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Efficient Mobility Management for Vertical Handoff between WWAN and WLAN

Efficient Mobility Management for Vertical Handoff between WWAN and WLAN. IEEE Communications Magazine November 2003. Authors. Qian Zhang Chuanxiong Guo Zihua Guo Wenwu Zhu All come from Wireless and Networking Group, Microsoft Research Asia. Teammates. 資工所 廖翊均 692410001

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Efficient Mobility Management for Vertical Handoff between WWAN and WLAN

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  1. Efficient Mobility Management for Vertical Handoff between WWAN and WLAN IEEE Communications Magazine November 2003

  2. Authors • Qian Zhang • Chuanxiong Guo • Zihua Guo • Wenwu Zhu • All come from Wireless and Networking Group, Microsoft Research Asia

  3. Teammates • 資工所 廖翊均 692410001 • 資工所 林世敏 692410035 • 資工所 陳崇凱 692410078

  4. Outline • Introduction • Connection manager • Virtual connectivity manager • Performance evaluation • conclusions

  5. Introduction • WLAN vs. WWAN • IEEE 802.11 vs. GPRS • Horizontal handoff vs. Vertical handoff • Mobile IP • HA, FA, CoA • Routing, scalability • Migrate • Reference [8], Proc. Mobicom 2000 • End-to-end • Two limitations • Cannot make mobility transparent to application • Cannot maintain connection under NAT & simultaneous movement

  6. Introduction • Proposed approach • IP-centric • Connection Manager (CM) • Detect conditions and availability of networks • Virtual Connectivity Manager (VC) • Maintain connection’s continuity • Local Connection Translation (LCT) • subscription/notification service (S/N) • Roaming decision maker • Context database

  7. Connection Manager • Handoff from WWAN to WLAN • Physical Layer Sensing • Detect the available of the stable WLAN signal • MAC Layer Sensing • NAV (Network Allocation Vector) • Traffic load vs. NAV occupation • Network-condition-aware handoff • Adaptation of upper layers • Best QoS selected

  8. Connection Manager • Handoff from WLAN to WWAN • FFT-Based Decay Detection • FFT：Fast Fourier Transform • To detect signal decay • X(1)/N：threshold • N：RSSI sampled number

  9. Connection Manager • Adaptive Threshold Configuration • To set an appropriate RSSI threshold • RSSI：Received Signal Strength Indication • S1 = S2 + Δ

  10. Virtual Connectivity Manager • Problems caused by mobility • Transparency to application • Especially important for UDP applications • Transparency to NAT • Simultaneous movements • The VC protocol • Peer negotiation • Connection maintenance • S/N protocol

  11. Virtual Connectivity Manager • Local Connection Translation (LCT) • Mapping relationship between the original and the current connection information • Solve “transparency to application” problem • Subscription/Notification service (S/N) • To bridge the two communication parties so that they can exchange address information • S/N server is publicly addressed and never moves • Solve “transparency to NAT” & “simultaneous movement” problems

  12. Performance Evaluation • OS：Windows 2000 • CM：manipulates and monitors all wireless network interfaces via the NDIS device interface, and provides related information to the roaming decision maker, which runs in the system as a background service. • VC：implemented in the system together with the TCP/IP stack, and is located naturally between the network and transport layers.

  13. Conclusions • In this article a novel mobility management system is proposed for vertical handoff between WWAN and WLAN. • The system integrates a CM and a VC. Collaboration between the CM and VC accomplishes seamless handoff between WWAN and WLAN.

  14. Conclusions • CM：detect the wireless network changes • MAC sensing • FFT detection • adaptive threshold configuration • VC：maintain connectivity using the end-to-end principle • LCT：support application transparency • S/N： support working under NAT and handling of simultaneous movement

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