1. INTRODUCTION

In computer networking, an Ad Hoc Network refers to a network connection established for a

single session and does not require a router or a wireless base station.Mobile nodes that are

within each other's radio range communicate directly via wireless links that. Here mobile

nodes are cause the di erent topology in the networks.

FIG 1.1 RADIO STATION

In the above diagram nodes A and D have direct connection between them. In the rst radio

station shows that in same radio stations both A and D are directly connected. But as the

show in the second radio station, when nodes d are goes away from the these station the

connection link was broken between them. But still A and D are connected via nodes A-B-C-

D. So this type of networks connections is held in ad hoc networks. So it is widely used in the

military application and other temporary networks. For example, military units (e.g., soldiers,

tanks, or planes), equipped with wireless communication devices, could form an ad hoc

network when they roam in a battle eld. Ad hoc networks can also be used for emergency,

law enforcement, and rescue missions.

1.1 Characteristics

Operating without a central coordinator

Multi-hop radio relaying

Frequent link breakage due to mobile nodes

Constraint resources (bandwidth, computing power, battery lifetime)

Instant deployment

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1.2 Applications

Military applications

Collaborative computing

Emergency rescue

Mesh networks

Wireless sensor networks

Multi-hop cellular networks

Wireless Community Network

1.3 Major Issues and Challenges

Hidden terminal problem

Exposed terminal problem

Channel e ciency

Access delay and fairness

Di erential service

Realistic mobility modeling

power-aware routing

Constructing virtual backbone

Distinguish contention, packet drop, and noise errors

Security

E cient multicasting

1.4 Ad Hoc versus Infrastructure based Networks

In infrastructure based Networks , communication typically takes place only between the

wireless nodes and the access point , but not directly between the wireless nodes.

Infrastructure Networks contain special nodes called access points(APs), which are con-

nected via existing networks. APs are special in the sense that they can interact with wireless

nodes as well as with the existing wired network. The other wireless nodes , also known as

mobile stations , communicate via APs. The APs also act as bridges with other networks. Ad

hoc LANs do not need any xed infrastructure. These networks can be set up on the y at any

place. Nodes communicate directly with each other or forward messages through other nodes

that are directly accessible. The design of infrastructure based networks is simpler because

most of the network functionality lies within the access point ,whereas the client can remain

quite simple. In Ad hoc networks, the complexity of each node is higher because every node

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has to implement medium access mechanisms to provide certain quality of service.

Infrastructure based networks lose some of the exibility which wireless networks can o er.

They cannot be used for disaster relief in cases where no infrastructure is left, where ad hoc

networks can be used.

2. ARCHITECTURE OF AD HOC NETWORK

The architecture of ad hoc network can be explained by IEEE 802.11 standards.

2.1 IEE 802.11

IEEE 802.11 is a set of IEEE standards that govern wireless networking transmission

methods.

2.1.1 History

802.11 technology has its origins in a 1985 ruling by the U.S. Federal Communications

Commission that released the ISM band for unlicensed use. In 1991 NCR Corporation (now

Alcatel-Lucent and LSI Corporation) invented the precursor to 802.11 in Nieuwegein, The

Netherlands. The inventors initially intended to use the technology for cashier systems; the

rst wireless products were brought on the market under the name WaveLAN with raw data

rates of 1 Mbit/s and 2 Mbit/s. Vic Hayes, who held the chair of IEEE 802.11 for 10 years

and has been called the "father of Wi-Fi" was involved in designing the initial 802.11b and

802.11a standards within the IEEE. In 1992, the Commonwealth Scienti c and Industrial

Research Organisation (CSIRO) obtained a patent in Australia for a method of wireless data

transfer technology based on the use of Fourier transforms to "unsmear" the signal. In 1996,

CSIRO obtained a patent for the same technology in the US. In April 2009, 14 tech

companies selling Wi-Fi devices, including Dell, HP, Microsoft, Intel, Nintendo, and

Toshiba, agreed to pay CSIRO 250 dollors million for infringements on the CSIRO patents .

