The present disclosure relates to the field of network slicing in wireless communication. In accordance with an aspect of the disclosure, a method performed by an access and mobility function (AMF) entity is provided. The method includes receiving, from a user equipment (UE), a registration request including a requested network slice selection assistance information (NSSAI); transmitting, to a Network Slice Admission Control Function (NSACF) entity, a request for determination of an availability of a number of UEs based on the registration request; and in case that a rejection for the request is received from the NSACF, transmitting, to the UE, information on a back-off timer.