A small cell communication system is disclosed in which an apparatus (e.g. a central controller) controls allocation of frequency resources in the cells. The apparatus obtains respective information (e.g. RSRP) representing a quality of communication at each user equipment (UE) in the cells; determines, based on the received information, whether a corresponding UE is a subject of interference and, when the corresponding UE is a subject of interference, identifies at least one aggressor causing the interference to that UE. In each cell, the UEs served by that cell are grouped such that UEs having a common aggressor (or common aggressors) are grouped into respective group(s), and any UEs not subject to interference are grouped into another group. The apparatus allocates at least one frequency for each UE based on the respective group into which that UE has been grouped.