A base station identifier management method comprising steps performed in a Self Organizing Network, SON, server, comprising: receiving (370, 410) a first Neighbor Relation Table, NRT, including first macro base station information from a first pico base station, wherein the first pico base station is located within a macro cell managed by a first macro base station; comparing (380, 430) the first NRT with a second NRT of a second pico base station that is previously stored; determining, based on a result of the comparison, whether a PCI of the first pico base station and a PCI of the second base station is same; and reallocating (390, 470), if the PCI of the first pico base station and the PCI of the second base station is same, new PCIs to the first pico base station and the second pico base station having the same PCI, wherein said reallocating comprises: checking second macro base station information included in the second NRT of the second pico base station using same PCI as the PCI of the first pico base station; determining whether the second macro base station information matches the first macro base station information included in the first NRT; and reallocating (390, 470), upon determining that the second macro base station information matches the first macro base station information included in the first NRT, the new PCIs to the first pico base station and the second pico base station having the same PCI. receiving (370, 410) a first Neighbor Relation Table, NRT, including first macro base station information from a first pico base station, wherein the first pico base station is located within a macro cell managed by a first macro base station; comparing (380, 430) the first NRT with a second NRT of a second pico base station that is previously stored; determining, based on a result of the comparison, whether a PCI of the first pico base station and a PCI of the second base station is same; and reallocating (390, 470), if the PCI of the first pico base station and the PCI of the second base station is same, new PCIs to the first pico base station and the second pico base station having the same PCI, wherein said reallocating comprises: checking second macro base station information included in the second NRT of the second pico base station using same PCI as the PCI of the first pico base station; determining whether the second macro base station information matches the first macro base station information included in the first NRT; and reallocating (390, 470), upon determining that the second macro base station information matches the first macro base station information included in the first NRT, the new PCIs to the first pico base station and the second pico base station having the same PCI. checking second macro base station information included in the second NRT of the second pico base station using same PCI as the PCI of the first pico base station; determining whether the second macro base station information matches the first macro base station information included in the first NRT; and reallocating (390, 470), upon determining that the second macro base station information matches the first macro base station information included in the first NRT, the new PCIs to the first pico base station and the second pico base station having the same PCI.