Abstract
This paper studies the problem of constructing maximum-lifetime data gathering trees in sensor networks in which the power level of each sensor is adjustable and in-network data aggregation is used in the process of forwarding sensor data toward the base station. The network model considered in this paper is more general than the model considered in previous work that take the same approach. Under this more general model, this paper derives a lower bound on the normalized load of the optimal data gathering tree. An algorithm is developed to iteratively improve the lifetime of an initial tree until no improvement can be made to any heavily loaded node. The worst case computational complexity of the algorithm is shown to be polynomial.