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WLAN – Cellular Interworking. Stephen McCann, Siemens Roke Manor stephen.mccann@roke.co.uk. Who am I?. I work for Siemens in the UK. I don’t represent ETSI, MMAC or any working group within it, nor does this presentation - PowerPoint PPT Presentation
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November 2003
Stephen McCann, Siemens Roke Manor
Slide 1
IEEE P802 Handoff ECSG
Submission
WLAN – Cellular Interworking
Stephen McCann, Siemens Roke Manorstephen.mccann@roke.co.uk
November 2003
Stephen McCann, Siemens Roke Manor
Slide 2
IEEE P802 Handoff ECSG
Submission
Who am I?
• I work for Siemens in the UK.• I don’t represent ETSI, MMAC or any
working group within it, nor does this presentation
• However, this is an attempt to be a non-partisan overview of previous interworking activities in ETSI, MMAC and IEEE 802.11
November 2003
Stephen McCann, Siemens Roke Manor
Slide 3
IEEE P802 Handoff ECSG
Submission
Coupling Approaches• Loosely, classify against two extremes:
– Re-use WLAN radio layer within existing public network– Deploy public network services on WLAN network
• The ‘tight’ approaches are more specific, complex, functional– (and disruptive to existing standards)
• The ‘loose’ approaches don’t rule out operators falling into the more specific categories
Also, alternative directions for other mobile standards (CDMA etc.)
tighter
R'99 UMTS UMTS 3G 2/3G Any operatorwith an HLR
Anyoperator
looser
November 2003
Stephen McCann, Siemens Roke Manor
Slide 4
IEEE P802 Handoff ECSG
Submission
Previous work
November 2003
Stephen McCann, Siemens Roke Manor
Slide 5
IEEE P802 Handoff ECSG
Submission
WLAN Standardisation
} WIG
November 2003
Stephen McCann, Siemens Roke Manor
Slide 6
IEEE P802 Handoff ECSG
Submission
IEEE 802.11 & WIG
• Plenary Motion Approved in 2002Plenary Motion Approved in 2002
– Move that the WNG Standing Committee Move that the WNG Standing Committee requests the 802.11 WG to accept the requests the 802.11 WG to accept the invitation from ETSI-BRAN and MMAC invitation from ETSI-BRAN and MMAC to participate in the “to participate in the “WLAN – 3G and WLAN – 3G and other Public Access networks other Public Access networks “interworking” (WIG) project.“interworking” (WIG) project.
November 2003
Stephen McCann, Siemens Roke Manor
Slide 7
IEEE P802 Handoff ECSG
Submission
What was WIG all about ?
• To establish a joint-effort between 802.11 and ETSI BRAN/MMAC HSWA for the interworking of WLANs to 3G Cellular systems.
• 802.11 should be represented by its own interworking group.
November 2003
Stephen McCann, Siemens Roke Manor
Slide 8
IEEE P802 Handoff ECSG
Submission
Previous work• At engineering level, TGi already has
similar approach to external authentication (EAPoL) to that of other WLAN standards (e.g. Hiperlan & HiSWAN)
• Previous interworking activities done by ETSI BRAN and MMAC HSWA have similar approach to that of 802.1x
November 2003
Stephen McCann, Siemens Roke Manor
Slide 9
IEEE P802 Handoff ECSG
Submission
WIG Intended Output ?
• WIG Baseline Document• Common text, which will then be passed
based to recognised WLAN standards bodies (ETSI, IEEE & MMAC) for their regulatory approval.
• WIG cannot NOT approve final output
November 2003
Stephen McCann, Siemens Roke Manor
Slide 10
IEEE P802 Handoff ECSG
Submission
Why bother ?
• To create a world wide standard for WLAN interworking with Cellular and Public Access networks.
• To encourage the proliferation of world wide WLAN hotspots, regardless of local regulatory constraints.
November 2003
Stephen McCann, Siemens Roke Manor
Slide 11
IEEE P802 Handoff ECSG
Submission
IEEE 802.11 activities
• Necessity to align interworking work from TGe, TGi, WNG and 802.1
• Procedural requirement to establish some kind of interworking group within 802.11 to address these issues.
