Hierarchical multicast in wireless sensor networks with mobile sinks

In most studies of wireless sensor networks (WSNs), sensor nodes and sinks are typically stationary. However, mobile sinks are required in various applications of real-life environments, and delivering sensed data to mobile sinks using ordinary routing protocols is very inefficient. Multicasting is an important process in the minimization of the number of transmissions in WSNs. Since sensor nodes have limited resources, many studies have focused on how to send data to specific receivers efficiently. This work presents a grid-based hierarchical multicast (HM) routing protocol for WSNs with mobile sinks. Location servers (LSs) are adopted to manage the information about the locations of receivers and then a multicast tree is constructed distributively to reduce the update cost and energy consumed by sink mobility. The multicast tree can be shared by multiple sources, reducing the path construction overhead. Furthermore, effective maintenance mechanisms that make the multicast tree more stable and robust are presented. Finally, the performance of the proposed HM is investigated by simulation. Simulation results demonstrate that the proposed protocol has a lower energy consumption and higher multicast efficiency than distributed multicast routing protocol (DMRP) and hierarchical geographic multicast routing (HGMR), especially when many sources and receivers are involved. Copyright (C) 2010 John Wiley & Sons, Ltd.