8 ............................................................................................. 5
5.3. Release 10 ........................................................................................... 7
5.4. Release 11 ......................................................................................... 10
5.5. Release 12 ......................................................................................... 11
5.6. Release 13 ......................................................................................... 13
6. 결론 .......................................................................................................... 14
부록 I. 참고 문헌 ............................................................................................ 16
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기술보고서
Contents
1. Introduction .................................................................................................. 1
2. Constitution and Scope .................................................................................. 1
3. Reference Standards .................................................................................... 1
4. Terms and Definitions, Abbreviations ................................................................ 2
5. 3GPP Standardization Status for Inter-operability with other RATs ........................ 3
5.1. Release 6 ............................................................................................... 3
5.2. Release 8 ............................................................................................... 5
5.3. Release 10 ............................................................................................. 7
5.4. Release 11 ........................................................................................... 10
5.5. Release 12 ........................................................................................... 11
5.6. Release 13 ........................................................................................... 13
6. Conclusion ................................................................................................. 14
Appendix I. References .................................................................................... 16
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기술보고서
3GPP 이종망 연동 기술 표준 분석(기술보고서)
(3GPP Standardization Status for Inter-operability with other
RATs(Technical Report))
1. Introduction
Since the amount of traffic carried over wireless network has grown dramatically in
recent years, WLAN can be an important tool for wireless carriers to meet the capacity
demands of their mobile data users. So, for most operators with the dedicated carriers,
WLAN is considered as an integral part of their mobile-broadband strategy. 3GPP
defines I-WLAN(Interworking WLAN) functionality which provides the utilization of
resources and access to services within the 3GPP system. The 3GPP-WLAN
interworking is intended to extend 3GPP services and functionality to the WLAN access
environment to make the WLAN effective complementary radio access technology to
the 3GPP system. Starting with TR 22.934 of TSG-SA WG1, 3GPP defines the
architecture and related functionalities to be able to provide 3GPP services through
WLAN access. In Release 8, seamless handover and service continuity between 3GPP
access and WLAN were defined. After Release 10, more evolved technologies to
support WLAN in 3GPP network have been introduced. This Technical Report has the
purpose of providing the technologies and standardization status considering the active
discussions in 3GPP and WLAN interworking. This Technical Report is expected to a
reference to develop global standards and lead the markets on the interworking
between 3GPP LTE/LTE-A and WLAN.
2. Constitution and Scope
This Technical Report introduces the standardization status from 3GPP Release 6 to
Release 13 on the 3GPP-WLAN interworking. This report includes the technologies of
seamless handover and traffic steering between 3GPP and WLAN access based on the
standards and draft documents.
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3. Reference Standards
- None
4. Terms and Definitions, Abbreviations
4.1. Terms and Definitions
4.1.1. Evolved Packet System
An evolution of the 3G UMTS characterized by higher-data-rate, lower-latency,
packet-optimized system that supports multiple RATs, comprising the Evolved
Packet Core together with the evolved radio access network(E-UTRA and EUTRAN)
4.1.2. Interworking WLAN(I-WLAN)
WLAN that interworks with a 3GPP system
4.1.3. 3GPP-WLAN Interworking
Interworking between the 3GPP system and the WLAN family of standards
4.2 Abbreviations
ANDSF
Access Network Discovery and Selection Function
ANQP
Access Network Query Protocol
APN
Access Point Name
CS
Circuit Switched
DM
Device Management
DSMIPv6
Dual-Stack Mobile IPv6
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EAP
Extensible Authentication Protocol
EPS
Evolved Packet System
FMC
Fixed-Mobile Convergence
GAS
Generic Advertisement Service
GPRS
General Packet Radio Service
GSM
Global System for Mobile communications
GTP
GPRS Tunneling Protocol
HA
Home Agent
HPLMN
Home PLMN
IARP
Inter-APN Routing Policy
IFOM
IP Flow Mobility
IP
Internet Protocol
IP-CAN
IP Connectivity Access Network
ISMP
Inter-System Mobility Policy
ISRP
Inter-System Routing Policy
I-WLAN
Interworking WLAN
MAPCON
Multi Access PDN Connectivity
MAPIM
Multi Access PDN connectivity and IP flow Mobility
MO
Management Object
NSWO
Non-Seamless WLAN Offload
OMA
Open Mobile Alliance
PCRF
Policy and Charging Rules Function
PDN
Packet Data Network
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PLMN
Public Land Mobile Network
PMIP
Proxy Mobile IPv6
PS
Packet Switched
PSPL
Preferred Service Provider List
RAT
Radio Access Technology
SaMOG
S2a Mobility based on GTP
SMOG
S2b Mobility based on GTP
TFT
Traffic Flow Template
TSG-RAN
Technical Specification Group – Radio Access Network
TSG-SA
Technical Specification Group – Service & Systems Aspects
UMTS
Universal Mobile Telecommunications System
UTRAN
Universal Terrestrial Radio Access Network
VoIP
Voice over IP
VPLMN
Visited PLMN
WFA
Wi-Fi Alliance
WLAN
Wireless Local Area Network
WLANSP
WLAN Selection Policy
WORM
Optimized Offloading to WLAN in 3GPP-RAT Mobility
WPA2
Wi-Fi Protected Access v2
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기술보고서
5. 3GPP Standardization Status for Inter-operability with other RATs
5.1. Release 6
