2. Wireless Sensor Networks: An Introduction Algorithms in Computer Networks March 2009

3. 2 Outline Introduction to Wireless Sensor Networks Components of WSN Applications of WSN Factors influencing WSN design Communication architecture of WSN

4. 3 Introduction A sensor network is composed of a large number of sensor nodes, which are densely deployed either inside the phenomenon or very close to it. Random deployment Cooperative capabilities Wireless connected

5. 4 Introduction Sensor networks VS ad hoc networks: The number of nodes in a sensor network can be several orders of magnitude higher than the nodes in an ad hoc network. Sensor nodes are densely deployed. Sensor nodes are prone to failures. The topology of a sensor network changes very frequently? Sensor nodes mainly use broadcast, most ad hoc networks are based on p2p. Sensor nodes are limited in power, computational capacities and memory. Sensor nodes may not have global ID.

6. 5 Confusion of Terms Berkeley Mote ZigBee Directed Diffusion Localization Rumor Routing Crossbow MAC Protocols Self-Organizing Networks Tiny-OS Tiny-DB Power Management RSSI ISM Band RFID Smart Dust ?

7. 6 Mote “ Tiny piece of anything ” Low-power (RF) transceiver Microcontroller Operating system Crossbow mote with battery

8. 7 Tmote from Sentilla (Moteiv) Key Features: Standard Form Factor: miniSDIO, allowing for standardized connections Small size: 25.4 mm x 20 mm (less than 1 square inch) Ultra-low power consumption (<1uA sleep, 2 mA active, 19mA tx/rx) Texas Instruments MSP430 microcontroller (8Mhz, 16-bit, 48kB Flash, 10kB RAM) TI/Chipcon CC2420 2.4 Ghz IEEE 802.15.4-compliant transceiver ST Micro M25P80 1MB EEPROM onboard memory Multiple interfaces for UART, SPI, I2C, 1-wire as well as 8 ADC signal inputs and 2 DAC output channels FCC-based RF shielding standard

9. 8 Mote Transceiver 400 MHz and up Line-of-sight Short range Unlicensed operation Microcontroller ATmega 128 - 16 MHz, 128KB Flash, 4 KB RAM Low power, sleep modes TinyOS Makes programming much, much easier

10. 9 Operating Systems MSDOS, Windows, Linux, TinyOS NOT the interface, but The program that manages all other software and the hardware resources Provide services to other programs “ applications ” (encapsulate common tasks) Isolate programmer from hardware

11. 10 Sensor Network Interface electronics, radio and microcontroller Soil moisture probe Mote Antenna Gateway Server Internet Communications barrier Sensor field

12. 11 Sensor Network Gateway Server Internet Sensor field Watershed

13. 12 How Did We Get Here? Advances wireless technology MEMS, VLSI Bandwidth explosion Changes in regulation Cultural changes Wireless devices are everywhere and people are receptive to new applications The concept of networks are ingrained in culture Open source Computer Science Operating system theory, network theory Inexpensive compilers

14. 13 Wireless Revolution Boston central telephone station at 40 Pearl Street after the blizzard of 1881

15. 14 Wireless Revolution TI REGENCY TR- 1, 1955, $450 (today) 1 st Transistor, 1947 Sony TR- 610, 1958 Integrated Circuit, 1963 1 st Integrated Circuit, ~1958 Today ~$5

16. 15 Wireless Revolution Size reduction of cellular telephones

17. 16 Micro-Electro-Mechanical-Systems (MEMS) ~ 1mm

18. 17 Micro-Electro-Mechanical-Systems (MEMS) ~ 1mm

19. 18 Small Sensors ~ 5 mm Sensor uses electrochemical and photonic properties to perform bioanalysis

20. 19 RF MEMS MEMS Filters: Qs of 98,000 in vacuum, very small Conventional LC Filters - Qs of 100-200, significant board space

21. 20 Transceiver

22. 21 Computer Revolution Original IBM PC (1981)MICAZ Mote (2005) 4.77 MHz4 MHz 16 KB RAM + 160KB Floppies 128 KB RAM + 512 KB Flash ~ 64 W~ 14 mW ~ $6K (today)~ $35 11.5 Kg, 50 x 14 x 41 cm15 cm 3, 5.7 x 3 x 0.6 cm

