When the UE 300 serves as a receiving UE, the feedback information generator 320 can receive, via the receiver 314, some sidelink data from a transmission UE via the sidelink between the two UEs. The feedback information generator 320 may then generate feedback information based on the receipt of the sidelink data. For example, the feedback information generator 320 may generate an acknowledgement (ACK) to signify successful receipt of the data transmitted via the sidelink, or a negative acknowledgement (NACK) to signify a rejection or error of the data transmitted via the sidelink. In other example, the feedback information may include some channel quality indications other than ACK/NACK to indicate the sidelink channel quality, based on the sidelink transmissions.

When the UE 300 serves as a transmission UE, the sidelink data generator 322 may inform the feedback information forwarder 324 to wait for a feedback from the receiving UE. The feedback information forwarder 324 can receive, via the receiver 314, the feedback information generated by the receiving UE (by the feedback information generator 320 in the receiving UE). Then, the feedback information forwarder 324 may forward the feedback information to a BS for controlling and/or adjusting the sidelink communications, e.g. by generating a wireless signal based on the feedback information and transmitting the wireless signal, via the transmitter 312, to the BS. In one embodiment, the wireless signal is transmitted via at least one of: (a) radio resource control (RRC) signaling, and (b) media access control (MAC) control element (CE) with logical channel identity (LCD) that indicates a type of the MAC CE.