Comparison of Cell-Based and Topology Control-Based Energy Conservation in Wireless Sensor Networks

In this chapter we compare the effectiveness of two popular energy conservation strategies, namely topology control protocols and cooperative cell-based approaches, to reduce the energy consumption, and thus extend the lifetime, of wireless sensor networks. To this end, we define a realistic (although necessarily idealized in some respects) and unified framework of investigation. Using this framework, we prove lower bounds on network lifetime for cell-based cooperative strategies with node densities that are known to be sufficient to ensure a connected network. We also perform a number of simulation experiments, under a traffic model specifically designed for sensor networks, to evaluate and compare cell-based approaches with topology control. This is the first attempt at a comprehensive understanding of the conditions under which one of these approaches outperforms the other. Indeed, our study reveals a number of properties of the techniques investigated, some of which are not at all obvious. As expected, cell-based cooperative approaches, which completely power down network interfaces of certain nodes for extended time periods, produce longer network lifetimes when node density is very high. However, even with moderately high density of nodes, cell-based approaches do not significantly extend lifetime when it is defined in terms of connectivity. While it is not surprising that cell-based approaches do not extend lifetime under low density conditions, we find that topology control techniques can significantly increase network lifetime under those conditions and, in fact, they substantially outperform cooperative approaches in this respect. More details on the precise findings can be found in Section 31.7.