A method of supporting an initial access of a user equipment by a temporary serving base station in a wireless communication system, the method comprising: broadcasting (S1205) system information including a plurality of thresholds for a mission critical service, MCS, in which error free transmission is required, a maximum number of multiple links for the MCS, and a list of neighboring base stations of the temporary serving base station; determining (S1210) whether or not a user equipment requesting a radio resource control, RRC, connection setup for an initial access supports the MCS; requesting (S1215) a report about a load status to candidate base stations to which the user equipment is able to access, if the user equipment supports the MCS; requesting (S1225) multi-connection setup with the user equipment to the candidate base stations according to the report about the load status obtained from the candidate base stations; determining a base station for setting a serving link with the user equipment based on a response for the multi-connection setup request; and transmitting (S1235), to the user equipment, an RRC connection setup response message including information about the base station for setting the serving link, wherein the plurality of thresholds include a first threshold related to a quality of the serving link for searching for a first alternative link to replace the serving link, a second threshold related to a quality of the serving link for releasing an RRC connection of the serving link, a third threshold related to a quality of the first alternative link for searching for a second alternative link to replace the first alternative link, and a fourth threshold related to a quality of the first alternative link for releasing an RRC connection of the first alternative link. broadcasting (S1205) system information including a plurality of thresholds for a mission critical service, MCS, in which error free transmission is required, a maximum number of multiple links for the MCS, and a list of neighboring base stations of the temporary serving base station; determining (S1210) whether or not a user equipment requesting a radio resource control, RRC, connection setup for an initial access supports the MCS; requesting (S1215) a report about a load status to candidate base stations to which the user equipment is able to access, if the user equipment supports the MCS; requesting (S1225) multi-connection setup with the user equipment to the candidate base stations according to the report about the load status obtained from the candidate base stations; determining a base station for setting a serving link with the user equipment based on a response for the multi-connection setup request; and transmitting (S1235), to the user equipment, an RRC connection setup response message including information about the base station for setting the serving link, wherein the plurality of thresholds include a first threshold related to a quality of the serving link for searching for a first alternative link to replace the serving link, a second threshold related to a quality of the serving link for releasing an RRC connection of the serving link, a third threshold related to a quality of the first alternative link for searching for a second alternative link to replace the first alternative link, and a fourth threshold related to a quality of the first alternative link for releasing an RRC connection of the first alternative link. <EOS>