Introduction to Distributed Networks

Wireless Sensor Networks

Rabie A. Ramadan, PhDCairo University

http://rabieramadan.org

rabie@rabieramadan.org

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WebSite

Website: • http://rabieramadan.org/classes/2014/sensor/

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Class Format Presentations by myself and others Assignments Survey on one of the following topics :

• Topics

• Survey Format

• Prepare a presentation for your topic – some will be publically presented and others will be in private

• 4 persons per survey (effort should be equivalent to the number of persons)

• Not less than 6 pages 3

Textbooks

Some other materials will be provided

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Introduction and Basic Concepts

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Wireless Networks Most of the traditional wireless networks

occur over fixed infrastructure

• Access points Many wireless protocols (heterogeneity

problem)

• Bluetooth, WiFi, WiMax We need Seamless network

• Connects everyone from his/her home to work,..

Disasters may be a drive force for such networks

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Katrina hurricane, 2006

General Types of Wireless Networks

Wireless Cellular Networks

• First , Second, 2.5 , third, and 4th generations Wireless Ad Hoc Networks

• Nodes function as host and router

• Dynamic topology

• Nodes may departure

• Requires efficient routing protocols

• Mobile Ad Hoc Networks (MANET)

• Wireless Sensor Networks (WSN)

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Wireless Sensor Networks

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Definitions and Background Sensing:

• Is a technique used to gather information about a physical object or process, including the occurrence of events (i.e., changes in state such as a drop in temperature or pressure).

Sensor: • An object performing such a sensing task

• Converts energy of the physical worlds into electrical signal.

• Sometimes named “TransducerTransducer” converts energy from one form to another.

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Definitions and Background

Examples on remote sensors:

• eyes: capture optical information (light)

• ears: capture acoustic information (sound)

• nose: captures olfactory information (smell)

• skin: captures tactile information (shape, texture)

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Sensing Task

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e.g. amplification, filtering, ..etc

An example of a sensor: Passive infrared

PIR is a differential sensor: detects target as it crosses the

“beams” produced by the optic

PIR signal: Amplitude

Human 3 mph @ 10m

Car 20-25 mph @ 25m

Communication Unit

Sensing Unit

Sensors

ADC

Processing Unit

Processor

Storage

Power Unit

Mobility Support Unit Location Finding Unit

What is a Smart Sensor Node?

Node’s Responsibilities

Data Collection

In-Network Analysis

Data Fusion

Decision Making

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Sensors Classification

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Type Examples

Temperature Thermistors, thermocouples

Pressure Pressure gauges, barometers, ionization gauges

Optical Photodiodes, phototransistors, infrared sensors, CCD sensors

Acoustic Piezoelectric resonators, microphones

Mechanical Strain gauges, tactile sensors, capacitive diaphragms, piezoresistive cells

Motion, vibration Accelerometers, mass air flow sensors

Position GPS, ultrasound-based sensors, infrared-based sensors, inclinometers

Electromagnetic Hall-effect sensors, magnetometers

Chemical pH sensors, electrochemical sensors, infrared gas sensors

Humidity Capacitive and resistive sensors, hygrometers, MEMS-based humidity sensors

Radiation Ionization detectors, Geiger-Mueller counters

Physical property to be monitored determines type of required sensor

Other Classifications Power supply:Power supply:

• active sensors require external power, i.e., they emit energy (microwaves, light, sound) to trigger response or detect change in energy of transmitted signal (e.g., electromagnetic proximity sensor)

• passive sensors detect energy in the environment and derive their power from this energy input .

Electrical phenomenon:Electrical phenomenon:

• resistive sensors use changes in electrical resistivity (ρ) based on physical properties such as temperature

• capacitive sensors use changes in capacitor dimensions or permittivity (ε) based on physical properties

• inductive sensors rely on the principle of inductance (electromagnetic force is induced by fluctuating current)

• piezoelectric sensors rely on materials (crystals, ceramics) that generate a displacement of charges in response to mechanical deformation

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What is a sensor Network?

Sink Node

Internet

Monitored field

Wireless Sensor Network (WSN)

Multiple sensors (often hundreds or thousands) form a network to cooperatively monitor large or complex physical environments

Acquired information is wirelessly communicated to a base station (BS), which propagates the information to remote devices for storage, analysis, and processing

History of WSN

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History of Wireless Sensor Networks

DARPA:

• Distributed Sensor Nets Workshop (1978)

• Distributed Sensor Networks (DSN) program (early 1980s)

• Sensor Information Technology (SensIT) program UCLA and Rockwell Science Center

• Wireless Integrated Network Sensors (WINS)

• Low Power Wireless Integrated Microsensor (LWIM) (1996) UC-Berkeley

• Smart Dust project (1999)

• concept of “motes”: extremely small sensor nodes Berkeley Wireless Research Center (BWRC)

• PicoRadio project (2000) MIT

• μAMPS (micro-Adaptive Multidomain Power-aware Sensors) (2005)

Sample Sensor Hardware: Berkeley motes

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Communication and Computation Rene Mote

• Communication =

• Computation =

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Commercial Effort

Crossbow (www.xbow.com), Sensoria (www.sensoria.com), Worldsens (http://worldsens.citi.insa-lyon.fr), Dust Networks

(http://www.dustnetworks.com ), and Ember Corporation (http://www.ember.com ).

