ETSI TR 143 902 V13.0.0 (2016-01)

ETSI TR 1143 902 V13.0.0 (201616-01)

TECHNICAL REPORT
Digital cellular telecocommunications system (Phahase 2+);
Enhanced Genericic Access Networks (EGAN) s) study
(3GPP TR 43.9.902 version 13.0.0 Release 13 13)

R
GLOBAL SYSTTEME FOR
MOBILE COMMUUNNICATIONS
3GPP TR 43.902 version 13.0.0 Release 13 1 ETSI TR 143 902 V13.0.0 (2016-01)

Reference
RTR/TSGG-0143902vd00
Keywords
GSM
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3GPP TR 43.902 version 13.0.0 Release 13 2 ETSI TR 143 902 V13.0.0 (2016-01)
Intellectual Property Rights
IPRs essential or potentially essential to the present document may have been declared to ETSI. The information
pertaining to these essential IPRs, if any, is publicly 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 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 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 identities. 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 "shall", "shall not", "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 expression of
provisions).
"must" and "must not" are NOT allowed in ETSI deliverables except when used in direct citation.
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3GPP TR 43.902 version 13.0.0 Release 13 3 ETSI TR 143 902 V13.0.0 (2016-01)
Contents
Intellectual Property Rights . 2
Foreword . 2
Modal verbs terminology . 2
Foreword . 6
Introduction . 6
1 Scope . 7
2 References . 7
3 Definitions, symbols and abbreviations . 8
3.1 Definitions . 8
3.2 Symbols . 8
3.3 Abbreviations . 8
4 Requirements . 10
4.1 Objectives . 10
4.2 Benefits . 11
4.3 For further investigation . 11
5 Architecture alternatives. 11
5.1 A/Gn based architectures . 11
5.1.1 Enhanced Up . 11
5.1.1.1 Architecture . 11
5.1.1.2 Protocol stacks . 13
5.1.1.2.1 PS Control Plane. 13
5.1.1.2.2 PS User Plane . 14
5.1.1.3 Affected Procedures . 14
5.1.1.3.1 PS mobility overview . 14
5.1.1.3.2 PDP Context Activation /De-Activation . 20
5.1.1.3.3 PS Handover procedures between GAN and GERAN/UTRAN . 26
5.1.1.3.4 CS+PS Handover between GAN and GERAN/UTRAN . 29
5.1.1.3.5 APN resolution in EGAN mode . 35
5.1.1.3.6 SMS in EGAN mode . 38
5.1.1.3.7 EGAN Registration and subscriber management in PS Domain . 39
5.1.1.3.8 Network Requested PDP Context Activation (NRPCA) . 42
5.1.1.3.9 Roaming aspects . 45
5.1.1.4 Terminal architecture and impacts . 46
5.1.1.4.1 Introduction . 46
5.1.1.4.2 CS domain Control Plane . 47
5.1.1.4.3 CS domain User Plane . 48
5.1.1.4.4 PS domain. 48
5.1.1.5 EGAN handovers and LA/RA Update signalling . 51
5.1.1.5.1 Introduction . 51
5.1.1.5.2 GERAN/GAN Scenario . 51
5.1.1.5.3 UMTS/GERAN/GAN Scenario . 53
5.1.1.5.4 GAN Enhancement alternatives . 53
5.1.1.6 Proxy-Gn Load and Performance . 54
5.1.1.6.1 Introduction . 54
5.1.1.6.2 Assumptions . 55
5.1.1.6.3 CPU Load . 55
5.1.1.6.4 Memory Consumption . 56
5.1.1.6.5 Signalling Delay . 56
5.1.2 Combined GANC/SGSN . 57
5.1.2.1 Introduction . 57
5.1.2.2 Architecture . 58
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5.1.2.3 Protocol stacks . 59
5.1.2.3.1 PS Control plane . 59
5.1.2.3.2 PS User plane . 60
5.1.2.4 Affected procedures . 60
5.1.2.5 Terminal architecture and impacts . 60
5.1.2.6 Optimization for LLC and SNDCP Layers . 61
5.2 GAN Iu Mode . 62
5.2.1 Functional Architecture . 62
5.2.2 Functional entities . 64
5.2.2.1 Mobile Station (MS) . 64
5.2.2.2 Generic Access Network Controller (GANC) . 64
5.2.3 Control and User Plane Architecture . 64
5.2.3.1 Circuit Switched (CS) Domain . 65
5.2.3.1.1 CS Domain - Control Plane . 65
5.2.3.1.2 CS Domain - User Plane . 66
