table cell and initiates a connection reestablishment. If the UE context is available at the selected eNode B (i.e., if the UE reselects to a cell belonging to the source eNode B or to a cell of an eNode B that has been prepared for a handover), the UE context can be recovered. In such cases, the interruption time and the user-perceived performance will be almost as good as in the nonfailure case. In all other cases, the UE has to reestablish connectivity via an idle to active state transition, which will take a somewhat longer time. Also, if the source eNode B wants to decrease the impact of a potential handover failure, it can prepare multiple target cells; later, after the handover has been successfully completed, it can cancel the preparation in the other cells. 4.2.5 Intercell Interference Coordination (ICIC) Intercell interference coordination has the task to manage radio resources (notably the radio resource blocks) SO that intercell interference is kept under control. The specific ICIC techniques that will be used in LTE are still in some key points that have already been agreed to [46]. ICIC is inherently a multicell RRM function that needs to take into account the resource usage status and traffic load situation of multiple cells. The presingle-antenna, as well as multiple-antenna systems, has been actively studied by the research community (see, for instance, references 24-41). In this chapter we focus on the process. Within the 3GPP there is a fairly wide consensus that LTE should be a reuse-1 system in which all resource blocks should be used by each cell. In such systems, UEs served by neighboring cells may cause (uplink) interference to eNode Bs, as illustrated in Figure 4.9, while eNode Bs may cause downlink interference to served UEs. However, eNode Bs can employ scheduling strategies that allow them to reduce the probability for causing such intercell interference by carefully selecting the scheduled resource blocks. A resource block collision between two cells, as described in Figure 4.9, can b