Mobile terminals can operate in two modes under IEEE 802.11 :

Infrastructure Mode

Ad Hoc Mode

2.2 Ad Hoc Mode

IEEE 802.11 only covers PHY layer and MAC layer

PHY layer is subdivided into

Physical Layer Convergence Protocol (PLCP)

Physical Medium Dependent sub layer (PMD)

PHY management include channel tuning and responsible for higher layer functions (e.g. 3

control of bridging). MAC management controls authentication mechanism and power man-

agement to save battery power.

2.2.1 Medium Access Control Layer

The basic servies provided by the MAC layer are the mandatory "Asynchronous data service"

and an optional "Time bounded service". while 802.11 only o ers the Asynchronous data

service in ad-hoc mode,both service types can be o ered using an Infrastructure based

network. The following three mechanisms for IEEE 802.11 : The mandatory basic method

based on a version of CSMA/CA, an optional method avoiding the hidden terminal

problem,and nally a contention free polling method for time bounded service. The rst two

methods are also summarized as "Ditributed Coordination Function(DCF)", the third method

is called "Point Coordination Function(PCF)". The MAC Mechanisms are also called

"Distributed Foundation Wireless Medium Access Control(DFWMAC)".

2.2.2 Basic DFWMAC-DCF using CSMA/CA

The mandatory access mechanism of IEE 802.11 is based on Carrier Sense Multiple Access

with Collision Avoidance(CSMA/CA) ,which is random access scheme with carrier sense

and collision avoidance through random backo . The basic CSMA/CA mechanism shown in

gure 2.1:

FIGURE 2.1: COTENTION WINDOW AND WAITING TIME

If medium is idle for at least the duration of DIFS , a node can access the medium at

once.This allows for short access delay under light load. If medium is busy , nodes have to

wait for the duration of DIFS , entering a contention phase afterwards. Each node now choose

a random back o time within a contention window and delays medium access for this random

amount of time. The node cntinues to sense the medium. As soon as a node senses the

channel is busy , it has lost this cycle and has to wait for the next chance. But if the

randomized additional waiting time for a node is over and the medium is still idle ,the node

can access the medium immediately. The basic CSMA/CA mechanism is not

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fair.Independent of the overall time a node has already waited for transmission;each node has

the same chances for transmitting data in the next cycle.To provide fairness , IEEE 802.11

adds back o timer. Each node selects random amount of waiting time within the range of

contention window. If certain station does not get access to the medium in rst cycle, it stops

its back o timer , waits for the channel to be idle again for DIFS and starts the counter again.

As soon as the counter expires, the node accesses medium. This means that de ered stations

do not choose a randomized backo time again, but continue to countdown. Stations that have

waited longer have the advantage over stations that have just en-tered,in that they only have

to wait for the remainder of their backo timer from the previous cycle.

2.2.3 DFWMAC-DCF with RTS/CTS

Hidden terminal problem may occur in 802.11, if one station can receive two others, but

those cannot receive each other. To deal with this problem, mechanism using two control

packets , RTS and CTS. After waiting for DIFS , the sender can issue a request to send (RTS)

control packet. Every node receiving this RTS now has to set its net allocation vector (NAV)

in accor-dance with the duration eld The NAV than speci es earliest point at which the station

can try to access the medium. If the receiver receives the RTS , it answers with the clear to send

(CTS) waiting for SIFS.

This CTS packet contains duration eld and receivers have to adjust their NAV. Now all

nodes within receiving distance around sender and receiver are informed that they have to

wait more time before accessing the medium. This mechanism reserves the medium for one

sender exclusively. It is also called a Virtual Reservation Scheme.

3. ROUTING IN AD-HOC NETWORKS

3.1 Requirement of the Routing

It should be fully distributed, as centralized routing involves high control

overhead and hence is not scalable. Distributed routing is more fault-tolerant than

centralized routing, which involves the risk of single point of failure.

It must be adaptive to frequent topology changes caused by the mobility of nodes.

It must be localized, as global state maintenance involves a huge state propagation

control overhead.

It must be loop-free and free from stale routes.

It must converge to optimal routes once the network topology becomes stable. The

convergence must be quick.

It must optimally use scare resources such as bandwidth, computing power,

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memory and battery power.

