Mobile Ad-Hoc NetworkingMobile Ad-Hoc Networking

By Jared RobertsBy Jared Roberts

OverviewOverview

What is a MANET?What is a MANET?Problems with routing in a MANETProblems with routing in a MANETOh Node! (laugh!)Oh Node! (laugh!)Current SolutionsCurrent Solutions

What is a MANET?What is a MANET?

MANET – (Mobile Ad-Hoc NETwork) a system of MANET – (Mobile Ad-Hoc NETwork) a system of mobile nodes (laptops, sensors, etc.) interfacing mobile nodes (laptops, sensors, etc.) interfacing without the assistance of centralized without the assistance of centralized infrastructure (access points, bridges, etc.)infrastructure (access points, bridges, etc.)

The ProblemThe Problem

Unstable pathsUnstable pathsProcessing powerProcessing powerBattery lifeBattery lifeTime delaysTime delaysHigh cost of memoryHigh cost of memory

Factors Affecting MANETsFactors Affecting MANETs

ScalabilityScalabilityPower vs. LatencyPower vs. Latency Incompatible StandardsIncompatible StandardsData RatesData RatesUser EducationUser EducationSecuritySecurityCoverageCoverage

SolutionsSolutions Table DrivenTable Driven

DSDVDSDV CGSRCGSR WRPWRP

Source-initiated On-Demand DrivenSource-initiated On-Demand Driven AODVAODV DSRDSR LMRLMR TORATORA ABRABR SSRSSR

The Family TreeThe Family Tree

Destination-Sequenced Distance-Destination-Sequenced Distance-Vector Routing (DSDV)Vector Routing (DSDV)

Every node maintains a routing table.Every node maintains a routing table. ““Full” vs. “incremental” updateFull” vs. “incremental” updateSettling time – the weighted average time Settling time – the weighted average time

that routes to a destination will fluctuate that routes to a destination will fluctuate before the route with the best metric is before the route with the best metric is received.received.

Clusterhead Gateway Switch Clusterhead Gateway Switch Routing (CGSR)Routing (CGSR)

A central “clusterhead” node is chosen.A central “clusterhead” node is chosen. The clusterhead is chosen by the “Least Cluster The clusterhead is chosen by the “Least Cluster

Change” algorithmChange” algorithm Traffic is routed to the current clusterhead who Traffic is routed to the current clusterhead who

forwards the traffic through a gateway node to forwards the traffic through a gateway node to the next clusterhead in line until the clusterhead the next clusterhead in line until the clusterhead of the destination node is located.of the destination node is located.

Each node must maintain a cluster member Each node must maintain a cluster member tabletable

CGSR (cont.)CGSR (cont.)

Wireless Routing Protocol (WRP)Wireless Routing Protocol (WRP)

4 tables: Distance, routing, link-cost, and 4 tables: Distance, routing, link-cost, and message retransmission listmessage retransmission list

Neighboring nodes broadcast update Neighboring nodes broadcast update messagesmessages

Uses Uses hellohello messages to establish messages to establish connectivityconnectivity

Checks all incoming update informationChecks all incoming update information

Comparing Table Driven Routing Comparing Table Driven Routing ProtocolsProtocols

Ad-hoc On-demand Distance Ad-hoc On-demand Distance Vector Routing (AODV)Vector Routing (AODV)

Route Request Packets (RREQ)Route Request Packets (RREQ)The source node broadcasts an RREQ to The source node broadcasts an RREQ to

all neighboring nodes.all neighboring nodes.Nodes record the source of the first RREQ Nodes record the source of the first RREQ

received to establish a reverse path.received to establish a reverse path.

AODV (cont.)AODV (cont.)

Route Reply Packets (RREP)Route Reply Packets (RREP) The destination or node with a route to the The destination or node with a route to the

destination unicasts a RREP back to the source destination unicasts a RREP back to the source to establish a route.to establish a route.

Dynamic Source Routing (DSR)Dynamic Source Routing (DSR)

Each node maintains a route cache.Each node maintains a route cache. If a source node has no route in its cache, If a source node has no route in its cache,

it broadcasts a route request.it broadcasts a route request.A route reply is generated when either the A route reply is generated when either the

destination or a node with a route to the destination or a node with a route to the destination is found.destination is found.

Supports symmetric linksSupports symmetric links

DSR (cont.)DSR (cont.)

Maintenance is accomplished by route error Maintenance is accomplished by route error packets and acknowledgements.packets and acknowledgements.

If a node fails to send an acknowledgement, any If a node fails to send an acknowledgement, any route that contains that node is truncated.route that contains that node is truncated.

Temporally-Ordered Routing Temporally-Ordered Routing Algorithm (TORA)Algorithm (TORA)

Used in highly dynamic networksUsed in highly dynamic networksProvides multiple routes for Provides multiple routes for

source/destination pairsource/destination pairUses direct acyclic graphs to measure Uses direct acyclic graphs to measure

“height”“height”Assumes all nodes have synchronized Assumes all nodes have synchronized

clocksclocksClassifies links as upstream and Classifies links as upstream and

downstreamdownstream

TORA (cont.)TORA (cont.)

Associativity-Based Routing (ABR)Associativity-Based Routing (ABR)

Uses Uses degree of association stabilitydegree of association stability as a metric as a metric Strives to build “longer-lived” routesStrives to build “longer-lived” routes

Signal Stability Routing (SSR)Signal Stability Routing (SSR)

Selects routes based on signal strength Selects routes based on signal strength and location stabilityand location stability

Periodic beacons update signal strength Periodic beacons update signal strength tablestables

Only requests that are received over Only requests that are received over strong channels are forwarded unless the strong channels are forwarded unless the PREF field in the header is set to allow PREF field in the header is set to allow weak channelsweak channels

Comparing Source-Initiated On-Comparing Source-Initiated On-Demand Routing ProtocolsDemand Routing Protocols