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Doc.: IEEE 802.11-00/xxx SubmissionSlide 1 WLAN-Cellular Interworking Rajesh S. Pazhyannur GTSS, Motorola.

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Presentation on theme: "Doc.: IEEE 802.11-00/xxx SubmissionSlide 1 WLAN-Cellular Interworking Rajesh S. Pazhyannur GTSS, Motorola."— Presentation transcript:

1 doc.: IEEE 802.11-00/xxx SubmissionSlide 1 WLAN-Cellular Interworking Rajesh S. Pazhyannur GTSS, Motorola

2 doc.: IEEE 802.11-00/xxx SubmissionNovember 21, 2002Slide 2 Contributors Chad Fors Nat Natarajan Johanna Wild All from GTSS, Motorola Contact Address Rajesh S. Pazhyannur, QA6283@email.mot.com

3 doc.: IEEE 802.11-00/xxx SubmissionNovember 21, 2002Slide 3 Outline Introduction Architectural Approaches Standardization Efforts Experiences from Feasibility Study

4 doc.: IEEE 802.11-00/xxx SubmissionNovember 21, 2002Slide 4 Introduction WLAN Segments –Public Hotspots Airports, Cafes, etc –Enterprises –Residences Primary Focus –Public Hotspots and Cellular Data Systems –Integrated “Data” Services Important Area not Discussed –Integrating Enterprise WLAN with Cellular Voice need picture

5 doc.: IEEE 802.11-00/xxx SubmissionNovember 21, 2002Slide 5 Cellular Coverage Area WLAN Hotspots Motivation Ubiquitous Wireless Data Network –WLAN in Hotspot, GPRS/CDMA-1X in Macro Cellular Operator Benefits – Augment Cellular Data Service –Leverage/Reuse existing investment in Cellular Data System for WLAN service –Attract WLAN users to Cellular Data Service

6 doc.: IEEE 802.11-00/xxx SubmissionNovember 21, 2002Slide 6 High-Level Requirements Authentication –authentication provided by cellular operator –“common” authentication Billing –Single Bill based on combined data usage Session Mobility –Handoff between WLAN and Cellular Support WLAN Roaming –Third Party owned WLAN Hotspots Access to Applications from WLAN –IMS (Messaging)

7 doc.: IEEE 802.11-00/xxx SubmissionNovember 21, 2002Slide 7 Architectural Approaches

8 doc.: IEEE 802.11-00/xxx SubmissionNovember 21, 2002Slide 8 WLAN-Cellular Integration Multiple Approaches –Loosely coupled architecture –Tightly coupled architecture –No coupling –Proprietary architectures (vendor-specific solutions)

9 doc.: IEEE 802.11-00/xxx SubmissionNovember 21, 2002Slide 9 Tight and Loose Coupling Tight Coupling –Hierarchical relationship between WLAN and Cellular WLAN as an alternate access network WLAN traffic routed through cellular core network Loose Coupling –WLAN as peer IP access network –Maintain distinct systems for bearer traffic –Reuse AAA services for WLAN

10 doc.: IEEE 802.11-00/xxx SubmissionNovember 21, 2002Slide 10 Tightly Coupled WLAN-GPRS System WLAN Network GPRS RAN GPRS Core Internet Operator’s IP Network GGSN Firewall Billing System Billing System S-CDR CG Billing Mediator IWU HLR (AuC) SIM SGSN Gi

11 doc.: IEEE 802.11-00/xxx SubmissionNovember 21, 2002Slide 11 Loosely Coupled WLAN-GPRS System GPRS RAN SGSN Internet GGSN Operator’s IP Network WLAN System (operator owned) Firewall HLR (AuC) AAA server WLAN System (Third party) Billing Mediator Billing Mediator Billing System Billing System CG Home Agent HLR IWU Proxy AAA

12 doc.: IEEE 802.11-00/xxx SubmissionNovember 21, 2002Slide 12 Loose Coupling Point Tight Coupling Point GPRS Tight Coupling Point UMTS Reference Architecture

13 doc.: IEEE 802.11-00/xxx SubmissionNovember 21, 2002Slide 13 No Coupling Maintain separate systems Two separate services –Separate sign-on for WLAN and Cellular Data –Separate bills

14 doc.: IEEE 802.11-00/xxx SubmissionNovember 21, 2002Slide 14 Standardization Efforts