5.2.3.2 Packet Switched (PS) Domain . 67
5.2.3.2.1 PS Domain - Control Plane . 67
5.2.3.2.2 PS Domain - User Plane . 68
5.2.3.3 GA-RC (Generic Access Resource Control) . 68
5.2.3.3.1 General . 68
5.2.3.3.2 States of the GA-RC sub-layer . 69
5.2.3.4 GA-RRC (Generic Access Radio Resource Control) . 70
5.2.3.4.1 General . 70
5.2.3.4.2 States of the GA-RRC sub-layer . 70
5.2.4 Security Mechanisms . 71
5.2.5 High Level Procedures . 71
5.2.5.1 Mode Selection in Multi-mode terminals . 71
5.2.5.2 PLMN Selection . 72
5.2.5.3 Re-selection between GERAN/UTRAN and GAN modes . 73
5.2.5.3.1 Rove-in (from GERAN/UTRAN mode to GAN mode) . 73
5.2.5.3.2 Rove-out (from GAN mode to GERAN/UTRAN mode) . 73
5.2.5.4 GAN Discovery and Registration related procedures . 74
5.2.5.4.1 Discovery and Registration for Generic Access . 74
5.2.5.4.2 De-Registration. 80
5.2.5.4.3 Registration Update . 81
5.2.5.4.4 Keep Alive . 82
5.2.5.4.5 Cell Broadcast Information . 82
5.2.5.5 Void. 83
5.2.5.6 Void. 83
5.2.5.7 GA-RRC Connection handling . 83
5.2.5.7.1 GA-RRC Connection Establishment . 83
5.2.5.7.2 GA-RRC Connection Release . 83
5.2.5.8 Security Mode Control . 84
5.2.5.9 NAS Signalling Procedures . 84
5.2.5.10 Mobile Originated CS Call . 85
5.2.5.11 Mobile Terminated CS Call . 87
5.2.5.12 CS Call Clearing . 88
5.2.5.13 CS Handover . 88
5.2.5.13.1 CS Handover from GERAN to GAN . 88
5.2.5.13.2 CS Handover from UTRAN to GAN . 90
5.2.5.13.3 CS Handover from GAN to GERAN . 92
5.2.5.13.4 CS Handover from GAN to UTRAN . 93
5.2.5.14 Void. 95
5.2.5.15 Void. 95
5.2.5.16 Void. 95
5.2.5.17 GA-RRC Packet Transport Channel Management Procedures . 95
5.2.5.17.1 States of the GA-RRC Packet Transport Channel . 96
5.2.5.17.2 PTC Initial Activation . 97
5.2.5.17.3 PTC Data Transfer . 98
5.2.5.17.4 MS initiated PTC Deactivatio n . 99
5.2.5.17.5 MS initiated PTC Re-activation . 100
5.2.5.17.6 Network initiated PTC De-activation . 101
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5.2.5.17.7 Network initiated PTC Re-activation . 101
5.2.5.17.8 Implicit PTC De-activation due to MS De-registration . 102
5.2.5.18 PDP Context Activation . 103
5.2.5.19 Network Requested PDP Context Activation. 104
5.2.5.20 PS Handover between GERAN and GAN . 105
5.2.5.20.1 PS Handover from GERAN to GAN . 105
5.2.5.20.2 PS Handover from GAN to GERAN . 105
5.2.5.21 SRNS Relocation between UTRAN and GAN . 105
5.2.5.21.1 SRNS Relocation from UTRAN to GAN . 105
5.2.5.21.2 SRNS Relocation from GAN to UTRAN . 107
5.2.6 Terminal Architecture Impacts . 109
5.2.6.1 Assumptions and Definitions . 109
5.2.6.2 Impact on CS Control Plane . 110
5.2.6.2.1 CS Control Plane - Before . 110
5.2.6.2.2 CS Control Plane-After . 111
5.2.6.2.3 Summary of CS Control Plane Changes . 111
5.2.6.3 Impact on CS User Plane . 112
5.2.6.3.1 CS User Plane-Before . 112
5.2.6.3.2 CS User Plane-After . 113
5.2.6.3.3 Summary of CS User Plane Changes . 113
5.2.6.4 Impact on PS Control Plane . 113
5.2.6.4.1 PS Control Plane-Before . 113
5.2.6.4.2 PS Control Plane-After . 114
5.2.6.4.3 Summary of PS Control Plane Changes . 115
5.2.6.5 Impact on PS User Plane . 116
5.2.6.5.1 PS User Plane-Before . 116
5.2.6.5.2 PS User Plane-After . 117
5.2.6.5.3 Summary of PS User Plane Changes . 117
6 Evaluation Section . 118
6.1 Enhanced Up . 118
6.2 Combined GANC/SGSN . 122
6.3 GAN Iu Mode . 124
6.4 Comparison of the Proposed Solutions . 126
7 Conclusion . 132
Annex A: Change history . 134
History . 135

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Foreword
rd
This Technical Report has been produced by the 3 Generation Partnership Project (3GPP).
