A Survey on Sensor Networks

1
A Survey on Sensor Networks

• Rick Han
• CSCI 7143 Secure Sensor Networks
• Fall 2004

2
Introduction

• Overall architecture
• Sensor node components
• Sensor nets vs. traditional ad hoc nets
• Design factors
• Protocol stack
• Physical layer
• Data link layer
• Network layer
• Transport layer
• Application layer
• Conclusion

3
Differences Between Sensor Nets and Ad Hoc Nets

• 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

4
Sensor Network Overview
5
Sensor Node Components
6
Design Factors

• Fault Tolerance
• Scalability
• Production Costs
• Hardware Constraints
• Sensor Network Topology
• Transmission Media
• Power Consumption

7
Protocol Stack
8
Protocol Stack Physical Layer
Responsible for

• Frequency selection
• Carrier frequency generation
• Signal detection
• Modulation
• Encryption

9
Protocol Stack Physical Layer
Issues

• Hardware cost
• How do we get down to 1/node?
• Radio
• Ultrawideband?
• Zigbee/IEEE 802.15.4

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Protocol Stack Data Link Layer
Responsible for

• The multiplexing of data streams
• Data frame detection
• Medium access
• Error control

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Data Link Layer Medium Access Control
Goals

• Creation of the network infrastructure
• Fair and efficient sharing of of communication
  resources between sensor nodes

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Data Link Layer Medium Access Control
Problems with existing MAC protocols

• Cellular system - single hop network is
  impractical for sensor networks
• Power conservation is not stressed
• Security is not considered!
• WEP for 802.11 is broken
• Do we care about link layer security?

13
Data Link Layer Medium Access Control
Current technology

• Bluetooth and Mobile Ad Hoc Network (MANET)
• Both technologies are designed for smaller
  numbers of nodes
• Power consumption is still an issue

14
Data Link Layer Medium Access Control
Alternative MAC schemes

• 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

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Data Link Layer Medium Access Control
Power Savings

• Basic strategy turn off radio transmitter when
  idle
• This can be ineffective due to startup costs
• Dynamic power management schemes may provide an
  answer

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Data Link Layer Medium Access Control
Issues

• MAC for mobile sensor networks
• Power saving modes
• Link-layer ARQ and FEC

17
Protocol Stack Network Layer
Design principles

• Power efficiency
• Data-centric nodes
• Data aggregation is not always desirable
• Attribute-based addressing and location awareness

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Minimum Energy Routing

• Maximum PA route
• Minimum energy route
• Minimum hop (MH) route
• Maximum minimum PA node route

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Directed Diffusion

• Route based on attributes and interests

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Protocol Stack Network Layer
Approaches

• Maximum PA route
• Minimum energy route
• Minimum hop (MH) route
• Maximum minimum PA node route

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Protocol Stack Network Layer
Schemes

• Data-centric routing
• 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)

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Protocol Stack Transport Layer

• End-to-end Reliability
• Multi-hop retransmission
• Congestion
• End-to-end security
• Like SSL authentication, encryption, data
  integrity

23
Protocol Stack Application Layer

• Sensor network management
• Database queries
• Time synchronization/calibration?
• Other?

24
Omissions

• Operating system discussion is missing
• TinyOS
• MANTIS OS
• Smart Card OS
• Security
• Encryption
• Authentication
• Data Integrity
• Availability DOS attacks
• Also, Non-repudiation and Authorization

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Conclusion

• Overall architecture
• Sensor node components
• Sensor nets vs. traditional ad hoc nets
• Design factors
• Protocol stack