sensor net
DESCRIPTION
TRANSCRIPT
Large scale sensor networks are only recently emerging with a large spectrum of applications .
Distributed relaying will be shown to decrease the power consumption per relaying sensor node.
Figure 12: Distributed relaying sensor network for fire detection in forests.
© 2003 –2004 by Yu Hen Hu 3
Smart sensors
Transducers
Power
On-board processor, storage
Wireless transceivers
Ad hoc network
No predefined, fixed network configuration
Transmit, receive, and relay information
Wireless communication
Radio, infrared, optical, and other modalities
Vision Smart environment:
▪ Monitoring▪ Control, interaction
Large number of low cost sensor nodes deploy-n-play, self-configuration to form network, Collaborative in-situ information processing
Applications Environmental monitoring Civil structure/earth quake
monitoring Premises security Machine instrument diagnosis Health care
wireless sensor prototype by Wang et al. (2005).
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Wireless Sensor Networks
Sensing and Processing Unit
Wireless Transceiver
Ad Hoc Network Topology
Battlefield surveillance, disaster relief, border control, environment monitoring, … etc.
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1,1x
Manager node
2,1x 1,2x 2,2x
1,3x 2,3x
• Data fusion– Feature vectors from different node
measurements are combined – Higher computational burden since
higher dimensional (vector) data is jointly processed
– Higher communication burden– Larger training data requirement
1,1x
Manager node
2,1x 1,2x 2,2x
1,3x 2,3x
• Decision fusion– Decisions (hard or soft) based on
node measurements are combined – Lower computational burden since
lower dimensional data (scalar decisions) is jointly processed
– Lower communication burden– Lower training data requirement
Two Extremes
destination
Code and communicate all data to a central point for processing and analysis
Local processing and communication between nodes; communicate result to central point
data estimate
destination
Physical Limitations
Low density network
• low bandwidth/energyconsumption
• low spatial resolution
High density network
• high bandwidth/energyconsumption
• high spatial resolution
Key Questions
How dense should we sample ?
What are the transmission rate limitationsfor a given network density ?
What are the energy/power requirementsfor a given network density ?
What accuracy is achievable under bandwidthand energy constraints ?
Signal + Noise Model
noiseless field noisy sensor measurements
1. D(n): Achievable accuracy using n sensors ?
2. E(n): Energy required to transmit data or estimates ?
3. How do accuracy and energy scale with node density ?
MSE-Energy Analysis
higher density
higher resolutionmore averaging
higher density
more datamore communication
Ex: Estimating a Piecewise Constant Field
Estimation
n sensorseach makes a noisymeasurement of thefield at its location
(e.g., each contaminatedwith Gaussian noise)
Energy and Communication
Goal: transmit a goodestimate of field to upperleft corner via multi-hop communication
Hierarchical Comm and Data Processing
• hierarchical pyramid structure for sensor networkcomm and data handling (Ganesan, Estrin, Heidiman ’02
Madden et al ’02, Hellerstein et al ‘03)
Hierarchical Communication
Hierarchical Data Fusion
Estimation in Action
FIGURE Sensor network protocol stack. (Reprinted from Akyildiz, I.F. et al., Computer Networks,Vol. 38, 393–422, 2002. With permission.)
Sensor Nodes:sense target events, gather sensor readings, manipulate informations, send them to gateway via radio link
Base station/sink: communicate with sensor nodes and user/operator, (database-stores the data)
Operator/user: task manager, send query
Task Management Plane
Mobility Management Plane
Power Management Plane
Application Layer: middleware, OSNetwork Layer: Routing
Application Layer
Transport Layer
Network Layer
Data Link Layer
Physical Layer
State of the art routing protocols are distributed and reactive : the systems start looking for a route only when they have application data to transmit
We study here Ad hoc On demand Distance Vector (AODV) and Dynamic Source Routing (DSR) for the sensor network
Route DiscoveryA node sends a Route Request message to all of its neighbours.Any node receiving such a request, either answers to it or rebroadcasts it.The procedure finishes either when the request sender has received theroute information, or when the request times out. With AODV, each node remembers the next hop information associated with
the destination. The route knowledge itself is distributed in the network.
With DSR, the complete route is sent to the route requester. Message transmission
With AODV, the message is sent to the next hop as recorded in the routing table, and this procedure is repeated at each hop.
With DSR, the message is sent with its complete route as header.
Rumor Routing
"Rumor Routing Algorithm for Sensor Network" by Braginsky and Estrin
How to make information available in a sensor network
Assumption: sense particular eventt when requested, don't know the existence or the location of the event
An event sends out agents which travel the network from node to node on a random path.Each visit leaves information about the event in the node's database. After a predefined TTL the agent stops
A requester also sends out an agent. After some time it will hopefully come across the path of the information agent by checking the node's databases. It can then travel the backward references the first agents left in the nodes to reach the event.
