A UE (10) provides information on potential S′eNB(s). The information is forwarded from an MeNB (20_1) to an M′eNB (20_2) such that the M′eNB (20_2) can determine, before the handover happens, whether the M′eNB (20_2) will configure a new SeNB (S′eNB) and which S′eNB the M′eNB (20_2) will configure. In one of options, the MeNB (20_1) derives a key S′-KeNB for communication protection between the UE (10) and the S′eNB (30_1), and send the S′-KeNB to the M′eNB (20_2). In another option, the M′eNB (20_2) derives the S′-KeNB from a key KeNB* received from the MeNB (20_1). The M′eNB (20_2) sends the S′-KeNB to the S′eNB (30_1). Moreover, there are also provided several variations to perform SeNB Release, SeNB Addition, Bearer Modification and the like, in which the order and/or timing thereof can be different during the handover procedure.