7112009 1 An Introduction to Sensor Networks Content Reference

7/11/2009 An Introduction to Sensor Networks MoustafaYoussef Wireless Intelligent Networks Center, Nile University and Alexandria University Content Definition  Applications  Challenges  Reference  Sensor Networks Definition 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  Self-organizing capabilities  Cooperative capabilities  Wireless sensor networks: a survey I.F. Akyildiz, W. Su,Y. Sankarasubramaniam, E. Cayirci, Computer Networks 2002. Sensor Networks Applications  Communication Architecture The sensor nodes are usually scattered in a sensor field  Each of these scattered sensor nodes has the capabilities to collect data and route data back to the sink  Data are routed back to the sink by a multi-hop infrastructureless architecture  The sink may communicate with the task manager node via Internet or satellite  Sensors can sense ◦ ◦ ◦ ◦ ◦ ◦ ◦ ◦ ◦ ◦ Temperature Humidity Vehicular movement Lightning condition Pressure Soil makeup Noise levels Presence or absence of certain kinds of objects Mechanical stress levels on attached objects Current characteristics such as speed, direction, and size of an object 1 7/11/2009 Example of Sensor Networks Data Delivery Models Continuous: sensors communicate their data continuously at a prespecified rate  Event driven: sensors report information only when the event of interest occurs  Observer initiated (request-reply): sensors only reports their results in response to an explicit request from the observer  Hybrid: all three approaches coexist  Sensor Networks Applications  Sensor Networks Applications  Military ◦ Monitoring friendly forces, equipment and ammunition ◦ Reconnaissance of opposing forces and terrain ◦ Battlefield surveillance ◦ Battle damage assessment ◦ Nuclear, biological and chemical attack detection Environmental applications ◦ ◦ ◦ ◦ Forest fire detection Biocomplexity mapping of the environment Flood detection Precision agriculture Sensor Networks Applications  Sensor Networks Applications  Health applications ◦ Tele-monitoring of human physiological data ◦ Tracking and monitoring patients and doctors inside a hospital ◦ Drug administration in hospitals Home and other commercial applications ◦ ◦ ◦ ◦ ◦ Home automation and Smart environment Interactive museums Managing inventory control Vehicle tracking and detection Detecting and monitoring car thefts 2 7/11/2009 Sensor Devices and Applications Berkeley Motes  iBadge - UCLA  MIT d'Arbeloff Lab – The ring sensor  Nose-on-a-chip  Zilog’s eZ80  iButton  Berkeley Motes Small (under 1” square) microcontroller  It consists of:  ◦ Microprocessor ◦ A set of sensors for temperature, light, acceleration and motion ◦ A low power radio for communicating with other motes  C compiler inclusion Berkeley Motes MIT d'Arbeloff Lab – The Ring Sensor An ambulatory, telemetric, continuous health monitoring device developed by d'Arbeloff Laboratory for Information Systems and Technology at MIT  Monitor the physiological status of the wearer and transmit the information to the medical professional over the Internet  Clinical trials have been done in conjunction with Massachusetts General Hospital's Emergency Room, and researchers are now working on commercialization of the ring-sized device. Nose-on-a-chip Nose-on-a-chip is a MEMS-based sensor, developed at Oak Ridge National Laboratory  Can detect 400 species of gases and transmit a signal indicating the level to a central control station  Consists of an array of tiny sensors on one integrated circuit and electronics on another. The chip can be customized to detect virtually any chemical or biological species. 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 18 3 7/11/2009 iButton Applications  iBadge - UCLA   Caregivers Assistance ◦ Do not need to keep a bunch of keys. Only one iButton will do the work Investigate behavior of children/patient Features: ◦ ◦ ◦ ◦ Speech recording / replaying Position detection Direction detection / estimation(compass) Weather data: Temperature, Humidity, Pressure, Light  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 19 20 iBadge - UCLA Content Definition Applications  Challenges   21 Differences from Adhoc Networks Number of nodes Densely deployed Prone to failures Topology changes frequently Mainly use broadcast communication Limited in power, computational capacities, and memory  May not have global identification (ID) because of the large amount of overhead and large number of sensors  Task oriented       Factors Influencing Sensor Network Design Fault Tolerance Scalability  Hardware Constrains  Sensor Network Topology  Environment  Transmission Media  Power Consumption   24 4 7/11/2009 Factors Influencing Sensor Network Design Fault tolerance  Scalability Depending on the application, the number may reach an extreme value of millions. New schemes must be able to work with this number of nodes.  Basically, the density gives the number of nodes within the transmission radius of each node in a region.  Must also utilize the high density of the sensor networks.  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 25  Factors Influencing Sensor Network Design Scalability  Factors Influencing Sensor Network Design Production costs  Density = (R) =(NR2)/A R – Radio Transmission Range 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  27 28 Factors Influencing Sensor Network Design Hardware constraints Sensor Network Topology Pre-deployment and deployment phase, either thrown in as a mass or placed one by one  Post-deployment phase, topology changes are due to change in sensor nodes’ position, reachability, available energy, malfunctioning, and task details  Re-deployment of additional nodes phase, additional sensor nodes can be redeployed at any time to replace malfunctioning nodes or due to changes in task dynamics  29 5 7/11/2009 Factors Influencing Sensor Network Design Environment            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 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 31 32 Factors Influencing Sensor Network Design Power Consumption        Content Definition Applications  Challenges   Sensing Communication Data processing Limited power source Battery lifetime is limited Each sensor node plays a dual role of data originator and data router (data processor) The malfunctioning of a few nodes consumes lot of energy (rerouting of packets and significant topological changes) 33 Communication Architecture of Sensor Networks    Five Layers   Combine power and routing awareness Integrates date with networking protocols Communicates power efficiently through the wireless medium Promotes cooperative efforts among sensor nodes     The physical layer addresses the needs of simple but robust modulation, transmission, and receiving techniques The MAC protocol must be power-aware and able to minimize collision with neighbors’ broadcasts The network layer takes care of routing the data supplied by the transport layer The transport layer helps to maintain the flow of data if the sensor networks application requires it Different types of application software can be built and used on the application layer 35 6 7/11/2009 Three Plans The power management plane manages how a sensor node uses its power  The mobility management plane detects and registers the movement of sensor nodes, so a route back to the user is always maintained, and the sensor nodes can keep track of who their neighbor sensor nodes are  The task management plane balances and schedules the sensing tasks given to a specific region  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 38 Communication Architecture of Sensor Networks Propagation Effects Minimum output power (dn 2=