“…Although there is active research on maximizing network lifetime (see, e.g., [1,3,9,19]) or network capacity (see, e.g., [6,10,13,15,20]), most of these efforts consider a sensor network under a given physical topology. Indeed, the location problems for base stations have been very difficult to analyze (shown to be NP-complete in [2]) and only very special cases have been investigated for optimal placement, e.g., single-hop communication between sensor node and base station [11] or special grid topology [2].…”