Method of fast-retransmitting uplink data in wireless communication system and apparatus therefor

A method for transmitting, by a base station, uplink (UL) data in a wireless communication system that supports a low latency system, the method comprising:

• transmitting, to a user equipment (UE), a first UL grant for initial data;
• receiving, from the UE, the initial data;
• transmitting, to the UE, a second UL grant and a negative acknowledgement (NACK), when decoding of the received initial data is failed,
• wherein the second UL grant includes a position of a physical resource for a transport block related to a retransmission of the initial data;
• and
• receiving, from the UE, the transport block on the physical resource.

A user equipment (UE) transmitting uplink (UL) data in a wireless communication system that supports a low latency system, the UE comprising:

• a radio frequency (RF) unit for transmitting and receiving a radio signal;
• and
• a processor functionally connected to the RF unit,
• wherein the processor is configured to perform:
• receiving, from a base station, a first UL grant for initial data;
• transmitting, to the base station, the initial data based on the first UL grant;
• generating a transport block related to a retransmission of the initial data;
• receiving, from the base station, a negative acknowledgement (NACK) for the initial data and a second UL grant,
• wherein the second UL grant includes a position of a physical resource for the transport block;
• mapping the transport block to the position of the physical resource based on the second UL grant;
• and
• transmitting, to the base station, the transport block on the physical resource.