conjunction with previous measurements and can relate the target cell downlink timing to the source cell downlink timing with a time offset, the corresponding delay is going to be less than 1 ms. The data forwarding between the two eNBs is initiated before the UE moves and establishes connection to the target cell, and because the backhaul is faster than the radio interface, forwarded data is already awaiting transmission in the target cell when the user-plane with the target cell is re-established. The latter delay component thereby does not affect the overall delay. Based on the analysis shown in Table 12-25, the minimum handover interruption time is 10.5 ms for the FDD mode and 12.5 ms for the TDD mode. Note that this delay does not depend on the frequency of the target cell as long as the cell frequency has already been measured by the UE during the measurement gap. As explained earlier, the minimum handover interruption time is 10.5 ms for FDD and 12.5 ms for TDD regardless of the frequency of the target cell and measurements. Note that in the FDD mode, the CHAPTER 12 Performance of IEEE 802. 16m and 3GPP LTE-Advanced TABLE 12-25 Breakdown of Handover Interruption Time [13] FDD Mode Processing TDD Mode Processing Procedure Time (ms) Time (ms) Radio synchronization to the target cell Average delay due to RACH scheduling period assuming 1 ms periodicity RACH preamble Preamble detection and transmission of Random Access (RA) response (time between the end RACH transmission and UE's reception of scheduling grant and timing adjustment) Decoding of scheduling grant and timing alignment Transmission of downlink data Handover Interruption Time average delay due to RACH scheduling is 0.5 ms assuming 1 ms RACH periodicity, whereas in the TDD mode, the minimum delay is obtained with configuration 0 (i.e., six normal uplink subframes); however, when taking into account the average waiting time for a downlink subframe to receive the RA response and to initiate transmission of downlink data, the TDD configuration 1 (with 