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DESCRIPTIONOn Ad-Hoc networks
Submitted to Submitted by Submitted by
Mr.Hemant Kumar Jyotendra Sharma
(EC-A III Yr)
There are the times when silence speaks so much more
loudly than the words of praise to only as good as belittle a
person, whose words do not express, but only put a veneer
over true feelings, which are of gratitude at this point of time.
Firstly, I would like to express my sincere gratitude to my
mentor Mr. Hemant Kumar, for her vital support, guidance
and encouragement without which this report would not
have come forth.
Heartily, I would like to thank God, dear parents, my friends,
respected HOD sir and all readable books which help me to
make such a knowledgeable report.
This is to certify that Jyotendra Sharma of Electronics &
Communication, 5th Semester, Shri Vaishnav Institute of
Technology and Science has successfully completed his
project on the topic:
Ad-Hoc wireless communication under supervision and
guidance of Mr. Hemant Kumar.
Teacher in charge:
Mr. Hemant Kumar
I hear by declare that the present work on the Topic: Ad-Hoc
wireless communication is done by me myself only under the
guidance of Mr.. Hemant Kumar
. Jyotendra Sharma
Table of contents Page no.
3)-Important keywords 11
4)-Features of Ad-Hoc 12
5)-Establishment of Ad-Hoc 13
6)-Network Architecture 15
8)- References 17
An ad-hoc network is a local area network (LAN) that is
built spontaneously as devices connect. Instead of relying
on a base station to coordinate the flow of messages to
each node in the network, the individual network nodes
forward packets to and from each other. It is a type of
peer to peer networking.
In the Windows operating system, ad-hoc is a
communication mode (setting) that allows computers to
directly communicate with each other without a router.
Ad-Hoc, in beginning, was used as a mode of
communication between military elements.
DARPA first used motes to detect enemys truck
movement in a remote area. A mote is an electronic
sensor that can sense vibrations caused by massive
vehicles such as trucks, tanks etc. A mote is equipped
with a magnetometer and GPS (Global Positioning
System) receiver that helps it to pin point its location and
then can inform an administrator to know whereabouts of
An airplane flies over the area and scatters thousands of
motes in target area.
Each mote wakes up, on sensing vibration generated by
heavy vehicles, senses its position and then sends out a
radio signal to find its neighbors.
Neighboring motes pick up the transmissions and forward
them to their neighbors and so on, until the signals arrive
at the collection node and are transmitted to the
commander. The commander can now display the data on
a screen and see, in real time, the path that the truck is
following through the field of motes.
(Figure depicting motes communicating with each other)
(Figure depicting close view of motes)
2.2-PRNET : ANOTHER APPLICATION OF AD-HOC
PRNet (Packet Radio Network) was to provide an efficient
means of sharing broadcast radio channel among many radios.
Packet radio is a form of packet switching technology used to
transmit digital data via radio or wireless communications
Few characteristics of PRNet are:
Presence of mobile repeaters : Used to receive, amplify and retransmit signals. They operates
in zones i.e. they act as transmitter for terminals falling under
there zone. Mobile terminals :
These are the end users who shall receive data transmitted by
mobile repeaters. Static station for routing:
This is the type of routing which is used to transmit data
between various nodes. Data flow in certain pattern within
various nodes. This path followed by data is called route and
route can be specified by maintaining routing table.
Static routing means that there is no automated way of route
formation and it has to be specified manually by an
Not entirely infrastructure less: Unlike actual Ad-Hoc PRNet is not completely infrastructure
less as it does require mobile repeaters for transmission of data
and routing table has to be manually maintained unlike Ad-Hoc
which uses dynamic routing.
It is responsible for maintenance of routing table and transmission of
data to mobile terminals.
Figure depicting implementation of PRNet
In computer networking a routing table, or Routing Information Base (RIB), is a data
table stored in a router or a networked computer that lists the routes to particular
network destinations, and in some cases, metrics (distances) associated with those
The routing table contains information about the topology of the network immediately
around it. The construction of routing tables is the primary goal of routing protocols.
Static routes are entries made in a routing table by non-automatic means and which
are fixed rather than being the result of some network topology "discovery" procedure.
