In this paper we consider a WSN comprising homogeneous static sensor nodes. The sink can be static or mobile (for details see Section 2), and can be placed at different locations in the WSN. In the case of a static sink, nodes located in the vicinity of the sink deplete their energy (and die) much earlier compared to the nodes located farther away from the sink due to higher data relaying load. In order to address this issue, sink mobilization has been introduced, where the sink moves along a certain path through the network (see Section 2.2). It has also been shown that in most cases sink mobility helps in balancing the routing load and hence energy dissipation of the nodes [7] and [8].