A communication apparatus for predicting effects of changes in at least one radio network parameter on a cellular network, the apparatus comprising one or more processors adapted to: (a) select a first cell in a cellular network; (b) select, from among a first plurality of cells being neighbors of said first cell, a second plurality of neighboring cells thereby defining a reference cluster that includes said first cell and said second plurality of cells, wherein cells are selected from among the first plurality of cells to belong to the second plurality of cells if: (i) a number of handovers carried out from said first cell to each of said selected second plurality of cells within a pre-defined period of time, divided by a total number of handovers carried out from said first cell to all of its neighboring cells belonging to the first plurality of cells within that pre-defined period of time exceeds a pre-defined threshold; and/or (ii) a geographical distance extending between said first cell and each of the selected second plurality of cells is equal to or less than a predetermined value; and (c) using said reference cluster to predict the effect of carrying out one or more changes in at least one radio network parameter on at least one network performance indicator of said reference cluster, and based on said prediction, establishing an expected impact of the one or more changes in the at least one radio network parameter on a cellular network performance. (a) select a first cell in a cellular network; (b) select, from among a first plurality of cells being neighbors of said first cell, a second plurality of neighboring cells thereby defining a reference cluster that includes said first cell and said second plurality of cells, wherein cells are selected from among the first plurality of cells to belong to the second plurality of cells if: (i) a number of handovers carried out from said first cell to each of said selected second plurality of cells within a pre-defined period of time, divided by a total number of handovers carried out from said first cell to all of its neighboring cells belonging to the first plurality of cells within that pre-defined period of time exceeds a pre-defined threshold; and/or (ii) a geographical distance extending between said first cell and each of the selected second plurality of cells is equal to or less than a predetermined value; and (c) using said reference cluster to predict the effect of carrying out one or more changes in at least one radio network parameter on at least one network performance indicator of said reference cluster, and based on said prediction, establishing an expected impact of the one or more changes in the at least one radio network parameter on a cellular network performance. (i) a number of handovers carried out from said first cell to each of said selected second plurality of cells within a pre-defined period of time, divided by a total number of handovers carried out from said first cell to all of its neighboring cells belonging to the first plurality of cells within that pre-defined period of time exceeds a pre-defined threshold; and/or (ii) a geographical distance extending between said first cell and each of the selected second plurality of cells is equal to or less than a predetermined value; and (c) using said reference cluster to predict the effect of carrying out one or more changes in at least one radio network parameter on at least one network performance indicator of said reference cluster, and based on said prediction, establishing an expected impact of the one or more changes in the at least one radio network parameter on a cellular network performance.