Introduction to Mobile adhoc-network

MOBILE AD HOC NETWORKS

Seminar Report

Submitted in partial fulfilment of the requirements

for the award of the degree of

Bachelor of Technology

in

Computer Science Engineering

of

Cochin University Of Science And Technology

by

PRAVEEN KUMAR P

(12080059)

DIVISION OF COMPUTER SCIENCE

SCHOOL OF ENGINEERING

COCHIN UNIVERSITY OF SCIENCE AND TECHNOLOGY

KOCHI-682022

OCTOBER 2010

DIVISION OF COMPUTER SCIENCE

SCHOOL OF ENGINEERING

COCHIN UNIVERSITY OF SCIENCE AND TECHNOLOGY

KOCHI-682022

Certificate

Certified that this is a bonafide record of the seminar entitled

“MOBILE AD HOC NETWORKS”

Presented by the following student

“PRAVEEN KUMAR P”

of the VIIth

semester, Computer Science and Engineering in the year 2010

in partial fulfillment of the requirements in the award of Degree of

Bachelor of Technology in Computer Science and Engineering of Cochin

University of Science and Technology.

Mr. SUDHEEP ELAYIDOM Dr. DAVID PETER

Seminar guide Head Of Division

ACKNOWLEDGEMENT

I thank GOD almighty for guiding me throughout the seminar. I would like to thank all those

who have contributed to the completion of the seminar and helped me with valuable

suggestions for improvement.

I am extremely grateful to Dr. David Peter, Head Of Division, Division of Computer

Science, for providing me with best facilities and atmosphere for the creative work guidance

and encouragement. I am profoundly indebted to my seminar guide, Mr. Sudheep Elayidom,

sr.Lecturer, Division of Computer Science, for innumerable acts of timely advice,

encouragement and I sincerely express my gratitude to him. I thank all Staff members of my

college and friends for extending their cooperation during my seminar.

Above all I would like to thank my parents without whose blessings; I would not have been

able to accomplish my goal.

PRAVEEN KUMAR P

i

TABLE OF CONTENTS

CHAPTER NO TITLE PAGE NO.

LIST OF FIGURES ii

LIST OF TABLES iii

1. INTRODUCTION 1

2. BASICS OF MANET 2

2.1 WIRELESS AD HOC NETWORKS 2

2.2 CHARACTERISTICS OF MANET 4

3. AD HOC ROUTING PROTOCOLS 5

3.1 WHY ROUTING PROTOCOLS 5

3.2 AD HOC ROUTING PROTOCOLS 5

3.3 TABLE DRIVEN ROUTING PROTOCOLS 7

3.3.1 DESTINATIONSEQUENCED

DISTANCE VECTOR ROUTING ALGORITHM 7

3.3.2 CLUSTERHEAD GATEWAY SWITCH

ROUTING (CGSR) 10

3.4 SOURCE INITIATED ON DEMAND ROUTING 11

3.4.1 AD HOC ON DEMAND DISTANCE VECTOR

ROUTING (AODV) 11

3.4.2 DYNAMIC SOURCE ROUTING PROTOCOL

(DSR) 14

3.5 HYBRID SCHEME 16

3.5.1 ZONE ROUTING PROTOCOLS (ZRP) 16

3.6 COMPARISON 19

ii

4. VEHICULAR AD HOC NETWORK (VANET) 20

4.1 ARCHITECTURE OF VANET 21

4.2 APPLICATIONS OF VANET 22

5. APPLICATIONS OF MANET 25

6. CONCLUSION 26

7. REFERENCE 27

LIST OF FIGURES

FIGURE NO TITLE PAGE NO.

2.1 WIRELESS AD HOC NETWORK 2

3.1 CATEGORIZATION OF AD HOC ROUTING

PROTOCOLS 6

3.2 AD HOC NETWORK HAVING ROUTING

TABLES 9, 10

3.3 CGSR ROUTING 11

3.4 AODV ROUTING PROTOCOL 13

3.5 DSR ROUTING PROTOCOL 15

3.6 ZONE ROUTING PROTOCOLS 17

4.1 TYPICAL VEHICULAR AD HOC NETWORK 20

4.2 LAYERED ARCHITECTURE 22

iii

4.3 UNLAYERED ARCHITECTURE 22

LIST OF TABLES

TABLE NO. TITLE PAGENO.

3.1 COMPARISON BETWEEN TABLE DRIVEN

AND ON DEMAND ROUTING PROTOCOLS 19

Mobile ad hoc networks 1

Division Of Computer Science Engineering, SOE, CUSAT

Chapter 1

INTRODUCTION

Communication is the primary factor which influenced the development of

mankind. One of the primary goal of communication is exchanging information between two

persons. Today we have advanced technologies for communication. Communication can be

between human beings or between machines. For the purpose of communication between

machines we provided networks, generally connected by physical channels. Then to avoid the

difficulties with wired networks there come wireless networks. Then need for more advanced

technology arise and we thought about mobility. Mobile networks established due to this

demand and the communication become more flexible. MANET is a type of wireless mobile

network.

A mobile ad hoc network (MANET), sometimes called a mobile mesh network, is a

self-configuring network of mobile devices connected by wireless links. Each device in a

MANET is free to move independently in any direction, and will therefore change its links to

other devices frequently. Each must forward traffic unrelated to its own use, and therefore be

a router. The primary challenge in building a MANET is equipping each device to

continuously maintain the information required to properly route traffic. Such networks may

operate by themselves or may be connected to the larger Internet.

