Collision mitigation procedures for grant-less uplink multiple access

A method for use in a base station for grant-less (GL) uplink (UL) reception, the method comprising:

• transmitting one or more GL transmission configurations, including a first indication of a first set of resource blocks (RBs) for a first resource pool and a second indication of a second set of RBs for a second resource pool;
• determining whether UL data has been received successfully, via a subset of RBs within the second set, from a first WTRU;
• on a condition that the UL data has not been received successfully, determining, based on a first resource pool to second resource pool mapping, whether the first WTRU and at least a second WTRU have selected the subset of RBs of the second set;
• on a condition that the first WTRU and at least the second WTRU have selected the subset of RBs of the second set, transmitting to the WTRU a negative acknowledgement (NAK) with a third indication for a first transmission failure reason and receiving from the WTRU a UL self-decodable data retransmission, wherein the first transmission failure reason is due to UL collision;
• and
• on a condition that the first WTRU and at least the second WTRU have not selected the subset of RBs of the second set, transmitting to the WTRU a NAK with a third indication for a second transmission failure reason, wherein the second transmission failure reason is due to UL low Signal-to-Noise Ratio (SNR).

A method for use in a wireless transmit/receive unit (WTRU) for grant-less (GL) uplink (UL) transmissions, the method comprising:

• receiving one or more GL transmission configurations, including a first indication of a first set of resource blocks (RBs) for a first resource pool, and a second indication of a second set of RBs for a second resource pool;
• selecting a subset of RBs in the first set;
• determining a subset of RBs in the second set based on the selected subset of RBs in the first set;
• transmitting UL data, via the determined subset of RBs in the second set, to a base station;
• receiving a negative acknowledgement (NAK) with a third indication for at least one of a first transmission failure reason and a second transmission failure reason, wherein the first transmission failure reason is due to UL collision and the second transmission failure reason is due to UL low Signal-to-Noise Ratio (SNR);
• adjusting a backoff and determining a retransmission scheme based on the received third indication, wherein on a condition that the third indication is for the first transmission failure reason, the adjustment is increasing the backoff and the retransmission of the UL data is self-decodable;
• and
• retransmitting the UL data to the base station using the adjusted backoff and determined retransmission scheme.