WLAN-Cellular Interworking Rajesh S. Pazhyannur GTSS, Motorola 4/15/2017 WLAN-Cellular Interworking Rajesh S. Pazhyannur GTSS, Motorola

Contributors Chad Fors Nat Natarajan Johanna Wild All from GTSS, Motorola Contact Address Rajesh S. Pazhyannur, QA6283@email.mot.com November 21, 2002

Outline Introduction Architectural Approaches Standardization Efforts Experiences from Feasibility Study November 21, 2002

Introduction WLAN Segments Primary Focus Important Area not Discussed 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 need picture                         November 21, 2002

Motivation Ubiquitous Wireless Data Network Cellular Operator Benefits 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 Cellular Coverage Area WLAN Hotspots November 21, 2002

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) November 21, 2002

Architectural Approaches November 21, 2002

WLAN-Cellular Integration Multiple Approaches Loosely coupled architecture Tightly coupled architecture No coupling Proprietary architectures (vendor-specific solutions) November 21, 2002

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 November 21, 2002

Tightly Coupled WLAN-GPRS System RAN Operator’s IP Network HLR (AuC) GPRS Core Firewall SGSN Internet Gi GGSN CG S-CDR Billing Mediator Billing System WLAN Network SIM IWU November 21, 2002

Loosely Coupled WLAN-GPRS System HLR IWU AAA server GPRS RAN Home Agent HLR (AuC) Operator’s IP Network Internet SGSN Firewall GGSN CG Billing Billing Billing Billing Mediator Mediator Mediator Mediator Proxy AAA Billing Billing Billing System System System WLAN System (operator owned) WLAN System (Third party) November 21, 2002

Reference Architecture Loose Coupling Point Tight Coupling Point GPRS Tight Coupling Point UMTS November 21, 2002

No Coupling Maintain separate systems Two separate services Separate sign-on for WLAN and Cellular Data Separate bills November 21, 2002

Standardization Efforts November 21, 2002

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 November 21, 2002

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 November 21, 2002

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 November 21, 2002

Non Roaming Reference Model The shaded area refers to scenario 3 functionality. November 21, 2002

Roaming Reference Model The shaded area refers to scenario 3 functionality. November 21, 2002

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 November 21, 2002

Potential Solutions WLAN based Solutions EAP Based Solution Multiple SSIDs in the beacon Round Robin SSIDs Multiple BSSIDs: One Beacon per SSID EAP Based Solution Prior to Authentication, probe the AP for Systems supported November 21, 2002

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 November 21, 2002

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 November 21, 2002

EAP-SIM Operation RADIUS Server IWU HLR IP Network Get Triplets SS7 link Get Triplets Triplets RADIUS Server Client Device Challenge Response Authentication Request EAP-SIM Client EAP-SIM Server Success SIM Challenge November 21, 2002

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) November 21, 2002

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 November 21, 2002

WLAN-Cellular Handover (Mobile IP) 4/15/2017 WLAN-Cellular Handover (Mobile IP) Web Server Internet Home Address: 192.10.10.10 Care-of-Address (Cellular) 68.10.10.10 MIP Home Agent Tunnel Setup Tunnel 192.10.10.10 to 68.10.10.10 Registration WLAN System Cellular Network Free form. Could be a diagram including superimposed message flows. Could have bullets on the side. November 21, 2002

WLAN-Cellular Handover (Mobile IP) 4/15/2017 WLAN-Cellular Handover (Mobile IP) Web Server Internet Home Address: 192.10.10.10 Care-of-Address (WLAN) 104.10.10.10 MIP Home Agent Tunnel Setup Tunnel 192.10.10.10 to 104.10.10.10 Registration WLAN System Cellular Network Free form. Could be a diagram including superimposed message flows. Could have bullets on the side. November 21, 2002

Session Mobility Issues Support for Mobile IP in Cellular Systems NATs and Firewalls Interaction between VPN and MIP Clients MIP Handover Performance November 21, 2002

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 Integrated MIP and VPN Make VPN more “tolerant” of changes November 21, 2002

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? November 21, 2002

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 November 21, 2002

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 November 21, 2002

Post-Paid Billing CDMA Network WLAN Hot-Spot Billing System Billing Mediator Home AAA WLAN APs Proxy AAA PDSN Single Bill 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. November 21, 2002

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 November 21, 2002

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 November 21, 2002

Backup November 21, 2002