It should be able to provide a certain level of quality of service (Qos) as demanded

by the applications,and should also o er support for time-sensitive tra c.

The ooding must be less.

3.2 General Issues for Ad Hoc Network Routing

Secure delivery and the capability to handle constant connectivity are the most important

issues for routing protocols in wireless mobile ad hoc networks. Once the path will establish

between the source end destination, the source will send message to the destination without

worried.If the connectivity of any two nodes changes and routes are a ected by this change,

the routing protocol should be able to recover if an alternate path exists.

There are some other issues related to routing in wireless ad hoc networks. For example:

overhead is particularly important in a wireless network with limited bandwidth.

Power consumption may also be a problem in an ad hoc network with battery-

powered nodes.

Quality of service may be required in an ad hoc network supporting delay

sensitive applications such as video conferencing .

A routing protocol may need to balance tra c based on the tra c load on links.

Scalability of routing protocols is an important issue for large networks .

The routing protocol may need to implement security to protect against attacks, such as sni

er, man-in-the-middle. Routing protocols may rely on information based on other layers. For

example, the Global Positioning System (GPS) can be used in wireless ad hoc networks

deployed in battle elds or connecting vehicles. Mobility prediction can improve routing in

wireless networks with known movement patterns, such as the IRIDIUM system satellite

network . Information from the medium access control layer may be propagated to the

network layer so that neighbours can be detected via MAC layer protocols. The power of

received signals from a neighbouring node can be used to decide whether neighbour is

moving closer or further away .

4. ROUTING PROTOCOLS

4.1 Classification

Routing protocols for ad hoc wireless networks can be classi ed into several types based on di

erent criteria. The routing protocols for ad hoc wireless networks can be broadly classi ed

into four categories base on :-

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� Routing Information update mechanism

� Use of Temporal information for routing

� Routing Topology

� Utilization of speci c resources

4.1.1 Based on the routing information update mechanism.

� Proactive or table-driven routing protocols

� Reactive or on demand routing protocols

� Hybrid routing protocols

4.1.2 Based on the use of Temporal information for Routing

Since ad hoc wireless networks are highly dynamic and path breaks are much more frequent

than in wired networks, the use of temporal information regarding the lifetime of the wireless

links and the lifetime of the path selected assumes signi cance.

Routing protocols using past temporal information

Routing protocols that use future temporal information

4.1.3 Based on Routing Topology

Routing topology being used in the Internet is hierarchical in order to reduce the state

information maintain at the core routers.

Flat topology routing protocols

Hierarchical topology routing protocols

4.1.4 Based on the Utilization of speci c Resources

� Power aware routing

� Geographical information assisted routing

4.2 Proactive or table-driven routing protocols

These protocols are extension of the wired network routing protocols. They maintain the

global topology information in the form of the tables at every node. These tables are updated

frequently in order to maintain consistent and accurate network state information. The

distance-vector routing protocol (DSDV),wireless routing protocol (WRP),source-tree

adaptive routing protocol (STAR),and cluster-head gateway switch routing protocol (CGSR)

are some example for the protocols that belong to this category.

4.2.1 Destination sequenced distance-vector protocol

This protocol also called as the DSDV routing protocol. It is the enhanced version of the

distributed Bellman-Ford algorithm where each node maintains a table that contains the

shortest distance and the rst node on the shortest path to every other node in the network. It

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incorporate table update with increasing sequence number tag to prevent loops, to counter to

the count-to-in nity problem, and for faster convergences. As describe this is the table driven

so that at nite interval the tables of the each node exchange to update and which are reachable

from all the nodes. If the topologies of the network are change then all tables are forwarded

to their neighbor. Here in the table updating, we have two types:- One is the full dump in

which done either when the local topology changed signi cantly or when a more incremental

change required in the table. Second is the incremental update in which node does not

observe change in the topology. Here one example is given for table updating and node table

creation.

FIGURE 4.1: DSDV PROTOCOL

Desination Next Hop Distance

A A 0

B B 1

C C 1

D D 1

E D 2

F D 2

TABLE 4.1: ROUTING TABLE OF DSDV PROTOCOL

Here consider the example, here node A is the source node and F is the destination node.

