B Algorithms As mentioned, static load balancing via mobility threshold tuning is most usable for tuning average utilization between layers. As it often happens, congestion tends to be localized at cell or site level; one sector of a site can be congested while the other sectors have only moderate or little load. In this case static load balancing is difficult to apply and offers only limited counter-measures at cell level. For this reason cell-level dynamic load balancing algorithms are required. 3GPP has not defined any details, and the realization of such procedures is left to the eNodeB implementation. For this reason only general description can be given in this section. Two typical template algorithms for congestion-triggered load balancing are Adaptive mobility threshold tuning Load balancing handover The former method changes handover thresholds (e.g. A3 offset) adaptively based on some measure of cell load, therefore shrinking the cell size and off-loading cell edge UEs to another layer. Optionally also the idle mode thresholds broadcasted on BCCH may be changed. 17 The second method, in turn, directly triggers a handover for one or more candidate UEs in order to off-load the cell. While the former can be considered 'soft' load balancing with slow reaction time the latter one is able to handle fast congestion peaks and also off-load UEs that are not at the cell edge. Both methods can be used in parallel. For the load balancing handover, the generic process could be as follows: 1. eNodeB constantly measures cell load based on some congestion metric, for example, PRB utilization, UE throughput, scheduling delay, transmit buffer occupancy, PDCCH blocking, 16 Path loss difference based on carrier frequencies alone is around 20 X og10(2.6/1.8) = 3.2 dB. Here all other factors are neglected for simplicity. UE can be informed of change in system information via the paging channel. LTE Small Cell Optimization number of UEs scheduled per TTI or even S1 transport load [11]. The actual metric used, like the whole a