Critical review+ Only a small number of nodes have to adopt the same information
+ Only a small number of nodes have to process the request When or whether requested information can be delivered is a random process.- The failure of nodes can interrupt the path to the event (depending on how broad it is).- The actual behavior of a node is very different from what is shown in the former slides
Sensing: sensor --a transducer that converts a physical, chemical, or biological parameter into an electrical signal
Processing: microprocessor(CPU)
data storage(Mem)AD converter
Communicating: data transceiver(Radio),
Energy source: battery
68HC11
Node
Specific
OS Modules
Middleware
Middleware
Sensor
Driver
Node
Specific
OS Modules
Hardware Sensor
Middleware
ARMTemperature
Sensor
Sensor
Driver
Node
Specific OS
Modules
68HC11Pressure
Sensor
Node
Specific
OS Modules
Sensor
Driver
Middleware
Sensor Node
Model
• 68HC11 µC
• No Sensor
• ARM Microcontroller
• Temperature Sensor
• 68HC11 Microcontroller
• Pressure Sensor
Picoradio
(UCB)
WINS
(UCLA)Smart
Dust
(UCB)
Sensor,
Actuator
Battery
Processor HF
Characteristics of Sensor Nodes Limited capacity of Battery (Lifetime: day - 10 years) Processing capabilities (10MHz) Transmission range (5 - 20 meters)
Data rates: Bit/s - KB/s Transmission methods: 802.11 (WiFi) Bluetooth – short distance, other applications ZigBee – for sensor network
Price: some cents
Storage
persistent storage for data streams
Integrity Service/
Access Control
Query Manager
Storage
Sensor Manager
Query Manager
manages active queries
query processing
delivery of events and query results to registered, local or remote consumers
Integrity Service/
Access Control
Query Manager
Storage
Sensor Manager
Integrity Service/
Access Control
Query Manager
Storage
Sensor Manager
Top layer: access control and integrity service
OS examples: TinyOS: when an event
occurs, it calls the appropriate event handler to handle the event.
Others: Contiki, MANTIS, and SOS.
Create Hardware-optimized software components (driver, operating system )
Create hardware- independent software components (middleware, services)
Combining of predefined components Source code generation Removing unused components Optimizaion of interface Optimizaion to node's hardware
Distribution of nodes in different environments
Monitoring the execution Creation of logfiles
Evaluation of logfiles
Components
Design & Edit
Complie/Link
Distribute
Execute/Administrate
Evaluation
Resource Hardware
driven
Monitoring
Optimization
www.themegallery.com
2:Securityapplication
4:Medical Application
1: Militaryapplications
3:Environmental application
5:Commercial application
Location of combatants, vehicles and weapons
on the battlefield
It may be used to monitor patients from a distance
•Report a possible outbreak of fire•Detect dry areas
Detect movements of the earth to predict earthquake
Facilitate stock management
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Based on the IEEE 802.15.4 Standard
Popular for WSN devices.
ZigBee adds:
Network topologies
Interoperability with other wireless products
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TinyOS is a free and open source operating system.
TinyOS is an embedded operating system written in the
nesC.
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Given:
Field A
N sensors
How well can the field be observed ?
Closest Sensor (minimum distance) only
Worst Case Coverage: Maximal Breach Path
Best Case Coverage: Maximal Support Path
Multiple Sensors: speed and path considered
Minimal Exposure Path
Applications of Wireless Sensor Networking:
In the present era there are lot of technologies which are used for monitoring are completely based on the wireless sensor networking. Some of important applications are environmental monitoring, traffic control application, weather checking, regularity checking of temperature etc. Wireless sensor networks can also be used for detecting the presence of vehicles such as motor cycles up to trains. These are some important wireless sensor networking based technologies which help us in our daily life. Some of there daily life applications are: used in agriculture, water level monitoring, green house monitoring, landfill monitoring etc.
In studying the performance or a wireless sensor network, you must take into consideration the deployment scenario which includes; topology, radio ranges, trajectory of targets and event traffic, and trajectories of user nodes and query traffic. All of these affect design trade-offs, and therefore any algorithm or protocol chosen should be evaluated under diverse deployment scenarios.
© 2003 –2004 by Yu Hen Hu 45
Sensor network is a new application area for computer vision, graphics and image processing
It requires multi-modality, multimedia processing under the constraint of minimizing communication and energy consumption.
Sensor Network can be used in many applications, such as Military, Environmental and Health…etc.
Its characteristics are tiny node, low power, limited resources, dynamic network topology and various scales of network deployment.
Middleware is used to connect the network hardware, operating systems, network stacks, and applications in different approaches.
For examples, Virtual Machine, Mobile Agent, Database and Message Oriented.
Security in Sensor Networks. Public/Private Key
▪ Key establishment beyond sensor network capabilities.
Shared Key▪ Simple solution, but single node may reveal the secret key.▪ Scalability? → each node stores n-1 keys (n(n-1) keys need to be
established)
Solution? Privacy Aspects in Sensor Networks. Sensor technology may be used for illegal surveillance. Providing awareness of the presence of sensor nodes? Solution?
FIGURE Sensor signal processing flow.
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ISI team experimented with three iPAQ-based video sender nodes and collected video baseline of several vehicles. RTP packet dumps and VHS video tape.
VT team supported BBN integrated experiment with Sensoria 2.0 nodes.
UCLA ran developmental experiments on sensor field coverage algorithms (under Sensorware project).
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