Here in the table rst Column is destination node which is all nodes in the network. Second

Column is the next node in the shortest path to the source path. Third column is the distance

between two nodes- source to destination. And fourth column is the sequence number of each

packet to be received by them. Here routing table for node A is indicating that the shortest

path to the destination node F is available through node D and the distance to it is two. And

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the packets to be received at that place which has number as shown in table. If any link

between two node is broken then the distance is assign in nite to that node and update the all

node's routing table.

Advantages

The availability of the routers to all destination at all times implies that much less

delay is involved in the route setup process.

The mechanism of incremental updates with sequence number tags makes the

existing wired network protocol adaptable to ad hoc networks. Hence wired

network protocol can be applied to the ad hoc network by less modi cation.

Disadvantages

A small network with high mobility or a large network with low mobility can

completely choke the available bandwidth. Hence this protocol su ers from excessive

control overhead that is proportional to the number of nodes in the network.

In order to obtain information about a particular destination node, a node has to wait

for a table update message initiated by the same destination node.

4.2.2 Wireless routing protocol

The WRP protocols is the basically same as the DSDV protocols, but it is di er from it only in

the their routing protocol. The routing table contain the up-to-date view of the network for

the network for all known destination. The routing table keeps the shortest distance, the

predecessor node and ag indicating the status of the path. The path status may be a simple

path(correct) ,or a loop(error) ,or the destination node not marked(null). The LTC(Link cost

table) contain the cost of relaying message through each link. The MRL(Message

transmission list) contains an entry for the every update message that is to be retransmitted

and maintain the counter for the each entry. When a node detects a link break, it sends an

update message to its all neighbors with the link cost is in nite (?). And that all neighbors nd

the alternate path to reach the destination and resend the message.

Advantages

� It is the faster convergence and involves fewer table updates.

Disadvantages

Complexity of maintenance of multiple tables demands a larger memory and

greater processing power from the nodes.

At the high mobility, the control overhead involved in updating table entries is

almost the same as DSDV. So it is not suitable for highly dynamic and also for

very large ad hoc networks.

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4.2.3 Cluster head Gateway Switch Routing protocol

The CGSR protocol uses a hierarchical network topology that employs at topologies. CGSR

organizes nodes into clusters, with coordination among the member of each cluster instructed

nodes named "cluster head". This cluster head selected dynamically by employing a least

cluster change (LCC) algorithm. According to this algorithm ,nodes creates to be a cluster-

head only if it comes under the range of another cluster-head, where tie is broken either using

the lower ID or highest connectivity algorithm. CGSR protocol creates a xed region in the

network. Each node in the cluster region is known as cluster member and they all are

connected with pivot node which is called cluster-head .Two cluster region are connected via

node which are place in intersection region of two cluster region and called cluster-gateway.

FIGURE 4.2: CGSR PROTOCOL

Here in the gure three cluster area are shown ,the all are overlapped in each other .so between

their intersection one node is placed as the gateway which transfer the information of one

cluster area to the other.

Advantages

CGSR is a hierarchical routing scheme which enables partial coordination between

nodes by electing cluster-heads. Hence , better bandwidth utilization is possible.

It is easy to implement priority scheduling scheme with token scheduling and gateway

code scheduling.

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Disadvantages

It increases in path length and instability in the system at high mobility when the

rate of change of cluster-heads is high.

To avoid gateway con icts, more resources are required.

The power consumption at the cluster-head node is also a matter of concern

because the battery-draining rate at the cluster-head is higher than that at a normal

node.

4.3 On-Demand routing protocols

This type of protocols execute the path nding process and exchange routing information only

when path is required by the node to communicate with a destination. There some of the

routing protocols like Dynamic Source Routing Protocol (DSR) , Ad Hoc On-Demand

Distance Vector Routing Protocol (AODV) .

