ion. The UE also performs neighboring cell measurements and measurement reporting, and acquires system information. Figure 4-25 illustrates the RRC states in E-UTRA and shows the mobility support between E-UTRAN, UTRAN, and GERAN, where a Cell Change Order (CCO) message is used to command the UE to change to another radio access technology [17]. The mobility support between E-UTRAN, cdma2000 1xRTT [20,21,23], and cdma2000 High Rate Packet Data (HRPD) or cdma 1xEV-DO [22,23] radio access technologies are shown in Figure 4-26. The inter-RAT handover procedures support signaling, conversational, and non-conversational services. The mobility between E-UTRA and non-3GPP systems other than cdma2000 has also been studied [23-25]. In addition to the state transitions shown in Figures 4-25 and 4-26, there is support for connection release with redirection information from E-UTRA RRC_CONNECTED to GERAN, UTRAN, and cdma2000 (HRPD Idle/ 1xRTT Dormant modes). As a general principle, in RRC_IDLE to RRC_CONNECTED state transitions, RRC protection keys and user-plane protection keys are generated, while keys for non-access stratum protection as well as higher layer keys are assumed to be already available in the MME. On the other hand, in xiv Note: The DRX cycle in 3GPP LTE idle mode is conceptually similar to Paging Available/Unavailable cycles in IEEE 802.16m idle mode. 4.6 3GPP LTE user equipment states and state transitions GSM_CONNECTED E-UTRA CELL_DCH Handover Handover RRC_CONNECTED GPRS PACKET TRANSFER MODE CELL_FACH CELL_PCH UTRA_PCH Connection Connection Establishment and Establishment and Release Release Connection Establishment and Release Re-selection GSM_IDLE E-UTRA UTRA_IDLE Re-selection RRC_IDLE CCO, Re-selection PACKET_IDLE FIGURE 4-25 E-UTRA states and Inter-RAT mobility procedures [18] E-UTRA 1xRTT ACTIVE Handover Handover HRPD ACTIVE RRC_CONNECTED Connection Establishment and Release E-UTRA 1xRTT DORMANT Re-selection Re-selection HRPD IDLE RRC_IDLE FIGURE 4-26 Mobility procedures between E-UTRA and cdma2000 [1