EC8702-ADHOC AND WIRELESS SENSOR NETWORKS-UNIT NOTES.pdf

EC8702
Ad Hoc and Wireless Sensor Networks
UNIT-I AD HOC NETWORKS –
INTRODUCTION AND ROUTING PROTOCOLS
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Computer Network
A set of independent computers connected together
for exchanging data and other resources
Interlinked by physical media such as copper cable,
fiber optic and wireless radio waves
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Wireless communication
• Information can be transmitted through air
without requiring any cables or wires
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• Topics to be covered:
1. Fundamentals of Wireless communication
2. Electromagnetic Spectrum
i. Types
ii. Frequency Bands
iii. Spectrum allocation methods
3. Radio Propagation mechanisms
i. Reflection
ii. Diffraction
iii. Scattering
4. Characteristics of Wireless channel.
5. Mobile Adhoc Networks (MANET)
6. Wireless Sensor Networks (WSN)
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1. Fundamentals
• Users can communicate from remote areas
• Information can be communicated without
wires, cables or any electrical conductors
• Examples of wireless devices are
Cordless telephones
Mobiles
GPS units
Satellite television
Wireless computer parts
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Wireless devices
Cordless telephones
Mobiles
GPS units
Satellite television
Wireless computer parts
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Wireless communication
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Difference between wired and wireless
communication
• Wired N/W
Ethernet cable
• Wireless n/w
Infrared / radio frequency signals
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Advantages
• Self configuring
• Easy to use
• Communication has enhanced due to convey the
information very quickly
• Military areas, flooded areas, hazardous area
etc..
• Medical applications…
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Applications
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Disadvantages
 More attack by unauthorized users
 Requires strong security protocols.
 Disturbed by abnormal climate, noise interference etc..
 Limited bandwidth
 Stability of network is less
 Speed is slower
 Coverage problem etc
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Types of wireless communication
• Infrared wireless communication
• Cellular systems
• Cordless phones
• WLANs
• Satellite communication
• Bluetooth technology
• Zigbeee
• WiMax
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Infrared wireless communication
• Infrared waves are used
• Short to medium range
communication
Features:
 Line of sight
communication
 Intrusion detectors
 Motion detectors
 Home entertainment
control units
 Medical diagnostic devices
 Headsets, modems,
printers etc..
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Cellular systems
• 1960 - Analog communication
•Provide voice and data communication
Working
Coverage area is divided into non-overlapping
cells – mobile devices
Fixed point base station
Mobile switching center – allocating channels
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Various levels…
• 1G- Advanced Mobile Phone Services (FDMA+
30KHz FM modulated voice channel)
• 2G – Global System for Mobile communication
(100kbps)
• 3G- different data rate depends on the
mobility and location
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Cordless phones
• 1970s - initiated
• Low cost and short wireless link
• Radio waves with specific frequency
• Specific distance from base station
• It uses Base station and handset
• BS  call as Electrical signal– radio signal–
handset of the user
• Radio signal – electrical signal – speaker -
sound form
• Base station & handset --- > frequency pair
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Wireless LAN
• It link more wireless devices by wireless
distribution method
• Limited area – home, school computer lab,
office building etc..
• IEEE 802.11 standard – high frequency radio
waves
• WLAN – LAWN
• WLAN – AP – internet
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Cond….
• AP- transmits and receives the radio
frequency signals - routers
• AP -- client
• Clients – several devices….
• CSMA/CA for path sharing also include
encryption method -- security
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Satellite communication
• It connect any where on the earth
• It rotate around the earth for gathering and
transmitting useful information
Working Principle
• Satellite (sensors)  earthstation
• Earth station – GHz signals Satellite
• Satellite – signal to earth (all stations with in
coverage area)
• Tracking and command system – uplink and
down link
• Bigger in size, consumes more power and more
expensive
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Bluetooth technology
• Short distance commn. using short wavelength
• IEEE 802.15.1
• Uses ultra high frequency radio waves
• Connecting two point to point devices
• It transmits voice and data
• Range – 32 feet (10 meters)
• Data rate – 1 Mbps
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Zigbee
• low cost and low power
consumption
• Radio communication for
prolong period without
recharging
• IEEE 802.15.4
• Machine to machine
network
• Data rate 250kbps
• Coverage range 30m
• Coverage area is higher
than bluetooth
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WiMAX
-
• Worldwide process for Microwave access
broadband wireless technology
• IEEE 802.16
• Data rate 30-40 Mbps
• Higher speed over greater distance
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The Electromagnetic Spectrum
Principle of wireless communication
 transmits and receives the electromagnetic waves
 Low freq radio waves 30 Hz to high freq cosmic rays (>
10 million trillion Hz)
 Amount of information is carried by the electro
magnetic waves = width of the wavelength band
 Freq, wave length and speed of the waves are related
by
c = λ x f
‘c’ is 3x108 m/s
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Types of electromagnetic radiation
• Gamma radiation
• X-ray radiation
• Ultraviolet radiation
• Visible radiation
• Infrared radiation
• Microwave radiation
• Radio waves
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Electromagnetic spectrum
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Frequency bands in electromagnetic
spectrum
• Defined by International Telecommunication
Union
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Low frequency bands
• Radio waves
• Micro waves
• Infrared waves
• Visible light portions