5.1.1. WLAN-UMTS Interworking
The feasibility document TR 22.934 includes a number of different scenarios of
3GPP-WLAN interworking ranging from common billing to the provision of services
seamlessly between the WLAN and the 3GPP system, referred as Scenarios 1 to 6 [1].
 Scenario 1: Common Billing, Common Customer Care
 Scenario 2: System based Access Control, 3GPP System based Access
Charging
 Scenario 3: Access to 3GPP System PS based Services from WLAN
 Scenario 4: Service Continuity
 Scenario 5: Seamless Service Continuity
 Scenario 6: Access to 3GPP System CS based Services with seamless mobility
The stage 1 in TS 22.234 takes the conclusions of the feasibility study and defines
the high level requirements for I-WLAN. The global architecture provided in TS 22.234
is shown as below:
3GPP Home Network
Ww
Wn
D'
HLR
r'
/G
Wo
Wm
WAG
Offline
Charging
System
Wf
OCS
Wz
3GPP AAA
Server
Wg
WLAN Access Network
Wx
Dw
Wa
WLAN
UE
HSS
SLF
Wy
Intranet / Internet
Wp
PDG
Wi
WLAN 3GPP IP Access
Wu
(Figure 5-1) Non-roaming reference model [2]
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기술보고서
As shown in the figure, Release 6 addresses different possibilities of interconnection
with the internet. Scenario 1 refers to a pure commercial agreement between a "WLAN
operator" and a UMTS operator, so that the user pays one single bill and does not need
to subscribe to two different contracts. Scenario 2 refers to the case where the internet
is accessed directly from the WLAN, i.e. the WLAN is seen as a parallel system to the
3GPP. Scenario 3 refers to the case where the actual bearer connection is supported
by the UMTS Core Network and the WLAN is used instead of the UTRAN. Stage 3
protocol description defines several reference points for the WLAN-3GPP interworking:
Dw, Wa, Wd, Wx, Wm, Wg, Pr.
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기술보고서
5.2. Release 8
5.2.1. I-WLAN Network Selection Principle
The growth of public WLANs provides an opportunity for appropriately-equipped UEs
to access HPLMNs and VPLMNs via the WLANs. The WLANs that provide this
functionality are referred to as I-WLANs. TSG-SA WG1 aligned the requirements for the
selection of I-WLAN access in TS 22.234 to the ones applicable to PLMN network
selection in TS 22.011.
 Automatic PLMN selection procedure by WLAN UE
 Manual PLMN Selection Mode Procedure by WLAN UE
 Operator management of network preferences for I-WLAN
(Figure 5-2) Interworking Model
5.2.2. Mobility between 3GPP-WLAN Interworking and 3GPP Systems
TS 23.234 provides the possibility to offer access to IP services via WLAN by
interworking with Release 6 3GPP systems [3]. As defined in Release 6 TR 22.934,
service continuity(scenario 4) and seamless services(scenario 5) at a change of the
access network(between I-WLAN and GPRS) are desirable enhancements to improve
the user experience. The work was based on architectural/functional/procedural
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기술보고서
definitions described in TS 23.234(3GPP system to WLAN interworking; System
description) and TS 23.060(GPRS; Service description; Stage 2).
New TSG-SA WG2 TS 23.327 specifies the stage 2 system descriptions for providing
mobility between 3GPP Wireless Local Area Network Interworking(I-WLAN) and 3GPP
Systems [4]. It defines a technical solution based on the working principles of DSMIPv6 with necessary enhancement of the I-WLAN architecture for supporting mobility
and roaming between 3GPP WLAN Interworking system and 3GPP Systems so that
ongoing 3GPP PS based services can be maintained with minimal impact on the end
user's perceived quality on the services at a change of the access network between IWLAN and 3GPP Access Systems.
TS 23.327 includes both non roaming and roaming scenarios and covers all aspects,
including mobility between 3GPP Systems and I-WLAN with access authentication and
charging.
5.2.3. Service continuity between mobile and WLAN networks
For Fixed-Mobile Convergence(FMC), some scenarios require seamless roaming
between GSM/GPRS/3G mobile and WLAN networks. Both networks may independently
be authenticated. To maintain the quality of the customer experience and due to the
difference of networks, handovers to support service continuity may require that the
handset is authenticated to both networks simultaneously, for relatively short periods of
time.
One use case is where the user, on the way to office, is having a call on a 3GPP
access network using the mobile phone. Roaming onto the office WLAN(and vice
versa), while still being on the line and the call is transferred without the user noticing
any interruption to the network served by the WLAN.
The study proposes requirements while roaming between a GSM/GPRS/3G mobile
network and a WLAN network for:
 seamless roaming and service continuity;
 maintaining service quality and service continuity;
 charging;
 security, in particular when networks may be independently authenticated.
TR 22.937 developed use cases and requirements for service continuity between a
3GPP network and another network [5].
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5.2.4. Access Network Discovery and Selection Function(ANDSF)
3GPP IP Access or
Trusted/Untrusted
Non-3GPP IP
Access
UE
S14
H-ANDSF
(Figure 5-3) Non-Roaming Architecture for Access Network Discovery Support Functions
ANDSF is the data management and control functionality to provide network
discovery and selection assistance data per operators’ policy. The ANDSF responds to
UE requests for network discovery information(pull mode operation) and may initiate
data transfer to the UE(push mode operation), based on network triggers or as a result
of previous communication with the UE.
The Management Object(MO) consists of relevant parameters for intersystem mobility
policy and access network discovery information that can be managed by the ANDSF
[6]. The MO is compatible with the OMA Device Management(DM) protocol
specification. The ANDSF MO is used to manage Inter-System Mobility Policy(ISMP),
Inter-System
Routing
Policy(ISRP),
Inter-APN
Routing
Policy(IARP),
RuleSelectionInformation and WLAN Selection Policy(WLANSP) as well as access
network discovery information stored in a UE supporting provisioning of such
information from an ANDSF. In addition, the ANDSF MO is also used to manage the
HomeOperatorPreference Policy stored in a UE supporting provisioning of Preferred
Service Provider List(PSPL) and S2a Connectivity Preference information from an
ANDSF.

