Abstract: When optimising the performance of the network, first of all, the relevant key performance indicators for a specific entity within the network as well as first parameters, which influence the key performance indicators, are determined. A number of entities similar to said specific entity is selected, wherein relevant key performance indicators are associated to every entity. The key performance indicators as well as the selected number of entities are used as elements in a first cost function, i.e. said first cost function is calculated on the basis of the KPI and the number of entities. Said first cost function is calculated in order to evaluate the network performance. Accordingly, since said first parameters directly relate to the key performance indicators, the network performance will depend on the values of said first parameters.