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Radio waves
• Long distance communication – cross the
buildings easily
• Omni directional – no need to align
transmitter and receiver
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High frequency bands
• X-rays
• Gamma rays
• Ultraviolet radiation
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Gamma rays
• Wavelength : <0.01nm
• Highest frequency
• Medical applications - treat the cancer patient
• Produced by atomic nucleus
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Ultraviolet radiation
• Wavelength: 400 nm -10nm
• Sun and hot stars emitted UV rays
• VLF,LF and MF  ground waves few100km
• HF and VHF are observed – near the earth
surface
• Sky wave  radio wave reflected fromthe
ionosphere -- > military communication
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X-rays
• Wavelength : 0.01nm to 10nm
• Temp: million to 10 million degree
• Generated by super heated gas from
exploding stars
• Produced by accelerating electrons
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Auctioning method
• Allocated based on higher bidding company in
auction
Example
ITU designed ISM frequency bands for unlimited
usage – wireless LAN
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Radio Propagation Mechanisms
• Radio waves with different frequencies ->
propagate in different ways
• wave length compared to the dimension of
the building
• Propagation mechanisms are,
Reflection
Diffraction
Scattering
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Propagation mechanism
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Reflection
• Electromagnetic waves – hit on an object
(larger dimension> wavelength)- reflected
wave
• 180 degree phase shift b/w incident wave and
reflected wave
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Diffraction
• Waves hit an edge of the object – propagated
in different direction
• Hit in Impenetrable (hidden) object –
diffraction
• Amount of diffraction is frequency dependent
• Low frequency -- > diffraction more
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Scattering
• Waves hit at irregular objects ( trees, walls
with rough surfaces, furniture and vehicles)
• Propagate into number of outgoing weaker
signal
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Characteristics of Wireless channel
• Path loss
 Free space propagationmodel
 Realistic path loss model
 Two-ray model
• Fading
 Fast fading
 Slow fading
• Interference
 Adjacent channel interference
 Co-channel interference
 Inter-symbol interference
• Doppler shift
• Transmission rate constraints
 Nyquist’stheorem
 Shannon’stheorem
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Path loss
• Ratio of transmitted power to received power
• Expressed in dB
• Depends on the radio frequency and nature of the ground
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Free space propagation model
• Direct path between sender and receiver
• Free space path loss
• Transmitted power – Pt
• Transmitted gain - Gt
• Received power - Pr
• Received gain - Gr
Relation between transmitted power and receiver
power
• Pr = Pt Gt Gr (λ/4πd)2
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Realistic path loss model
• Various propagation effects
• Maxwell’s equations – complex algorithms
and intensive operations
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Two-ray model
• Line of sight path & reflected path
Pr = Pt Gt Gr (hthr/d2)2
Pr = Pt Gt Gr (λ/4π)2 (1/dγ)
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Fading
• Fluctuations in signal strength when received
by the receiver.
Fast fading/ Small scale fading
Slow fading/Large scale fading
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Fast fading
(different version of tx-ed signal)
• Fast fluctuations in amp, phase and delay of the received
signal.
• Fluctuations due to ?
• Interference between multiple copies of the same transmitted
signal reaching the receiver at a little different times.
• Occurs due to three propagation mechanisms
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Slow fading (object blockings)
• Shadow fading
• Receiver inside the building or transmitted signal pass through
the wall
• Little variation in received power
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Interference
• Interaction of waves that are correlated with each
other.
• Either they travel from the same source
• Or they have same frequency.
• This incident occurs when two waves meet at a point
while traveling along the same transmission medium.
– Adjacent channel interference
– Co-channel interference
– Inter symbol interference
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Adjacent channel interference
• Near by freq interfere with on-going
transmission signal
• Avoided by using guard band
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Co-channel interference
• Narrow band interference
• Same frequency can be
reused by nearby systems
• Avoided by multiuser
detection mechanism,
directional antennas and
dynamic channel allocation
mechanisms
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Inter symbol interference
• Distortion in telecommunication
• One or more symbols interfere with other
symbol
• Due to multipath propagation and consequent
overlapping of individual pulses – blur or
mixture of signal
• Adaptive equalization – allocate the time to
each pulses
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Doppler shift
• Transmitter and receiver moves :
– Towards – high freq
– Away – low freq
• Doppler shift
fd =v/λ
V= relative velocity between transmittter andreceiver
λ= wavelength of the signal.
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Transmission rate constraints
• Todetermine the maximum data rate of
transmission
• Nyquist’s theorem
• Shannon’s theorem
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Nyquist’s theorem
• Gives the maximum data rate of the channel
(noiseless)
• Number of changes (values or voltages of the
transmitted signal) per second – baud rate
• Ex:
Transmission value 0,1,2,3 --- 00,01,10,11
C = 2xBxlog2L bits/sec
B= bandwidth
L= Number of discrete signal levels/ voltage levels
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Shannon’s Theorem
• Find the data rate of noise channel
SNR = 10log10(S/N)
Channel capacity
C = Bxlog2(1+(S/N)) bits/sec
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Basic concepts of Ad Hoc
Networks
•What is adhoc network ?
It is a network which is formed
Without any central infrastructure.
•Adhoc network can be formed ?
Instantly
•Communication can be carried out using ?
Radio waves.
•Any where & Any time.