MANETs are a kind of wireless ad hoc networks that usually has a routable networking

environment on top of a Link Layer ad hoc network. They are also a type of mesh network,

but many mesh networks are not mobile or not wireless.

The growth of laptops and 802.11/Wi-Fi wireless networking have made MANETs a

popular research topic since the mid- to late 1990s. Different protocols are used for the

communication between the mobile nodes. There is no particular access points in this

networks, instead the nodes itself transfer data between the communication nodes. Like any

other networks there is also some algorithms used for the routing of information between

nodes.



Chapter 2

BASICS OF MANET

MANET (Mobile Ad hoc Network) is a wireless ad hoc network, which uses mobile

devices like laptops, PDAs, mobile phones etc. as nodes which communicate each other for the

purpose of information transfer between nodes. MANET does not have any particular infrastructure

due to the absence of access points and due to the presence of mobile nodes. To know about

MANET first we need to know about a wireless ad hoc network.

2.1WIRELESS AD HOC NETWORKS

A wireless ad hoc network is a decentralized network. The network is ad hoc because it

does not rely on a pre existing infrastructure, such as routers in wired network or access points in

wireless networks. Instead each node participate in routing by forwarding data for other nodes, and

so the determination of which nodes forward the data is done dynamically, based on the network

connectivity.

Fig 2.1 Wireless ad hoc network

Above figure shows a typical wireless ad hoc network in which the communication is happening in

between mobile nodes. There is also a single base station which is not connected to each and every

node in the network, instead there are two nodes which directly communicate with the base station.

These nodes will have the complete responsibility of information exchange between the base



station and any node in the network. Such a node must know protocols for communicating with the

nodes in the network as well as protocols required for the communication with base station

An ad hoc network is made up of multiple ―nodes‖ connected by ―links‖. Links are influenced

by the node's resources (e.g. available energy supply, transmitter power, computing power and

memory) and by behavioural properties (reliability, and trustworthiness), as well as by link

properties (e.g. line-of-sight interference, length-of-link and signal loss, interference and noise).

Since new and old links can be connected or disconnected at any time, a functioning network must

be able to cope with this dynamic restructuring, preferably in a way that is timely, efficient,

reliable, robust and scalable.

The network must allow any two nodes to communicate, often via other nodes that relay

the information. A ―path‖ is a series of links that connects two nodes. Often there are multiple

paths between any two nodes. Nodes are often limited by transmitter power (transmission

range) and available energy resources. Transmitter power often consumes the most energy in

the node. According to the inverse square law, it is more energy efficient to relay information

across a network via multiple nodes

The decentralized nature of wireless ad hoc networks makes them suitable for a variety of

applications where central nodes can't be relied on, and may improve the scalability of

wireless ad hoc networks compared to wireless managed networks, though theoretical and

practical limits to the overall capacity of such networks have been identified.

Minimal configuration and quick deployment make ad hoc networks suitable for

emergency situations like natural disasters or military conflicts. The presence of a dynamic

and adaptive routing protocol will enable ad hoc networks to be formed quickly. Wireless ad

hoc networks can be further classified according to their applications

- Mobile ad hoc networks (MANET): It is a wireless ad hoc network in which mobile

nodes are mobile devices like laptops, PDAs, mobile phones etc. In this type of

networks each node will act as routers hence no need of access points. One or more

nodes can be connected to an external router, which is connected to the internet, so

that each node in the network, if need can connect to internet and can transfer

information bi directionally.



- Wireless mesh networks (WMN): It is a communication network made up of radio

nodes organised in a mesh topology. Wireless mesh networks often consist of mesh

clients, mesh routers and gateways. The mesh clients are often laptops, cell phones

and other wireless devices while the mesh routers forward traffic to and from the

gateways which may but need not connect to the Internet.

- Wireless sensor networks (WSN): This type of networks consist of spatially

distributed autonomous sensors to cooperatively monitor physical or environmental

conditions, such as temperature, sound, vibration, pressure, motion or pollutants. The

development of wireless sensor networks was motivated by military applications such

as battlefield surveillance and are now used in many industrial and civilian application

areas, including industrial process monitoring and control, machine health monitoring,

environment and habitat monitoring, healthcare applications, home automation, and

traffic control

2.2 Characteristics of MANET

- Dynamic Topologies: Since nodes are free to move arbitrarily, the network topology

may change randomly and rapidly at unpredictable times. The links may be

unidirectional bidirectional.

- Bandwidth constrained, variable capacity links: Wireless links have significantly

lower capacity than their hardwired counterparts. Also, due to multiple access, fading,

noise, and interference conditions etc. the wireless links have low throughput.

- Energy constrained operation: Some or all of the nodes in a MANET may rely on

batteries. In this scenario, the most important system design criteria for optimization

may be energy conservation.

- Limited physical security: Mobile wireless networks are generally more prone to

physical security threats than are fixed- cable nets. The increased possibility of

eavesdropping, spoofing, and denial-of-service attacks should be carefully considered.

Existing link security techniques are often applied within wireless networks to reduce

security threats. As a benefit, the decentralized nature of network control in MANET

provides additional robustness against the single points of failure of more centralized

approaches.



