When deploying sensors in the field in order to collect useful information,
one of the most important issues is how to prolong the lifetime of the network
because of energy constraint of the sensors while guaranteeing that every
point in the network is covered. In this paper, we propose the formulation of integer
linear programming (ILP) model to find the optimal network flow in the
sensor fields in order to maximize the network lifetime while maintaining the
coverage and connectivity. By dividing the network into grid structure, the problem
can become manageable in size and complexity thus can be applied to large
network with high number of nodes. The experimental results show that our proposed
scheme outperforms previous protocols in terms of coverage lifetime.