The contents of the present document are subject to continuing work within the TSG and may change following formal
TSG approval. Should the TSG modify the contents of the present document, it will be re-released by the TSG with an
identifying change of release date and an increase in version number as follows:
Version x.y.z
where:
x the first digit:
1 presented to TSG for information;
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 substance, i.e. technical enhancements, corrections,
updates, etc.
z the third digit is incremented when editorial only changes have been incorporated in the document.
Introduction
During the course of Release 6, 3GPP TS 43.318 [2] (Generic access to the A/Gb interface; Stage 2) and
3GPP TS 44.318 [3] (Generic access to the A/Gb interface; Stage 3) were developed that provide access to the 3GPP
core network using generic IP connection. Generic Access Networks, or GAN, is an extension of GSM/GPRS mobile
services into the customer's premises that is achieved by tunnelling certain GSM/GPRS protocols between the
customer's premises and the Core Network over broadband IP network, and relaying them through an unlicensed radio
link inside the customer's premises. GAN is a complement to traditional GSM/GPRS radio coverage, used to enhance
customer premises coverage, increase network capacity and potentially lower costs.
Early deployments of GAN are now ongoing. As part of the continuous process of optimizing their network to better
meet customer demand a number of operators have indicated a need to further enhance the GAN system. Various goals
for such enhancements are documented in section four of the present document. After presentation of the goals, the
present document technical alternatives for how to implement such enhancements to GAN.
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1 Scope
The present document contains the results of the feasibility study into the enhancements to Generic Access Networks or
GAN. Considerations include overall requirements for enhancements, architectural requirements, evaluation of potential
architectural solutions and alternative architectures.
The objective is to identify an architectural solution that best meets the requirements as specified in first section. The
feasibility study shall also investigate mechanisms for selecting the most appropriate network domain to serve the user.
Existing solutions developed by the 3GPP should be reused as much as possible.
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 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 that document in the same
Release as the present document.
[1] 3GPP TR 21.905: "Vocabulary for 3GPP Specifications".
[2] 3GPP TS 43.318: "Generic access to the A/Gb interface; Stage 2".
[3] 3GPP TR 44 318: "Generic Access (GA) to the A/Gb interface; Mobile GA interface layer 3
specification".
[4] 3GPP TS 24.008: "Mobile radio interface Layer 3 specification; Core network protocols; Stage 3".
[5] 3GPP TS 29.060: "General Packet Radio Service (GPRS); GPRS Tunnelling Protocol (GTP)
across the Gn and Gp interface".
[6] 3GPP TS 23.060: "General Packet Radio Service (GPRS); Service description; Stage 2".
[7] 3GPP TS 23.078: "Customized Applications for Mobile network Enhanced Logic (CAMEL) Phase
X; Stage 2".
[8] 3GPP TS 32.251: "Telecommunication management; Charging management; Packet Switched
(PS) domain charging".
[9] 3GPP TS 24.007: "Mobile radio interface signalling layer 3; General aspects".
[10] 3GPP TS 33.107: "3G security; Lawful interception architecture and functions".
