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LOW POWER WIRELESS SENSOR
NETWORK
Shikha yadav
12EJTEC075
ECE, 5th sem
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CONTENTS
 Introduction
 Definition
 Example of WSN
 Types of WSN
 Characteristics of a
WSN
 Power saving protocols
for WSN
 Applications
 Challenges
 Advantages
 Disadvantages
 Future Scope
 Conclusion 2

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INTRODUCTION
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 Low power wireless sensor Networks are
networks that consists of sensors which are
distributed in an ad hoc manner.
 These sensors work with each other to sense
some physical phenomenon and then the
information gathered is processed to get relevant
results.
 Low power Wireless sensor networks consists of
protocols and algorithms with self-organizing
capabilities.

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CONTINUED.........
 Sensor networks are highly distributed networks of small,
lightweight wireless node, deployed in large numbers to
monitor the environment or system.
 Each node of the sensor networks consist of three subsystem:
 Sensor subsystem: senses the environment
 Processing subsystem: performs local computations on the
sensed data
 Communication subsystem: responsible for message exchange
with neighboring sensor nodes
 The features of sensor nodes
 Limited sensing region, processing power, energy
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DEFINITION
Low power Wireless Sensor Networks :
Highly distributed networks of small, lightweight wireless
nodes,
Deployed in large numbers,
Monitors the environment or system by measuring phys
parameters such as temperature, pressure, humidity.
Node:
sensing + processing + communication

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EXAMPLE OF LPWSN

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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

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CHARACTERISTICS OF A LPWSN
1. Self – Organization
2. Concurrency processing
3. Low cost
4. Restricted energy resources
5. Tiny
6. Small radio range 8

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POWER SAVING PROTOCOLS
THERE ARE SOME PROTOCOLS WHICH IS USED
FOR POWER SAVING……..
 Unified Network Protocol Framework (UNPF)
 Low-Energy Adaptive Clustering Hierarchy
(LEACH)
 MAC PROTOCOL
 NETWORK LAYER
 BATTERY MODEL
and some other…

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LAYERED ARCHITECTURE
 A single powerful base station
(BS)
 Layers of sensor nodes around
BS
 Layer i: All nodes i-hop away
from BS
 Applications:
 In-building: BS is an access point
 Military
 Short-distance, low power tt tx

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UNIFIED NETWORK PROTOCOL
FRAMEWORK (UNPF)
 A layered architecture
 A set of protocols
 Integrates three operations:
 Network Initialization & Maintenance Protocol
 MAC Protocol
 Routing Protocol

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UNIFIED NETWORK PROTOCOL
FRAMEWORK (UNPF)
 Network Initialization & Maintenance Protocol:
 BS broadcasts its ID using CDMA common control channel
(BS reaches all nodes in one hop)
 Nodes record BS ID & send beacon signal with their own
IDs at their low default power levels
 All nodes the BS can hear are at 1-hop distance
 The BS broadcasts a control packet with all layer one node
IDs
 All nodes send a beacon signal again
 The layer one nodes record the IDs they hear-layer 2
 The layer one nodes inform the BS of the layer 2
 The BS broadcasts the layer2 nodes IDs,…
 To maintain: periodic beaconing updates are required

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POWER SAVING MODE
 Turning the transceiver off may not always be
efficient. Operation in a power-saving mode is
energy-efficient only if the time spent in that mode
is greater than a certain threshold
MULTIPLE HOPS
 Using several short hops may be more energy
efficient than using one large hop.

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CLUSTERED ARCHITECTURE
 A clustered architecture organizes the sensor nodes into clusters, each
governed by a cluster-head. The nodes in each cluster are involved in
message exchanges with their cluster-heads, and these heads send message
to a BS.
 Clustered architecture is useful for sensor networks because of its inherent
suitability for data fusion. The data gathered by all member of the cluster
can be fused at the cluster-head, and only the resulting information needs to
be communicated to the BS.
 The cluster formation and election of cluster-heads must be an autonomous,
distributed process.

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CLUSTERED ARCHITECTURE

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LOW-ENERGY ADAPTIVE CLUSTERING HIERARCHY
(LEACH)
 Self-organizing and adaptive clustering protocol
 Evenly distributes the energy expenditure among
the sensors
 Performs data aggregation where cluster heads
act as aggregation points
 Two main phases:
 Setup phase: organizing the clusters
 Steady-state phase: deals with the actual data
transfers to the BS

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 Setup phase:
 Each sensor chooses a random number m between 0 and 1
 If m < T(n) for node n, the node becomes a cluster-head where
 P : the desired percentage of cluster heads
 r : the round number
 G : the set of nodes that have not been cluster heads during the last
1 / P rounds
 A cluster head advertises its neighbors using a CSMA MAC.
 Surrounding nodes decide which cluster to join based on the signal
strength of these messages
 Cluster heads assign a TDMA schedule for their members
1 [ * mod(1/ )]( )
0 ,
P
if n G
P r PT n
otherwise


