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

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.

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, energy4

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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 physical

parameters such as temperature, pressure, humidity.

Node:

sensing + processing + communication

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EXAMPLE OF LPWSN

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

CHARACTERISTICS OF A LPWSN

1. Self – Organization

2. Concurrency processing

3. Low cost

4. Restricted energy resources

5. Tiny

6. Small radio range8

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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 ,

Pif 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.

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.

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 monitoring26

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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

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 life30

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

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.

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 periods

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

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/technology-research/wsn2.pdf

http://www.researchgate.net/publication/228695105_Service-

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