A user device, UE, for a wireless communication system, the wireless communication system including a plurality of user devices, UEs, wherein the UE is configured to • communicate with one or more transmitting UEs using a sidelink, • support a certain number of HARQ processes, and • buffer one or more transmissions for each HARQ process, wherein, during a unicast communication with a transmitting UE using the sidelink, the UE is configured to • receive from the transmitting UE a transmission during a transmission time interval, the transmission associated to control data including a HARQ process ID, • buffer the received transmission for the HARQ process, and • combine the buffered transmissions prior to decoding, and wherein the UE is configured to signal • a first state indicating a successful transmission over the sidelink, and • a second state indicating a non-successful transmission over the sidelink so as to request a retransmission from the transmitting UE, characterized in that in case a successfully identified transmission, which is a transmission for which the UE decoded the control data, is not buffered, the UE is configured to indicate to the transmitting UE that the successfully identified transmission is not buffered at the UE, the UE is configured to signal a third state indicating that the successfully identified transmission over the sidelink is not buffered by the UE. wherein the UE is configured to • communicate with one or more transmitting UEs using a sidelink, • support a certain number of HARQ processes, and • buffer one or more transmissions for each HARQ process, • communicate with one or more transmitting UEs using a sidelink, • support a certain number of HARQ processes, and • buffer one or more transmissions for each HARQ process, wherein, during a unicast communication with a transmitting UE using the sidelink, the UE is configured to • receive from the transmitting UE a transmission during a transmission time interval, the transmission associated to control data including a HARQ process ID, • buffer the received transmission for the HARQ process, and • combine the buffered transmissions prior to decoding, and • receive from the transmitting UE a transmission during a transmission time interval, the transmission associated to control data including a HARQ process ID, • buffer the received transmission for the HARQ process, and • combine the buffered transmissions prior to decoding, and wherein the UE is configured to signal • a first state indicating a successful transmission over the sidelink, and • a second state indicating a non-successful transmission over the sidelink so as to request a retransmission from the transmitting UE, • a first state indicating a successful transmission over the sidelink, and • a second state indicating a non-successful transmission over the sidelink so as to request a retransmission from the transmitting UE, characterized in that in case a successfully identified transmission, which is a transmission for which the UE decoded the control data, is not buffered, the UE is configured to indicate to the transmitting UE that the successfully identified transmission is not buffered at the UE, the UE is configured to signal a third state indicating that the successfully identified transmission over the sidelink is not buffered by the UE.