When a handover is to be performed of a user equipment from a serving radio base station to a target radio base station, it is ensured before the handover that the user equipment is operating in a MIMO mode that is supported by the serving radio base station and by the target radio base station. This can be done by comparing a first mode list, which includes potential MIMO modes jointly supported by the user equipment and the serving radio base station, and a second mode list, which includes potential MIMO modes jointly supported by the user equipment and the target radio base station, to form a common mode list.