November 2003
Stephen McCann, Siemens Roke Manor
Slide 12
IEEE P802 Handoff ECSG
Submission
IEEE 802.11 Interworking
• No specific group in IEEE802.11 dedicated to interworking issues
• Many external activities in this area, 3GPP, 3GPP2, GSMA, WiFi Alliance all addressing interworking issues.
• Bits of interworking done in WNG, TGi, TGe, 802.1 (802.1x and 802.1aa)
November 2003
Stephen McCann, Siemens Roke Manor
Slide 13
IEEE P802 Handoff ECSG
Submission
IEEE 802.11Interworking Study Group
Proposed Scope The scope of the study group is to consider whether there is a requirement
to enhance the IEEE 802.11 standard (and amendments), to add interworking capability to both cellular and external IP based networks.
The intention is to re-use the output of existing Task Groups to form a complete interworking solution, and to fill in any gaps.
November 2003
Stephen McCann, Siemens Roke Manor
Slide 14
IEEE P802 Handoff ECSG
Submission
Coupling
November 2003
Stephen McCann, Siemens Roke Manor
Slide 15
IEEE P802 Handoff ECSG
Submission
Traditional Coupling Models• Loose Coupling
– Avoids use of core network gateways (e.g. SSGN)
– Applicable to many 2.5G, 3G systems
• Tight Coupling– WLAN is an alternative UTRAN– Specific to particular network technology
• Hybrid – bit of both
November 2003
Stephen McCann, Siemens Roke Manor
Slide 16
IEEE P802 Handoff ECSG
Submission
Control Plane Interworking
• Defines a ‘control plane only’ convergence layer
• Handles primarily AAA issues– Can authenticate using SIM or other identifier– Focus is on security and roaming support– Intra-network mobility and QoS are handled in
‘user plane’
November 2003
Stephen McCann, Siemens Roke Manor
Slide 17
IEEE P802 Handoff ECSG
Submission
Architecture
WLAN
AP Router
AAAL
Authentication Information Service Provider
Network
AAAH
Diameter/RADIUS is used to communicate with the
AAAH /HSS
User traffic
MT
Internet
3GPP System IWU
IETF IWU
IETF (Wireless ISP) flavour MT does not have (U)SIM card functionality therefore the IWU is used to inter-operate with the AAAH/HLR/HSS UMTS-HSS flavour MT has (U)SIM card functionality therefore the IW U will be used to inter-operate with the AAAH/HLR/HSS
User traffic
MAP
In the simplest case the IETF IWU may not exist.
Diameter/RAD HLR
HSS
November 2003
Stephen McCann, Siemens Roke Manor
Slide 18
IEEE P802 Handoff ECSG
Submission
Control & User Plane Interworking
• WLAN becomes a ‘peer’ RAN to UTRAN– Similar status to GERAN for GSM/GPRS– Re-use many UMTS functions as is (e.g. idle mode?)