A router is a device that forwards data packets between computer networks, creating
an overlay internetwork. A router is connected to two or more data lines from different
networks. When a data packet comes in one of the lines, the router reads the address
information in the packet to determine its ultimate destination. Then, using
information in its routing table or routing policy, it directs the packet to the next
network on its journey.
4-Features of Ad-Hoc:
Ad-Hoc provides us with following features, which gives it ace over
It doesnt require any established infrastructure like wired
network. Wired network transmits data through system of
complex network via. Gateways, nodes, routers etc. Whereas,
Ad-Hoc just require two devices which have transmission and
reception capabilities and some set of protocols to transmit data.
Ad-Hoc wireless network can be established on the go i.e. even
devices in motion can establish connection.
As depicted earlier that even devices in motion can establish
connection, hence Ad-Hoc is very flexible and is capable of
handling situations like change in geography, or addition of new
Supports short range communication.
Ad-Hoc does feature encryption of data however is not as secure
as other data transmission techniques.
5-Establishment of Ad-Hoc
5.1-Bringing up an ad-hoc:
Ad hoc network begins with at least two nodes broadcasting their
presence (beaconing) with their respective address information.
They may also include their location info if they are GPS equipped
Beaconing messages are control messages. If node A is able to
establish a direct communication with node B verified by
appropriate control messages between them, they both update their
If Third node C joins the network with its beacon signal, two
scenarios are possible:
I. A & B both try to determine if single hop communication is
II. Only one of the nodes e.g. B tries to determine if single hop
communication is feasible and establishes a connection.
The distinct topology updates consisting of both Address and the
route updates are made in three nodes immediately.
In first scenario, all routes are direct i.e. A->B, B->C, and A->C
(Lets assume bi-directional links).
In the second scenario, the routes are updated
First between B & C,
then between B & A,
Then between B & C again confirming that A and C both
can reach each other via B.
5.2-Topology update due to link failure:
Mobility of nodes may cause link breakage requiring route
updates. Assume link between B & C breaks because of some
reason however observe that nodes A & C are still reachable via D
So old route between A &C was A->B->C is replaced by
All five nodes are required to incorporate this change in their
This change will happen
First in nodes B & C
Then in A & E
Then in D
6-Network architecture of Ad-Hoc
All ad hoc networks operate in TDD (Time division duplexing)
mode. Time Division Duplex (TDD) refers to multiplexing of
transmission and reception in different time periods in the same
frequency band .Time-division duplexing (TDD) is the application
of time-division multiplexing to separate outward and return
signals. It emulates full duplex communication over a half-duplex
FDD is another mode of communication, however is not employed
in present Ad-Hoc system as it increases circuit complexity. FDD
is Frequency Division Duplex (FDD); it refers to using different
frequency bands for uplink and downlink transmissions.
Ad-Hoc is a type of distributed wireless type network. It acts as a
whole i.e. there are no dedicated hardware, all is done by devices
themselves. Wireless nodes communicate with each other without
any fixed infrastructure.
Terminals have an RF or infrared interface to communicate with
All data transmission and reception occurs in the same frequency
band (there is no special node to do the frequency translation).
There is no centralized control for managing the network e.g. node
failures etc. And Ad-Hoc operates in unlicensed frequency band of
2.4 GHz, thus no transmission fee!!
7-Disadvantages of wireless / Ad-Hoc communication
Wired transmission is much more secured because it consists of
physical cables that have fixed destination and are buried deep
inside ground so that no one can easily dig them out.
Wireless transmission is much more prone to hacking techniques
such as masking- in which the hacker shows himself as a host
and lures the user to enter his vital information on his computer.
It is very hard to avoid packet collisions in case of wireless
Mobility affects routing- routing table changes.
Wireless transmission, reception, retransmission, beaconing,
consumes power that calls for use of huge power sources.
1. How Stuff Works Perfect guide for beginners to understand
2. Wikipedia- Wireless Ad-Hoc network.
3. Carroll, Robert T. (23 February 2009), "Ad hoc hypothesis".
4. Article on Design and Implementation of Ad Hoc by Chih-
Yung Chang and Jang-Ping Sheu ,Department of Computer and
Information Science, Aletheia University.