Access network discovery information: information to help the UE to discover
networks in its surrounding area(e.g. network type, radio frequency, channel)

Inter-System Mobility Policy(ISMP): if the UE can route IP traffic over a single
radio network, the ISMP indicates which is the preferred access network(e.g.
3GPP, Wi-Fi, etc)

Inter-System Routing Policy(ISRP): it contains indication on traffic distribution
for UEs that are configured for IFOM, MAPCON or non-seamless WLAN offload.

UE location information
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5.3. Release 10
5.3.1. IP Flow Mobility and seamless WLAN offload(IFOM)
It is triggered by TR 23.861(Study on Multi Access PDN connectivity and IP flow
mobility – MAPIM) [7].
When the subscriber happens to be under WLAN coverage, it is beneficial for the
operator to offload some traffic(e.g. best effort) to the WLAN access. At the same time
it may be beneficial to still keep some traffic(e.g. VoIP flow) in the cellular access. With
this IP flow mobility solution the operator can lower it data access costs while the
subscriber just experiences maximized bandwidth without any service disruption or
interruption. It is therefore of interest to 3GPP community to specify a solution for
operators for a seamless WLAN offload via IP flow mobility. Based on this solution,
operators can use WLAN as a seamless extension of their cellular access and thus
increase the overall system capacity while minimizing the access cost. Service
requirements for IP Flow Mobility are partially documented in TS 22.278 [8].
In stage 2, this work item specifies a mechanism for a UE to simultaneously connect
to a 3GPP access and WLAN and transmit/receive traffic belonging to different IP flows
through different accesses. The mechanism enables both seamless and non-seamless
IP flow mobility between a 3GPP access and WLAN. Seamless offload indicates the
capability to seamlessly move one or more selected IP flows from a 3GPP network to
WLAN(and vice-versa) while providing IP session continuity. Seamless offload is based
on DSMIPv6. Non-seamless offload indicates the possibility to exchange the traffic of
one or more selected IP flows using WLAN IP address(referred also as Direct IP Access
in I-WLAN) without providing any IP session continuity.
In stage 3, the work item enhances the specification to define the followings:

Required procedures in UE to initiate and manage IP flows simultaneously
connected to a 3GPP access and WLAN access;

Extensions to S2c and H1 interfaces enabling the UE to indicate to the HA how
IP flows should be distributed between a 3GPP access and WLAN access.

