wireless sensor network

1、Wireless Sensor Networks34OutlinenIntroductionnApplications of sensor networksnFactors influencing sensor network designnCommunication architecture of sensor networksnConclusion5Introduction A sensor network is composed of a large number of sensor nodes, which are densely deployed either inside the

2、phenomenon or very close to it. nRandom deploymentnCooperative capabilities6Applications of Sensor networks7Applications of sensor networksMilitary applicationsnMonitoring friendly forces, equipment and ammunition(弹药)nMonitoring of opposing forces and terrainnBattlefield surveillancenBattle damage a

3、ssessmentnNuclear, biological and chemical attack detection最早可以追溯二十世纪70年代越战时期使用的传统的传感器系统。胡志明小道胡志明小道热带树热带树轰炸机枪声定位反恐系统11Applications of sensor networksEnvironmental applicationsnForest fire detectionnFlood detectionnPrecision agriculture无人干扰监测鸟 巢海 燕大 鸭 岛沈阳玫瑰园14Applications of sensor networksHealth app

4、licationsnMonitoring of human datanTracking and monitoring patients and doctors inside a hospitalnDrug administration in hospitals15Some Other Interesting ApplicationsnThe ring sensornMonitors the physiological status of the wearer and transmits the information to the medical professional over the I

5、nternet 16Applications of sensor networksHome and other commercial applicationsnHome automation and Smart environmentnInteractive museumsnManaging controlnVehicle tracking and detectionnDetecting and monitoring car thefts18Factors Influencing Sensor Network Design19Factors influencing sensor network

6、 design20WSN constraintsnResource constraintsnlimited energynshort communication rangenlow bandwidthnlimited processing nlimited storagenDesign constraintsnapplication dependentnenvironment dependentnsize of the network / number of nodendeployment schemennetwork topology (obstacle)321Factors influen

7、cing sensor network designnFault TolerancenScalabilitynHardware ConstrainsnSensor Network TopologynEnvironmentnTransmission MedianPower Consumption22Factors influencing sensor network designFault tolerancenFault tolerance is the ability to sustain sensor networknThe fault tolerance level depends on

8、the application of the sensor networks.23Factors influencing sensor network designScalabilitynScalability measures the density of the sensor nodes.nDensity = (R) =(N R2)/AR Radio Transmission Range24Factors influencing sensor network designProduction costsnThe cost of a single node is very important

9、 to justify the overall cost of the networks.nThe cost of a sensor node is a very challenging issue given the amount of functionalities with a price of much less than a dollar.25Components of Sensor Node126Factors influencing sensor network designSensor network topologynPre-deploymentnPost-deploymen

10、tnRe-deployment of additional nodes27Factors 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.nRadioninfrared noptical media28F

11、actors influencing sensor network designPower ConsumptionnSensingnCommunicationnData processing29Communication architecture of sensor networks30Communication architecture of sensor networksnCombine power and routing awareness nIntegrates date with networking protocolsnCommunicates power efficiently

12、through the wireless mediumnPromotes cooperative efforts among sensor nodes.31Communication architecture of sensor networksPhysical layer: simple but robust modulation, transmission, and receiving techniques.nfrequency selection ncarrier frequency generationnsignal detection and propagationnsignal m

13、odulation and data encryption.32Communication architecture of sensor networksnPropagation Effects Minimum output power (dn 2=n4) Ground reflect Multihop in dense sensor net work33Communication architecture of sensor networksData link layer: The data link layer is responsible for the multiplexing of

14、data stream, data frame detection, the medium access and error control. nMedium Access Control nPower Saving Modes of OperationnError Control34Communication architecture of sensor networksMedium access controlnCreation of the network infrastructure nFairly and efficiently share communication resourc

15、es between sensor nodes35Communication architecture of sensor networksMAC for Sensor NetworksnSelf-organizing medium access control for sensor networksnCSMA-Based Medium AccessnTDMA/FDMA-Based36Communication architecture of sensor networksPower Saving Modes of OperationnSensor nodes communicate usin

16、g short data packetsnThe shorter the packets, the more dominance(优势) of startup energynOperation in a power saving mode is energy efficient only if the time spent in that mode is greater than a certain threshold.37Communication architecture of sensor networksError ControlnError control modes in Comm

17、unication Networks (additional retransmission energy cost) Forward Error Correction (FEC) Automatic repeat request (ARQ)nSimple error control codes with low-complexity encoding and decoding might present the best solutions for sensor networks. 38Communication architecture of sensor networksNetwork l

18、ayer:nPower efficiency is always an important consideration.nSensor networks are mostly data centric.nData aggregation is useful only when it does not hinder the collaborative effort of the sensor nodes.nAn ideal sensor network has location awareness.39Communication architecture of sensor networksMa

19、ximum 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 Routes40Communication architecture of sensor networksSeveral Network Layer Schemes for Sensor Networks4

20、1Communication architecture of sensor networksTransport layer:nThis layer is especially needed when the system is planned to be accessed through Internet or other external networks. nTCP/UDP type protocols meet most requirements (not based on global addressing).42Communication architecture of sensor

21、 networksApplication layer: Management protocol makes the hardware and software of the lower layers transparent to the sensor network management applications.nSensor management protocol (SMP)nTask assignment and data advertisement protocol (TADAP)nSensor query and data dissemination protocol (SQDDP)

22、4344Network servicesnLocalizationnSynchronizationnCoveragenCompression and aggregationnSecurity345Network services LocalizationnProblem: ndetermining the nodes location (position) nSolutions:nglobal positioning system (GPS)nSimplenExpensivenoutdoornbeacon (or anchor) nodesndoes not scale well in lar

23、ge networksnproblems may arise due to environmental conditionsnproximity-basednMake use of neighbor nodes to determine their position nthen act as beacons for other nodes346Network services SynchronizationnTime synchronization is important fornrouting npower conservationnLifetimenCooperationnScheduling347Network services CoveragenIs important in evaluating effectivenessnDegree of coverage is application dependentnImpacts on energy conservationnTechniques:nselecting minimal set of active nodes to