 



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 Steady-state phase:
 All source nodes send their data to their cluster heads
 Cluster heads perform data aggregation/fusion through
local transmission
 Cluster heads send them back to the BS using a single
direct transmission
 After a certain period of time, cluster heads are selected
again through the set-up phase

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LOW-ENERGY ADAPTIVE CLUSTERING
HIERARCHY (LEACH)
 Merits:
 Accounting for adaptive clusters and rotating cluster
heads
 Opportunity to implement any aggregation function at
the cluster heads
 Demerits:
 Highly dynamic environments
 Continuous updates
 Mobility

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MAC PROTOCOL
 During the data transmission phase, the distributed TDMA
receiver oriented channel (DTROC) assignment MAC protocol
is used.
 Two steps of DTROC :
 Channel allocation : Each node is assigned a reception channel
by the BS, and channel reuse is such that collisions are avoided.
 Channel scheduling : The node schedules transmission slots for
all its neighbors and broadcasts the schedule. This enables
collision-free transmission and saves energy, as nodes can turn
off when they are not involved on a send/receive operation.

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THERE ARE THREE TYPES OF MAC
PROTOCOLS
 Fixed-allocation
 Demand-based
 Contention-based
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 Fixed-allocation MAC protocol
 Share the common medium through a predetermined assignment.
 It is suitable for sensor network that continuously monitor and
generate deterministic data traffic
 Provide a bounded delay for each node
 However, in the case of bursty traffic, where the channel
requirements of each node may vary over time, it may lead to
inefficient usage of the channel.

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 Demand-based MAC protocol
 Used in such cases, where the channel is allocated according to
the demand of the node
 Variable rate traffic can be efficiently transmitted
 Require the additional overhead of a reservation process
 Contention-based MAC protocol
 Random-access-based contention for the channel when packets
need to be transmitted
 Suitable for bursty traffic
 Collisions and no delay guarantees, are not suitable for delay-
sensitive or real-time traffic

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HYBRID TDMA/FDMA
 A pure TDMA scheme minimize the time for which a node has to be
kept on, but the associated time synchronization cost are very high.
 A pure FDMA scheme allots the minimum required bandwidth for
each connection
 If the transmitter consumes more power, a TDMA scheme is favored,
since it can be switch off in idle slots to save power.
 If the receiver consumes greater power, a FDMA scheme is favored,
because the receiver need not expend power for time
synchronization.

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NETWORK LAYER
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APPLICATIONS OF LPWSN
 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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 Facility management
 Intrusion detection into industrial sites
 Control of leakages in chemical plants, …
 Machine surveillance and preventive maintenance
 Embed sensing/control functions into places no cable
has gone before
 E.g., tire pressure monitoring
 Precision agriculture
 Bring out fertilizer/pesticides/irrigation only where
needed
 Medicine and health care
 Post-operative or intensive care
 Long-term surveillance of chronically ill patients or the
elderly

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CHALLENGES
 Hardware :
1. Low cost
2. Tiny sensors
3. Lifetime maximization
4. Robustness and fault tolerance
5. Self-configuration
 Software :
1. Operating systems
2. Security
3. Mobility
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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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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 30

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FUTURE SCOPE
 More research work needs to be done in future.
 Needs to be implemented in a wireless sensor network
with mobile nodes.
 The effects of very large node densities need to be
investigated.
 The feasibility of using the clustering technique and data
aggregation needs to be tested in the same wireless
sensor network. 31

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FUTURE SCOPE
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FUTURE OF WSN
SMART HOME / SMART OFFICE
 Sensors controlling
appliances and
electrical devices in the
house.
 Better lighting and
heating in office
buildings.
 The Pentagon building
has used sensors
extensively.

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FUTURE SCOPE
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Intelligent transport,
industry and society,
smart utilities
Connected
Consumer
Electronics
 Development of a TDMA/CSMA hybrid MAC
 TinyOS currently has a CSMA MAC
 Hope to improve throughput by employing TDMA
 Time is divided into transmission periods and contention perio
 Nodes will contend with each other to join “the transmission
group” during the contention period.
 Nodes in the transmission group will be allocated a time-slot in
the transmission period.
 Development of data storage engine optimized for fast
retrieval

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CONCLUSION
This presentation shows all the techniques that are used
for wireless sensor network for low power consumption ,
for example MAC protocol, LEACH, Network layer, ect.
Most of the research on energy efficient controlled
access protocol has come at a cost of control
packets overhead. By investigating this research
area further, an enhanced energy efficiency
protocol may be developed that can revolutionise
WSN’s power consumption.
There are some another protocols which can be used for
less energy consumption like CDMA,FDMA,TDMA.
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REFERENCES
 www.wikipedia.org
 http://stakeholders.ofcom.org.uk/binaries/research/tec
hnology-research/wsn2.pdf
 http://www.researchgate.net/publication/228695105_S
ervice-
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