The formulation has the following constraints: (c1) is a constraint which imposes that the total traffic from each node is equal to the data sources generation rate b, (c2) is a constraint which guarantees that the upper limit of the flow rate on each link should not exceed the link capacity Q, (c3) is a constraint which ensures that the consumed energy will not exceed the initial energy Ei stored in each node, (c4) is a constraint which imposes that the delay should not go above the maximum limit imposed by user/application requirements Dmax, and (c5) is a constraint which imposes that the flow rate is always positive.
There are two different conflicting objectives optimized in this model. The first objective is the energy minimization to prolong the network lifetime, while the second objective is the delay minimization for fast delivery of the data. Weights are assigned to each objective based on its importance and they change from one iteration to another until the optimal solution is reached.