1. A spectrum manager for allocating a shared frequency spectrum in a wireless communication system having a plurality of base stations for wireless communication with terminals, the plurality of base stations being operated by at least two operators, the spectrum manager configured to: group the plurality of base stations into clusters based on spectrum demand related information; and determine a spectrum partition pattern for each cluster based on the spectrum demand related information and information of the grouped based station clusters, a spectrum partition pattern specifying the partition and allocation of frequency spectrum fragments to the at least two operators in a corresponding cluster of the wireless communication system, wherein a frequency spectrum fragment is allocated to only one of the at least two operators in each cluster, and forward information regarding the spectrum partition pattern to the plurality of base stations or to one or a plurality of network entities of the at least two operators; classify the base stations of each cluster into inner base stations and edge base stations, inner base stations being base stations inside the respective cluster without being affected by co-channel interference, and edge base stations being base stations located in an edge area of the respective cluster being affected by co-channel interference, an edge area of a cluster being the area which overlaps with at least one edge area of a neighboring cluster; categorize, for each edge base station, the frequency spectrum fragments, into different types of frequency spectrum fragments according to the spectrum partition patterns of all neighboring clusters of each edge base station, wherein said different types of frequency spectrum fragments comprise a first type of frequency spectrum fragments which are used by the operator of the edge base station in the neighboring clusters, a second type of frequency spectrum fragments which are used by different operators, including the operator of the concerned edge base station, in the neighboring clusters and a third type of frequency spectrum fragments which are not used by the operator of the edge base station in the neighboring clusters; forward, to each edge base station, information about spectrum partition patterns allocated to all neighboring clusters of the respective edge base station in order to enable the edge base stations to classify the fragments of the allocated spectrum partition patterns into different types depending on the spectrum partition patterns allocated to the neighboring clusters; and partition frequency spectrum fragments of the second type into sub-fragments, and allocate the different sub-fragments to the edge base stations of respective different operators.