Hamidreza TAVAKOLI†a) , Student Member and Majid NADERI †b) , Nonmember
SUMMARYOptimizing lifetime of a wireless sensor network has received considerable attention in recent years. In this paper, using the feasibility and simplicity of grid-based clustering and routing schemes, we investigate optimizing lifetime of a two-dimensional wireless sensor network. Thus how to determine the optimal grid sizes in order to prolong network lifetime becomes an important problem. At first, we propose a model for lifetime of a grid in equal-grid model. We also consider that nodes can transfer packets to a grid which is two or more grids away in order to investigate the trade-off between traffic and transmission energy consumption. After developing the model for an adjustable-grid scenario, in order to optimize lifetime of the network, we derive the optimal values for dimensions of the grids. The results show that if radio ranges are adjusted appropriately, the network lifetime in adjustable-grid model is prolonged compared with the best case where an equal-grid model is used. key words: wireless sensor networks (WSNs), radio range adjustment, network lifetime, energy consumption, grid lifetime
IntroductionWireless sensor nodes have emerged as a result of recent advances in Micro-Electro-Mechanical Systems (MEMS) technology which results in low power transceiver design and wireless sensor technology. These nodes can form a network in an ad hoc fashion and are electrically powered by only one or two small batteries. It is infeasible to replace batteries of nodes due to the large number of nodes and possibly harsh terrain and hostile environment in which they are deployed. Therefore, the most important problem in these networks is to perform its operations in an efficient manner to prolong their lifetimes. According to different application scenarios, the network lifetime can be defined as the time duration before 1) the first node dies, 2) the power of a certain percentage of active nodes drops below a threshold or 3) a loss of coverage occurs in the network due to mobility or failure of some nodes [8]. In this paper, we assume network lifetime is time span from the instant when the network is deployed to the instant when the first grid dies i.e. the power of all sensor nodes in the grid drops below a threshold.There are two major communication techniques for transmitting data from a source to a sink: single-hop communication and multi-hop communication [4]. In multi-hop communications, nodes next to sink nodes have to relay much more traffic than far from sink ones because in addi- tion to their own traffic, they have to relay other nodes' traffic. Therefore, the energy dissipation speed of these nodes is greater than that of the other nodes, and their batteries deplete more rapidly. However, in single-hop communications, nodes far from sink experience high energy drainage because of higher distances. Hence, this highly non-uniform energy usage causes some sensors to die earlier than others resulting in severe degradation of n...