Wireless Sensor Networking: Applications and Challenges

1. Wireless Sensor Networking: Applications and Challenges Sandeep Gupta Arizona State University Based on Slides by Prof. Loren Schwiebert, CS, Wayne State University

2. Wireless Sensor Node = Sensor + Actuator + ADC + Microprocessor + Powering Unit + Communication Unit (RF Transceiver) An ad hoc network of self-powered and self-configuring sensor nodes for collectively sensing environmental data and performing data aggregation and actuation functions reliably, efficiently, and accurately. Wireless Sensor Networks: Applications & Challenges What is a Wireless Sensor Network? GPS Sensor Node

3. Wireless Sensor Networks: Applications & Challenges Limitations of Wireless Sensors • Wireless sensor nodes have many limitations: • Modest processing power – 8 MHz • Very little storage – a few hundred kilobits • Short communication range – consumes a lot of power • Small form factor – several mm3 • Minimal energy – constrains protocols • Batteries have a finite lifetime • Passive devices provide little energy

4. Wireless Sensor Networks: Applications & Challenges Some Sample Applications • Industrial and Commercial Uses • Inventory Tracking – RFID • Automated Machinery Monitoring • Smart Home or Smart Office • Energy Conservation • Automated Lighting • Military Surveillance and Troop Support • Chemical or Biological Weapons Detection • Enemy Troop Tracking • Traffic Management and Monitoring

5. Wireless Sensor Networks: Applications & Challenges Sensor-Based Visual Prostheses Retinal Implant Cortical Implant

6. Wireless Sensor Networks: Applications & Challenges Organization into Ad Hoc Networks • Individual sensors are quite limited. • Full potential is realized only by using a large number of sensors. • Sensors are then organized into an ad hoc network. • Need efficient protocols to route and managedata in this network.

7. Wireless Sensor Networks: Applications & Challenges Why Wireless Sensors Now? • Moore’s Law is making sufficient CPU performance available with low power requirements in a small size. • Research in Materials Science has resulted in novel sensing materials for many Chemical, Biological, and Physical sensing tasks. • Transceivers for wireless devices are becoming smaller, less expensive, and less power hungry. • Power source improvements in batteries, as well as passive power sources such as solar or vibration energy, are expanding application options.

8. Current State of the Artin Wireless Sensors

9. Wireless Sensor Networks: Applications & Challenges Typical Sensor Node Features • A sensor node has: • Sensing Material • Physical – Magnetic, Light, Sound • Chemical – CO, Chemical Weapons • Biological – Bacteria, Viruses, Proteins • Integrated Circuitry (VLSI) • A-to-D converter from sensor to circuitry • Packaging for environmental safety • Power Supply • Passive – Solar, Vibration • Active – Battery power, RF Inductance

10. Wireless Sensor Networks: Applications & Challenges Advances in Wireless Sensor Nodes Consider Multiple Generations of Berkeley Motes

11. Wireless Sensor Networks: Applications & Challenges Historical Comparison Consider a 40 Year Old Computer

12. Wireless Sensor Networks: Applications & Challenges A Rosy Future for Wireless Sensors? • Is the effort on wireless sensor protocols a waste of time?? • Can we just wait 10-15 years until we have sensors that are very powerful?? • NO!! Will still face: • Very limited storage • Modest power supplies

13. Proposed Applications of Wireless Sensors

14. Wireless Sensor Networks: Applications & Challenges Pervasive Computing (Smart Home / Office) • Sensors controlling appliances and electrical devices in the house. • Better lighting and heating in office buildings. • The Pentagon building has used sensors extensively.

15. Wireless Sensor Networks: Applications & Challenges Biomedical / Medical • Health Monitors • Glucose • Heart rate • Cancer detection • Chronic Diseases • Artificial retina • Cochlear implants • Hospital Sensors • Monitor vital signs • Record anomalies

16. Wireless Sensor Networks: Applications & Challenges Military Remote deployment of sensors for tactical monitoring of enemy troop movements.

