Introduction to Sensor Networks

1. Introduction to Sensor Networks Rabie A. Ramadan, PhD Cairo University http://rabieramadan.org rabie@rabieramadan.org 1

2. WebSite • Website: • http://rabieramadan.org/classes/2013/sensor/

3. Class Format • Presentations by myself • Assignments • Survey on one of the following topics : • Topics • Survey Format

4. Textbooks • Some other materials will be provided

5. Introduction and Basic Concepts 5

6. 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 their home to work,.. Disasters may be a drive force for such networks Katrina hurricane, 2006

7. 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)

8. Wireless Sensor Networks

9. 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 “Transducer”  converts energy from one form to another.

10. 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)

11. Sensing Task e.g. amplification, filtering, ..etc

12. An example of a sensor: Passive infrared PIR is a differential sensor: detects target as it crosses the “beams” produced by the optic

13. PIR signal: Amplitude Car 20-25 mph @ 25m Human 3 mph @ 10m

14. What is a Smart Sensor Node? Sensing Unit Processing Unit Sensors Processor ADC Storage Power Unit Communication Unit MobilitySupportUnit Location Finding Unit

15. Node’s Responsibilities • Data Collection • In-Network Analysis • Data Fusion • Decision Making

16. Sensors Classification Physical property to be monitored determines type of required sensor

17. Other Classifications • 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 (e.g., passive infrared sensor) • Electrical phenomenon: • resistive sensors use changes in electrical resistivity (ρ) based on physical properties such as temperature (resistance R = ρ*l/A) • capacitive sensors use changes in capacitor dimensions or permittivity (ε) based on physical properties (capacitance C = ε*A/d) • 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

18. What is a sensor Network? Monitored field Internet Sink Node

19. 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

20. History of WSN

21. 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)

22. Sample Sensor Hardware: Berkeley motes

24. 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 ).

25. 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.

26. Wireless Range Controls the Network Topology Routing in multihop network is a challenge Relay node may aggregate the data

27. 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

28. 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-hop communication and try to avoid it.

29. Operating System • Energy affects the O.S. design : • Small memory footprint, • Efficient switching between tasks • security mechanisms

30. 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,

31. A 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.

32. Ad Hoc Deployment • Deterministic Vs. Ad Hoc Deployment

33. 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

34. Challenges 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

35. Challenges and Constraints • Wireless Networking • Sensing Range • Very small • Nodes might be close to each other • Data Redundancy • Coverage Problem

36. 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 attack

37. In Network Processing

38. Enable Data Base Like Operations

39. 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

40. Design Issues • FaultTolerance • 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 • Helpsnodes to reorganize themselves in case of a failure of any of the nodes • Attribute-BasedAddressing • Addresses are composed of group of attribute-value pairs • Ex. < temp > 35, location = area A>

41. Design issues • Location Awareness • Nodes’ data reporting is associated with location • Priority Based Reporting • Nodes should adapt to the drastic changes in the environment • QueryHandling • 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

42. Traditional networks Vs. wireless sensor networks