[11] IETF RFC 2784 (March 2000): "Generic Routing Encapsulation (GRE)".
[12] 3GPP TS 25.410: "UTRAN Iu interface: General aspects and principles".
[13] 3GPP TS 25.450: "UTRAN Iupc interface general aspects and principles".
[14] 3GPP TS 25.419: "UTRAN Iu-BC interface: Service Area Broadcast Protocol (SABP)".
[15] 3GPP TS 29.234, v11.2.0: "3GPP system to Wireless Local Area Network (WLAN) interworking;
Stage 3".
[16] 3GPP TS 25.412: "UTRAN Iu interface signalling transport".
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[17] 3GPP TS 25.414: "UTRAN Iu interface data transport and transport signalling".
[18] 3GPP TS 25.415: "UTRAN Iu interface user plane protocols".
[19] 3GPP TS 26.071: "AMR speech Codec; General description".
[20] 3GPP TS 33.102: "3G Security; Security architecture".
[21] 3GPP TS 33.234: "3G security; Wireless Local Area Network (WLAN) interworking security".
[22] 3GPP TS 23.122: "Non-Access-Stratum (NAS) functions related to Mobile Station (MS) in idle
mode".
[23] 3GPP TS 25.331: "Radio Resource Control (RRC); Protocol specification".
[24] 3GPP TS 44.064: "Mobile Station - Serving GPRS Support Node (MS-SGSN); Logical Link
Control (LLC) Layer Specification".
[25] 3GPP TS 44.065: "Mobile Station (MS) - Serving GPRS Support Node (SGSN); Subnetwork
Dependent Convergence Protocol (SNDCP)".
[26] 3GPP TS 23.003: "Numbering, addressing and identification".
[27] 3GPP TS 23.236: "Intra-domain connection of Radio Access Network (RAN) nodes to multiple
Core Network (CN) nodes".
[28] 3GPP TS 43.129: "Packed-switched handover for GERAN A/Gb mode; Stage 2".
3 Definitions, symbols and abbreviations
3.1 Definitions
For the purposes of the present document, the terms and definitions given in 3GPP 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].
3.2 Symbols
For the purposes of the present document, the following symbols apply:
Up Interface between UE and GANC
3.3 Abbreviations
For the purposes of the present document, the abbreviations given in 3GPP TR 21.905 [1] and the following apply. An
abbreviation defined in the present document takes precedence over the definition of the same abbreviation, if any, in
TR 21.905 [1].
AAA Authentication, Authorization and Accounting
AKA Authentication and Key Agreement
AP Access Point
AS Access Stratum
BSC Base Station Controller
BSS Base Station Subsystem
BSSGP Base Station System GPRS Protocol
BSSMAP Base Station System Management Application Part
CC Call Control
CGI Cell Global Identification
CM Connection Management
CN Core Network
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CS Circuit Switched
DNS Domain Name System
DTM Dual Transfer Mode
EAP Extensible Authentication Protocol
ETSI European Telecommunications Standards Institute
FQDN Fully Qualified Domain Name
GA-CSR Generic Access - Circuit Switched Resources
GAN Generic Access Network
GANC Generic Access Network Controller
GA-PSR Generic Access - Packet Switched Resources
GA-RC Generic Access - Resource Control
GA-RRC Generic Access - Radio Resource Control
GERAN GSM EDGE Radio Access Network
GGSN Gateway GPRS Support Node
GMM/SM GPRS Mobility Management and Session Management
GPRS General Packet Radio Service
GSM Global System for Mobile communications
GSN GPRS Support Node
HLR Home Location Register
HPLMN Home PLMN
IETF Internet Engineering Task Force
IKE Internet Key Exchange
IMEISV International Mobile station Equipment Identity and Software Version number
IMSI International Mobile Subscriber Identity
IP Internet Protocol
LA Location Area
LAI Location Area Identity
LLC Logical Link Control
MAC Medium Access Control
MAC Message Authentication Code
MM Mobility Management
MS Mobile Station
MSC Mobile Switching Center
MTP1 Message Transfer Part layer 1
MTP2 Message Transfer Part layer 2
MTP3 Message Transfer Part layer 3
NAS Non-Access Stratum
PDP Packet Data Protocol
PDU Protocol Data Unit
PLMN Public Land Mobile Network
PSTN Public Switched Telephone Network
P-TMSI Packet - TMSI
QoS Quality of Service
RA Routing Area
RAC Routing Area Code
RAI Routing Area Identity
RAT Radio Access Technology
RLC Radio Link Control
RTCP Real Time Control Protocol
RTP Real Time Protocol
SCCP Signalling Connection Control Part
SEGW SEcurity GateWay
SGSN Serving GPRS Support Node
SIM Subscriber Identity Module
SMLC Serving Mobile Location Center
SMS Short Message Service
SNDCP Sub-Network Dependent Convergence Protocol
TBF Temporary Block Flow
TC Transport Channel
TCP Transmission Control Protocol
TFO Tandem Free Operation
TMSI Temporary Mobile Subscriber Identity
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TrFO Transcoder Free Operation
