. For non-guaranteed bit rate data service a natural key performance indicator (KPI) to define service level is the downlink- or uplink-scheduled user throughput, LTE Small Cell Optimization which is the average rate at which the UE is served by the eNodeB during active TTIs. TTIs during which the transmit data buffer is empty should not be included into the calculation of scheduled throughput since TTI inactivity is caused by lack of data in the eNodeB or UE transmit buffer, for example, when downloading a web page the eNodeB may transmit only during a fraction of the available TTIs since it spends most of the time waiting for more data from the internet server. A useful user throughput KPI which is independent of traffic patterns and packet sizes is defined in 3GPP TS 36.314. For Guaranteed Bit Rate service the mobility criteria could be slightly different since the UE only needs sufficient bit rate instead of the best achievable one. Nevertheless, choosing the cell that offers highest scheduled throughput minimizes PRB consumption for the guaranteed bit rate and hence the user throughput criterion could also be used for GBR services. Many eNodeB implementations do not support handover triggering based on UE throughput, or any other service-level measure (such as low modulation and coding scheme, MCS), and triggering exit from the serving layer must in practice be based on some other measurement quantity. Potential measurement quantities include the following: Signal to noise and interference ratio (SINR): Throughput can be obtained from average SINR and the available bandwidth. Hence, a natural mobility trigger would be when SINR drops below a threshold level. Unfortunately, downlink SINR is not reported by the UE. In theory, the downlink SINR can be calculated from RSRQ if the RF utilization of the measured cell is known. For example, the serving cell should know its own PRB utilization, while for the calculation of a neighbour cell SINR the load could be obtained from the X2 Resource Status Reporting procedu