he use of ICIC techniques may mitigate the high cell edge interference effects (see Section 4.2.5 for more details on ICIC). Nevertheless, the fast deteriora- tion of the link quality at the cell edge means that the system needs to act rather quickly upon the changing link conditions before the link gets lost, which requires a fast handover execution and signaling mechanisms that are robust with respect to intercell interference. More specifically, the overall handover procedure time has to be reliable and short enough, including the time elapsed until the handover situ- ation is recognized, the time needed for preparing the handover at the target cell, and the time needed for executing the handover. Another consequence of the fast change of the link quality at the cell edge is that a large hysteresis in the source © 2009 by Taylor & Francis Group, LLC Long Term Evolution: 3GPP LTE Radio and Cellular Technology Latest HO completion Latest HO completion min SINR threshold: ~ -10 dB time with reuse-1 time with reuse-3 max HO delay: ~300 msec max HO delay: ~4 sec HO trigger (at ~3 dB path gain difference) Time (sec) SINR s-eNB (1-reuse) SINR t-eNB (1-reuse) SINR s-eNB (3-reuse) SINR t-eNB (3-reuse) Path Gain s-eNB Path Gain t-eNB Figure 4.7 Change of SINR at the cell edge for a reuse-1 and a reuse-3 system, simulated with a UE speed of 30 m/s. The time from when the handover is trig- gered (with 3-dB path gain hysteresis) until the source cell radio link SINR drops below -10 dB (where the radio link is assumed to be lost) is ~300 ms in the reuse-1 case and ~4 S in the reuse-3 case, which gives a maximum delay until the execution of the handover needs to be completed. and target cell path gain differences, used for the handover decision, may not be allowed. However, a smaller hysteresis may trigger more handovers. Figure 4.7 shows the change of SINR at the cell edge (obtained from simula- tions) in the function of time as the UE moves with a speed of 30 m/s from one cell to the other in a reuse-1 and in a reuse-3 sys