A user equipment performs downlink measurement on neighbour cells, but the measurement performance on a target cell (in terms of measurement period/sampling/accuracy etc) is dependent on the relative performance difference between the target cell and a reference cell. The reference cell may be the serving cell, or may be the strongest cell. The network is thus able to keep track of the required number of target cells without degrading the measurement performance of important cells. The UE on the other hand is still able to save its battery as much as possible while making full use of DRX.