15 doc.: IEEE 802.11-00/xxx SubmissionNovember 21, 2002Slide 15 Standardization Groups 3GPP –GPRS and UMTS Systems –One year ago –Interworking Scenarios Document 3GPP2 –CDMA 1X Systems –4Q, 2002 –Stage 1 Document IETF –Authentication/Security, Mobility

16 doc.: IEEE 802.11-00/xxx SubmissionNovember 21, 2002Slide 16 3GPP and WLAN Feasibility Study Highlights Six Interworking scenarios –Incremental Functionality Interworking based on IP as common layer –Independent of WLAN radio technology Reuse standard WLAN mechanisms

17 doc.: IEEE 802.11-00/xxx SubmissionNovember 21, 2002Slide 17 3GPP Six Scenarios for WLAN-Cellular Interworking –Scenario 1: Common Billing and Customer Care –Scenario 2: 3GPP system based Access Control and Charging –Scenario 3: Access to 3GPP system PS based services –Scenario 4: Service Continuity –Scenario 5: Seamless services –Scenario 6: Access to 3GPP CS Services Currently Focused on Scenarios 2 and 3 Advocating a Loose Coupling Architecture

18 doc.: IEEE 802.11-00/xxx SubmissionNovember 21, 2002Slide 18 Non Roaming Reference Model The shaded area refers to scenario 3 functionality.

19 doc.: IEEE 802.11-00/xxx SubmissionNovember 21, 2002Slide 19 Roaming Reference Model The shaded area refers to scenario 3 functionality.

20 doc.: IEEE 802.11-00/xxx SubmissionNovember 21, 2002Slide 20 Network Selection Access Point may have relationship with multiple 3GPP Network Providers User wishes to choose the service operator Operator 1 Operator 2 Operator 3

21 doc.: IEEE 802.11-00/xxx SubmissionNovember 21, 2002Slide 21 Potential Solutions WLAN based Solutions 1.Multiple SSIDs in the beacon 2.Round Robin SSIDs 3.Multiple BSSIDs: –One Beacon per SSID EAP Based Solution –Prior to Authentication, probe the AP for Systems supported

22 doc.: IEEE 802.11-00/xxx SubmissionNovember 21, 2002Slide 22 Motorola Feasibility Study Advanced Technology Effort –CDMA-1X and GPRS –Loosely Coupled Architecture –Investigate implementation issues –Evaluate commercial offering Focus on Functionality –EAP-SIM –Roaming and Session Mobility –Accounting and Single Bill

23 doc.: IEEE 802.11-00/xxx SubmissionNovember 21, 2002Slide 23 EAP-SIM Subscriber Identity Module (SIM) has a long history –Smart card that is removable from the phone equipment –Used to authenticate GSM/GPRS users EAP-SIM enables WLAN authentication based on SIM Why EAP-SIM? –Cellular Operators like it !! Single Point of Provisioning Leverage existing resources and assets –GSM users are conversant with SIM –Provides a degree of security within the 802.1X framework –Being standardized within IETF

24 doc.: IEEE 802.11-00/xxx SubmissionNovember 21, 2002Slide 24 EAP-SIM Operation Client Device IP Network RADIUS Server HLR IWU SS7 link EAP-SIMServer EAP-SIMClient Authentication Request GetTriplets Triplets SIM Challenge Success Challenge Response

25 doc.: IEEE 802.11-00/xxx SubmissionNovember 21, 2002Slide 25 EAP-SIM Issues How are SIM Cards administered? –Single SIM versus Multiple SIM How does the WLAN user connect to SIM card? –WLAN card is integrated with SIM –WLAN device (PDA, etc) connected to SIM dongle through USB –WLAN device has a sleeve to insert SIM (just like phones)

26 doc.: IEEE 802.11-00/xxx SubmissionNovember 21, 2002Slide 26 WLAN-Cellular Handover Handover is accomplished through MIP Requires Following Components –MIP Client –MIP Home Agent How does it work? –Mobile is assigned a Home Address. –When Mobile is away from home, it acquires a Care-of-address –Mobile IP Client registers Care-of-address with Home Agent –All IP packets destined to Home Address are intercepted by Home Agent. –Home Agent forwards IP packets to Care-of-Address –As Mobile Moves between WLAN and Cellular Care-of-Address Changes but Home Address remains same TCP/UDP Sessions based on Home Address are unaffected between handoffs

