  The applications require coverage of the whole monitored area for long
periods of time. Clustering is a way to reduce communications, minimize energy
consumption and organize messages among the cluster head and their members. The
message exchange of communication and data transmission between the different
sensor nodes must be minimized to keep and extended the lifetime of the network
because of limited energy resources of the sensors. In this paper, we take into
consideration the problem isolated nodes that are away from the cluster head
(CH) and by consequence or CH is not within the reach from these nodes. To
solve this problem, we propose O-LEACH (Orphan Low Energy Adaptive Clustering
Hierarchy) a routing protocol that takes into account the orphan nodes. Indeed,
a cluster member will be able to play the role of a gateway which allows the
joining of orphan nodes. Our contribution is to election a cluster head that
has enough energy for a better now to coordinate with these member nodes and
maintain the full coverage for applications which requires of useful data for
the entire area to be covered. The simulation results show that O-LEACH
performs better than LEACH in terms of connectivity rate, energy, scalability
and coverage.