Chapter 3

AD HOC ROUTING PROTOCOLS

3.1 Why Routing Protocols

Routing support for mobile hosts is presently being formulated as mobile IP technology.

When the mobile agent moves from its home network to a foreign (visited) network, the

mobile agent tells a home agent on the home network to which foreign agent their packets

should be forwarded. In addition, the mobile agent registers itself with that foreign agent on

the foreign network. Thus, the home agent forwards all packets intended for the mobile agent

to the foreign agent, which sends them to the mobile agent on the foreign network. When the

mobile agent returns to its original network, it informs both agents (home and foreign) that

the original configuration has been restored. No one on the outside networks need to know

that the mobile agent moved.

But in Ad Hoc networks there is no concept of home agent as it itself may be moving.

Supporting Mobile IP form of host mobility requires address management, protocol inter

operability enhancements and the like, but core network functions such as hop by hop routing

still presently rely upon pre existing routing protocols operating within the fixed network. In

contrast, the goal of mobile ad hoc networking is to extend mobility into the realm of

autonomous, mobile, wireless domains, where a set of nodes, which may be combined routers

and hosts, themselves to form the network routing infrastructure in an ad hoc fashion. Hence,

there is need to study special routing algorithms to support this dynamic topology

environment. Routing protocols for mobile ad-hoc networks have to face the challenge of

frequently changing topology, low transmission power and asymmetric links.

3.2 Ad Hoc Routing Protocols:

A number of routing protocols have been suggested for ad-hoc networks. These protocols can

be classified into two main categories:

Table driven routing protocols



Source initiated on demand routing protocols

Table Driven Routing Protocols:

Table-driven routing protocols attempt to maintain consistent, up-to-date routing

information from each node to every other node in the network. These protocols require each

node to maintain one or more tables to store routing information, and they respond to changes

in network topology by propagating updates throughout the network in order to maintain a

consistent network view. The areas in which they differ are the number of necessary routing-

related tables and the methods by which changes in network structure are broadcast.

Source Initiated On Demand Routing:

A different approach from table-driven routing is source-initiated on demand routing.

This type of routing creates routes only when desired by the source node. When a node

requires a route to a destination, it initiates a route discovery process within the network. This

process is completed once a route is found or all possible route permutations have been

examined. Once a route has been established, it is maintained by a route maintenance

procedure until either the destination becomes inaccessible along every path from the source

or until the route is no longer desired.

Fig 3.1: Categorization of ad hoc routing protocols.



3.3 TABLE DRIVEN ROUTING PROTOCOLS

3.3.1 Destination Sequenced Distance Vector Routing Algorithm:

The Destination Sequenced Distance Vector (DSDV) Routing Algorithm is based on the idea

of the Distributed Bellman Ford (DBF) Routing Algorithm with certain improvements. The

primary concern with using a Distributed Bellman Ford algorithm in Ad Hoc environment is

its susceptibility towards forming routing loops and counting to infinity problem. DSDV

guarantees loop free paths at all instants.

Each node maintains a routing table, which contains entries for all the nodes in the

network. Each entry consists of:

the destination's address

the number of hops required reaching the destination (hop count)

the sequence number as stamped by the destination.

Whenever a node B comes up, it broadcasts a beacon message ("I am alive message")

stamping it with a locally maintained sequence number. The nodes in its neighbourhood

listen to this message and update the information for this node. If the nodes do not have any

previous entry for this node B, they simply enter B's address in their routing table, together

with hop count and the sequence number as broadcasted by B. If the nodes had previous entry

for B, then sequence number of broadcasted information is compared to the sequence number

stored in the node for destination B. If the message received has a higher sequence number,

then this means that the node B has propagated a new information about its location so the

entry must be updated in accordance with the new information received. The information

with a newer sequence number is definitely new as the node B itself stamps sequence

number.

The new information that a node receives is scheduled for broadcasting to its neighbours

so that they can know about the changes in topology. The neighbouring nodes also follow the

same rule i.e. updating the information when information about a node with a newer sequence

number is received. The metrics for routes chosen from the newly received broadcast

information are each incremented by one hop. So, the new information is updated gradually

at all nodes and they now know the next hop node in order to correctly route the packet to

destination B. B also generates the new information with a newer sequence number when it

sees that it is moving. By moving, it is meant that B observes that there is a change in

topology because it's neighbours are changing, may be due to it's motion or other nodes



(neighbours) motion. And it comes to know that the neighbours are changing since it receives

new beacon messages or does not receive beacon messages from its current neighbours.

The information is broadcasted periodically to neighbours. It could be advertised when

specifically asked for or when there is a significant change in topology. Thus, it is both 'event

driven' and 'time driven'.

The routing table updates can be sent in two ways. The first is known as a full dump. This

type of packet carries all available routing information and can require multiple network

protocol data units (NPDUs). During periods of occasional movement, these packets are

transmitted infrequently. Smaller incremental packets are used to relay only that information

which has changed since the last full dump. Each of these broadcasts should fit into a

standard-size NPDU, thereby decreasing the amount of traffic generated. The mobile nodes

maintain an additional table where they store the data sent in the incremental routing

information packets.

Routes that show an improved metric are scheduled for an advertisement at a time which

depends on the average settling time for routes to the particular destination under

consideration.

