Grid-Based Group Communication Protocol for Mobile Sink Groups in WSNs

The mobility model of a mobile sink group typically consists of two movement behaviors as follows: a micro-level movement behavior and a macro-level one. In the micro-level, mobile sinks randomly move within a geographically restricted region while all the member sinks in the macro level collectively and slowly move together toward with similar direction. Recently, a group communication protocol has been proposed to support the mobile sink group. It exploits both data dissemination by restricted flooding within the group region for the micro-level movement and periodical updates of the group region to the source for the macro-level movement. However, such mechanism might causes the excessive energy consumption of sensor nodes due to the frequent flooding for both location requests of a leader sink for the group region calculation and data dissemination within the group. Also, since it calculates the group region through current location of member sinks, the group region might be moved in the macro-level even if only a sink moves in the micro-level in practice. It might bring frequent updates of the group information to the long-distance source. In this paper, we propose an energy-efficient group communication protocol that disseminates data without both the flooding and the group region calculation. In the proposed protocol, data of the source is only disseminated to grid headers of virtual grid structure in the group instead of all sensor nodes in the group, and then each member sink directly gets the data from the closest grid header. As the group region update performs locally in grid- level, the communication cost would be significantly reduced. Simulation results demonstrate that the proposed protocol has lower energy consumption than the previous one.