•Dynamic topology
•Data can be exchanged by wireless interface
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MANET Communication
• Single hop communication- direct
• Multi hop communication- for away source
node
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PROTOCOLS
• 1970- Norman Abramson & co – ALOHA –
Single hop
• 1973 – DARPA(DEFENCE RADIO) – PRNET –
Multi hop
• PRNET(PACKET RADIO NETWORK)
– ALOHA + CSMA : to access the common
wireless channel
• IETF – ad hoc working group – standard
protocol & functional specifications
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Types of wireless N/W
• Infrastructure based network
• Infrastructure less network
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Infrastructure based network
• Nodes – fixed base station (APs)
• Ex: Cellular N/W
• N/W area – cells
• BS – coverage area to each cell
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Infrastructure less network
• Communicate without any fixed infrastructure
• MANETs and (Vehicular)VANETs
• Each node act as router
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Difference b/w cellular and ad hoc N/Ws
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Applications of ad hoc N/W
• Military applications
• Emergency services
 Disaster relief efforts
 Flooded areas
• Commercial applications
 Industries
 On line payment
• Education
 Conferences
 Virtual class rooms
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soldiers – safety vehicles
• Emergency services
search and rescue operations also fire fighting areas
• Commercial applications
Data base maintenance in industry as well as on-
line payment for e-commerce applications
• Education
For organizing conferences, meetings, lectures,
virtual class rooms etc -- in universities, school &
colleges
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Design issues in ad hoc wireless N/Ws
• Medium access scheme
• Routing
• Multicasting
• Transport layer protocol
• Pricing scheme
• QoS
• Self-organization
• Security
• Addressing and service discovery
• Energy management
• Deployment considerations
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Medium access scheme
• Distributed operation
• Synchronization
• Hidden terminal problem
• Exposed terminal problem
• Throughput
Access delay
• Real time traffic support
• Resource reservation
• Ability to measure resource
availability
• Capability for power control
• Adaptive rate control
• Use of directional antennas
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Routing
• Route selected based on hop
count
Requirements of routing
 Minimum delay
 Quick route configuration
 Loop free routing
 Distributed routing approach
 Minimum control overhead
 Scalability
 QoS
 Time sensitive traffic and security
Major design issues
 Mobility
 Bandwidth constraint
 shared channel
 Battery power
 Storage capacity
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Multicasting
• What is Multicasting ?
Transmission of Same
message
• To ?
A group of mobile nodes
• In ?
Single transmission.
Major design issues
• Efficiency
• Control overhead
• QoS
• Scalability and security
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Transport layer protocol
• Protocols are used to Set up and maintain ?
End-to-end connection.
• Focus on?
Flow control and congestion control
• What is TCP ?
• Transfer Control Protocol.
• It is a connection oriented protocol.
• Used in ?
• Wired Networks.
• Performance in TCP is degraded due to
 frequent path breaks
 High mobility
 Bandwidth
 Power
 Channel error rate
 Frequent network partitions
• TCP is divided into two – More packet loss
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• Performance in TCP is
degraded due to
frequent path breaks
High mobility
Bandwidth
Power
Channel error rate
Frequent network
partitions
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Pricing scheme
• 1 (sender node)-5(receiver node)
• 2(power off)
• 1-2-5 (optimal path) – not effective
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QoS
• If there is a better coordination and cooperation between ?
- Service provider and the user
- then high QoS can be achieved.
QOS can differ from application to application.
• Bandwidth and delay are important parameters for ?
• Multimedia applications
• Identifying trusty nodes and routing packets through them are
key parameters of ?
• Defense applications.
• Multiple link disjoint paths and availability are the key
parameters of ?
• Emergency and rescue operations related applications.
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Self-organization
• Self – configure
• Self Organization includes ?
- Neighbour discovery.
- Topology organization.
- reorganization
• Topology can be varied – high mobility, node
failures and frequent N/W partitioning
• Every node maintain the updated information
• Beacon signals – transferred to all nodes
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Security
• Passive attack :
• Caused by ?
• Malicious nodes present in the network.
• Toobtain ?
• Information being exchanged in network.
• This type of attacks would not disturb network operation.
• Active attack - disturb the N/W operation
 Internal attack –attackers within the network
 External attack - attackers external the network.
• Some other security threats are ?
-DoS (Denial of service)
- Information disclosure and interference.
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Addressing and service discovery
• Address of mobile node is ?
Globally unique identifier
• Used for ?
Communication in Adhoc network.
• Since nodes join into a ?
new network and leave from the current network any time
• Any auto configuration scheme is required to ?
Allocate non duplicate addresses to the nodes.
• Adhoc n/w also requires ?
A duplicate address-detection mechanism
• In order to maintain ?
Unique addressing throughout the network.
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Energy management
• In a node,
• It is the process of managing ?
- the sources and consumers
• Of ?
- energy
• To ?
- boost up the lifetime of the node in the network.
Four categories.
• Transmission power management
• Battery energy management
• Processor power management
• Device power management
• Functions of energy management mechanisms are ?
• Battery life enhancing of a node
• Determine the routing path with minimum energy consumption.
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Deployment considerations
• Low cost deployment
• Short deployment time
• Re-configurability
• Non-estimation of future traffic
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Types of Wireless Ad-hoc network
• Mobile ad hoc networks
• Wireless sensor networks
• Wireless mesh networks
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• Wireless Sensor Network (WSN) research has enabled large
scale monitoring using small Sensors with radio links.
• The technological advance in wireless communications and
microelectronics has enabled the development of small, low-
cost Sensor Nodes.
• Wireless Sensor Networks are developed to organize and
control these Sensor Nodes, which have sensing, data
processing, communication and control capabilities.
Information collected from these Sensor Nodes is routed to a
sink Node via wireless communication approach.
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Mobile Ad Hoc Networks
• Basic concepts:
-Self configuring & decentralised n/w
-Each node– router
-Topology- dynamic topology
-installation- not require preplanning
MANET- interconnected to Internet
-Different services to the users.
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Characteristics of MANET
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Design challenges of MANET
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MANET Architecture
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• Networking:
Wired n/ w routing protocol- not suitable for MANET
Re –design protocol-
Toimprove robustness and adaptability
Enabling tech/ are used to provide end to end reliable
data delivery.
Locating receiver node is difficult- high mobility.
Localization mechanism-determine location of a mobile
node.
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• Middleware and applications:
Its is developed to rely on each
Application to handle all the services.
Specialized fields:
Emergency services.
Disaster recovery.
Environmental monitoring.
Widely used in:
Home n/w
search and rescue operation.
