Abstract: A method of sidelink communications by a plurality of user equipment (UE) without the control of a base station in a wireless communication system is disclosed. In one embodiment, the UE being a scheduler end is configured to allocate the resources for initial/repeated transmissions and ACK/NACK messages, and also transmit information regarding the allocated resources to both the UEs being a transmitter end and a receiver end. In one embodiment, retransmission is performed when none of the scheduler and transmitter ends has received the ACK message sent by the receiver end, so as to minimize redundant retransmission in consideration of transmission reliability. In one embodiment, retransmission is performed when at least one of the scheduler and transmitters end has received the NACK message sent by the receiver end before the retransmission timer has reached to zero, so as to minimize transmission latency.

Abstract: A method of sidelink communications by a plurality of user equipment (UE) without the control of a base station in a wireless communication system is disclosed. In one embodiment, the UE being a scheduler end is configured to allocate the resources for initial/repeated transmissions and ACK/NACK messages, and also transmit information regarding the allocated resources to both the UEs being a transmitter end and a receiver end. In one embodiment, retransmission is performed when none of the scheduler and transmitter ends has received the ACK message sent by the receiver end, so as to minimize redundant retransmission in consideration of transmission reliability. In one embodiment, retransmission is performed when at least one of the scheduler and transmitters end has received the NACK message sent by the receiver end before the retransmission timer has reached to zero, so as to minimize transmission latency.

Abstract: A method of side-link transmission for ultra-reliable and low latency communication (URLLC), for a first user equipment (UE) of a wireless communication system is disclosed. The method comprises receiving a radio resource control, RRC, signaling for a first resource configuration, from a second UE of the side-link communication, wherein the second UE receives a grant-free uplink resource reserved for a grant-free uplink transmission, from a base station the wireless communication system, and transmitting a first RRC signal for a second resource configuration, to the second UE when the first resource configuration cannot support requirements of URLLC transmission.