27 doc.: IEEE 802.11-00/xxx SubmissionNovember 21, 2002Slide 27 WLAN-Cellular Handover (Mobile IP) Cellular Network Cellular Network WLAN System WLAN System Internet Web Server MIP Home Agent Registration Tunnel Setup Tunnel 192.10.10.10 to 68.10.10.10 Home Address: 192.10.10.10 Care-of-Address (Cellular) 68.10.10.10

28 doc.: IEEE 802.11-00/xxx SubmissionNovember 21, 2002Slide 28 WLAN-Cellular Handover (Mobile IP) Cellular Network Cellular Network WLAN System WLAN System Internet Web Server MIP Home Agent Registration Tunnel Setup Tunnel 192.10.10.10 to 104.10.10.10 Home Address: 192.10.10.10 Care-of-Address (WLAN) 104.10.10.10

29 doc.: IEEE 802.11-00/xxx SubmissionNovember 21, 2002Slide 29 Session Mobility Issues Support for Mobile IP in Cellular Systems NATs and Firewalls Interaction between VPN and MIP Clients MIP Handover Performance

30 doc.: IEEE 802.11-00/xxx SubmissionNovember 21, 2002Slide 30 Interaction between VPN and MIP VPN Clients intolerant of changes in Route Table –Any Change in route table usually resets the VPN –Force VPN Re-authentication Assume VPN over MIP –MIP running on top of WLAN –Move out of WLAN coverage into Cellular –Acquire IP address from Cellular. –MIP handover from WLAN to Cellular Workarounds 1.Integrated MIP and VPN 2.Make VPN more “tolerant” of changes

31 doc.: IEEE 802.11-00/xxx SubmissionNovember 21, 2002Slide 31 Support for Mobile IP in Cellular Systems 3GPP2 has incorporated MIP –PDSN behaves as FA, Handsets have MIP clients 3GPP does not require MIP –Some GGSN providers have MIP capability Is FA Care-of-Address Registration important?

32 doc.: IEEE 802.11-00/xxx SubmissionNovember 21, 2002Slide 32 NATs and Firewalls Private IP addresses are a problem for MIP –MIP Clients can register with Home Agent –Home Agent tunnels packets to Private IP address (not the NATted public IP address) Potential Workarounds: –IETF is working on numerous NAT Traversal drafts. Tunnel MIP packets within UDP packets Firewalls may block tunneled packets –Mobile IP uses IP-in-IP tunnels between HA and Client Potential Workaround –Use GRE for tunneling –Change firewall policy to allow MIP packets

33 doc.: IEEE 802.11-00/xxx SubmissionNovember 21, 2002Slide 33 Handoff Delays Handoff Delays are still “large” (~4 secs) Sources of delay –IP address assignment (DHCP) and authentication –Detection of Loss of WLAN coverage –Cellular Data call-setup Impact of Delay (> 4 sec) on Applications –Some FTP clients will “hang” –Streaming Clients sometimes “freeze” Adjusting buffer size has “mixed” effect

34 doc.: IEEE 802.11-00/xxx SubmissionNovember 21, 2002Slide 34 Post-Paid Billing After successful authentication WLAN AP sends RADIUS Start message to Proxy AAA. After logoff (or suitable termination) WLAN AP sends RADIUS STOP message to Proxy AAA. AP may send Interim Update messages. RADIUS record contains duration, bytes sent/received, unique record identifier Home AAA collects RADIUS records from PDSN and WLAN systems Billing Mediator mediates WLAN and CDMA 1X records and presents to Billing System Billing System creates single bill based on Billing policy. CDMA Network WLAN Hot-Spot Billing System Billing Mediator Home AAA WLAN APs Proxy AAA PDSN Proxy AAA Single Bill

35 doc.: IEEE 802.11-00/xxx SubmissionNovember 21, 2002Slide 35 Billing Issues Accounting Records in WLAN Systems –No standards unlike 3GPP and 3GPP2 –Perhaps WECA (??) –3GPP2 uses RADIUS accounting records Quite different from what APs provide

36 doc.: IEEE 802.11-00/xxx SubmissionNovember 21, 2002Slide 36 Key Conclusions WLAN-Cellular Interworking is relatively easy to implement –Most components for Scenarios 1-4 exist –Does not affect 3GPP and 3GPP2 systems in any significant manner –High Reuse between 3GPP and 3GPP2 Systems Combination Devices may be potential trigger! –Combination PC cards –Dual-Mode WLAN-Cellular Phones

37 doc.: IEEE 802.11-00/xxx SubmissionNovember 21, 2002Slide 37 Backup


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