Educational applications
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MANET Operations
Each node act as router
Exchanges its own information to its
neighbors as beacon messages
Discover forwarder nodes to forward packets
Broadcast the packet to all other neighbors
which are in its transmission range
Mobile can join the network and leave the
network at any time
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MANET Routing
Process of finding path in
a network
Routing is a big
challenging issue due to
dynamic topology
MANET Routing protocols
 Proactive or table-driven
routing protocol
 On-demand or reactive
routing protocol
 Hybrid routing protocol
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Proactive or table-driven routing
protocol
• Each node maintains a routing
table to update the details of
its neighbors
• Each node exchanges hello
packet ( which includes node
identifier, message)
• Based on hello message
information, node updates the
routing table
• Easily find the route between
transmitter and receiver
• Reduce the time to determine
the route
• Ex: DSDV(Destination
sequenced distance vector)
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On-demand or reactive routing protocol
• Each node determines a routing path
• Each protocol uses two key phases
 Route discovery
Route maintenance
Route discovery
It uses route request and route reply messages
Route maintenance
If reliable path is broken, route maintenancephase
can be used
It send the route error message to sender for
intimating the broken route
ex: Dynamic Source Routing Protocol
Ad hoc On demand Distance Vector
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Hybrid routing protocol
• It combines the advantages of proactive
and reactive routing protocols
• Within coverage area – Proactive
• Communicate with out of coverage -
Reactive
• Ex: Zone Routing Protocol
Order One MANET Routing Protocol
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Applications of MANET
• Commercial Environments
E- commerce
Business
Vehicular services
• Home and enterprise networking
• Educational applications
Set up virtual class rooms
Set up communication during conferences, official
meetings etc
• Disaster management
• Medical emergency
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Wsn: wireless sensor network
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WSN
Distributed network
Formed by small, lightweight wireless nodes
It is deployed to monitor the environment
For measuring the physical parameters like
temperature, pressure, humidity, sound, characteristics
of objects and their motion
WSN is configured automatically with out any human
intervention
Sensor nodes are small, powerful and inexpensive
It performs multi-hop communication
Coverage area is limited due to low energy and simple
antenna
For data transmission, each node has to form ad hoc
network
WSN is a special type of MANET
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WSN : Wireless sensor network
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WSNs Vs MANET
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Subsystems of sensor node
• Sensor subsystem
• Processing subsystem
• Communication subsystem
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Sensor subsystem
• Senses the environment
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Processing subsystem
• It performs the local computations on the
sensed data
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Communication subsystem
• It is responsible for exchanging the
processed message with neighboring
sensor nodes
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Advantages
• Many sensor nodes are sensing same
event which tends to fault tolerant
• Data dissemination – Spreading
information
• Data gathering
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Limitations
• Cannot be protected from physical attack
• have very little storage capacity
• Works in short communication
• It provide little energy
• troubled processing power
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Terrestrial WSNs
m
e
d
Consists of hundreds to
thousands of WS nodes.
Deployed in Ad-Hoc or
structured manner-
communicating with base
station.
Sensor nodes dropped fro
a plane and randomly plac
into target area.
In preplanned deployment,
grid deployment,2-d, 3-d
placement models are used.
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Underground WSNs
• No. of sensor nodes- hidden in the
ground.
• Monitor underground conditions.
• Nodes- more expensive than terrestrial
WSNs.
• Maintenance, careful planning- require
high cost.
• Suitable components- reliable
communication-soil, rocks and other
mineral components.
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Cond…
• Communication between underground
sensor nodes-big challenge
• Due to signal losses and high level
attenuation.
• Require sink nodes to fwd message from
the sensor nodes to the base station.
• Limited battery power-very difficult to
recharge.
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Under water WSNs
• Consists of no. of sensor nodes and
vehicles.
• Under water vehicle are used-searching
and gathering data from sensor nodes.
• Sensor nodes –communicate themselves
– using acoustic waves.
• Acoustic waves are limited bandwidth,
long propagation delay, signal fading
problem.
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Multimedia WSNs
• Used to enable tracking and monitoring
purpose.
• Information in the form of imaging , video and
audio.
• Low cost sensor nodes equipped with
microphones and cameras.
• Challenges-high energy consumption, high
bandwidth Requirement, QoS, Data
processing and compression techniques.
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Mobile WSN
• Collection of mobile nodes.
• Have capability to compute, sense and
communicate with physical environment.
• Each mobile node can communicate with
other sensor nodes if it is in the visibility
of other sensor nodes.
• Data can be distributed using dynamic
routing.
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Design Challenges of Sensor
Networks
• 1) Sensor nodes are randomly deployed and
hence do not fit into any topology.
• Once deployed, do not require any human
intervention.
• Hence, setup and maintanence of the network
should be entirely autonomous.
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Design Issues/Challenges of WSN
• 2) Sensor networks are infrastructure less
networks.
• Therefore, all routing and maintanence
algorithms need to be distributed.
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• 4) Sensor nodes are battery
driven.
• Difficult to change/recharge
• Usually deployed in remote
places.
• Design based on
applications to minimize the
energy consumption
• So as to increase the battery
life.
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• 3) While designing sensor node , cost is also
an important factor to be considered.
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Design Issues/challenges of WSN
• 5) In forest sensor nodes
would be throwing from
aeroplane to deploy on
ground.
• In that situation, it is the
responsibiltiy of sensor
nodes to form ?
- network
- Connection
Identification
- Distribution
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• 7) Minimizing network life time for a prolong
period is a major design issue in WSNs.
• Thus the design of a good WSN needs to be
energy efficient.
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• 8) Toidentify the location of sensor nodes,
• Location discovery protocols are used.
• It must provide accurate location.
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• 9) Performing secured operations using sensor network is very critical.
• In ?
• Miltiary areas.
• Few issues are :
i) Secured key exchange
ii)key establishment
iii)authentication
iv) authorization
v) secure routing
vi) trust set up
vii) prevention of physical attack.
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Sensor Network Architecture
• A large number of sensors deployed on different areas
• Would form a network
• To?