Extensions to Gx, Rx and S9 interfaces to enable PCRF to cope with the
management of multiple simultaneous connections for a single IP CAN session.

Extensions to ANDSF Management Object(ANDSF MO) required to allow the
operator to influence(through downloaded policies) how and what and which IP
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flows are routed between 3GPP access and WLAN access. This includes the
possibility to indicate which IP flows and PDN connections(e.g. per APN) are
required to be seamlessly offloaded and under what conditions and situations
driven by the downloaded policies, and which are required to be nonseamlessly offloaded.

Required UE actions and procedures based on policies provided by ANDSF,
both in the case of non-roaming and in the case of roaming. The UE may
receive policies and indications from multiple ANDSFs: a method to resolve
possible conflicts and order or precedence of policies is expected to be
defined.

UE or HA behavior in case of abnormal or exceptional conditions are
encountered when performing IP flow mobility, if abnormal or exceptional
conditions are identified.
(Figure 5-4) and(Figure 5-5) show the baseline architecture reference model for
multi access PDN connectivity and IP flow mobility when EPS is deployed in the nonroaming case.
HSS
SWx
S6a
PCRF
Rx
Gxc
Gx
Operator's IP
Services (e.g.
IMS, PSS, etc.)
SGi
3GPP
Access
Serving
Gateway
S5
PDN
Gateway
S6b
Gxb
SWm
3GPP AAA
Server
ePDG
HPLMN
SWn
Non-3GPP
Networks
Gxa
Untrusted
Non-3GPP IP
Access
Trusted
Non-3GPP IP
Access
S2c
S2c
UE
SWa
STa
S2c
(Figure 5-4) Non-Roaming Architecture within EPS using S5, S2c
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HSS
SWx
S6a
PCRF
Gxc
Rx
Gx
SGi
3GPP
Access
Serving
Gateway
PDN
Gateway
Operator's IP
Services (e.g.
IMS, PSS, etc.)
S5
S6b
S2b
Gxb
SWm
3GPP AAA
Server
ePDG
S2a
SWn
HPLMN
Non-3GPP
Networks
Trusted
WLAN Access
Network
SWw
SWu
Untrusted
WLAN Access
Network
SWa
STa
UE
UE
(Figure 5-5) Non-Roaming Architecture within EPS using S5, S2a, S2b
5.3.2. S2b Mobility based on GTP(SMOG)
Network-based mobility between E-UTRAN and untrusted non-3GPP accesses is
provided by the S2b interface defined by TS 23.402 [9]. This interface is based on
PMIPv6. With real EPS deployments approaching the time to be going live, it is now
recognized it will be beneficial to also allow a GTP option for S2b network based
mobility as this would simplify the architecture and operations of EPS networks
supporting 3GPP and non-3GPP accesses by using a single mobility protocol. The
objective of this work item is to add an S2b based on GTP option according to the
conclusions of the feasibility study [10].
It is proposed to apply to the S2b interface the following GTP bearer model. For
untrusted non-3GPP access to the EPC the PDN connectivity service is provided by
IPsec connectivity between the WLAN UE and the ePDG concatenated with bearer(s)
for GTP-based S2b.
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WLAN
UEs
SWu
S2b
ePDG
IPSec
GTP Tunnel
GTP Tunnel
IPSec
GTP Tunnel
GTP Tunnel
GTP Tunnel
UL TFT
PGW
DL TFT
One-to-several mapping between one IPSec tunnel and
multiple GTP bearers (Default and dedicated bearers)
(Figure 5-6) Bearer model on GTP based S2b
5.4. Release 11
5.4.1. S2a Mobility based on GTP and WLAN access to EPC(SaMOG_WLAN)
It is triggered by TR 23.852(Study on S2a Mobility based on GTP and WLAN access
to EPC - SaMOG) [11].
No usage of WLAN access to EPC over S2a is currently documented in 3GPP
specifications whereas deciding whether a non 3GPP access network is to be
considered as trusted should not be mandated by the technology of this non 3GPP
access. There are requirements from some operators to use GTP or PMIP S2a for
