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get ecient network communication. With the use of fuzzy-logic, we expect to
get successful results in terms of network organization time and number of hops
from any node to the base station, always choosing the best parent in terms of
energy and number of hops to the sink.
5.1 Fuzzy-Logic-Based Routing
NORIA is an algorithm capable of route data in a network by creating a com-
munication tree. The process starts at the base station and it is then propagated
hop by hop until covering all the network nodes. Node conditions are evaluated
by using a fuzzy-logic-based mechanism, and only those nodes with better state
(battery, number of hops to the sink) act as data forwarders (parent nodes).
The algorithm establishes minimum paths, in terms of energy spending, from
every node to the base station, which gathers data coming from all the network
nodes. Roles are assigned to network nodes in order to balance the network
load. These roles are
leaf
: nodes that sense the environment and send data to
the base station, and
master
: nodes that as well as performing
leaf
node tasks,
also forward data from other nodes to the base station.
In order to perform network organization through parent election and role
assignment, NORIA stores neighboring data in a neighbor table, and uses the
output of a fuzzy-logic system as a metric to make decisions.
NORIA defines four kinds of messages in order to organize the network and
send collected data. These messages are: IPM (Information Propagation Mes-
sage), which includes local information; RDM (Role Decision Message), which
informs about selected role, MRM (Master Request Message), to request neigh-
bor role changing, and DM (Data Message), which includes requested and/or
forwarded data.
The algorithm consists of two stages: first, the algorithm organizes the network
by creating the communication tree, which is routed at the base station, and by fix-
ing as forwarder master nodes those with better conditions. The second stage is still
being developed, and performs periodical verification, which includes, if necessary,
role migration in order to provide load balancing and to avoid node overloading.
In the first stage of the algorithm, the communication tree is created and roles
are assigned to nodes. The organization procedure starts when the base station
sends an RDM. Nodes that receive this message send an IPM and start a timer.
In this period of time, they wait for information messages from neighboring
nodes. When the timer has expired, nodes perform parent election and make the
role decision. An MRM is sent in case of the elected parent having a
leaf
role.
Once the role has been decided, the nodes send an RDM to induce next-hop
neighbors to start the organization phase.
The input variables to be considered in this experiments are: the number of
hops to reach the base station, and the remaining energy. This parameters are an
example of the full set of parameters which can be also included in the decision
process (delivery probability, delay, signal strength... among others). The output
variable represents the suitability of the node to be selected as parent node.
Figure 2 shows fuzzy sets for input and output parameters.
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