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Challenges and Constraints

Energy • Sensors powered through batteries

sometimes impossible to do.

• Mission time may depend on the type of application (e.g. battlefield monitoring – hours or days)

• Node’s layers must be designed carefully.

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Wireless Range Controls the Network Topology

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Routing in multihop network is a challenge Relay node may aggregate the data

Medium Access Control layer (MAC)

Responsible for providing sensor nodes with access to the wireless channel.

Responsible of Contention free Transmission . MAC protocols have to be contention free as

well as energy efficient. • Contention free requires listening to the wireless

channel all the time

• Energy efficient requires turning off the radio

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Network Layer

Responsible for finding routes from a sensor node to the base station

Route characteristics such as length (e.g., in terms of number of hops), required transmission power, and available energy on relay nodes

Determine the energy overheads of multi-hopmulti-hop communication and try to avoid it.

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Operating System Operating System

Energy affects the O.S. design : Energy affects the O.S. design : • Small memory footprint,

• Efficient switching between tasks

• security mechanisms

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Challenges and Constraints

Self-Management• Sensors usually deployed in harsh environment.

• There is no pre-infrastructure setup.

• Once deployed, must operate without human intervention

• Sensor nodes must be self-managing in that • They configure themselves,

• Operate and collaborate with other nodes,

• Adapt to failures, changes in the environment,

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A A self-managing Network self-managing Network Self-organization

• A network’s ability to adapt configuration parameters based on system and Environmental state.

Self-optimization

• A device’s ability to monitor and optimize the use of its own system resources

Self-protection

• Allows a device to recognize and protect itself from intrusions and attacks

Self-healing

• Allows sensor nodes to discover, identify, and react to network disruptions.

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Ad Hoc Deployment

Deterministic Vs. Ad Hoc Deployment

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Challenges and Constraints

Wireless Networking

• Transmission Media

• Sensors use wireless medium

• Suffer from the same problems that wireless networks suffer from

• Fading

• High error rate

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Challenges and ConstraintsChallenges and Constraints

Wireless Networking• Communication range

• Communication ranges are always short

• It is required for the network to be highly connected

• Routing paths will be long

• What about critical applications where delay is not acceptable ?

• QoS will be an issue

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Challenges and Constraints

Wireless Networking

• Sensing Range

• Very small

• Nodes might be close to each other

• Data Redundancy

• Coverage Problem

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Challenges and Constraints

Decentralized Management• Requires Distributed Algorithms

• Overhead might be imposed

Security• Exposed to malicious intrusions and attacks due to

unattendance characteristics.

• denial-of-service

• jamming attack36

In Network Processing

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Enable Data Base Like Operations

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Network Characteristics Dense Node Deployment Battery-Powered Sensors Sever Energy , Computation , and Storage Constraints Self Configurable Application Specific Unreliable Sensor Nodes Frequent Topology Change No Global Identifications Many-to-One Traffic pattern ( multiple sources to a single Sink

node) Data Redundancy

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Design Issues Fault Tolerance

• Large number of nodes already deployed or

• Nodes do the same job. If one fails , the network still working because its neighbor monitors the same phenomenon .

Mobility

• Helps nodes to reorganize themselves in case of a failure of any of the nodes

Attribute-Based Addressing

• Addresses are composed of group of attribute-value pairs

• Ex. < temp > 35, location = area A>

Design issues Location Awareness

• Nodes’ data reporting is associated with location

Priority Based Reporting

• Nodes should adapt to the drastic changes in the environment

Query Handling • The sink node / user should be able to query the network

• The response should be routed to the originator

• We might have multiple sinks in the network

Traditional networks Vs. wireless sensor networks

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Traditional Networks Wireless Sensor Networks

General-purpose design; serving many applications Single-purpose design; serving one specific application

Typical primary design concerns are network performance and latencies; energy is not a primary concern

Energy is the main constraint in the design of all node and network components

Networks are designed and engineered according to plans

Deployment, network structure, and resource use are often ad-hoc (without planning)

Devices and networks operate in controlled and mild environments

Sensor networks often operate in environments with harsh conditions

Maintenance and repair are common and networks are typically easy to access

Physical access to sensor nodes is often difficult or even impossible

Component failure is addressed through maintenance and repair

Component failure is expected and addressed in the design of the network

Obtaining global network knowledge is typically feasible and centralized management is possible

Most decisions are made localized without the support of a central manager