p to four cells found in the search phase [2]. In the example, the second search discovers PCI 122 which is then added to measured cells. The time to trigger the measurement report depends on filter coefficient and time to trigger. If there are several LTE frequency layers the search and measurement time is multiplied accordingly since in the example the UE can only tune its RF receiver to one frequency during a measurement gap. The measurement procedure is similar if the target layer is UTRA. However, in that case the number of gaps required for cell search depends on the number of neighbour cells pro- vided in the measurement configuration. It should be noted that scrambling codes that are not provided in the neighbour list need not be measured by the UE or, in other words, no detected set reporting requirements during handover measurements have been specified by 3GPP.6 5 The measurement gap length of ms is enough to be able to search for primary and secondary synchronization channels of inter-frequency LTE cells, even for the worst-case frame timing where the gap starts at the beginning of the second or seventh subframe of the measured cell. This is because PSS/SSS is transmitted at 5-ms interval at the end of the first and sixth subframes. Inter-RAT measurement to detect new neighbour cells for self-organizing network (SON) purposes can be triggered by eNodeB separately. LTE Small Cell Optimization Periodic search of new cells Serving Measurement Detects PCI100 Detects PCI122 interval PCI122 PCI100 Figure 15.4 Inter-frequency measurement example in connected mode without C-DRX For GSM target layer, there is no need to perform initial cell search since the GSM frame timing need not be known for power (RSSI) measurement. The UE is, however, required to decode the BSIC on the eight strongest measured BCCH frequencies. If a cell is detectable and eligible to trigger a measurement report, the maximum time for UE to send the measurement report is called the cell identification time. The maximum allowed identificati