4.3.1 Dynamic Source Routing Protocol

This type of routing protocol is design to restrict the bandwidth consumed by control packets

in ad wireless networks by eliminating the periodic table-update message required in the table

driven approach. In this routing protocol does not require periodic 'hello' packet transmission,

which are used by a node to inform its neighbors of its presence. The basic approach of this

protocol during the routing construction phase is to establish a route by ooding Route-

Request packets in the network. The destination node, On receiving a Route-Request packet,

respond by sending Route

FIGURE 4.3: DSR PROTOCOL

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Here shown in the gure, the node 1 is the source node and the node 5 is the destination node.

when 1 has data packet to sent to the node 5, it initiate a Route-Request as BLUE arrow in

gure ,and sent it to all its neighbors or ooded. Each node receiving this request packet check

if it is the destination then it generate Reply packet and send to sender. If it is not proper

destination then again that node send request packets to their neighbor until destination node

not found. Each packet has unique sequence number so that in the network while ooding loop

will not generate. If duplicate the packet at any node then it will discarded by the particular

node where redundancy will observe.

Advantages

Do not exchange routing update periodically, so overhead transmission is greatly

re-duced Can refer to cache for the new route when link fails.

Disadvantages

Scalability problem: High route discovery latency for large network.

High mobility problem: although the packet dropped may not be substantional, the

overhead tra c will increase a lot.

4.3.2 Ad Hoc On-Demand Distance Vector Routing Protocol

The Ad hoc On-demand Distance Vector (AODV) routing protocol is a reactive protocol.

Similar to DSR,AODV broadcasts a route request to discover a route in a reactive mode. The

di erence is that in AODV, a eld of the number of hops is used in the route record, instead of

a list of intermediate router addresses. Each intermediate router sets up a temporary reverse

link in the process of a route discovery. This link points to the router that forwarded the

request. Hence, the reply message can nd its way back to the initiator when a route is

discovered. When intermediate routers receive the reply, they can also set up corresponding

forward routing entries. To prevent old routing information being used as a reply to the latest

request, a destination sequence number is used in the route discovery packet and the route

reply packet. A higher sequence number implies a more recent route request.

We use the example topology shown in Figure to illustrate the discovery procedure of

AODV. Note that Routers A and C are disconnected from each other while both of them

connect to B. When Router A starts a route discovery to C, a route request is broadcast. The

request packet contains the requested destination sequence number, which is 1 greater than

the one currently kept at A. The intermediate routers reply to the source if they know the

route to that destination with the same or higher destination sequence number. We assume

that B does not have a record for a route to C. Therefore, B rst sets up a temporary link

pointing back to A. In the second step, it increases the number of hops by 1 and rebroadcasts

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the request. When C receives that request, it creates a new destination sequence number. A

route reply with that new sequence number is sent by C. The initiator and all intermediate

routers build routing entries associated with this new sequence number when they receive the

reply. The number of hop values can be used to nd a shorter path if a router receives two

replies with the same destination sequence number.

FIGURE 4.4: AODV PROTOCOL

Advantages

� AODV is loop-free due to the destination sequence numbers associated with routes.

Therefore, it o ers quick convergence when the ad hoc network topology changes which,

typically, occurs when a node moves in the network

Disadvantages

� Poor scalability is a disadvantage of AODV.

4.4 Hybrid routing protocols

4.4.1 Zone Routing Protocol

The Zone Routing Protocol (ZRP) is a prototype routing protocol. ZRP is formed by two sub-

protocols, the Intrazone Routing Protocol (IARP) and the Interzone Routing Protocol (IERP).

IARP is "a limited scope proactive routing protocol used to improve the performance of

existing globally reactive routing protocols". It relies on the service of a certain neighbor

discovery protocol (NDP) to provide neighbor information. IARP may use a scheme based on

the time-to-live (TTL) eld in IP packets to control the zone range. IERP is the reactive

routing component of ZRP. This scheme is responsible for nding a global path. It avoids

global queries for destinations that would be sent to surrounding hop neighbors. When global

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queries are required, "the routing zone based broadcast service can be used to e ciently guide

route queries outward, rather than blindly relaying queries from neighbor to neighbor".

