Equitable Energy Consumption during Repeated Transmissions in a Multihop Wireless Network

This paper addresses the issue of network life during repeated broadcasts originating from the same source in large, strip-shaped wireless sensor networks. The proposed technique would also apply to a unicast over a strip-shaped cooperative route within a network. The proposed medium access control (MAC)-free "alternating sets" transmission strategy is based on a very low- overhead form of cooperative diversity called the opportunistic large array (OLA). The proposed alternating OLA with transmission threshold (A-OLA-T) uses a received power-based threshold to define mutually exclusive sets of nodes, such that the union of the sets includes all the nodes in the network or cooperative route during the initial broadcast. A-OLA-T alternates the set of cooperators (or OLAs) during successive transmissions to reduce the energy consumption and the duty cycles of nodes (measured in terms of the percentage time a node is on and transmitting), thereby avoiding the formation of "hot spots" (regions of overuse, high energy consumption, and traffic) in the network. Under the continuum assumption (very high node density) for two-dimensional strip networks (or routes), we obtain lower bounds (as a function of the number of alternating sets, m) on the node degree for achieving optimal load balancing in the network, and, consequently, prolonging the network life.