Embodiments of the present invention provide a base station, a terminal device, and a communication system for inter-base station carrier aggregation. A primary base station of the terminal sends a message including indication information to request the terminal device to report a timing offset between the primary base station and a secondary base station of the UE. The secondary base station calculates a corrected measurement gap information according to a measurement gap information and the timing offset. In a second measurement gap period indicated by the corrected measurement gap information, the terminal device is not scheduled.