17. Wireless Sensor Networks: Applications & Challenges Industrial & Commercial • Numerous industrial and commercial applications: • Agricultural Crop Conditions • Inventory Tracking • In-Process Parts Tracking • Automated Problem Reporting • RFID – Theft Deterrent and Customer Tracing • Plant Equipment Maintenance Monitoring

18. Wireless Sensor Networks: Applications & Challenges Traffic Management & Monitoring • Future cars could use wireless sensors to: • Handle Accidents • Handle Thefts • Sensors embedded in the roads to: • Monitor traffic flows • Provide real-time route updates

19. Driving Forces for AdoptingNew Technology

20. Wireless Sensor Networks: Applications & Challenges Economic Factors • New technologies replace existing technologies or fill new niches when there are economic advantages. • Wireless sensors will replace wired sensors • No wiring – lower costs • More flexible deployments • Wireless sensors will provide new services • Provide cost advantages or lower overhead • Improve product quality or product features

21. Wireless Sensor Networks: Applications & Challenges Novelty • Some early adopters use new technology simply for novelty or the fun of it. Examples include: • Java rings and internet watches. • Maybe wireless sensors for dating or meeting new people? • Personal wireless sensors for fun – a temperature monitor you carry around?

22. Wireless Sensor Networks: Applications & Challenges Legal / Liability • New technologies are adopted because of government mandates: • Air bags in automobiles • Child safety seats • Companies employ new technologies to avoid being sued!! • Temperature sensors to detect coffee that is too hot??

23. Wireless Sensor Networks: Applications & Challenges Entertainment • New technology is adopted for entertainment. • Playing games is major use of home PCs. • So is Internet browsing. • Games on cellular phones. • 3D visualization for … games. • Games of tag using wireless sensors? • Interactive role-playing games with sensors?

24. Wireless Sensor Networks: Applications & Challenges Not Technical Superiority • Useful technologies may not dominate the marketplace for several reasons. • Delay in getting to market. • Lack of standardization. • Limited applications. • Consumer preference – VHS vs. Betamax. • Weaker marketing or capitalization. • Unusual that there are no alternative technologies that can be used.

25. Uses of New Technology

26. Wireless Sensor Networks: Applications & Challenges Unexpected Killer Applications • Useful applications often follow available technology. For example, • PCs were available and people looked for a killer app – Visicalc. • The Internet was not created with these current applications in mind: • World Wide Web • E-Commerce • Peer-to-Peer Digital Music Sharing

27. Wireless Sensor Networks: Applications & Challenges Unanticipated Uses Arise • Once technology is available, creativity leads to new applications: • Sims Internet world • E-Bay auctions • Mirror for the Palm Pilot • Digital cameras with PC interface • What surprising applications for wireless sensor networks? • Depends on sensor node technology

28. Some Technical Challenges

29. Wireless Sensor Networks: Applications & Challenges Noisy Sensors Sensor readings can be inaccurate. Protocols need to recognize this. GPS Sensor Accurate within 2.8 meters Relative Humidity Sensor Accuracy of ±5% ±8% at 90% Relative Humidity ±2% with calibration

30. Wireless Sensor Networks: Applications & Challenges Wireless Channel Conditions • Limitations of wireless channels • Noisy • Interference • Link Contention • Unidirectional Links • But inherently a broadcast medium

31. Wireless Sensor Networks: Applications & Challenges Environmental Factors • Wireless sensors need to operate in conditions that are not encountered by typical computing devices: • Rain, sleet, snow, hail, etc. • Wide temperature variations • May require separating sensor from electronics • High humidity • Saline or other corrosive substances • High wind speeds

32. Networking Issues in Wireless Sensor Networks

33. Wireless Sensor Networks: Applications & Challenges Specific Destinations • Messages mostly routed to base stations • Not arbitrary source-destination pairs • Opportunities for optimization • Network traffic is not balanced

34. Wireless Sensor Networks: Applications & Challenges Hop-by-Hop Communication • Energy for wireless communication grows with distance d at the rate d2 – d4. • Multiple short hops are cheaper than one long hop. • Scheduling many nodes leads to high contention – not scalable.

