Flow routing for variable bit rate source nodes in energy-constrained wireless sensor networks

We consider a two-tier wireless sensor network and focus on the flow routing problem for the upper tier aggregation and forwarding nodes (AFNs). Assuming each AFN is equipped with directional antennas for transmission, we are interested in how to perform flow routing at each node such that the network lifetime is maximized. We present a flow routing algorithm that is provably to have the following property: (1) When the average source rate of each AFN is known a priori, the flow routing algorithm is optimal and gives maximum network lifetime performance; (2) When the average source rate of each AFN is unknown but is within a fraction of E of an estimated rate value, then the network lifetime given by the proposed flow routing algorithm is no more than 2 epsilon/1-epsilon from optimal. As a result, the proposed flow routing algorithm can provide predictable lifetime performance even when the source bit rate can be time-varying.