Wireless Sensor Networks: A SurveyI. F. Akyildiz, W. Su, Y. Sankarasubramaniam and E. Cayirci

Presented by Yuyan Xue11-30-2005

OutlineIntroductionApplications of sensor networksFactors influencing sensor network designCommunication architecture of sensor networksConclusion

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 deploymentCooperative capabilities

IntroductionSensor 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 networksMilitary applicationsMonitoring friendly forces, equipment and ammunitionReconnaissance of opposing forces and terrainBattlefield surveillanceBattle damage assessmentNuclear, biological and chemical attack detection

Applications of sensor networksEnvironmental applicationsForest fire detectionBiocomplexity mapping of the environmentFlood detectionPrecision agriculture

Applications of sensor networksHealth applicationsTele-monitoring of human physiological dataTracking and monitoring patients and doctors inside a hospitalDrug administration in hospitals

Applications of sensor networksHome and other commercial applicationsHome automation and Smart environmentInteractive museumsManaging inventory controlVehicle tracking and detectionDetecting and monitoring car thefts

Factors Influencing Sensor Network Design

Factors influencing sensor network design

Factors influencing sensor network designFault ToleranceScalabilityHardware ConstrainsSensor Network TopologyEnvironmentTransmission MediaPower Consumption

Factors influencing sensor network designFault toleranceFault 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 designScalabilityScalability measures the density of the sensor nodes.Density = (R) =(N R2)/AR Radio Transmission Range

Factors influencing sensor network designProduction costsThe 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 designHardware constraints

Factors influencing sensor network designSensor network topologyPre-deployment and deployment phasePost-deployment phaseRe-deployment of additional nodes phase

Factors influencing sensor network designEnvironmentBusy intersectionsInterior of a large machineryBottom of an oceanSurface of an ocean during a tornadoBiologically or chemically contaminated fieldBattlefield beyond the enemy linesHome or a large buildingLarge warehouseAnimalsFast moving vehiclesDrain or river moving with current.

Factors influencing sensor network designTransmission 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.Radioinfrared optical media

Factors influencing sensor network designPower ConsumptionSensingCommunicationData processing

Communication architecture of sensor networks

Communication architecture of sensor networksCombine power and routing awareness Integrates date with networking protocolsCommunicates power efficiently through the wireless mediumPromotes cooperative efforts among sensor nodes.

Communication architecture of sensor networksPhysical layer: Address the needs of simple but robust modulation, transmission, and receiving techniques.frequency selection carrier frequency generationsignal detection and propagationsignal modulation and data encryption.

Communication architecture of sensor networksPropagation Effects Minimum output power (dn 2=

Communication architecture of sensor networksOpen research issuesModulation schemesStrategies to overcome signal propagation effectsHardware design: transceiver

Communication architecture of sensor networksData 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 OperationError Control

Communication architecture of sensor networksMedium access controlCreation of the network infrastructure Fairly and efficiently share communication resources between sensor nodesExisting MAC protocols (Cellular System, Bluetooth and mobile ad hoc network)

Communication architecture of sensor networksMAC for Sensor NetworksSelf-organizing medium access control for sensor networks and Eaves-drop-and-register AlgorithmCSMA-Based Medium AccessHybrid TDMA/FDMA-Based

Communication architecture of sensor networksPower Saving Modes of OperationSensor nodes communicate using short data packetsThe shorter the packets, the more dominance of startup energyOperation 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 networksError ControlError 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 networksOpen research issuesMAC for mobile sensor networksDetermination of lower bounds on the energy required for sensor network self-organizationError control coding schemes.Power saving modes of operation

Communication architecture of sensor networksNetwork 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

Maximum available power (PA) route: Route 2Minimum energy (ME) route: Route 1Minimum hop (MH) route: Route 3Maximum minimum PA node route: Route 3Minimum longest edge route: Route 1

Energy Efficient Routes

Communication architecture of sensor networksInterest DisseminationSinks broadcast the interestSensor nodes broadcast the advertisementsAttribute-based namingThe areas where the temperature is over 70oF The temperature read by a certain node

Communication architecture of sensor networksData aggregation

Solve implosion and overlap ProblemAggregation based on same attribute of phenomenonSpecifics (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 networksOpen research issuesNew 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 networksTransport 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 networksOpen research issuesBecause acknowledgments are too costly, new schemes that split the end-to-end communication probably at the sinks may be needed.

Communication architecture of sensor networksApplication 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 networksSensor management protocol (SMP)Introducing the rules related to data aggregation, attribute-based naming, and clustering to the sensor nodesExchanging data related to the locationfinding algorithmsTime synchronization of the sensor nodesMoving sensor nodesTurning sensor nodes on and offQuerying the sensor network configuration and the status of nodes, and reconfiguring the sensor networkAuthentication, key distribution, and security in data communications

Some Other Interesting ApplicationsMIT d'Arbeloff Lab The ring sensorMonitors the physiological status of the wearer and transmits the information to the medical professional over the Internet Oak Ridge National LaboratoryNose-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

iButton

A 16mm computer chip armored in a stainless steel can Up-to-date information can travel with a person or objectTypes of i-ButtonMemory ButtonJava Powered Cryptographic iButtonThermochron iButton

iButton Applications

Caregivers AssistanceDo not need to keep a bunch of keys. Only one iButton will do the workElder AssistanceThey do not need to enter all their personal information again and again. Only one touch of iButton is sufficientThey can enter their ATM card information and PIN with iButtonVending Machine Operation Assistance

iBadge - UCLAInvestigate behavior of children/patientFeatures:Speech recording / replayingPosition detectionDirection detection / estimation(compass)Weather data: Temperature, Humidity, Pressure, Light

iBadge - UCLA

ConclusionApplications of sensor networksFactors influencing sensor network designCommunication architecture of sensor networks