Employing a Novel Two Tiered Network Structure to Extend the Lifetime of WSNs

Applications in wireless sensor networks (WSNs) experience the energy hole problem, i.e., nodes closer to the base station drain their energy much faster than nodes that are far from the base station; accordingly, the network lifetime is reduced. Recently, Medidi and Zhou have proposed a DDC approach to address the energy hole problem by assigning different duty cycles for nodes in different coronas. However, they do not consider how to balance the energy consumption between nodes in a corona and guarantee high packet delivery. In this paper, we describe TTNS, a novel two tiered network structure approach to prolong the network lifetime. TTNS defines the network as two tiers of coronas and sub-corona slices. With the proposed network structure, we balance energy consumption of nodes not only in every corona, but also in every slice within each corona. Moreover, a high packet delivery to the base station is also achieved by employing our clockwise packet routing method (an add-on algorithm for TTNS). Comprehensive computer simulations show that our schemes, TTNS and CWPR, balance the energy consumption between the nodes in the network; hence, they can extend network lifetime by 19.5% longer than DDC and maintain an average packet delivery ratio up to 87.4%.