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The characteristics of Ad-hoc Network
- (^) Self-creating
- not rely on a preexisting fixed infrastructure
- (^) Self-organizing
- no predetermined topology
- (^) Self-administering
- no central control
- (^) creating a network “on the fly”
- (^) Infrastructure less
- (^) No fixed routers
- (^) Highly mobile
- (^) Changing topology
The characteristics of Ad-hoc Network
- (^) Link instability
- (^) Resource poor
- (^) Limited energy resources
- (^) Limited wireless transmission range
- (^) Broadcast nature of the wireless medium
- (^) Hidden terminal problem
- (^) Packet losses due to transmission errors
- (^) Mobility-induced route changes
- (^) Mobility-induced packet losses
- (^) Battery constraints
- (^) Potentially frequent network partitions
- (^) Ease of snooping on wireless transmissions (security
hazard)
Application for Ad-Hoc
Network
• Military operations
• communication in a hostile environment
• disaster recovery, as well as search and
rescue (Emergency operations)
• rapid deployment of a communication
network where infrastructures don’t exist or
have been damaged
• Sporadic happenings coverage
• Civilian environments
– taxi cab network
– meeting rooms
– sports stadiums
– boats, small aircraft
• policing and fire fighting
Desirable Properties of
MANET
• DISTRIBUTED OPERATION
• LOOP FREE
• DEMAND BASED OPERATION
• UNIDIRECTIONAL LINK SUPPORT
• SECURITY
• POWER CONSERVATION
• MULTIPLE ROUTES
• QUALITY OF SERVICE SUPPORT
Ad-hoc Network Routing Protocols Ad-hoc Routing Protocols Proactive Protocols Reactive Protocols AODV Hybrid Protocols Hierarchical Protocols Geographical Protocols Power Aware Protocols Multicast Protocols Geocasting Protocols DSR TORA CBM Geo^ LBM TORA NZR LAR GLS PARO EADSR CBRP GSR ZRP DSDV OLSR WRP
Proactive Protocols
• Proactive: maintain routing information
independently of need for communication
• Update messages send throughout the network
periodically or when network topology changes.
• Low latency, suitable for real-time traffic
• Bandwidth might get wasted due to periodic
updates
• Pro-active (Table-driven) (DSDV (Highly Dynamic
Destination-Sequenced Distance Vector routing
protocol) , IARP (Intrazone Routing Protocol/pro-
active part of the ZRP)
• They maintain O(N) state per node, N = #nodes
Hybrid Routing
• Proactive for neighborhood, Reactive for far
away (Zone Routing Protocol, Haas group)
• Proactive for long distance, Reactive for
neighborhood (Safari)
• Attempts to strike balance between the two
• Hybrid (Pro-Active/Reactive) :- e.g. ZRP
(Zone Routing Protocol)
Hierarchical Routing
• Nodes are organized in clusters
• Cluster head “controls” cluster
• Trade of
– Overhead and confusion for leader election
– Scalability: intra-cluster vs intercluster
• One or Multiple levels of hierarchy
• Hierarchical :- CBRP (Cluster Based Routing
Protocol) , GSR (Global State Routing
protocol) , DDR (Distributed Dynamic Routing
Algorithm)
Power Aware
• Energy required to transmit a signal is
proportional to the square of the distance.
Transmitting a signal half the distance
requires one fourth of the energy and if
there is a node in the middle willing spend
another fourth of its energy for the second
half, data would be transmitted for half of
the energy than through a direct
transmission. This however introduces a
delay. e.g PARO (Power-Aware Routing
Optimization Protocol) , EADSR (Energy
Aware Dynamic Source Routing Protocol)
Multicast
- (^) When a message needs to be sent to a varying number of
receivers, it is more efficient to multicast the message to a
multicast group instead of unicasting an identical message to
many diferent receivers. Unfortunately, as noted in (Chiang
et al., 1997) multicast communication is difficult in an Ad-hoc
network. Ad-hoc networks are fundamentally dynamic in
nature; thus, multicast protocols that handle this dynamic
nature are needed. In a static network, multicast protocols
build a tree to route multicast messages. The root of the tree
is either the multicast source or a core, which is strategically
located near the middle of the multicast receivers.
Unfortunately, tree-based approaches for multicast
communication do not work well in an Ad-hoc network
because the tree often changes as the MNs move. Thus,
recent multicast protocols developed for an Ad-hoc network
are based on either flooding multicast messages or on
building a mesh to transmit multicast messages [(Chiang,
1998), (Lee et al., 1999), (Garcia-Luna-Aceves and Madrga,
1999), (Madruga and Garcia-Luna-Aceves, 1999)].e.g CBM
(Content Based Multicast) , MZR (Multicast Zone Routing)
ODMRP (On-Demand Multicast Routing Protocol)
Diferences between Distance vector and Link state Routing
Distance Vector routing protocols are based on Bellman and Ford algorithms. Link State routing protocols are based on Dijkstra algorithms. Distance Vector routing protocols are less scalable such as RIP supports 16 hops and IGRP has a maximum of 100 hops. Link State routing protocols are very much scalable supports infinite hops. Distance Vector are classful routing protocols which means that there is no support of Variable Length Subnet Mask (VLSM) and Classless Inter Domain Routing (CIDR). Link State routing protocols are classless which means that they support VLSM and CIDR. Distance Vector routing protocols uses hop count and composite metric Cost is the metric of the Link State routing protocols. Distance Vector routing protocols support Discontiguous subnets. Link State routing protocols support contiguous subnets. Contain knowledge about the whole network Contain knowledge about neighborhood Routing only to neighborhood Routing only to routers Information sharing at regular interval Information sharing when there is change in topology
