FUNDAMENTALS OF WSN

1. ENERGY EFFICIENT
WIRELESS SENSOR NETWORKS
A.SUMANTH
16241D5508
ECE, GRIET
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2. CONTENTS
 Introduction
 Types of WSN
 Power consumption in WSN
 Major sources of energy wastes in WSN
 General approaches to energy saving
 Duty cycling
 ArchitectureofaSensorNode
 Classification
 Applications
 Advantages
 Disadvantages
 Conclusion
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3. INTRODUCTION
 What is a wireless sensor network (WSN)…?
 Motivation of development
 Parts of a sensor node in the network
 Functions of a sensor node in the network
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Constraints
Cost Size Topology

4. TYPES OF WIRELESS SENSOR NETWORKS
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 Dense collection of nodes
 Ad-hoc
deployment
 Difficulty in network
maintenance
 Few and scarcely
distributed nodes
 Pre-planned deployment
 Lower network
maintenance
Unstructured WSN Structured WSN

5. Power consumption in WSN
 The power issue in the wireless sensor network is one of
the biggest challenges.
 Why limited source of power?
 Inexpensive nature.
 Limited size and weight.
 Redundant nature.
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6. Major Sources of Energy Waste in WSNs
1. Useful power consumption:
 Transmitting or receiving data.
 Processing query requests.
 Forwarding queries and data to the neighbours.
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7. 2. Wasteful power consumption:
 Idle listening to the channel “waiting for possible
traffic”.
 Retransmitting because of collisions “e.g. two
packets arrived at the same time at the same sensor”.
 Overhearing “when a sensor received a packet
doesn’t belong to it”.
 Generating and handling control packets.
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8. GENERAL APPROACHES TO ENERGY SAVING
 Duty Cycling.
 Data Driven.
Duty cycle
Duty cycle is defined as the fraction of time nodes
which are active during their lifetime.
Data Driven
Data driven approaches can be used to improve the
energy efficiency even more.
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9. DUTY CYCLING
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SENSOR
MODES
TRANSMISSION RECEPTION IDLE SLEEP
Goal: reduce the time where the sensor is being idle.

10. DUTY CYCLING
It can be achieved through two different approaches:
 It is possible to exploit node redundancy which is typical
in sensor networks and adaptively select only a minimum
subset of nodes to remain active for maintaining
connectivity.
 Nodes that are not currently needed for ensuring
connectivity can go to sleep and save energy.
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11. Architectureof a SensorNode
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12. CLASSIFICATION
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MAC (
medium
access
control)Contension
based
S(sensor)-
MAC
T(time
out)-MAC
TDMA
based
μ (energy-
efficient)-
MAC
DEE(dyna
mic)-MAC
Hybrid
A(advertise
ment)-
MAC

13. SMAC
Stand for:
Sensors Medium Access Control.
Strategy:
All node follow a periodic sleep/wake cycle, When a node is
idle, it is more likely to be asleep instead of continuously
listening to the channel. S-MAC reduces the listen time by
letting the node go into periodic sleep mode.
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14. Advantages:
 Periodic Listen.
 Collision Avoidance.
 Overhearing Avoidance.
 Message passing.
Disadvantages:
S-MAC fixed duty cycle i.e. active time is fixed
• if message rate is less energy is still wasted in idle-
listenin
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15. T-MAC
Stand for:
Timeout Medium Access Control.
Strategy:
It adaptively adjusts the sleep and wake periods based on the
estimated traffic flow.
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16. Advantage
Times out on hearing nothing.
Disadvantage
Early sleeping problem.
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17. μ- MAC
Stand for
Energy-Efficient Medium Access Control
Strategy
 μ-MAC assumes a single time slotted channel as shown
in Figure.
 Protocol operation alternates between a contention and
a contention-free period.
 The contention period is used to build a network
topology and to initialize transmission sub channels.
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18. DEE
Stand for
Dynamic Energy Efficient Medium Access Control
Strategy
 DEE-MAC is an approach to reduce energy
consumption.
 which lets the idle listening nodes go into sleep using
synchronization performed at the cluster head.
 DEE-MAC operation comprise of two phase:
1) Cluster formation phase
2) Transmission phase
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19. A-MAC
Stands for
Advertisement-based Medium Access Control
Strategy
node is active only when it is the sender or the receiver,
during other time it just goes to sleep.
Advantage
In prior the nodes that are going to receive are alerted.
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20. Data Driven Approach
Data-driven approaches can be used to improve the energy efficiency
even more.
 Data reduction can be divided two parts
1) in-network processing
2) Data prediction
 In-network processing consists in performing data aggregation (e.g.,
computing average of some values) at intermediate nodes between the
sources and the sink. In this way, the amount of data is reduced while
traversing the network towards the sink.
 Data prediction consists in building an abstraction of a sensed
phenomenon
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21. STANDARDS AND SPECIFICATIONS
 Predominant standards commonly used in WSN
communications include:
1. Bluetooth - Wireless technology standard for
exchanging data over short distances from fixed and
mobile devices by creating PANs’
2. 6LoWPAN - Defined encapsulation and header
compression mechanisms that allow IPv6 packets to be
sent to and received from over IEEE 802.15.4 based
networks
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22. APPLICATIONS OF WSN
 Area monitoring
 Health care monitoring
 Air pollution monitoring
 Forest fire detection
 Landslide detection
 Water quality monitoring
 Natural disaster prevention
 Industrial monitoring
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23. ADVANTAGES OF A WSN
 Avoids a lot of wiring
 Can accommodate new devices at any time
 Flexible to go through physical partitions
 It can be accessed through a centralized monitor
 Infrastructure
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24. DISADVANTAGES OF WSN
 Easy for hackers to hack a network
 Comparatively low speed of communication
 Gets distracted by various elements
 Costly at large
 Life of nodes
 Energy life
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25. CONCLUSION
As described, wireless sensor networks possess the
potential for many applications. The advance of
technology enabled the creation of prototype WSNs, but
the hardware and software both have a ways to go before
WSNs are practical, cost-effective, and use fully.
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26. REFERENCES
 www.wikipedia.org
 http://stakeholders.ofcom.org.uk/binaries/research/tec
hnology-research/wsn2.pdf
 http://www.researchgate.net/publication/228695105_S
ervice-
oriented_software_architecture_for_sensor_networks/f
ile/5046351a8ae5a75f8b.pdf
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