WLAN – Cellular Interworking

1. WLAN – Cellular Interworking Stephen McCann, Siemens Roke Manor stephen.mccann@roke.co.uk Stephen McCann, Siemens Roke Manor

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 Stephen McCann, Siemens Roke Manor

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.) Stephen McCann, Siemens Roke Manor

4. Previous work Stephen McCann, Siemens Roke Manor

5. } WLAN Standardisation WIG Stephen McCann, Siemens Roke Manor

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. Stephen McCann, Siemens Roke Manor

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. Stephen McCann, Siemens Roke Manor

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 Stephen McCann, Siemens Roke Manor

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 Stephen McCann, Siemens Roke Manor

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. Stephen McCann, Siemens Roke Manor

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. Stephen McCann, Siemens Roke Manor

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) Stephen McCann, Siemens Roke Manor

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. Stephen McCann, Siemens Roke Manor

14. Coupling Stephen McCann, Siemens Roke Manor

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 Stephen McCann, Siemens Roke Manor

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’ Stephen McCann, Siemens Roke Manor

17. Architecture Stephen McCann, Siemens Roke Manor

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) Stephen McCann, Siemens Roke Manor

19. Architecture • Similar interface methodology to UTRAN • Can extend to very seamless UTRA-WLAN handover (dual mode terminals) Stephen McCann, Siemens Roke Manor

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 Stephen McCann, Siemens Roke Manor

21. Architecture detail Stephen McCann, Siemens Roke Manor

22. Interworking architecture Stephen McCann, Siemens Roke Manor

23. EAP Method EAP Method EAP Method EAP Method EAP Radius EAP EAP EAP Diameter EAP EAP Diameter Radius 802.1x/EAPoL GST/EAPoH 802.1x/EAPoL GST/EAPoH 802.11 MAC 802.11 MAC IETF Transport IETF Transport IETF Transport IETF Transport 802.11 Phy 802.11 Phy HL2/HiSWANa DLC/RLC DLC/RLC Phy Phy Service providers net WLAN AN AP MT 802.11i Stephen McCann, Siemens Roke Manor

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 Stephen McCann, Siemens Roke Manor

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 Stephen McCann, Siemens Roke Manor

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 Stephen McCann, Siemens Roke Manor

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 Stephen McCann, Siemens Roke Manor

28. Way Forward • 802 Handoff produces generic solution to homogeneous and heterogeneous interworking. • 802.11 Interworking group (?) studies specific problems related to Cellular interworking. Stephen McCann, Siemens Roke Manor

29. Stephen McCann, Siemens Roke Manor