TTY Text Telephone or TeletYpewriter
UDP User Datagram Protocol
UMTS Universal Mobile Telecommunication System
VLR Visited Location Register
VPLMN Visited Public Land Mobile Network
4 Requirements
4.1 Objectives
1. GAN Enhancements shall be backwards compatible with GAN in 3GPP Rel-6 and Rel-7.
Two levels of enhancements may be considered that are either:
a) Forwards compatible from Rel-6: Rel-6 and Rel-7 terminals work with the enhancements i.e. network-only
enhancements
b) Not forwards compatible from Rel-6 (respectively Rel-7): Rel-6 (respectively Rel-7) terminals do not work
with the enhancements
GAN Enhancements shall:
• Support at minimum the same services as GAN in 3GPP Rel-6 and Rel-7; and
• Support existing QoS management as specified in 3GPP; and
• Minimize the impact on the Core Network.
2. GAN Enhancements shall abide as per the unchanged GAN principle to keep the transparent support for any
given service between UTRAN or GERAN, and GAN.
• E.g. preserve the existing APN mechanism.
3. GAN Enhancements shall minimize the additional complexity on existing GANCs if applicable.
4. GAN Enhancements shall minimize the additional complexity on terminals (see case 1b above).
5. GAN Enhancements shall reduce the complexity for delivery of CS and PS services.
• E.g. by reducing the number of functions and/or protocol overhead.
6. GAN Enhancements shall reduce the user-plane latency for delivery of PS services.
• E.g. by reducing the number of functions and/or protocol overhead.
7. GAN Enhancements shall be compatible / shall align with other 3GPP Core Network enhancements e.g. "one
tunnel approach" for PS services.
8. GAN Enhancements shall overcome the limitations imposed by using the Gb interface.
9. GAN Enhancements shall provide optimized support for operators using GSM-only, UMTS-only, or combined
GSM/UMTS networks.
• E.g. no changes to existing core network nodes/interfaces.
NOTE 1: The term "GSM" also refers to GPRS.
10. GAN Enhancements shall provide seamless mobility for CS and seamless mobility for PS including PS
conversational services.
11. GAN Enhancements shall minimize "Enhanced GAN mode" power consumption on handsets.
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NOTE 2: "Enhanced GAN mode" refers to the peer of GAN mode when operating as per a given GAN
Enhancement.
4.2 Benefits
The following items constitute a non-exhaustive list of benefits that may characterize the proposals on GAN
Enhancements:
• PS Optimization independent of CS Changes.
• Support the services/network deployed with GPRS APNs.
• No impact on 3GPP TS 24.008 [4].
• Minimize the load on existing network elements (e.g. HLR).
4.3 For further investigation
The following items require further investigation:
• Whether "Enhanced GAN" Terminals shall support GAN specified in 3GPP Rel-6 and Rel-7.
• Whether there is any limitations induced by LLC protocol.
5 Architecture alternatives
5.1 A/Gn based architectures
5.1.1 Enhanced Up
5.1.1.1 Architecture
Figure 1 shows the architecture of enhanced Up solution. The CS domain remains unchanged and the PS domain is
enhanced to increase the performance of the broadband data services.