• Communicate with Each other.
• Each sensor has a wireless communication capability.
• A sensor can gather information from?
• Other sensor nodes
• And can disseminate(broadcast) the processed information to?
• Other sensor nodes which is in the network.
• Architecture Types:
– Layered
– Clustured.
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Layered Architecture
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• UNIFIED NETWORK PROTOCOL FRAMEWORK.
(UNPF)
• UNPF:
• It integrates 3 operations in its structure:
-Network initialization and Maintenance
protocol
- MAC
- Routing protocols
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Network initialization and
Maintenance protocol
• BS Can communicate with all
nodes
• Using ?
One hop communication
• Over ?
Shared media.
• BS broadcasts its identifier (ID)
• To ?
Sensor nodes using CDMA .
Sensor nodes which receive the
ID of BS will store the ID.
• As a response message:
• Each sensor node sends its ID at
lowest power level.
• This can be listened by BS at layer
one
• Because ?
• All the nodes are single hop
distance away from BS.
• Now, the BS broadcasts control
message to all the layer one
nodes with their ID.
• All sensor nodes send a beacon
message again.
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• Layer 1 nodes form layer two
• With ?
• Nodes which are one hop away from layer one nodes
• And records its ID’s.
• Layer -1 node inform this to ?
• BS of Layer-2 nodes
• Which in turn will broadcast to all the nodes.
• In this manner, the layered architecture can be built by BS and
Sensor nodes.
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MAC Protocol
• For the data transmission,
• Distributed TDMA Receiver Oriented Channel
(DTROC) assignment MAC protocol is used.
• Two operations of DTROC protocol are:
– Channel allocating
– Channel scheduling
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• Channel allocation:
- What it is?
It is the process
of ?
• Channel Scheduling:
• Sharing of ?
• Reception channel
• With ?
Assigning reception
channel
to ?
every node.
• Neighbours.
• DTROC uses suitable
channel allocating
algorithms.
•
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• Separate receiving channel is
assigned
• for ?
• each node
• by ?
• BS.
• Each node make ?
• transmission slot schedule and
broadcast to ?
• its neighbours
• thereby enabling ?
• collision free transmission and
saves energy.
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UNPF - R
• It makes the sensor nodes
• To ?
• Vary their communication range
• To ?
• Improve performance.
• Small transmission range would make many network
partitions
• Whereas, large Covered area may reduce spatial reuse of
frequencies.
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Clustured Architecture
• It organized the nodes in n/w into clusters.
• Each cluster contains – Cluster head
• Nodes in each cluster would Exchange
message within the cluster.
• Each cluster head can also communicate with
the BS which is an access point and connected
to a wired network.
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Clustered architecture
• Used in ?
• Sensor networks to achieve data fusion.
• Clustering can be extended to various numbers of depths
hierarchically.
• Data collected by all the cluster members can be fused to
cluster head and the resulting information can be
communicated to BS.
• The cluster formation and the selection of cluster heads are
fully autonomous and distributed process.
• This could be achieved through network layer protocols such
as Low-Energy Adaptive Clustering Hierarchy.
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• What is LEACH ?
• One of the clustering based protocols
• What it do ?
• It minimizes energy dissipation
• In ?
• Sensor networks.
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UNIT-II
SENSOR NETWORKS – INTRODUCTION &
ARCHITECTURES
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• In ad hoc network,
• Each node contends for common shared wireless channel.
• To ?
Transmit data packet @ the same time
• If all the nodes are starting to transmit data packet
simultaneously,
- Then data would be corrupted.
• So , a suitable shared medium access control mechanism has to
be deployed .
• In a such a way that all nodes share the common channel in an
efficient manner.
• This task can be performed by a protocol called MAC.
• Responsibility of MAC Protocol:
– Transmitting data packets from one device to another device across a shared
channel.
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Responsibilities of MAC protocol
• Allocation of wireless channel
• To ?
- Different nodes
- Which are competing at the same time.
• No node is waiting for prolong period.
• Operation is distributed.
• Performs framing, physical addressing, flow control and
error control
• Total available bandwidth is allocated efficiently
• Hidden and exposed terminal problem has to be
eliminated
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Condt..
• Maximization of utilization of channel
• Minimize the delay
• Support different types of traffic
• It should be robust in equipment failure and
N/W failure
• Require well power control
• Provide QoS support
• Provide time synchronization among nodes
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Design issues
• Bandwidth efficiency
Bandwidth is restricted – MAC
protocol is responsible- divide the bandwidth
into effective manner
Efficiency = bandwidth used for actual data
transmission/ total bandwidth
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QoS support
• Due to mobility of nodes from time to time
QoS is not effective
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Synchronization
• Transmission between the
sender and receiver nodes
• has to be synchronized for ?
- achieving error free
-Minimized packet loss
transmission.
• Synchronization is also
important in ?
- bandwidth reservation.
• It requires ?
-exchange of control
packets between sender
and receiver.
