Wireless Sensor Networks: A Survey I. F. Akyildiz, W. Su, Y. Sankarasubramaniam and E. Cayirci Presented by Yuyan Xue 11-30-2005
Outline • Introduction • Applications of sensor networks • Factors influencing sensor network design • Communication architecture of sensor networks • Conclusion
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
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.
Applications of Sensor networks
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
Applications of sensor networks Environmental applications • Forest fire detection • Biocomplexity mapping of the environment • Flood detection • Precision agriculture
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
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
Factors Influencing Sensor Network Design
Factors influencing sensor network design • Fault Tolerance • Scalability • Hardware Constrains • Sensor Network Topology • Environment • Transmission Media • Power Consumption
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.
Factors influencing sensor network design Scalability • Scalability measures the density of the sensor nodes. • Density = (R) =(N R2)/AR – Radio Transmission Range
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.
Factors influencing sensor network design Hardware constraints
Factors influencing sensor network design Sensor network topology • Pre-deployment and deployment phase • Post-deployment phase • Re-deployment of additional nodes phase
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.
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
Factors influencing sensor network design Power Consumption • Sensing • Communication • Data processing
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.
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.
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 SchemeM-ary Modulation schemeUltra wideband(impulse radio)
Communication architecture of sensor networks Open research issues • Modulation schemes • Strategies to overcome signal propagation effects • Hardware design: transceiver
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
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)
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
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.
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.
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
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.
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
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 ”
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
Communication architecture of sensor networks Several Network Layer Schemes for Sensor Networks
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.
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.
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.
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)
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
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
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 iButton
Caregivers 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 iButton Applications
iBadge - UCLA • Investigate behavior of children/patient • Features: • Speech recording / replaying • Position detection • Direction detection / estimation(compass) • Weather data: Temperature, Humidity, Pressure, Light
Conclusion • Applications of sensor networks • Factors influencing sensor network design • Communication architecture of sensor networks