A method of acquiring timing advance (TA) for neighbor cells to reduce latency and interruption for inter-cell mobility is proposed. A UE is configured with a set of active cells for fast cell-switching. A neighbor cell in the active set is likely to be UE’s target cell. To reduce handover interruption, the UE acquires and maintains the TA corresponding to the cells in the active set. The UE performs early RACH for potential target cells and obtains the TA of the potential target cells. Once the UE receives handover command indicating one of the active cells as target cell, the UE can complete the handover without performing RACH again.