  Wireless Sensor Networks need to be organized for efficient data collection
and lifetime maximization. In this paper, we propose a novel routing structure,
namely k-DAG, to balance the load of the base station's neighbours while
providing the worst-case latency guarantee for data collection, and a
distributed algorithm for construction a k-DAG based on a SPD (Shortest Path
DAG). In a k-DAG, the lengths of the longest path and the shortest path of each
sensor node to the base station differ by at most k. By adding sibling edges to
a SPD, our distributed algorithm allows critical nodes to have more routing
choices. The simulation results show that our approach significantly
outperforms the SPD-based data collection approach in both network lifetime and
load balance.
