Method and apparatus for supporting supplementary uplink frequencies in next generation mobile communication system

A method performed by a base station connected with at least one of a first core network or a second core network in a wireless communication system, the method comprising:

• generating a system information block type 1 (SIB 1) message, the SIB 1 message including first information indicating if a cell associated with the base station is barred for connectivity to the first core network and second information indicating if the cell associated with the base station is barred for connectivity to the second core network;
• transmitting, to a terminal, the SIB 1 message including the first information and the second information;
• and
• receiving, from the terminal, an attach request message for connecting to the second core network, transmitted from the terminal based on the second information indicating that the cell associated with the base station is not barred for connectivity to the second core network,
• wherein a list of public land mobile networks (PLMNs) for the second core network, included in the SIB 1 message, is used for an attachment of the terminal to the second core network.