35. Wireless Sensor Networks: Applications & Challenges Data Centric Communication • Query-Response Mode of Communication • Nodes may not have unique global Ids • Data is retrieved by specifying some desirable properties e.g. • What is the temperature in Room SCOB 105?

36. Wireless Sensor Networks: Applications & Challenges Periodic or Event-Driven • Communication patterns for wireless sensor networks take one of two general forms: • Periodic transmissions from all sensors. • Reports from only those sensors that observe a specific event. • Based on different application requirements. • Routing protocols have been proposed for either type of traffic.

37. Wireless Sensor Networks: Applications & Challenges In-Networking/In-Situ Processing (Data Aggregation) • Neighboring sensors observe similar phenomenon – have similar readings. • Better to locally combine similar readings. • Increases accuracy and reliability. • Decreases energy consumption. • May be better to summarize readings. • Avoids base station traffic implosion. • Reduces energy consumption.

38. Wireless Sensor Networks: Applications & Challenges Time Synchronization • Data aggregation assumes time synchronization!!! • Need to know events at different sensors are temporally related. • Allows one to distinguish multiple targets. • Not trivial to accomplish in the constrained environment of sensor networks.

39. Wireless Sensor Networks: Applications & Challenges Scalability! • Size of sensor networks will grow because: • Sensors more affordable as cost decreases • Redundant sensors provide • Reliability • Fault tolerance • Longer network lifetime • Protocols will support large networks • Applications will exist for larger networks

40. What will Wireless Sensor Networks Look Like in the Near Future?

41. Wireless Sensor Networks: Applications & Challenges Large-Scale Deployments • Sensor networks will grow in size because of: • Lower cost • Better protocols • Advantages of dense networks

42. Wireless Sensor Networks: Applications & Challenges Heterogeneous Sensors • Homogeneous network of sensors is the typical assumption, but not the future!! • Combining sensors with different functions • Hierarchy of sensors – a few expensive powerful sensors with more cheap sensors • Useful for special communication nodes • A few sensor nodes with expensive sensors, such as GPS-equipped sensors

43. Wireless Sensor Networks: Applications & Challenges Mobile Sensors Sensors with Micromachines Low-Power Motors that Support Mobility

44. Wireless Sensor Networks: Applications & Challenges General Purpose Sensors • Single-purpose network is the typical assumption, but not the future!! • Sensors for evolving applications • Sensors that can adapt to changing objectives • More memory and CPU will allow more complex applications • Flexibility increases marketability

45. Wireless Sensor Networks: Applications & Challenges Overlapping Coverage Areas • Sensors will be deployed for specific applications, but • These deployments will overlap • Sensors will have different properties • Users will want to combine these different sensors for new applications: • Temperature sensors for fire fighting • Location tracking for rescue operations

46. Wireless Sensor Networks: Applications & Challenges Mixture of Wired and Wireless • Wireless sensors will become a seamlesspart of larger networks! • Combiningwired sensors with wireless sensors • Wired sensors can have more power • Wired sensors can run TCP/IP • Accessing wireless sensors through the Internet • Need a gateway to translate requests • Uploading/downloading information remotely • Modifying wireless sensor tasks remotely • Increased direct user interaction

47. Some Impediments toCreating Future Applications

48. Wireless Sensor Networks: Applications & Challenges Need a Standardized Interface • Automated interaction between sensors implies some standard mechanism for communication! • Requires compatible wireless technology • Standardization a common theme • TCP/IP for the Internet • Java for Internet programming • Jini, SLP, etc. for 802.11 wireless devices • Need a service discovery protocol • Enables standard interface among sensors

49. Wireless Sensor Networks: Applications & Challenges Service Discovery Protocol Anyone need a printer? "Dear Mom...I'm sitting..."

50. Wireless Sensor Networks: Applications & Challenges Service Discovery Protocol (cont.) • For a wireless sensor network, service discovery provides: • Automated calibration of new devices • Highly dynamic system configurations • Cooperation among resource poor devices • Solves resource sharing device • Storage and long-range networking services can be obtained from a nearby server • Reduces duplication of functionality • Supports novel interactions in the future