1. Wireless Sensor Networks: A Survey
I. F. Akyildiz, W. Su, Y. Sankarasubramaniam and E. Cayirci
Presented by Yuyan Xue

2. Outline Introduction Applications of sensor networks
Factors influencing sensor network design
Communication architecture of sensor networks
Conclusion

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

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 limited in power, computational capacities and memory.
Sensor nodes are prone to failures.
The topology of a sensor network changes frequently.
Sensor nodes mainly use broadcast, most ad hoc networks are based on p2p.
Sensor nodes may not have global ID.

5. Applications of
Sensor networks

6. Applications of sensor networks
Military applications
Monitoring friendly forces, equipment and ammunition
Reconnaissance of opposing forces and terrain
Battlefield surveillance
Battle damage assessment
Nuclear, biological and chemical attack detection

7. Applications of sensor networks
Environmental applications
Forest fire detection
Biocomplexity mapping of the environment
Flood detection
Precision agriculture

8. Applications of sensor networks
Health applications
Tele-monitoring of human physiological data
Tracking and monitoring patients and doctors inside a hospital
Drug administration in hospitals

9. Applications of sensor networks
Home and other commercial applications
Home automation and Smart environment
Interactive museums
Managing inventory control
Vehicle tracking and detection
Detecting and monitoring car thefts

10. Factors Influencing
Sensor Network Design

11. Factors influencing sensor network design

12. Factors influencing sensor network design
Fault Tolerance
Scalability
Hardware Constrains
Sensor Network Topology
Environment
Transmission Media
Power Consumption

13. Factors influencing sensor network design
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.

14. Factors influencing sensor network design
Scalability
Scalability measures the density of the sensor nodes.
Density = (R) =(N R2)/A R – Radio Transmission Range

15. Factors influencing sensor network design
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.

16. Factors influencing sensor network design
Hardware constraints

17. Factors influencing sensor network design
Sensor network topology
Pre-deployment and deployment phase
Post-deployment phase
Re-deployment of additional nodes phase

18. Factors influencing sensor network design
Environment
Busy intersections
Interior of a large machinery
Bottom of an ocean
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.

19. Factors influencing sensor network design
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
optical media

20. Factors influencing sensor network design
Power Consumption
Sensing
Communication
Data processing

21. Communication architecture of sensor networks

22. Communication architecture of sensor networks
Combine power and routing awareness
Integrates date with networking protocols
Communicates power efficiently through the wireless medium
Promotes cooperative efforts among sensor nodes.

23. Communication architecture of sensor networks
Physical layer:
Address the needs of simple but robust modulation, transmission, and receiving techniques.
frequency selection
carrier frequency generation
signal detection and propagation
signal modulation and data encryption.

24. Communication architecture of sensor networks
Propagation Effects Minimum output power (dn 2=<n<4) Ground reflect – Multihop in dense sensor net work
Power Efficiency Modulation Scheme M-ary Modulation scheme Ultra wideband(impulse radio)

25. Communication architecture of sensor networks
Open research issues
Modulation schemes
Strategies to overcome signal propagation effects
Hardware design: transceiver

26. Communication architecture of sensor networks
Data link layer:
The data link layer is responsible for the multiplexing of data stream, data frame detection, the medium access and error control.
Medium Access Control
Power Saving Modes of Operation
Error Control

27. Communication architecture of sensor networks
Medium access control
Creation of the network infrastructure
Fairly and efficiently share communication resources between sensor nodes
Existing MAC protocols (Cellular System, Bluetooth and mobile ad hoc network)

28. Communication architecture of sensor networks
MAC for Sensor Networks
Self-organizing medium access control for sensor networks and Eaves-drop-and-register Algorithm
CSMA-Based Medium Access
Hybrid TDMA/FDMA-Based

29. Communication architecture of sensor networks
Power Saving Modes of Operation
Sensor nodes communicate using short data packets
The shorter the packets, the more dominance of startup energy
Operation in a power saving mode is energy efficient only if the time spent in that mode is greater than a certain threshold.

30. Communication architecture of sensor networks
Error Control
Error control modes in Communication Networks (additional retransmission energy cost) 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.

31. Communication architecture of sensor networks
Open research issues
MAC for mobile sensor networks
Determination of lower bounds on the energy required for sensor network self-organization
Error control coding schemes.
Power saving modes of operation

32. Communication architecture of sensor networks
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.

33. Communication architecture of sensor networks
Energy Efficient Routes
Maximum available power (PA) route: Route 2
Minimum energy (ME) route: Route 1
Minimum hop (MH) route: Route 3
Maximum minimum PA node route: Route 3
Minimum longest edge route: Route 1

34. Communication architecture of sensor networks
Interest Dissemination
Sinks broadcast the interest
Sensor nodes broadcast the advertisements
Attribute-based naming “The areas where the temperature is over 70oF ” “The temperature read by a certain node ”

35. Communication architecture of sensor networks
Data aggregation
Solve implosion and overlap Problem
Aggregation based on same attribute of phenomenon
Specifics (the locations of reporting sensor nodes) should not be left out

36. Communication architecture of sensor networks
Several Network Layer Schemes for Sensor Networks

37. Communication architecture of sensor networks
Open research issues
New protocols need to be developed to address higher topology changes and higher scalability.
New internetworking schemes should be developed to allow easy communication between the sensor networks and external networks.

38. Communication architecture of sensor networks
Transport layer:
This layer is especially needed when the system is planned to be accessed through Internet or other external networks.
TCP/UDP type protocols meet most requirements (not based on global addressing).
Little attempt thus far to propose a scheme or to discuss the issues related to the transport layer of a sensor network in literature.

39. Communication architecture of sensor networks
Open research issues
Because acknowledgments are too costly, new schemes that split the end-to-end communication probably at the sinks may be needed.

40. Communication architecture of sensor networks
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)

41. Communication architecture of sensor networks
Sensor management protocol (SMP)
Introducing the rules related to data aggregation, attribute-based naming, and clustering to the sensor nodes
Exchanging data related to the location
finding algorithms
Time synchronization of the sensor nodes
Moving sensor nodes
Turning sensor nodes on and off
Querying the sensor network configuration and the status of nodes, and reconfiguring the sensor network
Authentication, key distribution, and security in data communications

43. Some Other Interesting Applications
MIT d'Arbeloff Lab – The ring sensor
Monitors the physiological status of the wearer and transmits the information to the medical professional over the Internet
Oak Ridge National Laboratory
Nose-on-a-chip is a MEMS-based sensor
It can detect 400 species of gases and transmit a signal indicating the level to a central control station

44. iButton A 16mm computer chip armored in a stainless steel can
Up-to-date information can travel with a person or object
Types of i-Button
Memory Button
Java Powered Cryptographic iButton
Thermochron iButton

45. iButton Applications Caregivers Assistance Elder Assistance
Do not need to keep a bunch of keys. Only one iButton will do the work
Elder Assistance
They do not need to enter all their personal information again and again. Only one touch of iButton is sufficient
They can enter their ATM card information and PIN with iButton
Vending Machine Operation Assistance

46. iBadge - UCLA Investigate behavior of children/patient Features:
Speech recording / replaying
Position detection
Direction detection / estimation(compass)
Weather data: Temperature, Humidity, Pressure, Light

47. iBadge - UCLA

48. Conclusion Applications of sensor networks
Factors influencing sensor network design
Communication architecture of sensor networks