  Wireless Sensor Networks (WSNs) are increasing to handle complex situations
and functions. In these networks some of the nodes become Cluster Heads (CHs)
which are responsible to aggregate data of from cluster members and transmit it
to Base Stations (BS). Those clustering techniques which are designed for
homogenous network are not enough efficient for consuming energy. Stable
Election Protocol (SEP) introduces heterogeneity in WSNs, consisting of two
type of nodes. SEP is based on weighted election probabilities of each node to
become CH according to remaining energy of nodes. We propose
Heterogeneity-aware Hierarchal Stable Election Protocol (HSEP) having two level
of energies. Simulation results show that HSEP prolongs stability period and
network lifetime, as compared to conventional routing protocols and having
higher average throughput than selected clustering protocols in WSNs.
