A radio access network, RAN, server, wherein the RAN server is connectable to a fifth generation mobile communications technology 5G core network by using an interface, the RAN server is configured to manage base stations of a plurality of wireless communications standards, and the RAN server comprises a receiver and a transmitter: the receiver is configured to receive an attach request message that is from a terminal and forwarded by a first base station, wherein the first base station is any one of the base stations of the plurality of wireless communications standards; the transmitter is configured to send the attach request message to the 5G core network by using the interface; the receiver is further configured to receive, by using the interface, an attach accept message returned by the 5G core network in response to the attach request message; and the transmitter is further configured to send the attach accept message to the terminal by using a second base station, wherein the second base station is any one of the base stations of the plurality of wireless communications standards, wherein the second base station is the same base station as the first base station or another base station of the of the base stations of the plurality of wireless communications standards; wherein the base stations of the plurality of wireless communications standards comprise at least a Long Term Evolution LTE base station and a Wireless Fidelity Wi-Fi base station; and wherein the RAN server is configured to merely implement functions of an access adaptation layer, an RRC layer, an Internet Protocol IP layer, and a Packet Data Convergence Protocol PDCP layer; or the RAN server is configured to merely implement functions of an access adaptation layer, an RRC layer, and an IP layer, wherein the access adaptation layer has a function of allocating, to the terminal, a base station responsible for processing the service, a function of managing a tracking area list, and a function of paging when the terminal initiates the service request and wherein the RRC layer has a function of performing radio resource management for various wireless communications standards and a function of performing radio resource management measurement configuration for various wireless communications standards. the receiver is configured to receive an attach request message that is from a terminal and forwarded by a first base station, wherein the first base station is any one of the base stations of the plurality of wireless communications standards; the transmitter is configured to send the attach request message to the 5G core network by using the interface; the receiver is further configured to receive, by using the interface, an attach accept message returned by the 5G core network in response to the attach request message; and the transmitter is further configured to send the attach accept message to the terminal by using a second base station, wherein the second base station is any one of the base stations of the plurality of wireless communications standards, wherein the second base station is the same base station as the first base station or another base station of the of the base stations of the plurality of wireless communications standards; wherein the base stations of the plurality of wireless communications standards comprise at least a Long Term Evolution LTE base station and a Wireless Fidelity Wi-Fi base station; and wherein the RAN server is configured to merely implement functions of an access adaptation layer, an RRC layer, an Internet Protocol IP layer, and a Packet Data Convergence Protocol PDCP layer; or the RAN server is configured to merely implement functions of an access adaptation layer, an RRC layer, and an IP layer, wherein the access adaptation layer has a function of allocating, to the terminal, a base station responsible for processing the service, a function of managing a tracking area list, and a function of paging when the terminal initiates the service request and wherein the RRC layer has a function of performing radio resource management for various wireless communications standards and a function of performing radio resource management measurement configuration for various wireless communications standards.