A Survey on Sensor Networks
Rick Han
CSCI 7143 Secure Sensor Networks
Fall 2004
Introduction
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Overall architecture
Sensor node components
Sensor nets vs. traditional ad hoc nets
Design factors
Protocol stack
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Physical layer
Data link layer
Network layer
Transport layer
Application layer
Conclusion
Differences Between Sensor
Nets and Ad Hoc Nets
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Greater number of sensor nodes
Sensor nodes are densely deployed
Sensor nodes are failure-prone
Topology of sensor net changes frequently
Broadcast, not point-to-point
Sensor node limitations: power,
computational capabilities, memory
Potentially, no global identification for sensor
nodes
Sensor Network Overview
Sensor Node Components
Design Factors
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Fault Tolerance
Scalability
Production Costs
Hardware Constraints
Sensor Network Topology
Transmission Media
Power Consumption
Protocol Stack
Protocol Stack: Physical Layer
Responsible for:
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Frequency selection
Carrier frequency generation
Signal detection
Modulation
Encryption
Protocol Stack: Physical Layer
Issues:
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Hardware cost
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How do we get down to $1/node?
Radio
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Ultrawideband?
Zigbee/IEEE 802.15.4
Protocol Stack: Data Link
Layer
Responsible for:
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The multiplexing of data streams
Data frame detection
Medium access *
Error control *
Data Link Layer: Medium
Access Control
Goals:
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Creation of the network infrastructure
Fair and efficient sharing of of
communication resources between
sensor nodes
Data Link Layer: Medium
Access Control
Problems with existing MAC protocols:
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Cellular system - single hop network is
impractical for sensor networks
Power conservation is not stressed
Security is not considered!
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WEP for 802.11 is broken
Do we care about link layer security?
Data Link Layer: Medium
Access Control
Current technology:
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Bluetooth and Mobile Ad Hoc Network
(MANET)
Both technologies are designed for
smaller numbers of nodes
Power consumption is still an issue
Data Link Layer: Medium
Access Control
Alternative MAC schemes:
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MAC for sensor networks
Self-Organizing Medium Access Control for
Sensor Networks (SMACS) and the
Eavesdrop-And-Register (EAR) Algorithm
CSMA-Based Medium Access
Hybrid TDMA/FDMA-Based
Data Link Layer: Medium
Access Control
Power Savings:
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Basic strategy: turn off radio transmitter
when idle
This can be ineffective due to startup
costs
Dynamic power management schemes
may provide an answer
Data Link Layer: Medium
Access Control
Issues:
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MAC for mobile sensor networks
Power saving modes
Link-layer ARQ and FEC
Protocol Stack: Network Layer
Design principles:
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Power efficiency
Data-centric nodes
Data aggregation is not always
desirable
Attribute-based addressing and location
awareness
Minimum Energy Routing
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Maximum PA
route
Minimum
energy route
Minimum hop
(MH) route
Maximum
minimum PA
node route
Directed Diffusion
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Route based on
attributes and
interests
Protocol Stack: Network Layer
Approaches:
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Maximum PA route
Minimum energy route
Minimum hop (MH) route
Maximum minimum PA node route
Protocol Stack: Network Layer
Schemes:
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Data-centric routing
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Directed Diffusion
Data Aggregation
Small minimum energy communication network (SMECN)
Flooding
Gossiping
Sensor protocols for information via negotiation (SPIN)
Sequential assignment routing (SAR)
Low-Energy Adaptive Clustering Hierarchy (LEACH)
Protocol Stack: Transport
Layer
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End-to-end Reliability
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Multi-hop retransmission
Congestion
End-to-end security
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Like SSL: authentication, encryption, data
integrity
Protocol Stack: Application
Layer
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Sensor network management
Database queries
Time synchronization/calibration?
Other?
Omissions
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Operating system discussion is missing
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TinyOS
MANTIS OS
Smart Card OS
Security
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Encryption
Authentication
Data Integrity
Availability – DOS attacks
Also, Non-repudiation and Authorization
Conclusion
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Overall architecture
Sensor node components
Sensor nets vs. traditional ad hoc nets
Design factors
Protocol stack