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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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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

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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

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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

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Mes

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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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