To avoid a burst of new advertisements in case of rapidly changing routes, the Mobile

host delays the advertisement of such routes, when it can determine that a route with a better

metric is likely to show up soon. For this, the Mobile Host has to keep a history of weighted

average time that routes to a particular destination fluctuate until the route with the best

metric is received.

Though it delays advertising the new route, it uses it for routing. Thus, it maintains two

tables one for forwarding packets and another to be advertised. In order to bias the damping

mechanism

in favour of recent events, the most recent measurement of the settling time of a particular

route must be counted with a higher weighting factor than are less recent measurements. A

parameter must be selected which indicates how long a route has to remain stable before it is

counted as truly stable.

When no broadcasts are received from a neighbour within a particular time interval, the

link is supposed to be broken. Now, any route through that next hop is immediately assigned



an infinite metric (i.e. any number greater than the maximum allowed metric) and assigned an

updated sequence number. Note that this sequence number is assigned by the Mobile host

other that the destination Mobile Host. Sequence numbers defined by the originating Mobile

host are defined to be even numbers and sequence numbers generated to indicate infinite

metrics are odd numbers. This information is broadcasted to the neighbouring nodes. If the

neighbouring nodes have chosen this node as a next hop neighbour for any destination then

they also set the route to destination as infinity. If the neighbouring nodes, do have a path to

destination through some other neighbour and they ignore this information though it has a

higher sequence number, which is odd. Thus, it is just like any distance vector algorithm with

the added novelty of sequence numbers, which is used to distinguish stale routes from new

routes. The concept of sequence numbers also ensures loop free routes.

Destination Next

Hop

Distance Sequence

Number

A A 0 S205_A

B B 1 S334_B

C C 1 S198_C

D D 1 S567_D

E D 2 S767_E

F D 2 S45_F

A‘s routing table before change



Destination Next

Hop

Distance Sequence Number

A A 0 S304_A

B D 3 S424_B

C C 1 S297_C

D D 1 S687_D

E D 2 S868_E

F D 2 S164_F

A‘s routing table after change

Fig 3.2 ad hoc network having routing tables

3.3.2 Clusterhead Gateway Switch Routing (CGSR):

The Clusterhead Gateway Switch Routing (CGSR) protocol differs from the previous

protocol in the type of addressing and network organization scheme employed. Instead of a

flat network, CGSR is a clustered multi hop mobile wireless network with several heuristic

routing schemes. In that by having a cluster head controlling a group of ad hoc nodes, a

framework for code separation (among clusters), channel access, routing, and bandwidth

allocation can be achieved. A cluster head selection algorithm is utilized to elect a node as the

cluster head using a distributed algorithm within the cluster. The disadvantage of having a

cluster head scheme is that frequent cluster head changes can adversely affect routing

protocol performance since nodes are busy in cluster head selection rather than packet

relaying.

Hence, instead of invoking cluster head reselection every time the cluster membership

changes, a Least Cluster Change (LCC) clustering algorithm is introduced. Using LCC,

cluster heads only change when two cluster heads come into contact, or when a node moves

out of contact of all other cluster heads.

CGSR uses DSDV as the underlying routing scheme, and hence has much of the same

overhead as DSDV. However, it modifies DSDV by using a hierarchical cluster-head-to-

gateway routing approach to route traffic from source to destination. Gateway nodes are

nodes that are within communication range of two or more cluster heads. A packet sent by a

node is first routed to its cluster head, and then the packet is routed from the cluster head to a

gateway to another cluster head, and so on until the cluster head of the destination node is

reached. The packet is then transmitted to the destination. Figure illustrates an example of



this routing scheme. Using this method, each node must keep a cluster member table where it

stores the destination cluster head for each mobile node in the network. Each node

periodically using the DSDV algorithm broadcasts these cluster member tables. Nodes update

their cluster member tables on reception of such a table from a neighbor. In addition to the

cluster member table, each node must also maintain a routing table, which is used to

determine the next hop in order to reach the destination. On receiving a packet, a node will

consult its cluster member table and routing table to determine the nearest cluster head along

the route to the destination. Next, the node will check its routing table to determine the next

hop used to reach the selected cluster head. It then transmits the packet to this node.

Fig 3.3 CGSR routing from node 1 to node 8

3.4 SOURCE INITIATED ON DEMAND ROUTING

3.4.1 Ad Hoc On-Demand Distance Vector Routing (AODV):

The Ad Hoc On Demand Distance Vector (AODV) routing protocol builds on the DSDV

algorithm previously described. AODV is an improvement on DSDV because it typically

minimizes the number of required broadcasts by creating routes on a demand basis, as

opposed to maintaining a complete list of routes as in the DSDV algorithm. AODV classify

as a pure on-demand route acquisition system, since nodes that are not on a selected path do

not maintain routing information or participate in routing table exchanges .

When a source node desires to send a message to some destination node and does not

already have a valid route to that destination, it initiates a path discovery process to locate the



other node. It broadcasts a route request (RREQ) packet to its neighbors, which then forward

the request to their neighbors, and so on, until either the destination or an intermediate node

with a fresh enough routes to the destination is located. Figure 3.4(a) illustrates the

propagation of the broadcast RREQs across the network. AODV utilizes destination sequence

numbers to ensure all routes are loop free and contain the most recent route information. Each

node maintains its own sequence number, as well as a broadcast ID. The broadcast ID is

incremented for every RREQ the node initiates, and together with the node‘s IP address,

uniquely identifies an RREQ. Along with its own sequence number and the broadcast ID, the

source node includes in the RREQ the most recent sequence number it has for the destination.