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Hidden terminal problem
- sender nodes are hidden from each other
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Exposed terminal problem-
-block the current transmission due to neighboring
node transmit with some other node
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Error prone shared broadcast channel
• Due to each node broadcast the information
to be transmitted to designated receiver-----
• ----- Nodes do not start the communication
• Compete many nodes at a time
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• Lack of central coordination
• Mobility of nodes
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Classification of MAC protocols
• Contention – Based
Protocols
• Contention based
protocols with
reservation mechanism
protocols with
scheduling mechanism
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• Contention – Based
Protocols
protocols with
reservation mechanism
protocols with
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Reservation Contention
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Contention based protocols
• No nodes make prior reservation
• When node wants to transmit to other node-
compete with all other node – transmit
• Do not guarantee for QoS
Sender – initiated protocol
Receiver – initiated protocol
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Sender – initiated protocol
• Single channel sender
initiated protocol-
total bandwidth is not
divided
Multi- channel sender
initiated protocol –
bandwidth is divided
into several channels
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Receiver – initiated protocol
If receiver node ready to receive – initiate to
compete all the nodes to transmit the packets
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Contention based protocols with reservation
mechanism
• Provide guarantee for QoS
• Reserve the bandwidth prior
Synchronous protocols
Asynchronous protocols
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Synchronous protocol
• Time synchronization among all nodes
• So all nodes about reservation
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Asynchronous protocol
• Not required global time synchronization
• Use relative time information make
reservation
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Contention based protocols with
• Packet scheduling at nodes
• Scheduling nodes for accessing the channel
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Contention based MAC protocol
• No reservation
• Compete all the nodes
• Node capture the channel – winning node
• Protocols are,
Media access protocol for wireless LAN
Floor acquisition multiple access protocols
Busy tone multiple access protocols
MACA – by invitation
Media access with reduced handshake
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Media access protocol for wireless LAN
• Protocols used in wireless LAN
 MACA protocol
MACAW protocol
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MACA protocol
• Alternate for CSMA
• CSMA- sense the
channel & transmit
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• Channel busy – wait for
some time
• Channel idle – transmit
• Does not overcome
hidden and exposed
terminal problem
• Utilization of bandwidth
is less
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Condt..
• Drawbacks of CSMA is overcome by MACA
• It use RTS and CTS
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Solution to hidden & exposed terminal problem
By MACA protocol
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• Packet loss-
transmission.
• Nodes uses-Binary
Exponential Back off
algorithm.
• In BEB mechanism-
collision is detected.
• Nodes doubles the
maximum back-off
window.
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Solution to exposed terminal
problem
• B node ----- A node
• B node send RTS- A node--- heard by node C
• C node not actual receiver.- may not
response.
• C node can starts transmission
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IEEE 802.11
• What is this ?
• IEEE 802.11 refers to the set
of standards
• that define ?
Communication
• For ?
wireless LANs (wireless local
area networks, or WLANs).
• The technology behind
802.11 is branded to
consumers as Wi-Fi.
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WLAN provides support for ?
• Connection management
• Link reliability
• Power management in MANET.
• It uses three physical layer specifications which operate in ?
• 2400 to 2483.5 MHz band.
• 902-928 MHz
• 5.7 – 5.85 GHz region.
• 3 physical layers are ?
• FHSS-Frequency Hopping Spread Spectrum
• DSSS-Direct Sequence Spread Spectrum
• IF-Infrared Physical Layer.
• It deals with Physical and MAC layer in WLAN.
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Architecture
Operates into 2 modes:
• Infrastructure less
mode
• Infrastructure based
mode.
When two or more
stations communicate
with each other,
They form, Basic service
set (BSS).
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Physical layer of IEEE 802.11
• How many physical layers defined in 802.11 ?
• 3
• They are ?
• Radio techniques (2)
• IR (1)
• Radio techniques:
- 2.4 GHz ISM band.
- Increases reliability & throughput
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Physical Layer divided into?
• Two sublayers:
• Physical Medium Dependent sublayer (PMD)
• Physical layer convergence protocol sublayer (PLCP)
• PMD Performs:
-Encoding, Decoding , Modulation and Demodulation of
signals.
• PLCP provides:
-Service access point and a clear channel assignment carrier
sense signal to the MAC Layer of WLAN.
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MAC Layer
• 2 MAC Protocols used in WLAN.
• 1) Point Coordination Function (PCF)
• 2) Distributed Coordination Function (DCF)
• PCF:
- Centralized scheme
- Polling scheme
• DCF:
- Distributed scheme.
- Based on CSMA/CA
Hidden and exposed terminal problem can be avoided using handshaking
messages :
RTS & CTS
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IFS
• Time interval
• Between ?
the transmission
• Of ?
two successive frames
• By ?
Any node.
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• Short Inter Frame Spacing (SIFS)
• PCF Inter Frame Spacing (PIFS)
• DCF Inter Frame Spacing (DIFS)
• Extended Inter Frame Spacing (EIFS)
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SIFS
• Shortest IFS and takes highest priority to
access the medium.
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PIFS
• The waiting time values between SIFS and
DIFS.
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DIFS
• This amount of waiting time can be used by
the nodes if it operates under DCF mode.
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EIFS
• Extended Inter Frame Spacing :
• It is the longest IFS and gets least priority to
access the medium.
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UNIT-III
WSN NETWORKING CONCEPTS
AND PROTOCOLS
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Integrity
15
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ISSUES IN DESIGNING ROUTING PROTOCALS FOR
AD HOC NETWORKS.
• Mobility
• Bandwidth constraint
• Error prone shared broadcast radio channel
• Hidden and exposed terminal problems
• Resource constraints
• Security issues
17
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• Mobility cause frequent
path break.
19
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Bandwidth Constraint
20
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Error Prone Shared
• Collision occur at node because of ?
• Hidden and exposed terminal problem.
21
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Types of ad hoc routing protocol
• Proactive or table driven routing protocols
• Reactive or on demand routing protocols
• Hybrid routing protocols
22
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Proactive
• Other name table driven routing
protocol
• Each node maintains a routing
table.
• Routing table contains up to date
routing information of the entire
network.
• Whenever a node wants to send
a packet to the receiver node,
- it looks up in own routing table
To ?
Find the routing table
To ?
Find the routing path
From ?
Itself to receiver.
Tables – Updated periodically.
To ?
Maintain the current stable/
available paths.
This can be achieved by ?
Exchanging or broadcasting the
periodic beacon signals between
nodes.
So that,
Each node can have the knowledge
about the complete network
topology.
Hence,
Each node can update its routing
table based on beacon signal it
has received from its negihbours.