23. 22 Applications of WSN temperature humidity vehicular movement lightning condition pressure soil makeup noise levels the presence or absence of certain kinds of objects mechanical stress levels on attached objects the current characteristics such as speed, direction, and size of an object

24. 23 Applications of WSN Military applications Monitoring friendly forces, equipment and ammunition Battlefield surveillance Reconnaissance of opposing forces and terrain Battle damage assessment Nuclear, biological and chemical attack detection and reconnaissance

25. 24 Applications of WSN Environmental applications Forest fire detection Biocomplexity mapping of the environment Flood detection Precision agriculture

26. 25 Applications of WSN Health applications Telemonitoring of human physiological data Tracking and monitoring patients and doctors inside a hospital Drug administration in hospitals

27. 26 Applications of WSN Home applications Home automation Smart environment

28. 27 Applications of WSN Other commercial applications Environmental control in office buildings Interactive museums Managing inventory control Vehicle tracking and detection Detecting and monitoring car thefts

29. 28 Factors influencing WSN Fault tolerance Fault tolerance is the ability to sustain sensor network functionalities without any interruption due to sensor node failures. The fault tolerance level depends on the application of the sensor networks.

30. 29 Factors influencing WSN Scalability Scalability measures the density of the sensor nodes. Scalability is needed for applications that may range from a few to thousands of nodes.

31. 30 Factors influencing WSN Production costs The cost of a single node is very important to justify the overall cost of the networks. The cost of a sensor node is a very challenging issue given the amount of functionalities with a price of much less than a dollar.

32. 31 Factors influencing WSN Hardware constraints

33. 32 Factors influencing WSN Sensor network topology Pre-deployment and deployment phase Post-deployment phase Re-deployment of additional nodes phase

34. 33 Factors influencing WSN Environment Busy intersections Interior of a large machinery Bottom of an ocean Inside a tornado Surface of an ocean during a tornado Biologically or chemically contaminated field Battlefield beyond the enemy lines Home or a large building Large warehouse Animals Fast moving vehicles Drain or river moving with current.

35. 34 Factors influencing WSN Transmission media In a multihop sensor network, communicating nodes are linked by a wireless medium. To enable global operation, the chosen transmission medium must be available worldwide. Radio Infrared

36. 35 Factors influencing WSN design Power consumption Sensing Communication Data processing

37. 36 Communication architecture of WSN

38. 37 Communication architecture of WSN

39. 38 Communication architecture of WSN Application layer An application layer management protocol makes the hardware and software of the lower layers transparent to the sensor network management applications. Sensor management protocol (SMP) Task assignment and data advertisement protocol (TADAP) Sensor query and data dissemination protocol (SQDDP)

40. 39 Communication architecture of WSN Transport layer This layer is especially needed when the system is planned to be accessed through Internet or other external networks. No attempt thus far to propose a scheme or to discuss the issues related to the transport layer of a sensor network in literature (maybe you will found one meaning reference?)

41. 40 Communication architecture of WSN Network layer Power efficiency is always an important consideration. Sensor networks are mostly data centric. Data aggregation is useful only when it does not hinder the collaborative effort of the sensor nodes. An ideal sensor network has attribute-based addressing and location awareness.

42. 41 Communication architecture of WSN Maximum available power (PA) route: Route 2 Minimum energy (ME) route: Route 1 Minimum hop (MH) route: Route 3 etc

43. 42 Communication architecture of WSN Data aggregation

44. 43 Communication architecture of WSN Data link layer The data link layer is responsible for the medium access and error control. It ensures reliable point-to-point and point-to-multipoint connections in a communication network.

45. 44 Communication architecture of WSN Medium access control Creation of the network infrastructure Fairly and efficiently share communication resources between sensor nodes

46. 45 Communication architecture of WSN Power saving modes of operation Operation in a power saving mode is energy efficient only if the time spent in that mode is greater than a certain threshold.

47. 46 Communication architecture of WSN Error control Forward Error Correction (FEC) Automatic Repeat Request (ARQ). Simple error control codes with low- complexity encoding and decoding might present the best solutions for sensor networks.

48. 47 Communication architecture of WSN Physical layer The physical layer is responsible for frequency selection, frequency generation, signal detection, modulation and data encryption.

49. 48 Next presentation Some technical aspects of WSN communication: localized algorithms impact of radio irregularity