WLAN – Cellular Interworking : November 2003 Stephen McCann, Siemens Roke Manor Slide 1 WLAN – Cellular Interworking Stephen McCann, Siemens Roke Manor
stephen.mccann@roke.co.uk
Who am I? : November 2003 Stephen McCann, Siemens Roke Manor Slide 2 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
Coupling Approaches : November 2003 Stephen McCann, Siemens Roke Manor Slide 3 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.)
Previous work : November 2003 Stephen McCann, Siemens Roke Manor Slide 4 Previous work
WLAN Standardisation : November 2003 Stephen McCann, Siemens Roke Manor Slide 5 WLAN Standardisation } WIG
IEEE 802.11 & WIG : November 2003 Stephen McCann, Siemens Roke Manor Slide 6 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.
What was WIG all about ? : November 2003 Stephen McCann, Siemens Roke Manor Slide 7 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.
Previous work : November 2003 Stephen McCann, Siemens Roke Manor Slide 8 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
WIG Intended Output ? : November 2003 Stephen McCann, Siemens Roke Manor Slide 9 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
Why bother ? : November 2003 Stephen McCann, Siemens Roke Manor Slide 10 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.
IEEE 802.11 activities : November 2003 Stephen McCann, Siemens Roke Manor Slide 11 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.
IEEE 802.11 Interworking : November 2003 Stephen McCann, Siemens Roke Manor Slide 12 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)
IEEE 802.11Interworking Study GroupProposed Scope : November 2003 Stephen McCann, Siemens Roke Manor Slide 13 IEEE 802.11Interworking Study GroupProposed 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.
Coupling : November 2003 Stephen McCann, Siemens Roke Manor Slide 14 Coupling
Traditional Coupling Models : November 2003 Stephen McCann, Siemens Roke Manor Slide 15 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
Control Plane Interworking : November 2003 Stephen McCann, Siemens Roke Manor Slide 16 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’
Architecture : November 2003 Stephen McCann, Siemens Roke Manor Slide 17 Architecture
Control & User Plane Interworking : November 2003 Stephen McCann, Siemens Roke Manor Slide 18 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)
Architecture : November 2003 Stephen McCann, Siemens Roke Manor Slide 19 Architecture Similar interface methodology to UTRAN
Can extend to very seamless UTRA-WLAN handover (dual mode terminals)
Implications : November 2003 Stephen McCann, Siemens Roke Manor Slide 20 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
Architecture detail : November 2003 Stephen McCann, Siemens Roke Manor Slide 21 Architecture detail
Slide 22: November 2003 Stephen McCann, Siemens Roke Manor Slide 22 Interworking architecture
Slide 23: November 2003 Stephen McCann, Siemens Roke Manor Slide 23 Service
providers net AP MT WLAN
AN HL2/HiSWANa 802.11i Phy DLC/RLC DLC/RLC Phy
Security Issues : November 2003 Stephen McCann, Siemens Roke Manor Slide 24 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
Accounting and Charging : November 2003 Stephen McCann, Siemens Roke Manor Slide 25 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
Inter-System Handover Issues : November 2003 Stephen McCann, Siemens Roke Manor Slide 26 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
Quality of Service : November 2003 Stephen McCann, Siemens Roke Manor Slide 27 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
Way Forward : November 2003 Stephen McCann, Siemens Roke Manor Slide 28 Way Forward 802 Handoff produces generic solution to homogeneous and heterogeneous interworking.
802.11 Interworking group (?) studies specific problems related to Cellular interworking.
Slide 29: November 2003 Stephen McCann, Siemens Roke Manor Slide 29