Intermediate nodes can reply to the RREQ only if they have a route to the destination whose

corresponding destination sequence number is greater than or equal to that contained in the

RREQ.

During the process of forwarding the RREQ, intermediate nodes record in their route

tables the address of the neighbor from which the first copy of the broadcast packet is

received, thereby establishing a reverse path. If additional copies of the same RREQ are later

received, these packets are discarded.

Once the RREQ reaches the destination or an intermediate node with a fresh enough

route, the destination intermediate node responds by unicasting a route reply (RREP) packet

back to the neighbor from which it first received the RREQ(Fig3.4(b)). As the RREP is

routed back along the reverse path, nodes along this path set up forward route entries in their

route tables which point to the node from which the RREP came. These forward route entries

indicate the active forward route. Associated with each route entry is a route timer that will

cause the deletion of the entry if it is not used within the specified lifetime. Because the

RREP is forwarded along the path established by the RREQ, AODV only supports the use of

symmetric links. Routes are maintained as follows. If a source node moves, it is able to

reinitiate the route discovery protocol to find a new route to the destination. If a node along

the route moves, its upstream neighbor notices the move and propagates a link failure

notification message (an RREP with infinite metric) to each of its active upstream neighbors

to inform them of the erasure of that part of the route. These nodes in turn propagate the link

failure notification to their upstream neighbors, and so on until the source node is reached.

The source node may then choose to reinitiate route discovery for that destination if a route is

still desired.



An additional aspect of the protocol is the use of hello messages, periodic local

broadcasts by a node to inform each mobile node of other nodes in its neighborhood. Hello

messages can be used to maintain the local connectivity of a node. However, the use of hello

messages is not required. Nodes listen for retransmission of data packets to ensure that the

next hop is still within reach. If such a retransmission is not heard, the node may use any one

of a number of techniques, including the reception of hello messages, to determine whether

the next hop is within communication range. The hello messages may list the other nodes

from which a mobile has heard, thereby yielding greater knowledge of network connectivity.

Fig 3.4 AODV routing protocol



3.4.2 Dynamic Source Routing Protocol (DSR):

The Dynamic Source Routing (DSR) protocol presented in is an on-demand routing protocol

that is based on the concept of source routing. Mobile nodes are required to maintain route

caches that contain the source routes of which the mobile is aware. Entries in the route cache

are continually updated as new routes are learned.

The protocol consists of two major phases: route discovery and route maintenance. When

a mobile node has a packet to send to some destination, it first consults its route cache to

determine whether it already has a route to the destination. If it has an unexpired route to the

destination, it will use this route to send the packet. On the other hand, if the node does not

have such a route, it initiates route discovery by broadcasting a route request packet. This

route request contains the address of the destination, along with the source node‘s address

and a unique identification number. Each node receiving the packet checks whether it knows

of a route to the destination. If it does not, it adds its own address to the route record of the

packet and then forwards the packet along its outgoing links. To limit the number of route

requests propagated on the outgoing links of a node, a mobile only forwards the route request

if the mobile has not yet seen the request and if the mobile‘s address does not already appear

in the route record.

A route reply is generated when the route request reaches either the destination itself, or

an intermediate node, which contains in its route cache an unexpired route to the destination.

By the time the packet reaches either the destination or such an intermediate node, it contains

a route record yielding the sequence of hops taken. Figure 3.5 (a) illustrates the formation of

the route record as the route request propagates through the network. If the node generating

the route reply is the destination, it places the route record contained in the route request into

the route reply. If the responding node is an intermediate node, it will append its cached route

to the route record and then generate the route reply. To return the route reply, the responding

node must have a route to the initiator. If it has a route to the initiator in its route cache, it

may use that route. Otherwise, if symmetric links are supported, the node may reverse the

route in the route record. If symmetric links are not supported, the node may initiate its own

route discovery and piggyback the route reply on the new route request. Figure 3.5 (b) shows

the transmission of the route reply with its associated route record back to the source node.



Route maintenance is accomplished through the use of route error packets and

acknowledgments. Route error packets are generated at a node when the data link layer

encounters a fatal transmission problem. When a route error packet is received, the hop in

error is removed from the node‘s route cache and all routes containing the hop are truncated

at that point. In addition to route error messages, acknowledgments are used to verify the

correct operation of the route links. Such acknowledgments include passive

acknowledgments, where a mobile is able to hear the next hop forwarding the packet along

the route.

Fig 3.5 DSR routing protocol

One trade off between source routing and distance vector routing is the handling of partitioned

networks. Under dynamic source routing, if a host wishes to communicate with an unreachable host,

then though the rate at which route request are made will be reduced by a back off mechanism but



the protocol continues to make periodic efforts to find a route to the unreachable host, consuming

some network resources. Under distance vector routing, with the assumption that routes have had

time to converge once the host become unreachable, no network resources are used trying to send

packets to unreachable host, as none of the host in the sender's partition of the network has a

routing table entry for the destination.

3.5 HYBRID SCHEME

3.5.1 Zone Routing Protocol (ZRP)

Proactive routing uses excess bandwidth to maintain routing information, while reactive

routing involves long route request delays. Reactive routing also inefficiently floods the

entire network for route determination. The Zone Routing Protocol (ZRP) aims to address

the problems by combining the best properties of both approaches. ZRP can be classed as a

hybrid reactive/proactive routing protocol.

