Introduction to Wireless Sensor Networks: Concepts, Networks, and Challenges

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/2012/sensor/

3. Class Format • Presentations by myself • Assignments

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 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. • Examples on remote sensors: • Nose, ears, and eyes  They do not need to touch the monitored objects to gather information

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

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

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

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

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

15. Sensors Classification • Types of Measured Phenomena

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

18. History of WSN

19. Academic Effort • Defense Advanced Research Projects Agency (DARPA) organized the Distributed Sensor Nets Workshop (DAR 1978). • DARPA also operated the Distributed Sensor Networks (DSN) program in the early 1980s,

20. Academic Effort • Rockwell Science Center, the University of California at Los Angeles proposed the concept of Wireless Integrated Network Sensors or WINS. • One outcome of the WINS project was the Low Power Wireless Integrated Microsensor (LWIM), produced in 1996

21. Academic Effort • The Smart Dust project at the University of California at Berkeley focused on the design of extremely small sensor nodes called motes. (year of 2000). • The goal of this project was to demonstrate that a complete sensor system can be integrated into tiny devices, possibly the size of a grain of sand or even a dust particle.

22. Academic Effort

23. Sample Sensor Hardware: Berkeley motes

25. 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 ).

26. 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.

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

28. 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

29. 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.

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

31. 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,

32. 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.

33. Ad Hoc Deployment • Deterministic Vs. Ad Hoc Deployment

34. 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

35. 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

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

37. 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

38. In Network Processing

39. Enable Data Base Like Operations

40. 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

41. 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>

42. 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

43. Traditional networks Vs. wireless sensor networks

44. Technological Background MEMS Technology • Micro-Electro-Mechanical Systems • (MEMS) is a core technology that: • Leverages IC fabrication technology • Builds ultra-miniaturized components • Enables radical new system applications

45. Advantages of MEMS

46. Pressure Sensor Belt on Jet Planes

47. Hardware Platforms • Augmented General Purpose PCs • Embedded PCs (PC104), PDAs, etc.. • Usually have O.S like Linux and wireless device such as Bluetooth. • Dedicated Sensor Nodes • Commercially off the shelf components (e.g. Berkeley Motes) • System-on-chip Sensor • Platform like Smart dust, BWRC PicoNode

48. Software Platforms • Operating Systems and Language Platforms • Typical Platforms are: • TinyOS, nesC, TinyGALS, and Mote • TinyOS • Event Driven O.S. • Requires 178 bytes of memory • Supports Multitasking and code Modularity • Has no file system – only static memory allocation • Simple task scheduler • nesC – extension of C language for TinyOS- set of language constructs • TinyGALS -language for TinyOS for event triggered concurrent execution . • Mote’ - Virtual machine for Berkeley Mote

49. Wireless Sensor Network Standards • IEEE 802.15.4 Standard • Specifies the physical and MAC Layers for low-rate WPANs • Data rates of 250 kbps, 40 kbps, and 20 kbps. • Two addressing modes: 16 - bit short and 64 - bit IEEE addressing. • Support for critical latency devices, for example, joysticks. • The CSMA - CA channel access. • Automatic network establishment by the coordinator. • Fully handshaking protocol for transfer reliability. • Power management to ensure low - power consumption. • Some 16 channels in the 2.4 - GHz ISM band, 10 channels in the 915 – MHz band, and 1 channel in the 868 - MHz band.

50. Wireless Sensor Network Standards • IEEE 802.15.4 Standard • The physical layer is compatible with current wireless standards such as Bluetooth • MAC layer implements synchronization , time slot management , and basic security mechanisms.