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Introduction to Ad Hoc Networking

Perkin’s book: Ch 1 and Ch 2. Some data collected from the Internet

by Prof. Yu-Chee Tseng

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Model of Operations

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Assumptions Symmetric Links:

unidirectional links are difficult to dealt with, and sometimes at the verge of failure

Layer-2 Routing: Most protocols are presented in layer-3

routing, but can be easily retooled as a layer-2 ones.

Proactive vs. Reactive Protocols (to be elaborated later)

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Applications ad hoc conferencing home networking emergency services personal area network (PAN) ubiquitous computing

“computers are all around us, constantly performing mundane tasks to make our lives a litter easier”

“Ubiquitous intelligent internetworking devices that detect their environment, interact with each other, and respond to changing environmental condition will create a future that is as challenging to imagine as a science fiction scenario.”

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Sensor Dust: a large collection of tiny sensor devices

once situated, the sensors remain stationarylargely homogeneouspower is likely to be a scarce resource, which

determines the lifetime of the network can offer detailed information about terrain or

environmental dangerous conditions. Intelligent Transportation System:

may be integrated with cars, positioning devices, etc.

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Technical Factors scalability power budget vs. latency protocol deployment and incompatibility

standards “Unless a miracle happens (e.g., the IETF manet working group is able

to promulgate a widely deployed ad hoc networking protocol), ad hoc networks will gain momentum only gradually because users will have to load software or take additional steps to ensure interoperability.

wireless data rate e.g., TCP over multi-hop wireless links

security issues

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More Extensions (DoD’s Perspective) could be a group of hosts supported by one

or more radios

could across the Internet

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IEFT MANET Working Group goal:

to standardize an interdomain unicast routing protocol which provides one or more modes of operation, each mode specialized for efficient operation in a given mobile networking “context”, where a context is a predefined set of network characteristics.

a dozen candidate routing protocols have been proposed.

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Applications of Ad Hoc Networks

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Network Architectures No Infrastructure (ad hoc networks):

no base stations; no fixed network infrastructure

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MANET

MANET = Mobile Ad Hoc Networks multi-hop communication needs support of dynamic routing protocols

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Routing = Ants Searching for Food

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Three Main Issues in Ants’ Life Route Discovery:

searching for the places with food

Packet Forwarding: delivering foods back home

Route Maintenance: when foods move to new place

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Proactive vs. Reactive Routing

Proactive Routing Protocol:continuously evaluate the routesattempt to maintain consistent, up-to-date routing

informationwhen a route is needed, one may be ready immediately

when the network topology changes the protocol responds by propagating updates throughout the

network to maintain a consistent view Reactive Routing Protocol:

on-demand Ex: DSR, AODV

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Ad hoc routing protocols

AD-HOC MOBILE ROUTING PROTOCOLS

ON-DEMAND-DRIVEN REACTIVE

HYBRIDDSDV

CGSR

TABLE DRIVEN/ PROACTIVE

DSR

AODV

ZRP

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DSDV Destination Sequenced Distance Vector

Table-driven Based on the distributed Bellman-Ford routing

algorithm Each node maintains a routing table

Routing hops to each destinationSequence number

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DSDV Problem

A lot of control traffic in the network Solution

two types of route update packets Full dump

All available routing information Incremental

Only information changed since the last full dump

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Clustering Protocol Cluster Gateway Switch Routing (CGSR)

Table-driven for inter-cluster routing Uses DSDV for intra-cluster routing

C3

M2

C2

C1

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AODV Ad hoc On-demand Distance Vector

On-demand driven Nodes that are not on the selected path do not

maintain routing information Route discovery

The source node broadcasts a route request packet (RREQ)

The destination or an intermediate node with “fresh enough” route to the destination replies a route reply packet (RREP)

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AODV

N2

N4N1

N3

N5

N6

N7

N8

Source

Destination

N2

N4N1

N3

N5

N6

N7

N8

Source

Destination

(a) RREQ

(b) RREP

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AODV Problem

A node along the route moves Solution

Upstream neighbor notices the move Propagates a link failure notification message

to each of its active upstream neighbors The source node receives the message and re-

initiate route discovery

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DSR Dynamic Source Routing

On-demand driven Based on the concept of source routing Required to maintain route caches Two major phases

Route discovery Route maintenance

A route error packet

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DSR

N2

N4N1

N3

N5

N6

N7

N8

N1

N1

N1-N2

N1-N3-N4

N1-N3-N4

N1-N3-N4-N7

N1-N3-N4-N6N1-N3

N1-N3-N4

N1-N2-N5

N2

N4N1

N3

N5

N6

N7

N8N1-N2-N5-

N8N1-N2-N5-

N8

N1-N2-N5-N8

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ZRP Zone Routing Protocol

Hybrid protocolOn-demandProactive

ZRP has three sub-protocolsIntrazone Routing Protocol (IARP)Interzone Routing Protocol (IERP)Bordercast Resolution Protocol (BRP)

Zone Radius =

r Hops

Zone of Node Y

Zone of Node Y

Node X

Zone of Node X

Node Z

Zone of Node Z

Border Node

Border Node

Bordercasting

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LAR Location-Aided Routing

Location information via GPS Shortcoming

GPS availability is not yet worldwidePosition information come with deviation

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LAR

(Xs,Ys)

SRC

Request Zone Expected Zone

DEST

R

(Xd+R, Yd+R)

(Xd,Yd)

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PAR Power-Aware Routing

+

–

+

–

+

–

+

–

+

–

+

–

SRCN1 N2

DEST

N4N3