CSE 5392 By Dr. Donggang Liu 1

CSE 5392 Sensor Network Security

Introduction to Sensor Networks

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An Application of Sensor Networks

sensor

Communication and processing

module

1. Network protocol (e.g., routing)2. Data management (e.g., aggregation)3. Localization and time synchronization4. Energy management, robustness, etc.

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Sensor Node: Mica2

• Hardware– Processor: Atmega128L 4Mhz, 8-bit– Memory: 4K RAM, 512kB Flash– Communication: 19.2kbps Radio– Power supply: 2 AA Batteries

• Software – TinyOS / NesC Applications– Network management– Power management– Sensor drivers– Security package (TinySec)

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Sensing Capabilities

• Many types of sensors that are able to monitor:– Temperature– Humidity– Light– Pressure– Noise levels– The presence or absence of certain kinds of objects– Movement (speed, direction) of an object

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Military Applications

• Battlefield surveillance

• Monitoring friendly forces, equipment and ammunition

• Reconnaissance of opposing forces and terrain

• Target tracking

• Battle damage assessment

• Nuclear, biological and chemical attack detection and reconnaissance

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Civilian Applications

• Forest fire detection

• Biocomplexity mapping of the environment

• Flood detection

• Precision Agriculture: the pesticides level in the drinking water, soil erosion, and air pollution.

• Smart environment, smart kindergarten, and more

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Features of Sensor Networks

• Fault tolerance

• Scalability

• Production costs

• Hardware constraints

• Sensor network topology

• Transmission media

• Power consumption

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Fault Tolerance

• Failures due to:– lack of power– physical damage in harsh environment– Interference by other objects (e.g. radios) and other

sensors.

• Fault tolerance: the ability to maintain sensor network functionalities in the presence of failures

• The environment is important to the fault tolerance of algorithms and protocols

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Scalability

• Number of sensors: hundreds, thousands, to millions, depending on the applications.

• The density of the network usually depends on the applications

• Typically, people consider a large number of sensor nodes densely deployed in a target field.

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Costs

• Per node cost is important for large sensor networks. It has to be kept low.

• Bluetooth radio system: $5 now, but still too expensive for sensors. PicoNode: targeted to be < 50c.

• More challenging, with large amount of functionalities

• Reality: $150 for one Micaz mote

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Resource Constraints (Mica2)

• Processor: 8-bit 4MHz CPU (no division)

• Limited memory: 4K RAM

• Low bandwidth: 19.2K bps

• Small packet size: 29-byte long payload

• Limited energy supply: Battery powered

• Many traditional techniques are not practical

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Network Topology

• Sensor networks are usually formed in an ad hoc manner• Topology maintenance is a challenging task due to

– Number of nodes, failures, dynamics etc• Pre-deployment and deployment phase

– Reduce the installation cost,– Eliminate the need for any pre-organization and pre-planning– Increase the flexibility of arrangement– Provide better self-organization and fault tolerance.

• Post-deployment phase– Topology may changes are due to node movement, lack of energy,

node malfunctioning, etc• Re-deployment of additional nodes phase

– Adding new sensors

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Transmission media

• Wireless communication– Radio – Infrared – Optical media

• Multi-hop communication– Short distance wireless links

• Unreliable– Low bandwidth, low power

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Power consumption

• The lifetime of a node strongly depends on the battery lifetime

• Sensing, communication, and data processing.– Sensing power: depends on applications– Communication: expensive

• Involves both data transmission and reception

• The active power + the start-up power consumption

– Data processing: not expensive• In-network processing is crucial to minimize power

consumption in a multi-hop sensor network.

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Communication Architecture

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Protocol Stack

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Physical Layer

• Wireless radio signals– Frequency selection– Frequency generation– Signal detection – Modulation.

• Examples:– CC1000 chipset in Mica2

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Data Link Layer

• Media access control– Provide fair and efficient access to the channel– It provide point-to-point link– Example: CC1000RadioIntM.nc

• Error Control– Simple error correction scheme– CRC check– Example: RadioCRCPacket.nc

• Energy aware

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Network Layer

• Routing (infrastructureless network)– Ad hoc routing techniques (e.g., DSR) do not fit

• Power efficiency

• Data centric routing

• Data aggregation

• Example:– Flooding: each node receiving a packet repeats it by

broadcasting (simple flooding versus TTL-based)– Geographic forwarding: forward packets to the nodes close

to the destination node

• Energy aware

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Transport Layer

• An open research issue

• This layer is especially needed when the system is planned to be accessed through Internet or other external networks.

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Application Layer

• An open research issue

• Depends on applications:– Makes the hardware and software of the lower

layers transparent to the applications

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A Simple Protocol Stack

CC1000RadioIntM.nc CC1000ControlM.nc

A simple send/receive application

send receive control

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Active Research Area

• Routing

• Topology management

• Data management

• MAC protocols

• Target tracking, service discovery

• Monitoring and maintenance

• Security and privacy