Wassim JERBI¹, Abderrahmen GUERMAZI¹ and Hafedh TRABELSI², ¹Higher Institute of Technological Studies, Tunisia and ²University of Sfax, Tunisia.

The hierarchical routing protocol LEACH (Low Energy Adaptive Clustering Hierarchy) is referred to as the basic algorithm of distributed clustering protocols. LEACH allows clusters formation. Each cluster has a leader called Cluster Head (CH). The selection of CHs is made with a probabilistic calculation. It is supposed that each non-CH node join a cluster and becomes a cluster member. Nevertheless, some CHs can be concentrated in a specific part of the network. Thus several sensor nodes cannot reach any CH. As a result, the remaining part of the controlled field will not be covered; some sensor nodes will be outside the network. 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. If a gateway node has to connect a important number of orphan nodes, thus a sub-cluster is created and the gateway node is considered as a CH’ for connected orphans. As a result, orphan nodes become able to send their data messages to the CH which performs in turn data aggregation and send aggregated data message to the CH. The WSN application receives data from the entire network including orphan nodes. The simulation results show that O-LEACH performs better than LEACH in terms of connectivity rate, energy, scalability and coverage.

WSNs; routing; LEACH; O-LEACH; Orphan nodes; sub-cluster; gateway; CH’