A method of supporting direct communication between wireless devices, the method comprising: receiving, by a first wireless device from a base station , configuration information associated with direct data transmission between the first wireless device and one or more wireless devices, wherein the configuration information comprises information of a resource selection mode for direct data transmission, and wherein the information of a resource selection mode indicates a resource pool from which the first wireless device selects a resource for direct data transmission to one or more wireless devices; characterized by mapping a first target identity to a first group identity and a second target identity to a second group identity, wherein the first target identity is associated with at least one target wireless device of a first group of target wireless devices among a plurality of target wireless devices identified through a discovery procedure, and wherein the second target identity is associated with at least one target wireless device of a second group of target wireless devices among the plurality of target wireless devices identified through the discovery procedure; transmitting, to the base station , a radio resource control, RRC, message comprising information of the first target identity and information of the second target identity; and transmitting, to the base station , a signal associated with a MAC-layer message, wherein the MAC-layer message comprises: a first field that indicates the first target identity and indicates the first group identity; and a second field that indicates the second target identity and indicates the second group identity. receiving, by a first wireless device from a base station , configuration information associated with direct data transmission between the first wireless device and one or more wireless devices, wherein the configuration information comprises information of a resource selection mode for direct data transmission, and wherein the information of a resource selection mode indicates a resource pool from which the first wireless device selects a resource for direct data transmission to one or more wireless devices; characterized by mapping a first target identity to a first group identity and a second target identity to a second group identity, wherein the first target identity is associated with at least one target wireless device of a first group of target wireless devices among a plurality of target wireless devices identified through a discovery procedure, and wherein the second target identity is associated with at least one target wireless device of a second group of target wireless devices among the plurality of target wireless devices identified through the discovery procedure; transmitting, to the base station , a radio resource control, RRC, message comprising information of the first target identity and information of the second target identity; and transmitting, to the base station , a signal associated with a MAC-layer message, wherein the MAC-layer message comprises: a first field that indicates the first target identity and indicates the first group identity; and a second field that indicates the second target identity and indicates the second group identity. a first field that indicates the first target identity and indicates the first group identity; and a second field that indicates the second target identity and indicates the second group identity. <EOS>