WLAN to access EPC. The reasons to use S2a for WLAN to access EPC may vary from
operator to operator and depend on the operator’s network deployment policy. One
example is that many terminals do not support 3GPP extensions IKEv2/IPsec. Another
example is that in some cases the WLAN can be considered secure and it is
acceptable for the operator to consider it as trusted by use of S2a to access EPC.
Whether GTP or PMIP is used in the network for S2a is transparent to the UE. Upon
specifying GTP based S2a for trusted access to EPC, WLAN access to EPC will apply
for both GTP and PMIPv6 based interfaces. The objective of this work item is to enable
GTPv2 and PMIPv6 based S2a access to EPC through WLAN access.
For Trusted non-3GPP access to the EPC, the PDN connectivity is made up of the
concatenation of Non-3GPP connectivity(between the UE and the Trusted Non-3GPP
access) and of GTP bearer(s) over S2a. The GTP based S2a interface is similar to
GTP-S5/S8 and GTP-S2b. The Trusted Non 3GPP access handles the UL TFT received
from the PGW over GTP with the same way as an ePDG terminating GTP based S2b
handles the UL TFT received from the PGW. Whether GTP or PMIP is used in the
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network for S2a is transparent to the UE.
Trusted Non3GPP IP Access
UE
S2 a
PGW
GTP Tunnel
GTP Tunnel
GTP Tunnel
Non-3GPP connectivity
UL TFT
DL TFT
The mapping between Non-3GPP connectivity and
multiple GTP bearers (Default and dedicated bearers)
(Figure 5-7) Bearer model on GTP based S2a
5.5. Release 12
5.5.1. WLAN Network Selection for 3GPP Terminals(WLAN_NS)
The Hotspot 2.0 solution developed by WFA builds on the architecture and set of
protocols defined by IEEE 802.11u and develops key capabilities for network discovery
and selection of WLAN terminals based on the ANQP(Access Network Query Protocol)
defined in IEEE 802.11u. The Wi-Fi Alliance is working on a certification program that
improves WLAN hotspot discovery, network selection, and security. The program
leverages the ANQP protocol that is part of IEEE 802.11u(or IEEE 802.11-2012) as well
as WPA2 Enterprise security(includes EAP authentication over IEEE 802.1X). 3GPP
already has some support for IEEE 802.11u, GAS(Generic Advertisement Service) and
ANQP for I-WLAN as per TS 24.234. As Hotspot 2.0 also deals with network selection,
there is a need to analyze how a UE can interact with network selection framework of IWLAN, Hotspot 2.0 and ANDSF and specify a consistent procedure for WLAN network
selection.
The item enhances existing 3GPP solutions for network selection for WLAN networks
taking into account WFA Hotspot 2.0 solutions. The proposed work is based on
existing TS 23.402 architectures. 3GPP operator's policies for WLAN network selection
will be provisioned on 3GPP terminals via pre-configuration or using the ANDSF. The
scope of the item includes the followings:
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
Evaluate existing 3GPP WLAN PLMN and access network selection procedures
for 3GPP terminals which use Hotspot 2.0 procedures and provisioned network
operator policy(e.g. mechanisms based on WLAN and ANDSF) for any needed
changes to current specifications. This may require enhancements to the
ANDSF framework. The established 3GPP PLMN network selection(according to
TS 23.122) shall not be impacted. The work must ensure there are no conflicts
between existing 3GPP PLMN network selection and the 3GPP WLAN PLMN
access network selection procedures defined by this WID.

Ensure that the content in the Management Object related to 3GPP operator
policy provisioning for WLAN network selection procedures and the operator
policy provisioning in WFA MO for WLAN network selection are consistent.

