An interface method between a central-aggregate apparatus and an extension apparatus is provided, which includes: transmitting, by the central-aggregate apparatus, uplink signal indication information for a user equipment and an identifier of the user equipment to the extension apparatus; retaining, by the extension apparatus, the identifier and uplink signal information extracted from the received uplink signal indication information and transmitting an uplink signal indication to the user equipment; receiving an uplink signal transmitted from the user equipment based on one or both of the retained uplink signal information and identifier; extracting data information from the uplink signal, estimating uplink communication quality based on the uplink signal, and transmitting one or both of the extracted data information and the estimated uplink communication quality to the central-aggregate apparatus; and receiving, by the central-aggregate apparatus, one or both of the data information and the uplink communication quality from the extension apparatus.