ZRP tries to combine the advantages of reactive and proactive routing protocols. The

potential disad-vantage is the lack of route optimization. We use the example network in

Figure to brie y show the concept of ZRP. The range of the zone is set to one. So routers in

Subnets I and II use proactive IARP to nd routes to other routers in the same subnet. For

routes to the other subnet, reactive IERP is used.

FIGURE 4.5: ZONE ROUTING PROTOCOL

Advantages

� By combining the best features of proactive and reactive routing scheme, ZRP reduce the

control overhead compared to the Route-Request ooding mechanism employed in on-

demand approaches and the periodic ooding of routing information packets in table-driven

approaches.

Disadvantages

� In absence of a query control ,ZRP tends to produce higher control overhead than the

aforementioned schemes. This can happen due to the large overlapping of nodes' routing

zones. The query control must ensure that redundant or duplicate Route-Request are not

forwarded.

� The decision on the zone radius has a signi cant impact on the performance of the protocol.

5. WIRELESS AD HOC NETWORK

A wireless ad hoc network is a decentralized type of wireless network., The network is ad

hoc because it does not rely on a pre existing infrastructure, such as routers in wired networks

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or access points in managed (infrastructure) wireless networks. Instead,

each node participates in routing by forwarding data for other nodes, so the determination of

which nodes forward data is made dynamically on the basis of network connectivity. In

addition to the classic routing, ad hoc networks can use flooding for forwarding data. An ad

hoc network typically refers to any set of networks where all devices have equal status on a

network and are free to associate with any other ad hoc network device in link range. Ad hoc

network often refers to a mode of operation of IEEE 802.11 wireless networks. It also refers

to a network device's ability to maintain link status information for any number of devices in

a 1-link (aka "hop") range, and thus, this is most often a Layer 2 activity. Because this is only

a Layer 2 activity, ad hoc networks alone may not support a routeable IP network

environment without additional Layer 2 or Layer 3 capabilities.

The earliest wireless ad hoc networks were the "packet radio" (PRNETs) from the 1970s,

sponsored by DARPA after the ALOHAnet project.

5.1 Application

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

networks compared to wireless managed networks, though theoretical[3] and practical[4] 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 dynamic and adaptive routing protocols

enables ad hoc networks to be formed quickly.

Wireless ad-hoc networks can be further classified by their application:

mobile ad hoc networks (MANET)

5.2 Technical requirements

An ad hoc network is made up of multiple “nodes” connected by “links.”

Links are influenced by the node's resources (e.g., transmitter power, computing power and

memory) and behavioral properties (e.g., reliability), as well as link properties (e.g. length-of-

link and signal loss, interference and noise). Since 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 by relaying the information via other nodes. A “path” is

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a series of links that connects two nodes. Various routing methods use one or two paths

between any two nodes; flooding methods use all or most of the available paths.

5.3 Medium-access control

In most wireless ad hoc networks, the nodes compete for access to shared wireless medium,

often resulting in collisions (interference). Using cooperative wireless

communications improves immunity to interference by having the destination node combine

self-interference and other-node interference to improve decoding of the desired signal.

5.4 Mathematical models

In recent years mathematical models have been proposed to study various types of wireless

ad hoc networks. One class of models involves using stochastic processes to represent the

placement of the nodes in the ad hoc network. More specifically, stochastic geometry models

of wireless networks have been proposed and studied.

5.5 Security

Microsoft does not allow advanced encryption and security protocols for wireless Ad hoc

networks on Windows. In fact, the security hole provided by Ad hoc networking is not only

the Ad hoc network itself, but the bridge it provides into other networks (see Ad hoc

networks in the article Wireless security).

5.6 Simulation of wireless ad hoc networks

One key problem in Wireless Ad Hoc networks is foreseeing the variety of possible situations

that can occur. As a result, Modeling and Simulation using extensive parameter sweeping and

what-if analysis becomes an extremely important paradigm for use in ad hoc networks.

Traditional M&S tools include NS2,(and recently NS3), OPNET Modeler, and NetSim.