Identify solutions to resolve potential conflicts between policies provided by
non-3GPP providers via Hotspot 2.0 mechanisms and policies provided by
3GPP operators using ANDSF.
This wok applies to non-seamless WLAN offload as well as to trusted and untrusted
WLAN access to EPC with/without seamless offload [12].
5.5.2. S2a Mobility based on GTP and WLAN access to EPC(SaMOG)
In Release 11, support of GTP & PMIPv6 on S2a for WLAN access was developed
without any UE impact but as a consequence with certain limitations on supported
functions. In Release 12, this study is aiming at studying enhancements to the Release
11 solution to avoid these limitations(except emergency attach), and deciding which
feature & related solution should be developed into normative. In this phase it is
expected that there will be some impacts to the UE, although any such impact should
be minimized.
The SaMOG phase-2 solution supports single-PDN and multi-PDN UEs. The singlePDN UEs support only NSWO or a single PDN connection(with IP address preservation)
over a trusted WLAN and the multi-PDN UEs support multiple simultaneous PDN
connections over a trusted WLAN, in parallel to NSWO.
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5.5.3. Optimized Offloading to WLAN in 3GPP-RAT mobility(WORM)
In EPS, ANDSF has defined mechanisms that enable devices to determine which
access technology is preferable for certain IP traffic under specific conditions(e.g.
through the use of ISRP). In certain scenarios, WLAN access may be considered
preferable to certain 3GPP access technologies(e.g. for certain traffic, WLAN may be
preferable to UTRAN but not to E-UTRAN). However, at present ANDSF does not
provide for mechanisms to indicate preferences with granularity at the 3GPP RAT level
within network policies. This restricts the ability for the operator to provide policies that
favor a specific 3GPP RAT over another one with reference to the WLAN preference.
This study item identifies extensions to ANDSF ISRP and possibly ISMP policies in order
to enable policy differentiation of 3GPP RATs(e.g. E-UTRAN vs. UTRAN, GERAN vs.
UTRAN) with respect to WLAN. The following key issues are identified [13]:
 ANDSF WLAN preferences with respect to specific 3GPP RATs
 Undesired bearer handling
 Ping-pong offloading to WLAN
5.5.4. WLAN/3GPP Radio Interworking
The item was triggered by TR 37.834 [14]. UEs using WLAN networks controlled by
3GPP operators and their partners often make suboptimal offload to/from WLAN
decisions resulting in poor user experience and inefficient resource utilization of
operator's networks. TSG-RAN agreed that solutions for WLAN/3GPP radio interworking
shall support both deployments with and without ANDSF to satisfy different operator
deployments. The objective of this work item is to specify mechanism for WLAN/3GPP
access network selection and traffic steering that addresses requirements from all
operators.
Core objectives are to specify mechanism for WLAN/3GPP access network selection
and traffic steering.

Selected RAN assistance parameters are transferred via system broadcast
and/or dedicated signaling are used within:

RAN rules in case enhanced ANDSF is not deployed or not supported
by the UE
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
ANDSF policies in case enhanced ANDSF is deployed in the network
and supported by the UE

RAN
assistance
information
may
be
enhanced
with
traffic
routing
information(e.g. offload granularity) in case ANDSF is not deployed or not
supported by the UE.
SA2 objectives are to enhance the EPS with improved and operator controlled
WLAN/3GPP access network selection and traffic steering including the following
specific areas:

Support of deployments where the serving PLMN(Home or Visited) is operating
with ANDSF policies only or RAN rules only, or with both RAN rules and ANDSF
policies.
5.6. Release 13
5.6.1. Multi-RAT joint coordination
The coexistence of Multiple RATs introduces many operational coordination problems
for
network
operators.
The
co-existence
of
various
RATs(i.e.
LTE/UMTS/GSM/CDMA/WLAN) is an obvious reality and it will remain relevant in the
future. This raises important issues for operators in terms of coordination across the
RATs to achieve better user experience(QoE), efficient resource usage, higher network
capacity and easier maintenance, especially in a multi-vendor environment. For an
operator with multi-RAT networks, frequent updated information from all RATs(radio
resource management, mobility and traffic load) is required in order to enable efficient
coordination by the network. It will be beneficial to consider a general Multi-RATs
coordination from RAN perspective to meet the following requirements:

Service aware UE steering between different RATs to provide consistent user
experience and user satisfaction, e.g. by connecting to Multi-RATs(e.g. WiFi
and LTE).

