Clearly, the untethered and unattended nature of sensors constrain their actions as individual devices, since they must independently and efficiently utilize their limited energy resources. However, designing sensor network solutions that only optimize energy consumption will not always lead to efficient architectures, since the above constraints do not account for collaborative trade-offs between groups of sensors. Note that collaborative interaction among sensors provides some network-wide benefits (as opposed to “energy” benefits to individual sensors), where network-wide is a semantic term referring to overall goals of the entire network or to a sufficiently large group of sensors. Consider, for example, collaborative data mining/information fusion among sensors to respond meaningfully to queries [5,6]. Too many sensors simultaneously participating in the collaborative decision making required for aggregation of mined data will lead to excessive routing paths in the network, thereby increasing energy consumption and competition for communication resources. On the other hand, too little collaborative data aggregation will make distributed mining inaccurate and ineffective. Thus, sensors are implicitly constrained by a third factor: to increase information utilization of the network, sensors must cooperate to maximize network-wide objectives while maximizing their individual lifetimes. We label this paradigm for broad sensor network operation as sensor-centric.
