Efficient Mobility Management for Vertical Handoff between WWAN
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Transcript Efficient Mobility Management for Vertical Handoff between WWAN
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
資工所 林世敏 692410035
資工所 陳崇凱 692410078
Outline
Introduction
Connection manager
Virtual connectivity manager
Performance evaluation
conclusions
Introduction
WLAN vs. WWAN
Horizontal handoff vs. Vertical handoff
Mobile IP
IEEE 802.11 vs. GPRS
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
Introduction
Proposed approach
IP-centric
Connection Manager (CM)
Virtual Connectivity Manager (VC)
Detect conditions and availability of networks
Maintain connection’s continuity
Local Connection Translation (LCT)
subscription/notification service (S/N)
Roaming decision maker
Context database
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
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
Connection Manager
Adaptive Threshold Configuration
To set an appropriate RSSI threshold
RSSI:Received Signal Strength Indication
S1 = S2 + Δ
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
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
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.
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.
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