In an ad-hoc network, it can be assumed that the largest part of the traffic is directed to

nearby nodes. Therefore, ZRP reduces the proactive scope to a zone centered on each node.

In a limited zone, the maintenance of routing information is easier. Further, the amount of

routing information that is never used is minimized. Still, nodes farther away can be reached

with reactive routing. Since all nodes proactively store local routing information, route

requests can be more efficiently performed without querying all the network nodes.

Despite the use of zones, ZRP has a flat view over the network. Nodes belonging to

different subnets must send their communication to a subnet that is common to both nodes.

This may congest parts of the network. ZRP can be categorized as a flat protocol because the

zones overlap. Hence, optimal routes can be detected and network congestion can be reduced.

Further, the behavior of ZRP is adaptive. The behavior depends on the current configuration

of the network and the behavior of the users.

Architecture:

The Zone Routing Protocol, as its name implies, is based on the concept of zones. A

routing zone is defined for each node separately, and the zones of neighbouring nodes

overlap. The routing zone has a r-radius expressed in hops. The zone thus includes the nodes,

whose distance from the node in question is at most r-hops.



An example routing zone is shown in Fig 3.6, where the routing zone of S includes the nodes

A–I, but not K. In the illustrations, the radius is marked as a circle around the node in

question. It should however be noted that the zone is defined in hops, not as a physical

distance. The nodes of a zone are divided into peripheral nodes and interior nodes. Peripheral

nodes are nodes whose minimum distance to the central node is exactly equal to the zone

radius r. The nodes whose minimum distance is less than rare interior nodes, in figure, the

nodes A–F are interior nodes, the nodes G–J are peripheral nodes and the node K is outside

the routing zone. Note that node H can be reached by two paths, one with length 2 and one

with length 3 hops. The node is however within the zone, since the shortest path is less than

or equal to the zone radius.

Fig 3.6 Zone routing protocol with radius = 2.

ZRP refers to the locally proactive routing component as the Intra-zone Routing Protocol

(IARP). The globally reactive routing component is named Inter-zone Routing Protocol

(IERP). IARP maintains routing information for nodes that are within the routing zone of the

node. IERP offer enhanced route discovery and route maintenance services based on local

connectivity monitored by IARP. The fact that the topology of the local zone of each node is

known can be used to reduce traffic when global route discovery is needed. Instead of

broadcasting packets, ZRP uses a concept called border casting. Border casting utilizes the

topology information provided by IARP to direct query request to the border of the zone. The

Border cast Resolution Protocol (BRP) provides the border cast packet delivery service. In

order to detect new neighbor nodes and link failures, the ZRP relies on a Neighbor Discovery



Protocol (NDP) provided by the Media Access Control (MAC) layer. NDP transmits

―HELLO‖ beacons at regular intervals. Upon receiving a beacon, the neighbor table is

updated. Neighbors, for which no beacon has been received within a specified time, are

removed from the table

Route updates are triggered by NDP, which notifies IARP when the neighbor table is

updated. IERP uses the routing table of IARP to respond to route queries. IERP forwards

queries with BRP. BRP uses the routing table of IARP to guide route queries away from the

query source.

A node that has a packet to send first checks whether the destination is within its local zone

using information provided by IARP. In that case, the packet can be routed proactively.

Reactive routing is used if the destination is outside the zone.

The reactive routing process is divided into two phases: the route request phase and the route

reply phase. In the route request, the source sends a route request packet to its peripheral

nodes using BRP. If the receiver of a route request packet knows the destination, it responds

by sending a route reply back to the source. Otherwise, it continues the process by border

casting the packet. In this way, the route request spreads throughout the network. If a node

receives several copies of the same route request, these are considered as redundant and are

discarded. The reply is sent by any node that can provide a route to the destination. To be

able to send the reply back to the source node, routing information must be accumulated

when the request is sent through the network. The information is recorded either in the route

request packet, or as next-hop addresses in the nodes along the path. In the first case, the

nodes forwarding a route request packet append their address and relevant node/link metrics

to the packet. When the packet reaches the destination, the sequence of addresses is reversed

and copied to the route reply packet. The sequence is used to forward the reply back to the

source. In the second case, the forwarding nodes records routing information as next-hop

addresses, which are used when the reply is sent to the source. This approach can save

transmission resources, as the request and reply packets are smaller.

The source can receive the complete source route to the destination. Alternatively, the nodes

along the path to the destination record the next-hop address in their routing table. In the

border casting process, the border casting node sends a route request packet to each of its

peripheral nodes. This type of one-to-many transmission can be implemented as multicast to

reduce resource usage. One approach is to let the source compute the multicast tree and attach



routing instructions to the packet. This is called Root-Directed Border casting (RDB). The

zone radius is an important property for the performance of ZRP. If a zone radius of one hop

is used, routing is purely reactive and border casting degenerates into flood searching. If the

radius approaches infinity, routing is reactive. The selection of radius is a tradeoff between

the routing efficiency of proactive routing and the increasing traffic for maintaining the view

of the zone.

