There is provided a method for measuring a frame timing difference. The method performed by a User Equipment (UE) and comprises: based on (i) that an Evolved Universal Mobile Telecommunications System (UMTS) Terrestrial Radio Access (EUTRA) cell is configured for a primary cell and based on (ii) that a secondary cell is not configured, measuring the frame timing difference between the E-UTRA cell and a New Radio (NR) cell based on a Synchronization Signal (SS)/Physical Broadcast Channel (PBCH) Block (SSB) Measurement Time Configuration (SMTC) period, wherein the NR cell is found regardless of a position of a SSB of the NR cell; and reporting a System Frame Number (SFN) and Frame Timing Difference (SFTD) based on the frame timing difference to the E-UTRA cell.