Wireless Sensor Network

APPLICATIONS OF SENSOR NETWORKS

•    Many applications share some basic characteristics. There is a clear difference between sources of data - the actual nodes did sense data - and sinks - nodes where the  data Should be delivered to.
•     The sinks are sometimes part of the Sensor Network; some times they are CLEARLY system "outside" the network.
•   So, there are Usually, but not always, more sources than sinks and the sink is oblivious or not interested in the identity of the sources; The data itself is much more important.
•   The interaction patterns between sources and sinks show some typical patterns. 
• The most relevant ones are:

     EVENT DETECTION 

                           Sensor nodes Should report to the sink (s) once theyhave detected the occurrence of a specified event.

•     The simplest events can be detected locally by a single sensor node in isolation (eg a temperature threshold is exceeded); more complicated types of events require the collaboration of nearby or even remote sensor to decide Whether a (composite) event  has occurred (eg a temperature gradient Becomes too steep). 
•         If several different events can Occur, event classification Might Be on additional issue.

   PERIODIC MEASUREMENTS

                                                        Sensor can be tasked with Periodically reporting Measured values.

                                                      Often, synthesis reports can be triggered by a detected event; The reporting period is application dependent.

     FUNCTION APPROXIMATE AND EDGE DETECTION

•       The way a physical value like temperature changes from one place to another can be Regarded as a function of location. 
•        A WSN can be used to approximate this unknown function (to extract its spatial characteristics), using a limited number of samples taken at each individual sensor node. 
•     This approximate mapping Should be made available at the sink. How and when to update this mapping depends on the application's needs, as do the approximation accuracy and the inherent trade-off against energy consumption. 
•      Similarly, a relevant problem can be to find areas or points of the same value Given. 
•      This can be generalized to finding "edges" in search functions or to sending messages along the boundaries of Patterns in Both Space and / or time.

  

    TRACKING

•   The source of an event can be mobile (eg to intruder in surveillance scenarios).
•       The WSN can be used to report updates on the event source's position to the sink (s), potentially with estimates about speed and direction as well.
•      These interactions can be scoped Both in time and in space (reporting events only within a Given timespan, only from Certain areas, and so on).
•      These requirements can thus change dynamically over time; Sinks have to have a Means to inform the sensor of Their requirements at runtime.
•     More Over, thesis interactions can take place only for one specific request of a sink or They Could be long-lasting relationships between many sensors and many sinks.
•     In addition, sensor nodes can be mobile Themselves and compensate_for_errors Shortcomings in the deployment process by moving into a post-deployment phase, to position search did Their sensing tasks can be better Fulfilled.
•       They Could therefore be mobile Because They are attached to other objects and the network has to adapt itself to the location of nodes.