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”
th
of the VII 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
Seminar guide

Dr. DAVID PETER
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

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

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.

3.3.1 DESTINATIONSEQUENCED
DISTANCE VECTOR ROUTING ALGORITHM 7
3.3.2 CLUSTERHEAD GATEWAY SWITCH
ROUTING (CGSR)
3.4 SOURCE INITIATED ON DEMAND ROUTING

10
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
i

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

3.1

CATEGORIZATION OF AD HOC ROUTING
PROTOCOLS

3.2

2

6

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

ii

4.3

UNLAYERED ARCHITECTURE

22

LIST OF TABLES
TABLE NO.
3.1

TITLE

PAGENO.

COMPARISON BETWEEN TABLE DRIVEN
AND ON DEMAND ROUTING PROTOCOLS

iii

19

1

Mobile ad hoc networks

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.

Division Of Computer Science Engineering, SOE, CUSAT

2


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



3

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.



-

4

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.


5


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



6

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 routingrelated 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 .



7

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



8

(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


9


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
A
B
C
D
E
F

Next
Hop
A
B
C
D
D
D

Distance
0
1
1
1
2
2

Sequence
Number
S205_A
S334_B
S198_C
S567_D
S767_E
S45_F

A‘s routing table before change


10


Destination
A
B
C
D
E
F

Next
Hop
A
D
C
D
D
D

Distance

Sequence Number

0
3
1
1
2
2

S304_A
S424_B
S297_C
S687_D
S868_E
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-togateway 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



11

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



12

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.



13

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



14

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.


15


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

16


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.



17

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



18

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

19


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
Grows with increasing

Inform other nodes to
achieve a consistent routing
Greater than that of on

Signaling traffic generated

Tab 3.1 Comparison between table driven and on demand routing protocols


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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)



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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



22

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



23

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.


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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-tovehicle, 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-toroadside communication mode during a communication session in case that more than one
communication mode is simultaneously available.


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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.


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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.


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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