Lan F.Akyildiz,Weilian Su, Erdal Cayirci ,and Yogesh

sankarasubramaniamIEEE Communications Magazine 2002

Speaker:earl

A Survey on Sensor Networks

Outline

IntroductionCommunication architectureProtocol stackConclusion

Sensor Networks…low-cost, rapid deployment, self-organizing, and fault toleranceApplication areas: heath, military, and homeLarge number of sensor nodes that are densely deployedNodes use their processing abilities to locally carry out simple computations and transmit the required and partially processed data

Introduction

Application areas - heath

Compress data to reduce storage and communication bandwidth!

Application areas - military

Inactive Sensor

Application areas

Application areas

Active Sensor

Application areas

Ad hoc networks are not suitable for the sensor networks because of their unique features and application requirement The sensor network may have a much

larger number of nodes Transmission power and radio range Topology changes Mobility rate Power conservation

Introduction

Internet and Satellite

Sink

Task managernode

User

Sensor nodesSensor field

A

B

CDE

Communication Architecture

Fault Tolerance the ability to sustain sensor network functionalities

without any interruption due to sensor node failures

Scalability the density of sensor nodes can range from few

sensor nodes to few hundred sensor nodes in a region

Production Costs the cost of sensor node should be much less than

US$1 in order for the sensor network to be feasible

Environment can work in different environments

Design Factors

Power Unit Power

generator

Location finding system Mobilizer

TransceiverSensor ADC

SensingUnit

ProcessingUnit

Processor

Storage

Design FactorsHardware Constraints

Sensor Network Topology Predeployment and deployment phase Post-deployment phase Redeployment of additional nodes phase

Transmission Media links between nodes can be formed by

radio, infrared, or optical media

Power Consumption battery lifetime design of power-aware protocols and

algorithms

Design Factors

Protocol Stack

Application layer

Transport layer

Network layer

Data link layer

Physical layer

Pow

er m

an

ag

em

en

t pla

ne

Mob

ility m

an

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Task m

an

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Multiplexing of data streamsData frame detectionMedium access and error controlEnsures reliable point-to-point and point-to-multipoint connections in a communication network

The Data Link Layer

Goals share communication resources

between sensor nodes fairly and efficiently

The Data Link Layer - Medium Access Control

MAC protocol Power conservation

SMACS and EAR[13] Random wakeup during setup and turning off while idle

Hybrid TDMA/FDMA[8] Hardware-based approach for system energy minimization

CSMA-based[9] Constant listening time for energy efficiency

The Data Link Layer -Some of the proposed MAC protocols

Power saving modes of operation Turning the transceiver off during idling

may not always be efficient due to energy spent in turning it back on each time

Error control Two modes of error control:

Forward Error Correction(FEC) decoding complexities

Automatic Repeat Request (ARQ) additional retransmission energy cost and

overhead

The Data Link Layer

The Data Link Layer-Research issues

MAC for mobile sensor networksDetermination of lower bounds on the energy required for sensor network self-organizationError control coding schemesPower-saving modes of operation

Task: energy efficient routes

Sink

A (PA=2)

B (PA=2)

C (PA=2) T

D (PA=3)

E (PA=1)

F (PA=4)

α

1=1

α

α10=2

α

αα

α

α

α

α 5=2

3=2

4=2

2=1 6=2

7=1

8=2

9=2

Route 1: Sink-A-B-T, total PA=4, total α = 3 Route 2: Sink-A-B-C-T, total PA=6, total α = 6Route 3: Sink-D-T, total PA=3, total α = 4Route 4: Sink-E-F-T, total PA=5, total α = 6

Approaches:• Minimum PA route: route 4• Minimum Energy (ME) route: route 1• Minimum hop (MH) route: route 3• Maximum minimum PA node route: route 3

PA: available powerα:: energy required

Network Layer

Data Aggregation, data fusion

AB C

DE

FG

Sink

Network Layer

Floodingeach node receiving a data or management packet repeats it by broadcasting Deficiencies

Implosion Overlap

Gossipingsend the incoming packets to a randomly selected neighbor Deficiency: takes a long time to propagate

the message to all sensor nodes

Network Layer -Routing techniques

Sensor Protocols for Information via Negotiation (SPIN)

Step 1

ADV

Step 2

REQ

Step 3

DATA

Step 4

ADV REQ

Step 5 Step 6

DATA

Network Layer

Sequential Assignment Routing (SAR) Creates multiple trees where the root of

each tree is a one-hop neighbor from the sink

Low-Energy Adaptive Clustering Hierarchy (LEACH) Forms clusters to minimize energy

dissipation

Directed diffusion Sets up gradients for data to flow from

source to sink during interest dissemination

Network Layer

Network Layer

LEACH and Directed diffusionBS

Sensor node

Cluster head

Cluster

Base station

LEACHDirected diffusion

Conclusion

Sensor network is a new Research issue