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33 Outline Problem overview Scenarios OLSR as MIH user to assist in re-routing using only WiFi MIH is used to assist in interface switching between WiFi and WiMAX Conclusion
Citation preview
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IEEE 802.21 MEDIA INDEPENDENT HANDOVER DCN: 21-10-0047-00-0WNMTitle: Use of MIH Services in Ad hoc Networks Date Submitted: March 16, 2010IEEE 802.21 March meeting, Orlando, FloridaAuthors: John Lee, Anthony McAuley and Subir Das (Telcordia
Technologies), Hui Zeng, Jason H. Li (Intelligent Automation Inc.), Thomas Stuhrmann (US Army CERDEC)
Abstract: This document presents some simulation studies on use of MIH Services in Ad Hoc Networks
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IEEE 802.21 presentation release statementsThis document has been prepared to assist the IEEE 802.21 Working Group. It is offered as a basis
for discussion and is not binding on the contributing individual(s) or organization(s). The material in this document is subject to change in form and content after further study. The contributor(s) reserve(s) the right to add, amend or withdraw material contained herein.
The contributor grants a free, irrevocable license to the IEEE to incorporate material contained in this contribution, and any modifications thereof, in the creation of an IEEE Standards publication; to copyright in the IEEE’s name any IEEE Standards publication even though it may include portions of this contribution; and at the IEEE’s sole discretion to permit others to reproduce in whole or in part the resulting IEEE Standards publication. The contributor also acknowledges and accepts that this contribution may be made public by IEEE 802.21. The document is approved for public release and the distribution is unlimited.
The contributor is familiar with IEEE patent policy, as stated in Section 6 of the IEEE-SA Standards Board bylaws <http://standards.ieee.org/guides/bylaws/sect6-7.html#6> and in Understanding Patent Issues During IEEE Standards Development http://standards.ieee.org/board/pat/faq.pdf>
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Outline
• Problem overview
• Scenarios
•OLSR as MIH user to assist in re-routing using only WiFi
• MIH is used to assist in interface switching between WiFi
and WiMAX
• Conclusion
• Seamless handoff in ad hoc networks inherently incurs multiple layers
• Actual handoff at link layer but • Network layer stays aware to update routes
• No fixed infrastructure
• Multiple links may be active at each node • Simple on-off interface management is not enough
• What link to use with which neighbor ?• Which end-to-end path?
The Problem is Unique!
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Problem: Local decision NOT enough
5
Interface management: on or off, when?Should node N4 turn off its red interface after it is done with N7?
Problem: Now N4 moves away …
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Shall node N11 turn on its red interface?
• Session handover process• Look at multi-hop path quality (than one-hop in
infrastructure mode)• Make decisions to forward traffic on active interfaces• Provide transparent user experience
• Topology control process• Network-side• Manage interfaces throughout the network to maintain
connectivity
• Multi-domain Routing• Maintain robust end-to-end paths with fast re-convergence
Problem: Multiple Functions to Adapt
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Can we look at each problem independently?
• We looked at heterogeneous wireless networks• Interface types: WiFi and WiMAX • MANET routing protocols: Reactive AODV and Proactive OLSR• Functions: Session management, Topology management,
multi-domain MANET routing/handover, gateway functionality
• Various solutions in each domain • OLSR + WiFi + MIH• AODV + WiFi + WiMAX + MIH
• Experiments:• Simulation study• Simulation + real wireless nodes
What We Did?