Traffic steering between WAN and WLAN(e.g. LTE and WiFi)

Multi RAT joint radio resource coordination for an operator, especially between
LTE and GSM, to provide an operator a smooth transition from GSM to LTE,
while still keeping basic GSM coverage for e.g. voice or GSM M2M services.
Similar migration and spectrum sharing scenarios may also exist for
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기술보고서
UMTS/CDMA and LTE

Reducing core network impact caused by addition of a new RAT due to interRAT communication
This item identifies the general scenarios and requirements for Multi-RAT
coordination including LTE, UMTS, GSM, CDMA and WLAN. It also evaluates potential
benefits and functionalities for joint operation among different RATs, including the
followings [15]:

Steering of UEs among different RATs, taking into account service type, user
experience, processing capacity, backhaul constraints and/or traffic load, and
consequent mobility enhancement

Efficient multi RAT joint radio resource coordination to improve load balancing
and for an operator to enable, e.g. spectrum re-farming
6. Conclusions
This Technical Report presented the technologies and standardization status for
3GPP and WLAN interworking. I-WLAN, which determines how IP-interworking between
cellular and non-cellular networks takes place, has been part of 3GPP specifications
since Release 6. Session mobility between 3GPP and non-3GPP(such as WLAN)
access networks was introduced in Release 8. For both network-based and clientbased mobility between 3GPP and WLAN networks, 3GPP defined the 3GPP to WLAN
interfaces: S2a, S2b and S2c. 3GPP also introduced the ANDSF mechanism to provide
devices with additional information to expedite discovery and selection based on
operator-defined priorities according to management object. 3GPP is taking RAN
assistance parameters into consideration for more efficient resource utilization in
3GPP-WLAN interworking. This Technical Report is expected to a reference to develop
global standards and lead the markets on the interworking between 3GPP LTE/LTE-A
and WLAN.
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Appendix Ⅰ
References
This Technical Report refers to the following documents.
[1] 3GPP TR 22.934 Feasibility Study on 3GPP system to Wireless Local Area
Network(WLAN) interworking
[2] 3GPP TS 22.234 Requirements on 3GPP system to Wireless Local Area
Network(WLAN) interworking
[3] 3GPP TS 23.234 3GPP System to Wireless Local Area Network(WLAN)
interworking; System description
[4] 3GPP TS 23.327 Mobility between 3GPP-WLAN interworking and 3GPP systems
[5] 3GPP TR 22.937 Requirements for service continuity between mobile and
Wireless Local Area Network(WLAN) networks
[6] 3GPP TS 24.312 Access Network Discovery and Selection Function(ANDSF)
Management Object(MO)
[7] 3GPP TR 23.861 Study on Multi Access PDN Connectivity and IP Flow Mobility
[8] 3GPP TS 22.278 Service requirements for the Evolved Packet System(EPS)
[9] 3GPP TS 23.402 Architecture enhancements for non-3GPP accesses
[10] 3GPP TR 23.834 Study on S2b mobility based on GTP
[11] 3GPP TR 23.852 Study on S2a Mobility based on GTP and WLAN access to EPC
[12] 3GPP TR 23.865 WLAN Network Selection for 3GPP Terminals
[13] 3GPP TR 23.890 Study on Optimized Offloading to WLAN in 3GPP-RAT Mobility
