Method and apparatus for latency reduction of device to device (D2D) message in a wireless communication system

A method of a UE (User Equipment), comprising:

• the UE receives a grant on a first interface wherein the grant indicates a first resource for transmission of a first scheduling information, a second resource for transmission of a second scheduling information, and a time and frequency resource for a data transmission in a resource pool on a second interface;
• the UE transmits the first scheduling information in the first resource indicated by the grant on the second interface in a first timing interval;
• the UE transmits the second scheduling information in the second resource indicated by the grant on the second interface in a second timing interval;
• and
• the UE transmits the data transmission in the time and frequency resource indicated by the grant on the second interface,
• wherein a timing difference between the second timing interval in which the second scheduling information is transmitted in the second resource indicated by the grant and the first timing interval in which the first scheduling information is transmitted in the first resource indicated by the grant is indicated by the grant, wherein the second scheduling information is different than the first scheduling information.

A UE (User Equipment), comprising:

• a control circuit;
• a processor installed in the control circuit;
• and
• a memory installed in the control circuit and operatively coupled to the processor;
• wherein the processor is configured to execute a program code stored in the memory to:
• receive a grant on a first interface wherein the grant indicates a first resource for transmission of a first scheduling information, a second resource for transmission of a second scheduling information, and a time and frequency resource for a data transmission in a resource pool on a second interface;
• transmit the first scheduling information in the first resource indicated by the grant on the second interface in a first timing interval;
• transmit the second scheduling information in the second resource indicated by the grant on the second interface in a second timing interval;
• and
• transmit the data transmission in the time and frequency resource indicated by the grant on the second interface,
• wherein a timing difference between the second timing interval and the first timing interval is indicated by the grant,
• wherein the first timing interval is a first TTI (Transmission Time Interval), and
• wherein the second timing interval is a second TTI.