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Key Enabling Technology: MIH
Our Architecture
Integrated architectureMulti-layer and cross-layer designManagers at different layers render consistent solutionsPolicy based handoff
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OLSR as an MIH UserMotivation: In ad-hoc networks, bad- or no-route may occur; even ad-
hoc protocols (e.g. OLSR) cannot promptly respond to mobility without causing undue overhead
Objective: apply MIH to improve OLSR mobile performance Reduce routing convergence delay and packet dropNot increase routing overhead
Approach: OLSR as user of 802.21 MIH events and services
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802.11 MAC
Receive power measurement for neighboring nodes Provide measurement to MIH
802.21MIH
Link status for neighboring nodes Gives handover trigger to OLSR
OLSR registers as MIH user Takes actions based on MIH triggers
OLSR Routing
Mobile Ad Hoc Scenarios
source
receiver Overlapping Area
n5
n1
n0
n2
n3 n4
n6
11
source
receiver Overlapping Area
n1
n0
n2
n3
n4
Scenario 1 Scenario 2
Topology: Radio Range 200m Velocity 5m/second
Traffic Flow: 10 Packets/second 1000 Bytes/packet Duration 60 seconds
OLSR Parameters: Hello interval (HI): 1,2, or 3 secs TC interval: 3 seconds Neighbor Hold time: 6 seconds
Initial Flow
Initial Flow Flow after Handover
Flow after Handover
Route Convergence of OLSR without MIH (Baseline)
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source
receiver5m/second
n1
n0
n2
n3
n4
2 seconds of flow disruption (20 packet drops)
n0
n1
50.2 52.2
time
time
time
time
n0 is no longer within the coverage of n1
Hellofrom n1
Hellofrom n2
Hellofrom n0
Packet CollisionOr bad channel condition
Hellofrom n2Hello
from n2
Packet loss period (~2.0 seconds)
3-way handshakefor symmetric link
n2
n3Route update for n0 in routing table n3
Scenario 1
Route Convergence of OLSR without MIH (Baseline)
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source
receiver 5m/second
n5
n1
n0
n2
n3 n4
n6
9 seconds of flow disruption (88 packet drops)
Scenario 2
MIH-enabled Approaches for OLSR
MIH-Hello approach: OLSR invokes extra Hello messages once the MIH agent detects a new link (MIH Link_Detected event)
MIH-Hello-TC approach: Besides extra Hello messages, OLSR invokes extra update TC-message once the MIH agent detects a lost link (MIH Link_Going_Down event)
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802.11 MAC
Receive power measurement for neighboring nodes Provide measurement to MIH
802.21MIH
Link status for neighboring nodes Gives handover trigger to OLSR
OLSR registers as MIH user Takes actions based on MIH triggers
OLSR Routing
1. MIH Link_Detected event2. MIH Link_Going_Down event
MIH-Hello Approach in Mobility Scenario (1)
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n0
n1
50.2
time
time
time
time
n0 is no longer within the coverage of n1
n2
n3
Repeated Hellofrom n0 through MIH
MIH of n0 detects
MIH of n2 detects
Repeated Hellofrom n2 through MIH
50.5
Route update for n0 in routing table n3
Packet loss period (~0.3 seconds)
source
receiver
n1
n0
n2
n3
n4
0.3 second of flow disruption (3 packets drops)
Hello trigger
The MIH-Hello-TC Approach in Mobility Scenario (2)
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source
receiver
n5
n1
n0
n2
n3 n4
n6
0.3 second of flow disruption (3 packets drops)
Hello trigger
Link-down + TC trigger Hello + TC triggers
Link-down + TC trigger
Performance Comparison
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For each scheme, longer Hello intervals (1-, 2- to 3-seconds) reduces overhead at a cost of increased disconnection time
But MIH (MIH-Hello-TC) dramtically shifts the tradeoff
0100200300400500600700800900
0 2 4 6 8 10 12 14
Ove
rhea
d (H
ello
Mes
sage
s)
Disconnection time (seconds)
No MIH
With MIH
Hello every 1 second
Hello every 3 seconds
Handoff in a WiFi-WiMAX Network
WiFi-WiMAXWiMAX: IEEE 802.16e, IEEE802.16gWiFi : IEEE 802.11
Model and simulate handoff in heterogeneous WiFi-WiMAX networks
Implementation of mobile WiMAX– Simple PHY layer– Core MAC layer
Simulation study to show the validity– AODV routing protocol– WiMAX bridging
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Mobility Scenario
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Radio range: 200mPacket size: 1000 bytesData rate: 10 packets per secondDuration: 180 seconds (11 ~ 190)AODV Hello interval: 1 secondGrid unit: 125m
WiFi only WiFi + WiMax
Source: A, Destination: ENodes with dual interfaces: D, E, K
Allowed number of Hello packet losses = 2
Summary of Results
Hello Interval = 1 secondAllowed Hello Loss = 2
AODV-WiFi (mobile)
AODV-WiFi + WiMAX
AODV-WiFi + WiMAX + MIH
Received Packets 1414 1780 1800
Dropped Packets 386 20 0
Disrupted time (s) 38.6 2 0
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Less Hellos (longer intervals) lead to more packet losses during handoffMIH always help achieve seamless handoff, with even less overhead
Conclusion
Are MIH Events useful in ad hoc networks? E.g., Link_Going_Down event, where the received power level
threshold is set to a chosen trigger level (e.g., 1.03×Pmin) In our work, such events are used for
Within only a WiFi interface: re-routing Nodes with dual interfaces: switching
Results For re-routing, shorter Hello intervals (3-, 2- to 1-seconds) reduces
disconnection time at a cost of increased overhead But MIH dramatically shifts the tradeoff
For switching, we can get a similar tradeoff between disconnection time and overhead But MIH reduce loss in handover among
heterogeneous ad hoc network with lower overhead costs
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