n S6: Handover Request ACK Handover Command Detach from serving eNB and Deliver buffered and in transit synchronize to target eNB packets to target eNB S8: Sequence Number Status Transfer Data Forwarding Buffer packets from S9: Synchronization serving eNB S10: UL Allocation + Timing Advance for UE S11: Handover Confirm S12:I Path Switch Request S13: User plane update request End Marker S14: Switch DL path S15: User Plane update response S16: Path Switch Request ACK S17: UE Context Release Flush DL buffer, continue delivering in -transit packets Data Forwarding End Marker S18: Release Resources User Data User Data FIGURE 6-29 Intra-MME/S-GW handover procedures [13] 6.13 3GPP LTE radio resource control functions enabled, consistent with DRX configuration. In addition, the E-UTRAN can allocate semi-persistent downlink resources for the first HARQ transmissions to UEs where RRC defines the periodicity of the semi-persistent downlink grant and PDCCH indicates whether the downlink grant is a semi- persistent one, i.e., whether it can be implicitly reused in the following TTIs according to the periodicity defined by RRC. The re-transmissions are explicitly signaled via the PDCCH. In subframes where the UE has a semi-persistent downlink resource, if the UE cannot find its C-RNTI on the PDCCH, a downlink transmission according to the semi-persistent allocation that the UE has been assigned in the TTI is assumed. Otherwise, in the subframes where the UE has a semi- persistent downlink resource, if the UE finds its C-RNTI on the PDCCH, the PDCCH allocation overrides the semi-persistent allocation for that TTI and the UE does not decode the semi-persistent resources. In the uplink, the E-UTRAN can dynamically allocate resources to UEs at each TTI via the C-RNTI on PDCCH. A UE always monitors the PDCCH in order to find possible allocation for uplink transmission when its downlink reception is enabled, consistent with DRX configuration. In addition, E-UTRAN can allocate a semi-persistent uplink resource for the first HARQ tran