A signalling method for reducing the bandwidth needed for communicating measurement values from at least a first source base station (11, 12, 13, 14) to at least a 5 first target base station (21, 22, 23, 24, 25) connected through a core base station (10) comprising the steps of—reporting at least a first measurement value from the at least first source base station (11, 12, 13, 14) to the core base station (10), —preferably sorting the measurement values in descending order, 10—including, in the core base station (10) value information about the at least first measurement value in a multicast message, —transmitting the multicast message to the at least first target base station (21, 22, 23, 24, 25), characterized in that the value information is determined as a first difference between a maximum value and the first measurement value.