An Introduction on Ad-Hoc Networks

8/14/2019 An Introduction on Ad-Hoc Networks

1/24

1

An Introduction onAd-hoc Networks

WAN Chunfeng

ID: 80423623Mita Lab, System Design Department,

School of Science for Open and Environmental systems, Keio University

Presentation for wireless communication course


2/24

2

Wireless communication-1

Infrastructure based networks Uses fixed base stations (infrastructure)

which are responsible for coordinating

communication between the mobile hosts(nodes)


3/24

3

Wireless communication-2

Ad-hoc networks Consists of mobile nodes which

communicate with each other through

wireless medium without any fixedinfrastructure


4/24

4

Mobile ad-hoc network

Meaning of the word Ad hoc is for this, means forthis purpose only, implies it is a special network fora particular application.

A mobile ad-hoc network (MANET) is a self-configuring network of mobile routers (andassociated hosts) connected by wireless linkstheunion of which form an arbitrary topology.

The routers are free to move randomly and organizethemselves arbitrarily; thus, the network's wireless

topology may change rapidly and unpredictably.


5/24

5

History of ad-hoc network

The earliest mobile ad-hoc networks (MANETs) werecalled packet radio" networks, and were sponsoredby DARPA in the early 1970s.

SURANSurvivable Adaptive Network was proposedby DARPA in 1983 to support a larger scale network.

Ad-hoc was used to describe that kind of network byIEEE802.11 standard committee. Mobile ad-hocnetwork was also be named as MANET by IETF.


6/24

6

Why use ad-hoc network

Easy of deployment

Speed of deployment

Decreased dependence oninfrastructure


7/24

7

Characteristics and tradeoffs

Characteristics Decentralized

Self-organized

Self-deployed

Dynamic network topology

Tradeoffs Bandwidth limited

Multi-hop router needed Energy consumption problem

Security problem


8/24

8

Applications

Personal area networking Cell phone, laptop, ear phone

Emergency operations Search and rescue

Policing and fire fighting Civilian environments

Taxi cab network

Meeting rooms

Sports stadiums

Boats, aircrafts

Military use On the battle field


9/24

9

Ad-hoc routing protocols

Ad-hoc routing protocols

Table Driven Source-initiated On-demand Driven

DSDV WRP AODV DSR LMR ABR

CGSR TORA SSR


10/24

10

Table-Driven routing protocols

Table-Driven routing protocols include: DSDV:Destination-sequenced Distance-vector Routing CGSR: Clusterhead Gateway Switch Routing WRP: Wireless Routing Protocol

Requires each node to maintain one or more tables to storerouting information.

Relies on an underlying routing table update mechanism thatinvolves the constant propagation of routing information.

Packets can be forwarded immediately since the routes arealways available.

Cause substantial signaling traffic and power consumption

problems


11/24

11

Source-Initiated On-Demandrouting protocols

Source-Initiated On-Demand Rounting AODV: Ad-hoc On-Demand Distance Vector Routing DSR: Dynamic Source Routing TORA: Temporally-Ordered Routing Algorithm ABD: Associativity-Based Routing

SSR: Signal Stability Routing

Creates Routing only when desired by the sourcenode.

Packet on source node must wait until a route can bediscovered.

Periodic route updates are not required.


12/24

12

DSDV: Destination-sequencedDistance-vector Routing

Distance-Vector routingprotocol (table driven)

For each reachablenode in the network therouting entry contains:

Destination Address

Next Hop

Distance

Sequence NumberS45_F2DF

S767_E2DE

S567_D1DD

S198_C1CC

S334_B1BB

S205_A0AA

Sequence NumberDistanceNext HopDestination

A

D

B

E

FC


13/24

13

CGSR: Clusterhead GatewaySwitch Routing

CGSR is a clustered multihop mobile wirelessnetwork with several heuristic routing systems.

Cluster member table should be stored and

broadcasted periodically using DSDV algorism.

A

B

G

C

E

HF

D : Node

: Clusterhead

: Gateway

CGSR: Routing from node A to node H


14/24

14

DSR: Dynamic Source Routing

It is an on-demand routing protocol that is based on theconcept of source routing.

A

D

B

E

F

C

Initiate route discovery process byInitiate route discovery process by

sending asending a route request messagemessage

whichwhich contains:contains:

Destination and Source AddressesDestination and Source Addresses Request IDRequest ID

History of nodes it has visitedHistory of nodes it has visited

If the receiving node is not theIf the receiving node is not the

destination:destination: Check to see if it has alreadyCheck to see if it has already

received threceived thee routeroute requestrequest byby

checking the request ID.checking the request ID.

Add its address to the hop listAdd its address to the hop list

and broadcast the message to itsand broadcast the message to its

neighboursneighbours


15/24

15

Node localization

Nodes of Ad-hoc network systems are alwayscoupled to the physical world. Spatial informationis necessary for the raw data.

Useful to find a good route.

Helps to make the data aggregation more efficient.

Becomes a very important and popular issue now.


16/24

16

Ad-hoc localization algorisms

Centroid

= position of the beacon

k= the beacon number the receiver node can hear

),(),( 2121

k

YYY

k

XXXYX

ikiiikii

estest

LL ++++=

),(imim

YX


17/24

17

DV-hop

B

D

A

A-B lengt h: 12

3 hops

avg hop s ize: 4

C

A,B,C are beacons withpositions already known

From the known position of any

two beacons, say, A and B, thedistance between these twobeacons can be calculated.

Count the hops and average

hop size obtained.

By knowing the hops to abeacon, the distance from thenode to that beacon can be

obtained.


18/24

18

Beacon propagation

In order to know

how many hopsbetween twobeacons, beaconpropagation shouldbe applied.


19/24

19

APIT- Approximate Point In

Triangle Test

A nodes presence inside oroutside of these triangular regionsallows a node to narrow the area

in which it can potentially reside

Out

IN

IN

APIT employs a novelarea-based approach.

Anchors divide terrain into

triangular regions


20/24

20

APIT- Approximate Point In

Triangle Test

APIT grid SCAN a ppr oach

If the angle contains the node,then in area the anglecovered,the number add 1.

If the node is outside the angle,then minus 1.

Aggregation provides a goodaccuracy, even results by

individual tests are coarse anderror prone.


21/24

21

In-out test-1

M

A

C

B

M

A

C

B

Inside Case Outside Case

If there exists a direction in which M is departure from points A,B, and C simultaneously, then M is outside of ABC. Otherwise,M is inside ABC.


22/24

22

In-out test-2

A

C

1

23

4

M

B

Inside CaseOutSide Case

B

A

C

1

23

4

M

If no neighbor of M is further from/closer to all threeanchors A, B and C simultaneously, M assumes that itis inside triangle ABC. Otherwise, M assumes itresides outside ABC.


23/24

23

ROCRSSI

ROCRSSI only compares the relative strength of RSSI anddoes not depend on absolute RSSI values


24/24

24

Thank You!

Documents

An Introduction on Ad-Hoc Networks