 a high detected interference level on a specific resource block to neighbor eNode Bs. The details of OI-based ICIC and its joint operation with the proactive scheme have yet to be defined in 3GPP. 4.2.6 Load Balancing During the standardization process, it was early agreed that, for intrafrequency cells (for both idle and connected mode UEs), the best radio condition is the main mobility driver. Load balancing (LB) has the task to handle uneven distribution of the traffic load over multiple interfrequency and inter-RAT (radio access technology) cells. The purpose of LB is thus to influence the load distribution over multiple frequency and RAT layers in such a manner that radio resources remain highly utilized and the QoS of in-progress sessions is maintained to the largest possible extent while call dropping probabilities are kept sufficiently small. LB algorithms may result in handover and cell reselection decisions with the purpose of redistrib- uting traffic from highly loaded cells to underutilized cells. Load balancing in idle mode (called camp load balancing) as well as in connected mode (often referred to as load balancing) has been identified in Appendix E of reference 14 as mobility drivers. Both camp and traffic load balancing are applicable in interfrequency and inter-RAT cases only. 4.2.7 MIMO Configuration Control As it has been explained in Section 4.1.2, the radio resource domain in LTE can basically interpreted as a three-dimensional domain of [time, frequency, antenna port], corresponding to the time multiplexing, frequency multiplexing, and spatial multiplexing possibilities in LTE. The availability of multiple antennas at the trans- mitter and receiver sides, also called MIMO systems, enables the use of various diversity methods (transmit or receiver diversity) and the use of spatial multiplex- ing. In the case of spatial multiplexing, the same time-frequency resource is used to transmit different data belonging to the same or different streams, provided that the spatial "channels" are separab