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On Ad-Hoc networks


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    Submitted to Submitted by Submitted by

    Mr.Hemant Kumar Jyotendra Sharma

    (EC-A III Yr)

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    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.

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    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

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    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

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    Table of contents Page no.

    1)-Introduction 1


    2.1)-Motes 7

    2.2)-PRNet 9

    3)-Important keywords 11

    4)-Features of Ad-Hoc 12

    5)-Establishment of Ad-Hoc 13

    6)-Network Architecture 15

    7)-Disadvantages 16

    8)- References 17

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    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.

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    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

    enemy artillery.

    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.

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    (Figure depicting motes communicating with each other)

    (Figure depicting close view of motes)

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    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


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    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.

    Static station:

    It is responsible for maintenance of routing table and transmission of

    data to mobile terminals.

    Figure depicting implementation of PRNet

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    3-Important keywords:

    3.1-Routing table:

    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.

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    4-Features of Ad-Hoc:

    Ad-Hoc provides us with following features, which gives it ace over

    wired networks:

    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.

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    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

    routing tables.

    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.

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    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

    and E.

    So old route between A &C was A->B->C is replaced by


    All five nodes are required to incorporate this change in their

    routing table

    This change will happen

    First in nodes B & C

    Then in A & E

    Then in D

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    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

    communication link.

    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

    each other.

    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!!

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    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.

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    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.