Image Processing Reference
In-Depth Information
be handled in a completely distributed manner and it is a necessity for the networking
protocolstoworkevenwhenthenetworkscalesup.
•
Information clustering
: he sensor nodes can be grouped into information clusters based
on the services they can provide. his clustering structure belongs to the distributed ser-
vices layer and is built on top of the geographical clustering. Nodes using this clustering
scheme need not be direct neighbors from the physical point of view.
•
Security clustering
: A even higher hierarchy appears if security is taken into consideration.
Nodescanbegroupedbasedontheirtrustlevelsorbasedontheactionstheyareallowed
toperformorresourcestheyareallowedtouseinthenetwork.
Besides offering increased capabilities to the sensor network, clustering is considered one of the
principal building blocks for the sensor networks also from the point of view of energy consumption.
The overhead given by the energy spent for creating and organizing the sensor network is easily
recoveredinthelongtermduetothereducedtraicitleadsto.
4.3 Data-Centric Architecture
As we previously stated, the layered protocol stack description of the system architecture for a sensing
node cannot cover all the aspects involved (such as cross-layer communication, dynamic update,
etc.). he crossing planes though the protocol stack seems good as a solution, but in reality is almost
difficult to implement. Establishing communication between the blocks in the protocol stack on a
dynamic basis, being flexible with respect to the types of data being available at a certain moment
inside the node and tolerating misbehaving blocks (correctly designed but producing unusable data
due to effects of dynamics of the environment, mobility, out-of-date software, etc.) are some of the
constraints affecting the design of a software architecture.
In this section we propose a new flexible architecture design. he architecture was designed having
environmental dynamics in mind and is aimed at ofering maximum flexibility while still adhering to
the basic design concept of sensor networks: the devices should adapt at run time with the main goal
of keeping the network alive, under a variety of conditions (the designer being probably unaware of
most of them at design time).
4.3.1 Motivation
The sensor networks are dynamic from many points of view. Continuously changing behaviors can
be noticed in several aspects of sensor networks, some of them being:
•
Sensing process
: he natural environment is dynamic by all means (the basic purpose of
sensor networks is to detect, measure, and alert the user of the changing of its parameters).
The sensor modules themselves can become less accurate, need calibration, or even break
down.
•
Network topology
: One of the features of the sensor networks is their continuously chang-
ing topology. here are a lot of factors contributing to this, such as failures of nodes or the
unreliable communication channel, mobility of the nodes, variations of the transmission
ranges, clusters reconfiguration, addition/removal of sensor nodes, etc. Related to this
aspect, the algorithms designed for sensor networks need to have two main characteris-
tics: they need to be independent on the network topology and need to scale well with
the network size.
•
Available services
: Mobility of nodes, failures, or availability of certain kinds of nodes
might trigger reconfigurations inside the sensor network. he functionality of nodes may