• Covers the complete security/mobility/QoS problem, using UTRA-like internal model
• Retains 3GPP Iu interface, mainly unmodified• Whole family of new WLAN related interfaces
– IurWLAN, IubWLAN – network internal– UuWLAN – extensions or changes to air interface
protocols (mainly in RLC layer)
November 2003
Stephen McCann, Siemens Roke Manor
Slide 19
IEEE P802 Handoff ECSG
Submission
Architecture
• Similar interface methodology to UTRAN
• Can extend to very seamless UTRA-WLAN handover (dual mode terminals)
IWU RNC IWU
GGSN
SGSN SGSN SGSN
dual mode mobile
AP AP AP AP NODE B
NODE B
Iu Iu* Iur*/utr Iur*
Iub Iub* Iub*
Uu Uu*
November 2003
Stephen McCann, Siemens Roke Manor
Slide 20
IEEE P802 Handoff ECSG
Submission
Implications• Strong dependencies on what mobile network
considered– Even on UMTS release number (R5, R6)
• Strong dependencies on WLAN technology• Simpler AN functionality – Core does much more
of the work• Significantly greater impact on WLAN and non-
WLAN standards (apparently)– Re-engineering of one to fit into the assumptions of the
other
November 2003
Stephen McCann, Siemens Roke Manor
Slide 21
IEEE P802 Handoff ECSG
Submission
Architecture detail
November 2003
Stephen McCann, Siemens Roke Manor
Slide 22
IEEE P802 Handoff ECSG
Submission
Interworking architecture
W2 W3AI
WLAN Functions
EaLa
Epa
EsLs
Lp
Attendant
ResourceMonitor
AuthoriserEp
WLAN
User CredentialStorage
MT
AccountingFunction
AuthenticationFunction
User Data Flow
Interface
Application
AuthorisationFunction
User DataForwarding Function
Authenticator
Ms
WLAN Technology
Standard Network Protocols
WLAN Technology
Standard Network Protocols
November 2003
Stephen McCann, Siemens Roke Manor
Slide 23
IEEE P802 Handoff ECSG
Submission
802.11 Phy
802.11 MAC
802.1x/EAPoL
EAP
EAP Method
802.11 Phy
802.11 MAC
802.1x/EAPoL
EAP
Radius
IETF Transport
EAP
EAP Method
Radius
IETF Transport
Service providers netAPMT
WLAN AN
HL
2/H
iSW
AN
a80
2.11
i
GST/EAPoH
EAP
EAP Method
GST/EAPoH
EAP
Diameter
IETF Transport
EAP
EAP Method
Diameter
IETF Transport
Phy
DLC/RLC DLC/RLC
Phy
November 2003
Stephen McCann, Siemens Roke Manor
Slide 24
IEEE P802 Handoff ECSG
Submission
Security Issues
• Working assumption to use EAP• Method for transport of EAP over air is defined• Support for SIM/USIM authentication required by
2G/3G operators– But also required that this is not the only mechanism– AKA extension (i-d) for mapping 2G/3G messages to
EAP
November 2003
Stephen McCann, Siemens Roke Manor
Slide 25
IEEE P802 Handoff ECSG
Submission
Accounting and Charging• System level requirements :
– Basic access/session (pay by subscription)– Access/session duration– Credit card access/session/ Not real time pre paid– Calendar and time related charging – Duration dependent charging– Flat rate– Volume of transferred packet traffic – Multiple rate charge
• Useful features– Rate of transferred packet traffic (Vol/sec). – Toll free (like a 0800 call)– Premium rate access/session – Real time Pre-paid
November 2003
Stephen McCann, Siemens Roke Manor
Slide 26
IEEE P802 Handoff ECSG
Submission
Inter-System Handover Issues• Inter-system handover is a very hard problem
– Weakly supported in loose coupling case• Basically network reselection by terminal• Terminal has to accept that it will get a new IP address with
implications for session continuity
– Possible in tight coupling case but very hard• IurWLAN very complex and interacts strongly with existing
equipment• Main gain comes from joint management of the radio resource
(but main pain also)
– MobileIP is always a fall-back (and near-transparent)– Affects only multi-mode terminals anyway– Need in public environment needs to be examined
November 2003
Stephen McCann, Siemens Roke Manor
Slide 27
IEEE P802 Handoff ECSG
Submission
Quality of Service• If anything, can be even more complex than
security and mobility• Loose coupling approach leaves most options
open (TGe etc)• Tight coupling leverages UMTS QoS architecture • Need to distinguish carefully:
– What the operator wants to do– What the user wants to do– What the user’s applications are capable of doing
November 2003
Stephen McCann, Siemens Roke Manor
Slide 28
IEEE P802 Handoff ECSG
Submission
Way Forward• 802 Handoff produces generic solution to
homogeneous and heterogeneous interworking.
• 802.11 Interworking group (?) studies specific problems related to Cellular interworking.
November 2003
Stephen McCann, Siemens Roke Manor
Slide 29
IEEE P802 Handoff ECSG
Submission
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