The invention relates to sharing a radio spectrum between a first radio system and a second radio system which co-exist so that the radio spectrum is shared at least locally. A radio access point of the first radio system is provided with information on the co-existing second radio system and the constraints it causes to user terminals operating in the service area of the radio access point. The radio access point may retrieve or obtain information about the other radio system by any appropriate, such from a centralized database. Based on the information the radio access point creates and broadcasts beacon or control information to user terminals operating in the service area of the radio access point, to thereby enable the user terminals to adjust their operation so that they can co-exist with the second radio system. Thus, there are two processes: information retrieval about another (second) system and signalling of the spectrum sharing information.