lgorithm, is vendor specific. Some averaging would be typically applied to make the algorithm more robust. 2. If the congestion metric exceeds a pre-configured threshold, the cell is said to be congested. 3. Candidate UE selection: eNodeB should select one or more UEs as candidates for han- dover. The selection criteria could include UE buffer occupancy, UE PRB utilization, uplink/downlink quality, downlink level, uplink power headroom and SO on. Also a UE making an RRC setup could be considered as a candidate. Measurements with gaps are configured for the candidate UEs. The configured measurement event could be A3, A4 or A5, based on either RSRP, RSRQ, or both. 5. Target cell selection: Upon receiving a measurement report, eNodeB performs target cell selection and starts handover preparation towards the target eNodeB, possibly using X2 cause indicating that the handover attempt is due to source cell overload. The target cell selection can be blind or it could be based on X2 resource reporting procedure by which eNodeBs can exchange load information [9]. 6. Upon successful handover preparation a handover command is sent to the UE. The main optimization problem related to the above procedure is how to decide the thresh- old for high load in the source cell and if the target cell offers sufficient quality of service, that is, setting of the thresholds for the inter-frequency measurement events. This could also be automatically deduced by the eNodeB algorithm. For example, if the eNodeB has up-to-date information of the current PRB utilization of the candidate target cells this infor- mation could be used to automatically select the cell that offers the best throughput, at least approximately. Figure 15.21 illustrates the load balancing inter-frequency handover from 2.6 GHz to 800 MHz. In this example the load measure is the number of UEs with unacknowledged data in downlink RLC transmit buffer. The high band (2.6 GHz) cell has an average of 14 UEs with an active data transmission ongoing during busy hour, while the