less Sensor Networks

This work presents a class of unidirectional lifting-based wavelet transforms for an arbitrary communication graph in a wireless sen-sor network. These transforms are unidirectional in the sense that they are computed as data is forwarded towards the sink on a routing tree. We derive a set of conditions under which a lifting transform is unidirectional, then find the full set of those transforms. Among this set, we construct a unidirectional transform that allows nodes to transform their own data using data forwarded to them from their de-scendants in the tree and data broadcasted to them from their neigh-bors not in the tree. This provides a higher quality data representa-tion than existing methods for a fixed communication cost