Route maintenance

In ZRP, the knowledge of the local topology can be used for route maintenance. Link failures

and sub-optimal route segments within one zone can be bypassed. Incoming packets can be

directed around the broken link through an active multi-hop path. Similarly, the topology can

be used to shorten routes, for example, when two nodes have moved within each other‘s radio

coverage. For source-routed packets, a relaying node can determine the closest route to the

destination that is also a neighbor. Sometimes, a multi-hop segment can be replaced by a

single hop. If next-hop forwarding is used, the nodes can make locally optimal decisions by

selecting a shorter path.

3.6 COMPARISON

Parameters TABLE DRIVEN ON DEMAND

Availability of routing

information

Available when needed Always available regardless

of the need

Routing philosophy Flat Mostly flat except CGSR

Periodic route updates Not required Required

Coping with mobility Use localized route

recovery

Inform other nodes to

achieve a consistent routing

Signaling traffic generated Grows with increasing Greater than that of on

Tab 3.1 Comparison between table driven and on demand routing protocols



Chapter 4

VEHICULAR AD HOC NETWORK (VANET)

A Vehicular Ad-Hoc Network, or VANET, is a technology that uses moving cars as nodes in a

network to create a mobile network. VANET turns every participating car into a wireless router or

node, allowing cars approximately 100 to 300 metres of each other to connect and, in turn, create a

network with a wide range. As cars fall out of the signal range and drop out of the network, other

cars can join in, connecting vehicles to one another so that a mobile Internet is created. It is

estimated that the first systems that will integrate this technology are police and fire vehicles to

communicate with each other for safety purposes.

Fig 4.1 Typical vehicular ad hoc network (VANET)



4.1 ARCHITECTURE OF VANET

In general, protocol architecture achieves for communication among network nodes and

provides the framework for implementation. When designing the communication suit for VANETs

two approaches can be taken: First, following the traditional approach, the overall functionality

could be de-composed and organized in layers such that at the protocols fulfill small, well-defined

tasks and form a protocol stack as in TCP/IP and OSI. Second, one could try to build a customized

solution that meets the requirements of VANETs. With such non-layered .

The first approach—called layered approach and depicted in Fig. 1 attempts to retain the order

of functions and protocol layers with well-defined interfaces between them. It adapts system

functionalities to the needs of a VANET communication system resulting, e.g., in protocol layers

for single-hop and multi-hop communication. The limitations and inflexibility of traditional

network stacks when used in ad hoc networks are well known. E.g., each layer is implemented as

an independent module with interfaces (SAPs) only to the above and below layers. Consequently,

protocols cannot easily access state or metadata of a protocol on a different layer what makes data

aggregation difficult. Moreover, some of VANET-specific functions do not fit into the traditional

layered OSI model, such as those for network stability and control, and cannot be uniquely

assigned to a certain layer. It is also worth noting that every layer accesses external information

separately with no common interface which might lead to problems when this information

influences protocol flow.

The second un-layered approach would be the result of tailoring a whole new system

to the needs of VANETs‘ main focus, i.e., safety applications. Having accurate specifications of

these applications and willing to use the ‗probabilistic‘ channel in the most efficient manner leads

to have a highly coupled set of protocols. Therefore, all application and communication protocols

are placed in one single logical block right over the physical interface and connected to the external

sensors (Fig. 2). Inside this block, all protocol elements are modularized such that there are no

restrictions for interaction, state information is arbitrary accessible. Note though, that this

‗architecture‘ inherits a high design complexity due to arbitrary and complex interactions of their

modules. This makes protocol specification a complicated work and so, once designed becomes an

extremely inflexible system for other types of application. Also it would be tough to systematically



avoid control loop, what is rather easy in the layered approach with its clean top-down or bottom-

up packet traversal. While both approaches would certainly be feasible.

Fig 4.2 Layered architecture

Fig 4.3 Un-layered architecture

4.2 APPLICATIONS OF VANET

There are many applications for vehicular networks. Just name a few important ones: Collision

Avoidance – About 21,000 of the 43,000 deaths that occur each year on U.S. highways result from



vehicles leaving the road or travelling unsafely through intersections. Data transmitted from a

roadside base station to a vehicle could warn a driver that it‘s not safe to enter an intersection.

Communication between vehicles and between vehicles and the roadsides can save many lives and

prevent injuries. Some of the worst traffic accidents involve many vehicles rear-ending each other

after a single accident at the front of the line suddenly halts traffic. In this application, if a vehicle

reduces its speed significantly, it will broadcast its location to its neighbor vehicles. And other

receivers will try to relay the message further. And the vehicles behind the vehicle in question will

emit some kind of alarm to its drivers and other drivers behind. In this way, more drivers far behind

will get an alarm signal before they see the accident. Cooperative Driving – Like violation warning,

turn conflict warning, curve warning, lane merging warning etc. These services may greatly reduce

the life-endangering accidents. In fact, many of the accidents come from the lack of cooperation

between drivers. Given more information about the possible conflicts, we can prevent many

accidents.

Traffic Optimization – Traffic delays continue to increase, wasting more than a 40-hour

workweek for peak time travelers. A significant reduction in these numbers could be achieved

through vehicular networks.

Vehicles could serve as data collectors and transmit the traffic condition information for the

vehicular network. And transportation agencies could utilize this information to actively relieve

traffic congestion. To be more specifically, in this application, vehicles could detect if the number

of neighboring vehicles is too many and their speed is too slow, and then relay this information to

vehicles approaching the location.

