Mobile Ad Hoc NETworks(MANET)IntroductionAd Hoc Wireless Networks

OutlineMANET conceptsTechnical challengesFunctional issues of MANETApplications of MANET

*MANET concepts (1)The principle of ad hoc networking is multi-hop relaying: messages are sent from the source to the destination by relaying through the intermediate hops (nodes).In multi-hop wireless networks, communication between two end nodes is carried out through a number of intermediate nodes whose function is to relay information from one point to another. Multi-hop "ad hoc" networks: relaying nodes are in general mobile, and communication needs are primarily between nodes within the same network.

MANET concepts (2)

Cellular and Ad Hoc Wireless NetworksInfrastructure: cellular wireless networksNon-infrastructure: ad hoc wireless networksCellular Wireless Networks

Access Point

MANET concepts (3)

Ad Hoc Wireless Networks A Mobile Ad hocNETwork(MANET) is an autonomous system of mobile routers (and associated hosts) connected by wireless links, the union of which forms an arbitrary graph The routers are free to move randomly and organize themselves arbitrarily The networks wireless topology may change rapidly and unpredictablyABC DABC D

*MANET concepts (4)

Cellular NetworksAd Hoc Wireless NetworksFixed infrastructure-basedInfrastructurelessGuaranteed bandwidth (designed for voice traffic)Shared radio channel (more suitable for best-effort data traffic)Centralized routingDistributed routingCircuit-switched and packet switchingPacket-switchedSeamless connectivity (low call drops during handoffs)Frequent path breaks due to mobilityHigh cost and time of deploymentQuick and cost-effective deploymentReuse of frequency spectrum through geographical channel reuseDynamic frequency reuse based on carrier sense mechanismEasier to employ bandwidth reservationBandwidth reservation requires complex medium access control protocols

*MANET concepts (5)

Cellular NetworksAd Hoc Wireless NetworksApplication domains include mainly civilian and commercial sectorsApplication domains include battlefields, emergency search and rescue operations, and collaborative computingHigh cost of network maintenance (backup power source, staffing, etc.)Self-organization and maintenance properties are built into the networkMobile hosts are of relatively low complexityMobile hosts require more intelligence (should have a transceiver as well as routing/switching capability)Major goals of routing and call admission are to maximize the call acceptance ratio and minimize the call drop ratioMain aim of routing is to find paths with minimum overhead and also quick reconfiguration of broken pathsWidely deployed and currently in the third generation of evolutionSeveral issues are to be addressed for successful commercial deployment even though widespread use exists in defense

Technical Challenges (1)Limitations of the Wireless Networkpacket loss due to transmission errorsvariable capacity linksfrequent disconnections/partitionslimited communication bandwidth Broadcast nature of the communications

Technical Challenges (2)Limitations Imposed by Mobilitydynamically changing topologies/routeslack of mobility awareness by system/applications

Limitations of the Mobile Computershort battery lifetimelimited capacities

*Functional Issues of MANET (1)

Medium access schemeDistributed operation is required.Synchronization is required in TDMA-based systems.Throughput needs to be maximized.Access delay should be minimized.Fairness refers to provide an equal share to all competing nodes.Real-time traffic support is required for real-time services.Resource reservation is required for QoS.Ability to measure resource availability handles the resources.Capability for power control reduces the energy consumption.Adaptive rate control refers to the variation in the data bit rate.Use of directional antennas has advantages including increased spectrum reuse, reduced interference, and reduced power consumption.

Functional Issues of MANET (2)

RoutingMobilityBandwidth constraintLocation-dependent contention depends on the number of nodes.Other resource constraints such as computing power, battery powerMinimum route acquisition delayQuick route reconfigurationLoop-free routingDistributed routing approachMinimum control overheadScalabilityProvisioning of QoSSupport for time-sensitive traffic: hard/soft real-time trafficSecurity and privacy

Functional Issues of MANET (3)

The objectives of the transport layer protocols include:Setting up and maintaining end-to-end connectionsReliable end-to-end delivery of data packetsFlow controlCongestion controlConnectionless transport layer protocol (UDP), unaware of high contention, increases the load in the network.Pricing Schemes need to incorporate service compensation.Quality of Service ProvisioningQoS parameters based on different applicationsQoS-aware routing uses QoS parameters to find a path.

Functional Issues of MANET (4)

Self-Organization is required in ad hoc wireless networks:Neighbor discoveryTopology organizationTopology reorganizationSecurityDenial of serviceResource consumptionEnergy depletion: deplete the battery power of critical nodesBuffer overflow: flooding the routing table or consuming the data packet buffer spaceHost impersonation: A compromised node can act as another node.Information disclosure: a compromised node can act as an informer.Interference: jam wireless communication by creating a wide-spectrum noise.

*Functional Issues of MANET (5)

Addressing and Service Discovery is essential because of absence of a centralized coordinator.Energy ManagementTransmission power management: The radio frequency (RF) hardware design should ensure minimum power consumption.Battery energy management is aimed at extending the battery life.Processor power management: The CPU can be put into different power saving modes.Devices power management: Intelligent device management can reduce power consumption of a mobile node.Scalability is expected in ad hoc wireless networks.

Functional Issues of MANET (6)

Deployment considerationsLow cost of deploymentShort deployment timeReconfigurabilityScenario of deploymentMilitary deploymentEmergency operations deploymentCommercial wide-area deploymentHome network deploymentOperational integration with other infrastructureChoice of protocols at different layers should be taken into consideration.

MANET ApplicationsPersonal area networkingcell phone, laptop, ear phone, wrist watchMilitary environmentssoldiers, tanks, planesCivilian environmentstaxi cab networkmeeting roomssports stadiumsboats, small aircraftEmergency operationssearch-and-rescuepolicing and fire fighting

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