ning in the beginning and in the end of the measurement gap. The terminals detect synchroni- zation signals within the MGL and identify the cell ID and the reception timing. The ter- minal later performs measurements on the CRS. In NR, the SMTC window duration can be set to match the SSB transmission. However, a fixed MGL could cause potential deg- radation of the serving cell throughput. As an example, if the SMTC window duration is 2 ms and the MGL is 6 ms, a 4 ms interval will not be available for data transmission and reception in the serving cell [6,29]. In order to minimize such performance degradation, the MGL in NR can be configured and can be set to 1.5, 3, 3.5, 4, 5.5, or 6 ms. Fig. 5.16 illustrates the concept of measurement gap configuration in NR, which shows different SMTC window and MGLs. The measure- ment gap repetition period (MGRP) in NR can be more flexibly configured compared to LTE (Table 5.14). The NR supports 20, 40, 80, and 160 ms MGRPs compared to LTE that only supports 40 and 80 ms. As we mentioned earlier, an RF transceiver tuning time is pro- visioned in the beginning and the end of the measurement gap, during which the terminal cannot conduct measurements or transmit/receive data. As shown in Fig. 5.17, the SMTC window and the measurement gap start at the same time. The start of the SMTC window may overlap with the RF retuning time and the UE cannot perform measurements during that time. As such, the new measurement gap timing advance function has been introduced, which enables all SSBs (to be measured) within the SMTC window to be used by advancing the start of the RF retuning gap. The SMTC window and the measurement gaps are configured based on the SSB transmis- sion timing for the candidate cell. However, in some cases when measuring other cells, the serving BS may not have such information. In such cases, it is not possible to properly set the SMTC window and measurement gap for the UE. Therefore, NR defines an SFN and frame timing difference (SFTD) measurement function, where the