However, these tools focus primarily on the simulation of the entire protocol stack of the

system. Although this can be important in the proof-of-concept implementations of systems,

the need for a more advanced simulation methodology is always there. Agent-based modeling

and simulation offers such a paradigm. Not to be confused with multi-agent systems and

intelligent agents, agent-based modeling[6] originated from social sciences, where the goal

was to evaluate and view large-scale systems with numerous interacting "AGENT" or

components in a wide variety of random situations to observe global phenomena. Unlike

traditional AI systems with Intelligent agents, agent-based modeling is similar to the real

world. Agent-based models are thus effective in modeling bio-inspired and nature-inspired

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systems. In these systems, the basic interactions of the components the system, also

called Complex Adaptive System, are simple but result in advanced global phenomena such

as emergence.

6. MOBILE AD HOC NETWORK

A mobile ad hoc network (MANET) is a self-configuring infrastructureless network of

mobile devices connected by wireless. Ad hoc is Latin and means "for this purpose". 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 network that usually has a routable networking

environment on top of a Link Layer ad hoc network. The growth of laptops and 802.11/Wi-

Fi wireless networking have made MANETs a popular research topic since the mid-1990s.

Many academic papers evaluate protocols and their abilities, assuming varying degrees of

mobility within a bounded space, usually with all nodes within a few hops of each other.

Different protocols are then evaluated based on measures such as the packet drop rate, the

overhead introduced by the routing protocol, end-to-end packet delays, network throughput

etc.

6.1 Types

Vehicular Ad hoc Networks (VANETs) are used for communication among vehicles and

between vehicles and roadside equipment

Internet based mobile ad hoc networks (iMANETs) are ad hoc networks that link mobile

nodes and fixed Internet-gateway nodes. In such type of networks normal adhoc routing

algorithms don't apply directly.

Intelligent vehicular ad hoc networks (InVANETs) are a kind of artificial intelligence that

helps vehicles to behave in intelligent manners during vehicle-to-vehicle collisions,

accidents, drunken driving etc.

A mobile ad-hoc network (MANET) is an ad-hoc network but an ad-hoc network is not a

MANET.

6.2 Simulations

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There are several ways to study MANETs. One solution is the use of simulation tools

like OPNET, NetSim and NS2.

6.3 Data monitoring and mining

MANETS can be used for facilitating the collection of sensor data for data mining for a

variety of applications such as air pollution monitoring and different types of architectures

can be used for such applications. It should be noted that a key characteristic of such

applications is that nearby sensor nodes monitoring an environmental feature typically

register similar values. This kind of data redundancy due to the spatial correlation between

sensor observations inspires the techniques for in-network data aggregation and mining. By

measuring the spatial correlation between data sampled by different sensors, a wide class of

specialized algorithms can be developed to develop more efficient spatial data mining

algorithms as well as more efficient routing strategies. Also researchers have developed

performance models for MANET by applying Queueing Theory.

6.4 Security

A lot of research has been done in the past but the most significant contributions have been

the PGP (Pretty Good Privacy) and trust based security. None of the protocols have made a

decent trade off between security and performance. In an attempt to enhance security in

MANETs many researchers have suggested and implemented new improvements to the

protocols and some of them have suggested new protocols.

Attack classifications

These attacks on MANETs challenge the mobile infrastructure in which nodes can join and

leave easily with dynamics requests without a static path of routing. Schematics of various

attacks as described by Al-Shakib Khan [1] on individual layer are as under:

Application Layer: Malicious code, Repudiation

Transport Layer: Session hijacking, Flooding

Network Layer: Sybil, Flooding, Black Hole, Grey Hole. Worm Hole, Link Spoofing,

Link Withholding, Location disclosure etc.

Data Link/MAC: Malicious Behavior, Selfish Behavior, Active, Passive, Internal

External

Physical: Interference, Traffic Jamming, Eavesdropping

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7. CONCLUSION

It was revealed that ad hoc mobile devices can be highly mobile, powerful (in terms of

computation and memory capacity), and heterogeneous. Ad hoc wireless networks are not

limited to a homogeneous group of laptops. They can consist of a group of minute sensors,

communicating to each other and gathering environmental information.

Ad hoc networks need to possess self-organizing characteristics, and they must perform

routing and packet-forwarding functions. The topology of an ad hoc wireless network is

dynamically changing since devices are not tied down to specific locations over time. The

fact that nodes are not static implies that centralized media access is not entirely applicable.

