軟切換
宏分集:"Macro diversity" is a operation state in which a User
Equipment simultaneously has radio links with two or more
UTRAN access points for the sole aim of improving quality of
the radio connection or providing seamless handover.
活動集:“ Active Set” Set of radio links simultaneously
involved in a specific communication service between an User
Equipment and a UTRAN access point
硬切換流程(RNC內)1. Radio Link Setup Request
2. Radio Link Setup Response
3 ALCAP ub Data Transport Bearer Setup
4. Downlink Synchronisation
5.Uplink Synchronisation
6.DCCH : Physical Channel Reconfiguration
7. Radio Link Failure Indication
8. DCCH : Physical Channel Reconfiguration Complete
9. Radio Link Deletion Request
10. Radio Link Deletion Response
11. ALCAP Iub Data Transport Bearer Release
前向切換(Forward Handover)是UE發起的切換包括CELL UPDATE和URA UPDATE過程。其中，URA UPDATE過程只用于處于URA_PCH狀態的UE進行URA重選，以及檢查RRC連接是否正常。
對于CELL_FACH和CELL_PCH狀態的UE
小區重選
處于SA(Service Area) 定時器T305超時此定時器在廣播的系統信息中定義
對于CELL_PCH和URA_PCH狀態的UE
需要上傳數據時(進入CELL_FACH狀態)
當在PCCH上接收到尋呼消息時，發起小區更新
CELL UPDATE過程還可用來重建RLC實體不可恢復的錯誤(丟失連接)，以及監視RRC連接的狀態。