23
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Reactive routing protocol
• On demand routing protocols
• Mixed:
• Best features of two.
24
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Proactive Routing Protocols
• Protocols which use the concept of Proactive
routing
– Destination sequenced distance vector routing
protocol
– Wireless routing protocol
– Cluster –head gateway switch routing protocol
– Fisheye state routing
25
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Destination sequenced distance
vector routing protocol
• @ DSDV Protocol in adhoc.
• One of the Popular proactive routing protocols
• DSDV-each node keeps record of route
information- form of routing table
26
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Each node contains....
• ID of destination node
• Details of next hop
• Metric
• Sequence number
• Time to live parameter
27
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Cond...
• Each route broadcast message includes
• List of ID of Destination node
• No of hop required
• Next hop
• Recent sequence number
• Metric parameter
28
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• Each node updated its routing table with each
other
• Updation of routing in two ways
*Full dump update--node sends
whole routing table to neighbours-increases
network over head.
*Incremental update—recent
update only sent-suitable-large n/w &stable-
avoid heavy traffic.
30
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Table maintenance in DSDV
• Each node receives the route
information with most sequence
number from other nodes
• Updates its table
• Nodes looks –table –to find
shortest path
• According to path information-
each node construct another
routing table
• New table will broadcast
• On receipt of these messages –
neighbour node updates its table
31
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Maintaining metric field
• All nodes are moving
• Topology changes dynamically
• Each node sent routing table update packet to its neighbours
• Procedure:
- Routing table update packet starts with a metric one.
-Neighbour node increment this metric by 1 & rebroadcast the
updated packet to neighbours.
-This will be continued until all node receives update copy
message
- Receives more than 1 packet-select smallest metric value
34
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Significance of sequence number
• When node receives an update packet from its
neighbour node
• Sequence number = or > than the sequence
no.-routing packet will be updated in the table
35
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Wireless routing protocol
• It is one of the Proactive routing protocol
• When compare with DSDV , WRP differs-table
maintenance & procedures in updating
routing tables.
• WRP- maintains 4 tables
– Distance table
– Routing table
– Link cost table
– Message re-transmission list
36
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Fisheye state routing
• Each node broadcasts and exchanges the
details
• of ?
• farthest node
• Rather than ?
• broadcasting neighbours information
frequently in order to reduce the control
overhead.
40
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3 PHASES
• Neighbour discovery
• Information dissemination
• Route Computation
41
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Reactive Routing Protocols
• Dynamic source routing protocol
• Ad hoc On-demand routing protocol
• Temporarily ordered routing algorithm
• Location aided routing
• Associativity based routing
• Signal stability based routing protocol
• Flow oriented routing protocol.
43
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• Dynamic Source Routing (DSR) Protocol.
• It discover a route between ?
• Sender and destination when required.
• Operation is based on source routing.
• Sender knows complete route to reach the
destination.
• Each data packet carries the Source route in
the packet header.
44
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• Since each packet carries the complete route
information in the packet.,
• The intermediate nodes do not maintain
routing information to route the packets to
the destination.
• Nodes which use reactive routing protocol
does not maintain routing table.
• Hence, number of messages exchanges
between nodes is very low and hence leads to
less network overhead.
45
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Advantage of DSR
• Bandwidth usage is limited
• How ?
• By avoiding the periodic table updates.
• However,
• At the time of route discovery:
• The sender node has to exchange control messages
to establish a path between source and destination.
• DSR protocol comprises two phases
• Route discovery and Route maintenance.
46
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Route maintenance phase:
53
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AODV Protocol
• Ad hoc on demand routing protocols
• Used in MANET.
• Like DSR (Dynamic Source Routing) AODV Works in
two phases.
- Route discovery
- Route maintenance.
Only difference between DSR & AODV is:
Source will not carry the complete path.
Each node only knows its previous hop and next hop
information of the established path. 55
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Temporarily Ordered routing Algorithm.
(TORA)
• Reactive Routing protocol.
• Works on ‘link reversal algorithm’
• Main motive of TORA ?
• Reduce
• the transmission of ?
• Control messages in mobile environment.
• Performs?
- Route discovery
- Route maintenance
- Removing route if not valid.
• Every node maintains local topology based on ?
• Information received from its neighbours.
• In TORA, nodes have an ability to discover the network the partitions. 60
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LAR-Location aided routing
• @ Geographical Routing Protocol
66
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ABR-Associative Based Routing
72
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Hybrid Routing Protocol
• Advantages of both
• Nodes are grouped into zones(region).
• Nodes want to communicate within region
- Act Proactive / table driven
maintains routing table, path finding.
• Otherwise,
- Reactive / on demand.
78
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• Core extraction distributed adhoc routing
protocol (CEDAR)
• Zone Routing protocol (ZRP)
• Zone based hierarchical link state routing
protocol (ZHRP)
80
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TCP Over ADHOC n/w
• Why TCP ?
- reliable end-end connection
- single connection b/w sender and receiver
- error control
- flow control
Adhoc provides dynamic topology ,
88
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Feedback based TCP
89
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TCP Explicit link failure notification
92
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UNIT - IV
SENSOR NETWORK SECURITY
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• Single Node Architecture:
– Hardware Subsystems of sensor node.
– Software Subsystems of sensor node.
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Sensor node architecture
• Sensor node is a device used in sensor
network for performing
Data gathering
Processing
Communicating with other sensor nodes
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• Sensing Unit
• Processing Unit
• Communication Unit
• Battery
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Architecture of a sensor node
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Sensing unit
• Measure the physical quantities (temperature,
pressure etc..)
• Produce analog signals.
• ADC: Convert analog to digital signal
• Sensor node is small size, so it consumes
energy during operation.