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SMLC CBC
Lb
Ge
CAMEL
GSM-SCF
Ga HPLMN/VPLMN
CGF
A
MSC
Gn
Other
eGANC
Enhanced
Generic Access
Network Gb (for backward compatibility)
Generic Access
Controller Gn
Network
(eGANC)
SGSN
Controller
UUpp
GeneGeneriric Ic IPP
(GANC)
Gn
MSMS
Access Network
GGSN
Wx
HSS
AAA
Wm
Proxy/
Server
D’/Gr’
MSMS MobMobileile St Statiatioonn
SEGW
GAGANCNC GGAAN ConN Conttrorolllleerr HLR
SESEGGWW SSeeccuurriittyy G Gaatetewwaayy
Wd
Out of Scope
HPLMN (roaming case)
Figure 1: Enhanced Up A/Gn solution architecture
EGANC is a combination of legacy GANC and part of SGSN functionalities. The EGANC provides the Gn reference
point and enhanced Up reference point for enhanced PS efficiency and performance.
• Gn reference point: This reference point to GGSN removes one node in the path for PS services, hence reducing
the latency and overhead. It also moves the EGANC close to the core network, making the GERAN/UTRAN
radio-specific procedures unnecessary in the EGANC.
• Enhanced Up reference point: This reference point removes the unnecessary protocol stacks between UE and the
EGANC, hence enhancing the performance of the PS services. The Up reference point for CS domain remains
unchanged so that all the current procedures keep working. The legacy Up reference point for PS domain is also
supported for backward compatibility.
The main features of the architecture are as follows:
• No changes to CS domain - reuse of A interface.
• Reuse of Up procedures for authentication, security, discovery/registration. -reuse of Wm interface.
• This proposal only affects the PS domain.
• Direct connectivity to GGSN via unchanged Gn per 3GPP TS 29.060 [5].
• New Enhanced Up protocol for PS domain.
• GA-PSR and 3GPP TS 24.008 [4] MM/SM are not used in PS EGAN mode.
• Single enhanced Up PS stack in the terminal for 2G and 3G networks and terminals environment.
• Gb is kept for backward compatibility with R6 GAN terminals.
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• Other interfaces:
- Gd interface is not needed. SMS is provided via CS domain in the WLAN coverage via standardized 3GPP
mechanisms without any changes for the GERAN/UMTS coverage, where PS or CS preference can be kept
(refer to contribution on SMS).
- Gs interface is not used.
- The EGANC may interface with the GSM SCF for optional CAMEL control using Ge reference point
according to 3GPP TS 23.078 [7].
- The EGANC may interface with the CGF (Charging Gateway Functionality) using Ga interface for off-line
charging via CDRs to according to 3GPP TS 32.251 [8].
- The EGANC optionally interfaces ADMF (Administration Function), DF2 (Delivery Function 2) and DF3
(Delivery Function 3) via X1-1, X2 and X3 for lawful interception if required (refer to contribution on
Lawful Interception) according to 3GPP TS 33.107 [10].
5.1.1.2 Protocol stacks
The control plane and user plane CS domain protocol stacks are unchanged from existing GAN. CS domain protocols
stacks are not shown here. The PS domain proposed changes are independent from the CS domain.
5.1.1.2.1 PS Control Plane
The PS control plane protocol stack is shown in figure 2.
Up Interface Gn
GA-SM
GA-SM
GTP-c GTP-c
UDP UDP UDP
UDP GPRSGAN- SAP
Remote Remote
IP IP
IpSec IpSec
Transport Transport Transport L2 L2
Access Access Access Physical Physical
MS Generic Network EGANC-PS GGSN

Figure 2: A/Gn alternative PS control plane protocol stacks
The control plane is simplified in the following way:
• The two protocol stacks in a row (GA-PSR + BSSGP) can be replaced by one single upper layer protocol (GA-
SM).
• GA-SM (GAN Session Management) protocol takes the role of NAS 24.008, and it reuses 24.008 SM messages.
The parallel operation of the two radios of the terminal allow for a make-before-break handover.
• LLC is not required because user plane and control plane are separated, and because security is ensured by the
IPsec tunnel. Removing LLC provides enhancement to the whole performance.
Furthermore UDP is sufficient to address GA-SM via a well-known port: TCP is not needed as signalling in GPRS is
performed above LLC in unacknowledged mode (SAPI 1), and there is already a TCP connection to check the presence
of the terminal, established at GAN registration.
ETSI
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