 UE is capable of handling. Though the MRTD is defined as a UE requirement, it indirectly defines the phase synchronization requirement for base stations as well because any phase synchronization error between LTE and 5G base stations will directly impact the MRTD measured at the UE. The 3GPP specification [10] defines the MRTD for inter-band asynchronous EN-DC to be 500, 250, 125, and 62.5 us for 15, 30, 60, and 120 kHz subcarrier spacings, respectively. These MRTD values are half of the slot dura- tion of their corresponding subcarrier spacings hence they will always be met for any kind of deployment. Therefore, phase synchronization between LTE and 5G base sta- tions are not required for inter-band EN-DC. For intra-band EN-DC, [10] defines sup- port of synchronous EN-DC in the UE as mandatory with an MRTD requirement of 3 us, assuming that the LTE and 5G base stations are collocated, whereas asynchronous EN-DC needs to be explicitly signaled by the UE to the network via Radio Resource Control (RRC) signaling. It is important to note that LTE may still require certain timing 8 Deployment Aspects and phase accuracy in performing an aligned measurement gap to ensure good perfor- mance for the EN-DC setup. 8.7.8 Synchronization from Global Navigation Satellite System (GNSS) The GNSS is a general term describing any satellite constellation that provides position- ing, navigation, and timing services on a global basis. It is probably the most accurate timing system that is available globally and is economical for use by telecom operators. Different countries may want to have their own GNSS which can be operated indepen- dently of other countries. The most popular system today is GPS, but there are a few other global options as well: GPS is operated by the US military and is the most popular GNSS system worldwide. GLONASS is a global GNSS owned and operated by the Russian Federation. Beidou is a regional GNSS owned and operated by the People's Republic of China. China is currently expanding the system to provide glob