A method of supporting a buffer status report, BSR, associated with a device-to-device, D2D, communication, the method comprising: establishing a radio resource control, RRC, connection with an evolved NodeB, eNB; receiving, by a user equipment, UE, configuration information associated with a D2D communication from the eNB, the configuration information comprising information of a resource selection mode for a D2D data transmission, the information of the resource selection mode indicating a resource pool from which the UE selects a resource for a D2D data transmission to another UE; characterized by identifying, based on a D2D discovery procedure, D2D target identities of a plurality of target UEs; mapping a D2D target identity of a first target UE, among the plurality of target UEs, to a first group identity, and mapping a D2D target identity of a second target UE, among the plurality of target UEs, to a second group identity; generating an RRC message to be transmitted to the eNB, the RRC message comprising information of the D2D target identity of the first target UE and information of the D2D target identity of the second target UE; transmitting the RRC message to the eNB, the information of the identified D2D target identities being transmitted through UEinformation message for a D2D data transmission; generating the BSR to be transmitted to the eNB, the BSR comprising a first field that indicates mapping information between the first group identity and the D2D target identity of the first target UE and a second field that indicates mapping information between the second group identity and the D2D target identity of the second target UE; and transmitting the BSR to the eNB. establishing a radio resource control, RRC, connection with an evolved NodeB, eNB; receiving, by a user equipment, UE, configuration information associated with a D2D communication from the eNB, the configuration information comprising information of a resource selection mode for a D2D data transmission, the information of the resource selection mode indicating a resource pool from which the UE selects a resource for a D2D data transmission to another UE; characterized by identifying, based on a D2D discovery procedure, D2D target identities of a plurality of target UEs; mapping a D2D target identity of a first target UE, among the plurality of target UEs, to a first group identity, and mapping a D2D target identity of a second target UE, among the plurality of target UEs, to a second group identity; generating an RRC message to be transmitted to the eNB, the RRC message comprising information of the D2D target identity of the first target UE and information of the D2D target identity of the second target UE; transmitting the RRC message to the eNB, the information of the identified D2D target identities being transmitted through UEinformation message for a D2D data transmission; generating the BSR to be transmitted to the eNB, the BSR comprising a first field that indicates mapping information between the first group identity and the D2D target identity of the first target UE and a second field that indicates mapping information between the second group identity and the D2D target identity of the second target UE; and transmitting the BSR to the eNB.