Transcript doc.: IEEE 802.11

November 2003
IEEE P802 Handoff ECSG
WLAN – Cellular Interworking
Stephen McCann, Siemens Roke Manor
[email protected]
Submission
Slide 1
Stephen McCann, Siemens Roke Manor
November 2003
IEEE P802 Handoff ECSG
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 nonpartisan overview of previous interworking
activities in ETSI, MMAC and IEEE 802.11
Submission
Slide 2
Stephen McCann, Siemens Roke Manor
November 2003
IEEE P802 Handoff ECSG
Coupling Approaches
• Loosely, classify against two extremes:
– Re-use WLAN radio layer within existing public network
– Deploy public network services on WLAN network
Also,
alternative
directions for
other mobile
standards
(CDMA etc.)
R'99 UMTS
UMTS
3G
tighter
2/3G
Any operator
with an HLR
Any
operator
looser
• 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
Submission
Slide 3
Stephen McCann, Siemens Roke Manor
November 2003
IEEE P802 Handoff ECSG
Previous work
Submission
Slide 4
Stephen McCann, Siemens Roke Manor
November 2003
IEEE P802 Handoff ECSG
WLAN Standardisation
WIG
Submission
Slide 5
Stephen McCann, Siemens Roke Manor
November 2003
IEEE P802 Handoff ECSG
IEEE 802.11 & WIG
• Plenary Motion Approved in 2002
– Move that the WNG Standing Committee
requests the 802.11 WG to accept the
invitation from ETSI-BRAN and MMAC
to participate in the “WLAN – 3G and
other Public Access networks
“interworking” (WIG) project.
Submission
Slide 6
Stephen McCann, Siemens Roke Manor
November 2003
IEEE P802 Handoff ECSG
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.
Submission
Slide 7
Stephen McCann, Siemens Roke Manor
November 2003
IEEE P802 Handoff ECSG
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
Submission
Slide 8
Stephen McCann, Siemens Roke Manor
November 2003
IEEE P802 Handoff ECSG
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
Submission
Slide 9
Stephen McCann, Siemens Roke Manor
November 2003
IEEE P802 Handoff ECSG
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.
Submission
Slide 10
Stephen McCann, Siemens Roke Manor
November 2003
IEEE P802 Handoff ECSG
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.
Submission
Slide 11
Stephen McCann, Siemens Roke Manor
November 2003
IEEE P802 Handoff ECSG
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)
Submission
Slide 12
Stephen McCann, Siemens Roke Manor
November 2003
IEEE P802 Handoff ECSG
IEEE 802.11
Interworking 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.
Submission
Slide 13
Stephen McCann, Siemens Roke Manor
November 2003
IEEE P802 Handoff ECSG
Coupling
Submission
Slide 14
Stephen McCann, Siemens Roke Manor
November 2003
IEEE P802 Handoff ECSG
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
Submission
Slide 15
Stephen McCann, Siemens Roke Manor
November 2003
IEEE P802 Handoff ECSG
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’
Submission
Slide 16
Stephen McCann, Siemens Roke Manor
November 2003
IEEE P802 Handoff ECSG
Architecture
In the simp lest case the
IETF IWU may not exist.
Diameter/RADIUS is used to
communicate with the
AAAH /HSS
IETF
IWU
AAAL
WLAN
HSS
HLR
Authentication
Information
User traffic
Router
AAAH
Diameter/RAD
3GPP System
IWU
MAP
Service Provider
Network
AP
User traffic
MT
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
Inte rnet
Submission
Slide 17
Stephen McCann, Siemens Roke Manor
November 2003
IEEE P802 Handoff ECSG
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)
Submission
Slide 18
Stephen McCann, Siemens Roke Manor
November 2003
IEEE P802 Handoff ECSG
Architecture
GGSN
SGSN
SGSN
SGSN
Iu*
Iu
Iur*
Iur*/utr
IWU
IWU
Iub*
AP
RNC
Iub*
AP
AP
Iub
NODE
B
AP
Uu*
NODE
B
Uu
dual
mode
mobile
Submission
Slide 19
• Similar interface
methodology to
UTRAN
• Can extend to
very seamless
UTRA-WLAN
handover (dual
mode terminals)
Stephen McCann, Siemens Roke Manor
November 2003
IEEE P802 Handoff ECSG
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 nonWLAN standards (apparently)
– Re-engineering of one to fit into the assumptions of the
other
Submission
Slide 20
Stephen McCann, Siemens Roke Manor
November 2003
IEEE P802 Handoff ECSG
Architecture detail
Submission
Slide 21
Stephen McCann, Siemens Roke Manor
November 2003
IEEE P802 Handoff ECSG
Interworking architecture
User Data
Forwarding Function
MT
Application
User Credential
Storage
WLAN
Ms
WLAN Functions
Authenticator
Lp
Authoriser
Authorisation
Function
Ep
Epa
Standard Network Protocols
Standard Network Protocols
Resource
Monitor
WLAN Technology
WLAN Technology
La
Ls
Attendant
AI
W2
Accounting
Function
Ea
Authentication
Function
Es
W3
User Data Flow
Interface
Submission
Slide 22
Stephen McCann, Siemens Roke Manor
November 2003
IEEE P802 Handoff ECSG
EAP Method
EAP Method
EAP
EAP
GST/EAPoH
DLC/RLC
Phy
Phy
MT
Diameter
GST/EAPoH
DLC/RLC
WLAN
AN
EAP
IETF
Transport
AP
EAP Method
EAP
802.1x/EAPoL
802.1x/EAPoL
802.11 MAC
802.11 MAC
802.11 Phy
802.11 Phy
Submission
IETF
Transport
Service
providers net
EAP Method
EAP
Diameter
Slide 23
EAP
Radius
Radius
IETF
Transport
IETF
Transport
Stephen McCann, Siemens Roke Manor
November 2003
IEEE P802 Handoff ECSG
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
Submission
Slide 24
Stephen McCann, Siemens Roke Manor
November 2003
IEEE P802 Handoff ECSG
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
Submission
Slide 25
Stephen McCann, Siemens Roke Manor
November 2003
IEEE P802 Handoff ECSG
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
Submission
Slide 26
Stephen McCann, Siemens Roke Manor
November 2003
IEEE P802 Handoff ECSG
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
Submission
Slide 27
Stephen McCann, Siemens Roke Manor
November 2003
IEEE P802 Handoff ECSG
Way Forward
• 802 Handoff produces generic solution to
homogeneous and heterogeneous
interworking.
• 802.11 Interworking group (?) studies
specific problems related to Cellular
interworking.
Submission
Slide 28
Stephen McCann, Siemens Roke Manor
November 2003
Submission
IEEE P802 Handoff ECSG
Slide 29
Stephen McCann, Siemens Roke Manor