1. WGSN: WLAN-based GPRS Support Node
Student : Lin-Yi Wu
Advisor : Yi-Bing Lin
Lab 117
Department of Computer Science & Information Engineering,
National Chiao Tung University 1

2. Outline Introduction To Cellular And WLAN Interworking
The WGSN Approach
Design and Implementation of WGSN
Phase I
Phase II
Conclusion 2

3. Cellular/WLAN Interworking
Advantages
User can choose appropriate network access to acquire efficient service.
Provides can extend the service coverage, so as to increase competitiveness.
Related work
3GPP TR , v (2002) Services and System Aspects; Feasibility Study on3GPP System to Wireless Local Area Network (WLAN) Interworking.
Haverinen, H., Mikkonen, J., and Takamaki, T., “Cellular access control and charging for mobile operator wireless local area networks,” IEEE Wireless Communications, Volume: 9 Issue: 6,
Salkintzis, A.K., Fors, C., and Pazhyannur, R., “WLAN-GPRS integration for next-generation mobile data networks,” IEEE Wireless Communications, Volume: 9 Issue: 5, 3

4. Interworking Scenarios and Service Capabilities (by 3GPP 22.934)
Common Billing 
Common Customer Care
3G-based Access Control
3G-based Access Charging
Access to 3G PS Services
Service Continuity
Seamless Service Continuity
Access to 3G CS Services with Continuity Mobility 4

5. WGSN Architecture 5

6. Design and Implementation of WGSN
Phase I (Mar ~ Dec. 2002)
SIM-based authentication (GMM over IP)
VoIP service (SIP protocol)
OA&M: traffic monitoring, CDR, SNMP interface
Phase II (Jan ~)
Supporting 802.1x
Supporting PDA
Integrating with OSA(Open Service Access)/IMS (IP Multimedia Subsystem) 6

7. GPRS SIM-based Authentication7

8. Phase 1 : WGSN Protocol Stack8

9. Phase 1 : The MS Architecture9

10. Phase 1 : The WGSN Node Architecture10

11. SIP Message Traversal Problem 111

12. SIP Message Traversal Problem 212

13. SIP Application Level Gateway (SIP ALG)13

14. Phase 1 : The Attach Procedure14

15. Phase 1 : The Detach Procedure15

16. Disadvantage of WGSN Phase I
User gains IP address before being authenticated.
Solution
Perform SIM-based authentication based on EAP/EAPOL. 16

17. Phase II : Protocol Stack
EAP-GMM
EAP-GMM
EAP
EAP
MAP
MAP
RADIUS
RADIUS
TCAP
TCAP
EAP-OL
EAP-OL
UDP
UDP
SCCP
SCCP IP IP
MTP3
MTP3
Ethernet
Ethernet
MTP2
MTP2
802.11
802.11 L1 L1 L1 L1 MS AP
WGSN
HLR
(a) Control Plane 17
(b) User Plane

18. Phase II : The MS Architecture18

19. Phase II : The WGSN node Architecture19

20. SIP-based Push Center (SPC)
SPC provides MS terminated SIP services for the WGSN user who does not activate the SIP UA .
Step 1 : Calling party sends SIP INVITE message.
Step 2 : SPC sends a short message to the MS to activate the SIP UA.
Step 3 : After activating SIP UA, MS sends a response message to SPC.
Step 4 : SPC forwards the SIP INVITE message to the MS. 20

21. Phase II – Attach Procedure21

22. Conclusion
We proposed WGSN, a solution for integrating 3G and WLAN services.
The 3G mechanisms are re-used for WLAN user authentication and network access.
The WGSN features and implementation are described.
The WGSN prototype has been implemented in ITRI and NCTU Joint Research Center. 22