What?
Localization
is to determine the physical coordinates of a group of sensor nodes in a
wireless sensor network (WSN) due to application context, use of GPS is
unrealistic, therefore, and sensors need to self-organize a coordinate system.
Why?
Localization
is used to report data that is geographically meaningful and Services such as
routing rely on location information; geographic routing protocols;
context-based routing protocols, location-aware services.
In general,
almost all the sensor network localization algorithms share three main phases
} DISTANCE ESTIMATION
} POSITION COMPUTATION
} LOCALIZATION ALGHORITHM
Distance estimation
The distance
estimation phase involves measurement techniques to estimate the relative
distance between the nodes.
} ANGLE OF ARRIVAL method allows each
sensor to evaluate the relative angles between received radio signals
} TIME OF ARRIVAL method tries to
estimate distances between two nodes using time based measures
} TIME DIFFERENT OF ARRIVAL is a method
for determining the distance between a mobile station and nearby synchronized
base station
} THE RECEIVED SIGNAL STRENGTH
INDICATOR techniques are used to translate signal strength into distance.
Position computation
} The Position computation consists of
algorithms to calculate the coordinates of the unknown node with respect to the
known anchor nodes or other neighboring nodes.
} LATERATION
techniques based on the precise measurements to three non collinear
anchors. Lateration with more than three
anchors called multilateration.
} ANGULATION or triangulation is based
on information about angles instead of distance.
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