ments, stricter requirements to identify a detectable UTRA FDD cell apply if both CPICH and SCH Ec/NO are above -15 dB. The requirements given in Table 15.6 are for one layer. If there are two or more layers being measured the values should be multiplied by the number of layers. With measurement gap period of 40 ms one GERAN band counts as one layer, while with measurement gap period of 80 ms one GERAN band counts as one layer for up to 20 BCCH carriers and as two layers otherwise. It can be seen that C-DRX slows down the time to first measurement report and hence handover decisions. Especially for long DRX cycles the time to send a measurement report from measurement gap activation may be quite long, for example, up to 20 X 0.64 = 12.8 seconds for 640-ms-long cycle. For two measured layers, the time would be doubled to 25.6 seconds, and SO on. Obviously the UE vendor is free to implement faster search and measurement scheduling than required by 3GPP, but network parameters will in most cases need to be optimized for the worst-performing fraction of UE models in the network. For this reason, if allowed by the radio configuration parameters, C-DRX should be disabled for the duration of urgent inter-frequency measurements to reduce the probability of call drop due to measurement delay. Table 15.7 summarizes the maximum allowed measurement period for cells that have already been found in cell search. 7 Again, it can be seen that C-DRX, if not deactivated, may lengthen 7 As mentioned, no BSIC search is required to measure power on a BCCH frequency. However, after measuring RSSI on all the BCCH frequencies provided in measurement configuration, the UE is required to decode BSIC of the eight strongest BCCHs. LTE Small Cell Optimization the measurement interval considerably. With C-DRX long cycle of 320 ms and two layers the measurement interval should be at most 2 X 5 X 0.32 = 3.2 seconds. In comparison, intra- frequency measurement interval should be 200 ms or less when C-DRX is not in use, and five DRX long cycles ot