Many routing protocols based on clustering method for
WSNs have appeared in the literature. LEACH (Low Energy
Clustering Hierarchy) [2] is the first protocol proposed by W.
R.Heinzelman et. Al to minimize the energy consumption in
WSNs. In this clustering approach, each cluster contains a
Cluster-head which is selected among sensor nodes circularly
randomly. LEACH protocol operates in two phases; the Setup
State and the Steady State. During the set-up phase [3], each
sensor node tries to select itself as a cluster head according to
probability model. Each sensor node chooses a random number
between 0 and 1. The sensor node selects itself as a cluster
head for current round if the random generated number is less
than the threshold T (n). The steady phase [4] consists of the
transmission the data to the cluster head which processes
the data and further send it directly to the base station. A new
round begins after reaching all the data by the base station.
LEACH protocol avoids many problems but it still has some
restrictions such as stochastic selection of cluster heads and
choosing low energy nodes as cluster heads. To overcome
these drawbacks, many improved versions of LEACH protocol
are appeared.