A method of a base station may comprise: mapping at least one port of the base station to each of a plurality of user equipments (UEs) to be overloaded; configuring overloading signatures for a code division multiplexing (CDM) scheme; mapping the overloading signatures with the plurality of UEs to be overloaded, respectively; transmitting a message including configuration information of the overloading signatures to the plurality of UEs; and transmitting, to the plurality of UEs, signals multiplexed by the CDM scheme using the overloading signatures.