To make it work better, the information can be relayed by vehicles travelling in the other

direction so that it may be propagated faster to the vehicles toward the congestion location. In this

way, the vehicles approaching the congestion location will have enough time to choose alternate

routes. Vehicles can also collect the data about weather, road surface, construction zones, highway

rail intersection, emergency vehicle signal preemption and relay them to other vehicles.

Payment Services – Like toll collection. It‘s very convenient and desirable to pass a toll

collection without having to decelerate your car, waiting in line, looking for some coins and

something like that.



Location-based Services – Like finding the closest fuel station, restaurant, lodge etc. In fact,

these kinds of services are not specific to the vehicular networks. Many GPS systems have such

kinds of services already.

Intelligent vehicular ad hoc networks (InVANETs) use Wi-Fi IEEE 802.11p(WAVE

standard)and Wi-MAX IEEE 802.16 for easy and effective communication between vehicles with

dynamic mobility. Effective measures such as media communication between vehicles can be

enabled as well methods to track automotive vehicles. InVANET is not foreseen to replace current

mobile (cellular phone) communication standards. Automotive vehicular information can be

viewed on electronic maps using the Internet or specialized software. The advantage of Wi-Fi

based navigation system function is that it can effectively locate a vehicle which is inside big

campuses like universities, airports, and tunnels. InVANET can be used as part of automotive

electronics, which has to identify an optimally minimal path for navigation with minimal traffic

intensity. The system can also be used as a city guide to locate and identify landmarks in a new

city. Communication capabilities in vehicles are the basis of an envisioned InVANET or intelligent

transportation systems (ITS). Vehicles are enabled to communicate among themselves (vehicle-to-

vehicle, V2V) and via roadside access points (vehicle-to-roadside, V2R). Vehicular communication

is expected to contribute to safer and more efficient roads by providing timely information to

drivers, and also to make travel more convenient. The integration of V2V and V2R communication

is beneficial because V2R provides better service sparse networks and long distance

communication, whereas V2V enables direct communication for small to medium distances/areas

and at locations where roadside access points are not available. Providing vehicle-to-vehicle and

vehicle-to-roadside communication can considerably improve traffic safety and comfort of driving

and travelling. For communication in vehicular ad hoc networks, position-based routing has

emerged as a promising candidate. For Internet access, Mobile IPv6 is a widely accepted solution

to provide session continuity and reachability to the Internet for mobile nodes. While integrated

solutions for usage of Mobile IPv6 in (non-vehicular) mobile ad hoc networks exist, a solution has

been proposed that, built upon on a Mobile IPv6 proxy-based architecture, selects the optimal

communication mode (direct in-vehicle, vehicle-to-vehicle, and vehicle-to-roadside

communication) and provides dynamic switching between vehicle-to-vehicle and vehicle-to-

roadside communication mode during a communication session in case that more than one

communication mode is simultaneously available.



Chapter 5

APPLICATIONS OF MANET

The field of wireless networking emerges from the integration of personal computing,

cellular technology, and the Internet. This is due to the increasing interactions between

communication and computing, which is changing information access from "anytime

anywhere" into "all the time, everywhere."

1. Tactical networks: military communications and operation, automated battle fields

2. Emergency services: search and rescue operations, disaster recovery, replacement of

fixed infrastructure in case of environmental disaster, policing and fire fighting,

supporting doctors and nurses in hospitals

3. Commercial and civilian environments: E-commerce, dynamic database access,

mobile offices, road or accident guidance, transmission of road and weather

conditions, taxi cab network, inter-vehicle networks, sports stadiums, trade fairs,

shopping malls, networks of visitors at airports

4. Home and enterprise networking: home/office wireless networking, conferences,

meeting rooms, personal area networks, networks at construction sites

5. Education: universities and campus settings, virtual class rooms

6. Entertainment: multiuser games, wirelessP2P networking, outdoor internet access,

robotic pets, theme parks

7. Sensor networks: smart sensors and actuators embedded in household electronic

devices, body area networks, data tracking of environmental conditions, animal

movements, chemical or biological detection

8. Context-aware services: call forwarding, mobile workspace, location-specific

services, time dependent services, infotainment touristic information

9. Coverage extension: extending cellular network access, linking up with the internets

intranets etc.



Chapter 6

CONCLUSION

In conclusion, mobile ad-hoc networks allow the construction of flexible and adaptive

networks with no fixed infrastructure. These networks are expected to play an important role

in the future wireless generation. Future wireless technology will require highly-adaptive

mobile networking technology to effectively manage multi-hop ad-hoc network clusters,

which will not only operate autonomously but also will be able to attach at some point to the

fixed networks.



Chapter 7

REFERENCE

1. Ad-hoc networks: Fundamental properties and network topologies by Ramin Hekmat

2. Ad hoc networks technologies and protocols by Prasant Mohapatra and Srikanth V.

Krishnamurthy

3. Elizabeth M. Royer, Chai-Keong Toh, A Review of Current Routing Protocols for Ad

Hoc Mobile Wireless Networks , Proc. IEEE,1999.

4. http://en.wikipedia.org/wiki/Mobile_ad_hoc_network

Introduction to Mobile adhoc-network

Technology

mobile networks

routing protocols53

routing of information

wireless networks

routing tables9

routing protocols3

mobile nodes

mobile mesh network