[14] 3GPP TR 37.834 Study on WLAN/3GPP Radio Interworking
[15] 3GPP TR 37.870 Study on Multi-RAT Joint Coordination
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영문 기술보고서 해설서
1. 개요
전용망을 사용하는 이동통신 사업자 입장에서 WLAN 은 급증하는 무선 트래픽을
수용하기 위한 하나의 중요한 수단으로 활용할 수 있다. 3GPP 는 3GPP 시스템내에서
자원 활용 및 서비스 접근성을 제공하는 I-WLAN(Interworking WLAN) 기능을 정의하고
있으며, 보조적인 무선 접속 기술로 활용하기 위해 3GPP-WLAN 상호 운용 기능을
제공하고 있다. 3GPP 는 Release 6 부터 WLAN 엑세스망을 통해 3GPP 서비스 제공이
가능하도록 아키텍쳐와 관련 기능을 정의하였으며, Release 8 에서는 3GPP 엑세스망과
WLAN 사이의 Seamless 핸드오버와 서비스 연속성 기능을 정의하였다. Release 10
이후에는 3GPP 네트워크내에서 WLAN 을 지원하기 위한 좀더 진화된 기술을 정의하고
있다. 본 기술보고서는 3GPP 망과 WLAN 사이의 상호 운용에 관련된 기술과 표준
동향을 소개하며, 앞으로의 3GPP LTE/LTE-A 망과 WLAN 등의 이종망 간 연동에 관한
국제 표준 및 시장 동향을 예측하고 대응하기 위한 참고 문서로 활용되기를 기대한다.
2. 기술보고서의 구성 및 범위
본 기술보고서는 3GPP 기술 표준 및 기술보고서를 기반으로한 Seamless 핸드오버와
트래픽 스티어링 기술을 포함하여, 3GPP-WLAN 상호 운용에 관한 3GPP Release 6 부터
Release 13 까지의 표준 현황을 소개한다.
3. 참조 표준(권고)
- 해당 사항 없음.
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4. 용어 정의 및 약어
4.1. 용어 정의
4.1.1. Evolved Packet System
다양한 무선 엑세스 기술을 지원하며, 고속의 데이터 전송률, 저지연, 패킷 기반
전송 등의 특징을 갖는 3G UMTS 의 진화된 시스템으로 Evolved Packet
Core(EPC)와 Evolved Radio Access Network(E-UTRAN)으로 구성됨.
4.1.2. Interworking WLAN(I-WLAN)
3GPP 시스템과 상호 운용하는 WLAN
4.1.3. 3GPP-WLAN Interworking
3GPP 시스템과 WLAN 기반 표준 기술과의 상호 운용
5. 3GPP-이종망 연동 표준 기술
Release 6 의 ‘WLAN-UMTS Interworking’에서는 3GPP-WLAN 상호 운용에 관한
서비스 시나리오와 요구사항을 정의한다.
Release 8 의 ‘I-WLAN Network Selection Principle’에서는 WLAN UE 의 PLMN
네트워크 선택 절차를 정의한다. ‘Mobility between 3GPP-WLAN Interworking and 3GPP
Systems’에서는 I-WLAN 과 3GPP 시스템 사이의 이동성 지원을 위한 시스템을
기술하며, DSMIPv6 기반의 기술적 해법을 정의한다. ‘Service continuity between mobile
and WLAN networks’에서는 GSM/GPRS/3G 망과 WLAN 망사이의 Seamless 로밍과
서비스를 위한 요구사항을 정의한다. ‘Access Network Discovery and Selection
Function(ANDSF)’에서는 정책 기반의 네트워크 발견 및 선택을 지원하기 위한 ANDSF
아키텍쳐와 관련 절차를 정의한다.
Release 10 의 ‘IP Flow Mobility and seamless WLAN offload(IFOM)’에서는 IP flow
기반의
Seamless
WLAN
오프로딩
기법을
소개한다.
‘S2b
Mobility
based
on
GTP(SMOG)’에서는 S2b 인터페이스로 정의된 E-UTRAN 과 untrusted non-3GPP
access 간의 이동성을 지원하기 위한 GTP bearer 모델을 정의한다.
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Release
11
의
‘S2a
Mobility
based
on
GTP
and
WLAN
access
to
EPC(SaMOG_WLANB)’에서는 S2a 인터페이스로 정의된 E-UTRAN 과 trusted non-3GPP
access 간의 GTP bearer 모델을 정의한다.
Release 12 의 ‘WLAN Network Selection for 3GPP Terminals(WLAN_NS)’에서는
WFA 의 Hotspot 2.0 을 고려한 개선된 WLAN 네트워크 선택 기법을 소개한다. ‘S2a
Mobility based on GTP and WLAN access to EPC(SaMOG)’에서는 Release 11 의 UE
제약사항을 개선한 해법을 제시한다. ‘Optimized Offloading to WLAN in 3GPP-RAT
mobility(WORM)’에서는 3GPP RAT(E-UTRAN, UTRAN, GERAN)을 구분하는 개선된
ANDSF 기법을 제시한다. ‘WLAN/3GPP Radio Interworking’에서는 무선 엑세스 환경이
반영된 WLAN/3GPP 망 선택 기법을 정의한다.
Release 13 의 ‘Multi-RAT joint coordination’에서는 LTE, UMTS, GSM, CDMA,
WLAN 등의 다중 엑세스 기술의 통합 운용을 위한 일반적인 시나리오와 요구사항을
정의한다.
6. 결론
본 기술보고서에서는 3GPP 망과 WLAN 등의 이종망간의 상호 운용을 위한 기술과
Release 13 까지의 3GPP 표준 동향을 정리하였다.
부록 Ⅰ. 참고 문헌
본 기술보고서에서 참조한 3GPP 기술 규격 및 기술 보고서 목록을 나열한다.
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기술보고서
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3GPP 이종망 연동 기술 표준 분석(기술보고서)
(3GPP Standardization Status for Inter-operability with other
RATs(Technical Report))
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