Routing in Mobile Ad-hoc Networks CSE 6590

Ap

ril 21

, 20

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Mobile Ad hoc Networks (MANETs)

No infrastructure (no base stations or access points)

Mobile nodes Form a network in an ad-hoc manner Act both as hosts and routers Communicate using single or multi-hop wireless

links

Topology, locations, connectivity, transmission quality are variable.

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MANETs: Operations

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S

X

Y

D

S

X

Z

D

MANETs vs. WMNs

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• One type of radio on devices• Supporting end-user applications

MANETs vs. WMNs (2)

MANETs: end-user devices also perform routing and configuration functionalities for all other nodes.

WMNs: mesh routers perform these tasks.

Mesh routers vs. mobile devices: power and resource constraints mobility

MANETs: usually only one radio.WMNs: can have multiple channels,

multiple radios.5

MANETs: Applications

Civil Disaster recovery Taxi cabs Communications over water using floats Vehicular ad-hoc network

Military Battlefield communications Monitoring and planning

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MANETs: Challenges

Wireless channels: error-prone media Low bandwidth channels Security Unpredictable mobility Devices: low power, limited resources Maintaining connectivity, states

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Routing: Wired vs. Wireless

Ad-hoc networks have dynamic time-dependent topology Links (edges) added/deleted Nodes (vertices) added/deleted Bi-directional or uni-directional links

Wireless medium Inherently a broadcast medium Fading, shadowing cause burst errors and/or

intermittent connectivity

Network topology changes frequently Low bandwidth: routing protocols must

minimize the amount of control traffic generated.

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Routing Approaches

On-demand (reactive)acquiring and maintaining routes on

demandDSR, AODV

Proactive (table-driven)All nodes maintain routes to all

destinations in the network at all times. OLSR, MMESH

Hybrid: combines reactive and proactiveZone Routing Protocol (ZPR)

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Unicast Routing Protocol for MANETs (topology-based)

Table-Driven/Proactive

Hybrid On-Demand/ReactiveOn-Demand/Reactive

Clusterbased/HierarchicalClusterbased/Hierarchical

Distance-Vector

Link-State

ZRP DSRAODVTORA

DSRAODVTORA

LANMARCEDARLANMARCEDAR

DSDV OLSRTBRPFFSRSTAR

AODV Notes AODV uses a mechanism similar to distance vector

routing routing loops (e.g., due to “counting to infinity” problem).

AODV uses destination sequence numbers to ensure loop-freedom at all times.

AODV maintains (caches) forward and reverse routes (and sub-routes) as DSR. Difference from DSR: routing entries are associated with

DSNs (“side effect” of DSNs: help avoid obsolete routes)

Route caching speeds up route discovery, minimize control traffic overhead, minimize delay.

Reverse routes can be used for future data packets going in that direction (if the routes are still valid).

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