Routing protocols in ad hoc networks need to deal with the mobility of nodes and constraints

in power and bandwidth. Multicasting in ad hoc wireless networks needs to be efficient since

using flooding will only result in a massive consumption of available bandwidth and degrade

battery life. Ad hoc devices rely on batteries to operate; hence, any inefficiency in

communication protocols can drastically shorten the uptime of these devices. Current

transport protocols are not designed for wireless ad hoc networks. In particular, TCP is an

end-to-end protocol that cannot distinguish the presence of mobility from congestion. Finally,

new methods are needed to faciliate service location, provision, and access in ad hoc wireless

networks. In summary, many challenging technical issues have arisen that demand our

attention and investigation.

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8. REFERENCE

1) An Inter-domain Routing for Heterogeneous MobileAd   Hoc   Networks   Using Packet Conversion and Address Sharing

Fujiwara, S. ; Ohta, T. ; Kakuda, Y. 

Distributed Computing Systems Workshops (ICDCSW), 2012 32nd International Conference

on 

Digital Object Identifier: 10.1109/ICDCSW.2012.14 

Publication Year: 2012 , Page(s): 349 - 355 

Cited by:  Papers (4)

2) Optimized use of battery power in wireless  Ad   hocnetworks

Gupta, P. ; Saxena, P. ; Ramani, A.K. ; Mittal, R. 

Advanced Communication Technology (ICACT), 2010 The 12th International Conference

on 

Volume: 2

Publication Year: 2010 , Page(s): 1093 – 1097

3(Analyzing performance of  ad   hoc   network   mobility models in a peer-to-peer  network   application over mobile  ad   hoc   network

Amin, R. ; Ashrafch, S. ; Akhtar, M.B. ; Khan, A.A. 

Electronics and Information Engineering (ICEIE), 2010 International Conference On 

Volume: 2

Digital Object Identifier: 10.1109/ICEIE.2010.5559795 

Publication Year: 2010 , Page(s): V2-344 - V2-348

4) Route Discovery Protocol for Optimizing the Power Consumption in Wireless  Ad -hoc   Network

Chaturvedi, A. ; Tiwari, D. ; Bhadoria, R.S. ; Dixit, M. 

Communication Systems and  Network   Technologies (CSNT), 2013 International Conference

on 

Digital Object Identifier: 10.1109/CSNT.2013.68 

Publication Year: 2013 , Page(s): 290 – 294

5) A bi-directional connectivity framework for Mobile  adhoc   network   and the internet

Khan, K. ; Zaman, R.U. ; Reddy, A.V. 

20

Wireless Days, 2008. WD '08. 1st IFIP 

Digital Object Identifier: 10.1109/WD.2008.4812871 

Publication Year: 2008 , Page(s): 1 – 5

6) Hybrid mobile  ad   hoc   network   support for Proxy Mobile IPv6

Hun-Jung Lim ; Seon-Ho Park ; Young-Ju Han ;Tai-Myoung Chung 

Communications, 2008. APCC 2008. 14th Asia-Pacific Conference on 

Publication Year: 2008 , Page(s): 1 - 5

7) A dynamic  network   gateway selection scheme based on autonomous clustering for heterogeneous mobilead   hoc   network   environment

Okano, K. ; Ohta, T. ; Kakuda, Y. 

Globecom Workshops (GC Wkshps), 2012 IEEE 

Digital Object Identifier: 10.1109/GLOCOMW.2012.6477626 

Publication Year: 2012 , Page(s): 513 - 517 

Cited by:  Papers (1)

8)Performance evaluation AODV routing protocol on  adhoc   hybrid  network   testbed using

PDAs

Sari, R.F. ; Syarif, A. ; Ramli, K. ; Budiardjo, B. 

Networks, 2005. Jointly held with the 2005 IEEE 7th Malaysia International Conference on

Communication., 2005 13th IEEE International Conference on 

Volume: 1

Digital Object Identifier: 10.1109/ICON.2005.1635480 

Publication Year: 2005 

Cited by:  Papers (2)

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