A communication system comprising: a first base station that forms a first cell; a second base station that forms a second cell; a third base station that forms a third cell; and an identifier assignment device that is configured to assign an identifier for identifying the second cell, wherein the identifier assignment device is part of a centralized self organizing network, SON, function of an operations, administration and maintenance, OAM, system, wherein: the first cell, which is not connected to the SON function, is a neighbor cell of the second cell; the third cell is a neighbor cell of the first cell; the second cell and the third cell are connected to an element management system, EMS, having the SON function; the first base station is configured to transmit first neighbor cell information, containing identifier information of neighbor cells of the first cell to the second base station; the second base station is configured to transmit the first neighbor cell information, received from the first base station, and second neighbor cell information, containing identifier information of neighbor cells of the second cell, to the identifier assignment device; the third base station is configured to transmit third neighbor cell information, containing identifier information of neighbor cells of the third cell, to the identifier assignment device directly or through another base station that is connected to the identifier assignment device; and the identifier assignment of the identifier of the second cell is based on the third neighbor cell information, on the second neighbor cell information, and on the first neighbor cell information; wherein the identifier assignment device is configured to assign the identifier of the second cell by: creating an identifier candidate list containing only those identifiers that are not allocated to a cell in the first, second, and third neighbour cell information; determining an identifier to be assigned to the second cell from the identifier candidate list; and notifying the selected identifier to the second base station. a first base station that forms a first cell; a second base station that forms a second cell; a third base station that forms a third cell; and an identifier assignment device that is configured to assign an identifier for identifying the second cell, wherein the identifier assignment device is part of a centralized self organizing network, SON, function of an operations, administration and maintenance, OAM, system, wherein: the first cell, which is not connected to the SON function, is a neighbor cell of the second cell; the third cell is a neighbor cell of the first cell; the second cell and the third cell are connected to an element management system, EMS, having the SON function; the first base station is configured to transmit first neighbor cell information, containing identifier information of neighbor cells of the first cell to the second base station; the second base station is configured to transmit the first neighbor cell information, received from the first base station, and second neighbor cell information, containing identifier information of neighbor cells of the second cell, to the identifier assignment device; the third base station is configured to transmit third neighbor cell information, containing identifier information of neighbor cells of the third cell, to the identifier assignment device directly or through another base station that is connected to the identifier assignment device; and the identifier assignment of the identifier of the second cell is based on the third neighbor cell information, on the second neighbor cell information, and on the first neighbor cell information; the first cell, which is not connected to the SON function, is a neighbor cell of the second cell; the third cell is a neighbor cell of the first cell; the second cell and the third cell are connected to an element management system, EMS, having the SON function; the first base station is configured to transmit first neighbor cell information, containing identifier information of neighbor cells of the first cell to the second base station; the second base station is configured to transmit the first neighbor cell information, received from the first base station, and second neighbor cell information, containing identifier information of neighbor cells of the second cell, to the identifier assignment device; the third base station is configured to transmit third neighbor cell information, containing identifier information of neighbor cells of the third cell, to the identifier assignment device directly or through another base station that is connected to the identifier assignment device; and the identifier assignment of the identifier of the second cell is based on the third neighbor cell information, on the second neighbor cell information, and on the first neighbor cell information; wherein the identifier assignment device is configured to assign the identifier of the second cell by: creating an identifier candidate list containing only those identifiers that are not allocated to a cell in the first, second, and third neighbour cell information; determining an identifier to be assigned to the second cell from the identifier candidate list; and notifying the selected identifier to the second base station. creating an identifier candidate list containing only those identifiers that are not allocated to a cell in the first, second, and third neighbour cell information; determining an identifier to be assigned to the second cell from the identifier candidate list; and notifying the selected identifier to the second base station.