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Processing unit
• It perform specific task, processing data and
control the operation of other components in
the sensor node
• External memory – store the collected
information
• Flash memory – low cost and high storage
capacity
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Communication unit
• Communication media are
Radio frequency
Optical communication
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Power supply unit
• Consumes power for sensing, data gathering,
communicating and data processing
• Sensor nodes consumes more power for data
communication
• Changing the sensor node can be costly
• Ensure to take Adequate energy
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Hardware subsystems of a sensor node
• Computing subsystem
• Power supply subsystem
• Communication subsystem
• Sensing subsystem
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Computing subsystem
• Each sensor node consists of microprocessor
to control the sensor
• Microprocessor is responsible for
Executing and managing communication
protocol
Data processing and manipulation
Error correction and encryption
Digital modulation and demodulation
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Power supply subsystem
• Each sensor – battery – limited power
• Power supply subsystem – monitor the
amount of power used by the sensor node
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Communication subsystem
• Short range radios are used to enable the
communication between sensor nodes
• Transmit mode – high energy consumption
• Receive mode - high energy consumption
• Idle mode
• Sleep mode
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Sensing subsystem
• Sensing the environment and exchanging the
information with each other sensor nodes
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Software subsystems of a sensor node
1. Operating system (OS) microcode
2. Sensor drivers
3. Communication Processor
4. Communication drivers
5. Data-processing mini-apps
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Operating system (OS) microcode
• OS microcode is used by High level module of
node resident software
• It protect the software from the machine level
functionality
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Sensor drivers
• These drivers manage the
key functions of
transceivers which are
embedded in sensors
• Sensors are plug-in type
• Depending upon the
operating environment of
sensor nodes, the
configuration and settings
must be installed into the
sensor.
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Communication Processor
• Routing the packets
• Buffering
• Forwarding packets
• Contention mechanisms using MAC protocols
• Encryption and error correction
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Routing the packets
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Packet forwarding
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Error correction
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Error Correction 1
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Communication drivers
• Transmission through radio channels
• Synchronization
• Encoding and decoding
• Error correction and checking
• Counting of bits
• Signal levels
• Modulation and demodulation
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Data-processing mini-apps
• It is responsible for performing data
processing at node level in sensor network.
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Data Aggregation Strategies of WSN
• To avoid the usage of more resources and
battery power data sensed by sensor nodes
must be aggregated and disseminated to
other nodes.
• Collecting the information from several nodes-
data aggregation
• Enhance the life time
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Continuous packet sensing and Dissemination
• Does not perform actual aggregation – zero
aggregation
• Fixed time interval – sense the data –
immediately transmit the received data to
cluster head
• Need fresh message – very urgent case – CPSD
is required
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Continuous packet collection and
dissemination
• Each node uses buffer – to store the collected
and sensed data
• Sensor nodes sense the data – until fill the
buffer
• Buffer is filled – data dissemination will be
started
• It reduces highly network overhead and
consumption of power
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Programmed packet collection and
dissemination
• Dissemination time interval is set
• Buffer overflow occur before dissemination
time interval, old packet is replaced by new
packet
• This scheme is used when not a critical case.
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Programmed Packet aggregation and
Dissemination
• Each node stored only aggregated data not
sensed data
• Aggregation functions are AVG,MIN,MAX and
STDDEV etc.
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Programmed demand based aggregation and
dissemination
• On – demand basis
• Whenever data is required – data can be
disseminated to access point
• Data gathering is done by access point
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Weighted event and demand based
data aggregation
• Below or above the fixed threshold, sensed
data can be stored in each node
• Disseminated to cluster head
• Cluster head set the weight based on distance
between cluster head to sensor node
• Based on the weight data can be disseminated
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Data relaying in WSN
• Event node
collect the information and reported to some
other node
• Sink node
collect the events by a node
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Data diffusion
Two steps
• Interest propagation
Broadcast interest (temperature) – other node
maintain the received interest
• Data propagation
Data propagation includes the shortest path
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Algorithms used
• Flooding
• Gossiping
• Rumor routing
• Sequential assignment routing
• Directed diffusion
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Flooding
• Broadcasting the packets in the network
• Every node can broadcast its own information
or the information received from other nodes
• Does not require any specific routing
algorithm
• Disadvantage: high network overhead and life
time is reduced
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Gossiping
• Sending a packet to the randomly selected
neighbor node
• Adv: less network overhead
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Rumor routing
• Agent based routing algorithm
• Packets are in the form of agents or ants
disseminated among nodes to find out
shortest path
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Sequential assignment routing
• It generates more number of trees
• From sender node to which node has high
delay and low throughput that path will be
removed
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Directed Diffusion
• It improves the data diffusion
• For each path gradient is assigned.
• For positive path, data transmission is allowed
• For negative path, data transmission is
prevented
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MAC layer protocols
• Self-organizing
• Hybrid TDMA/FDMA
• CSMA based MAC
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Self-organizing
• Major functions are
 Network Initialization
 Link layer organization
 Neighbor discovery
 Channel assignment
• It has pair of time slots at a fixed frequency
• Each communication link has different frequency
• A channel is assigned to each link
• No interference between nodes due to large bandwidth
• Power can be saved while idle slot – turned off; data
transmission slot – turned on.
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Hybrid TDMA/FDMA
• Communicate nearby fixed station
• FDMA:
 Each cluster head uses fixed frequency
Neighboring nodes does not have same frequency
TDMA:
 Allot the time slot to the sender node
 Transmitter in idle – power off
 Receiver use more power for time synchronization
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CSMA based MAC
• S-MAC
• T-MAC
• D-MAC
• B-MAC
• X-MAC
• Wise - MAC
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EC8702-ADHOC AND WIRELESS SENSOR NETWORKS-UNIT NOTES.pdf

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EC8702-ADHOC AND WIRELESS SENSOR NETWORKS-UNIT NOTES.pdf