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1 Introduction
A wireless sensor network is composed of a large number of small and inexpensive
smart sensors for many monitoring, surveillance and control applications.
Each sensor makes its own local observation. All active sensors in the network
coordinate to provide a global view of the monitored area. It is anticipated
that such a network can be used in unattended environments or hostile physical
locations. Applications include habitat monitoring [7, 25], infrastructure
surveillance [40], target tracking in tactical environments [12], etc.
Almost all these applications require sensors to be aware of their physical
locations. For example, the physical positions should be reported together
with the corresponding observations in wildlife tracking, weather monitoring,
location-based authentication, etc [19, 24, 34]. Location information can
also be used to facilitate network functions such as packet routing [9, 23] and
collaborative signal processing [16], in which the complexity and processing
overhead can be substantially reduced. Further, each node can be uniquely
identified with its position, thus exempting the di?±culty of assigning a unique
ID before deployment [36].
However, many challenges exist in designing e?®ective and e?±cient sensor
self-positioning schemes for sensor networks. First, a localization algorithm
must scale well to large sensor networks. Further, the location discovery
scheme should not aggravate the communication and computation overheads
of the network, since low-cost sensors have limited resource budgets such
as battery supply, CPU, memory, etc.
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