V2X communication performance method performed by V2X terminal in wireless communication system, and terminal using the method

1. A method for performing a V2X communication based on a short transmission time interval (S-TTI) relatively shorter than a legacy transmission time interval (L-TTI) in a wireless communication system, the method performed by a vehicle-to-X (V2X) User Equipment (UE) comprising:

measuring a channel busy ratio (CBR) or a channel occupancy ratio (CR) for the V2X communication based on S-TTI; and

performing the V2X communication based on S-TTI based on the measured CBR or the measured CR,

wherein the S-TTI has a variable length,

wherein when the V2X UE measures the CBR or the CR, the measurement is performed in a subchannel unit based on the S-TTI and a duration of the measurement is determined in the S-TTI unit,

wherein when the S-TTI on a timing of subtracting a minimum processing time from the S-TTI for the V2X UE to perform a transmission corresponds to a Wth S-TTI in the L-TTI having index Z value, the V2X UE measures the CBR in a subchannel unit based on the S-TTI from a timing of subtracting 100 S-TTI lengths from the Wth S-TTI in the L-TTI having index Z value to a timing of subtracting 1 S-TTI length from the Wth S-TTI in the L-TTI having index Z value,

wherein the Z is an integer of 0 or more, and

wherein the W is a positive integer.

2. The method of claim 1 , wherein the L-TTI corresponds to a plurality of the S-TTIs.

3. The method of claim 2 , when the S-TTI is a basic resource unit, wherein the L-TTI is a combination of K basic resource units, and

wherein the K is a positive integer.

4. The method of claim 2 , when the L-TTI is a basic resource unit, wherein the S-TTI is a division of the basic resource unit divided into X, and

wherein the X is a positive integer.

5. The method of claim 2 , when the V2X UE measures the CBR or the CR, wherein the measurement is performed in a subchannel unit based on the L-TTI, and wherein a duration of the measurement is determined in the L-TTI unit.

6. The method of claim 2 , when the V2X UE measures the CBR or the CR, wherein the measurement is performed in a subchannel unit based on the S-TTI, and wherein a duration of the measurement is determined in the L-TTI unit.

7. The method of claim 1 , wherein the V2X UE determines whether the V2X communication based on L-TTI and the V2X communication based on S-TTI are coexisted, and

wherein the V2X UE measures the CBR or the CR based on whether the V2X terminal determines whether the V2X communication based on L-TTI and the V2X communication based on S-TTI are coexisted.

8. A vehicle-to-X (V2X) User Equipment (UE) for performing a V2X communication based on a short transmission time interval (S-TTI) relatively shorter than a legacy transmission time interval (L-TTI) in a wireless communication system, comprising:

a Radio Frequency transceiver for transmitting and receiving a radio signal; and

a processor operating with being combined with the RF transceiver,

wherein the processor is configured to perform:

measuring a channel busy ratio (CBR) or a channel occupancy ratio (CR) for the V2X communication based on S-TTI; and

performing the V2X communication based on S-TTI based on the measured CBR or the measured CR,

wherein the S-TTI has a variable length,

wherein when the V2X UE measures the CBR or the CR, the measurement is performed in a subchannel unit based on the S-TTI and a duration of the measurement is determined in the S-TTI unit,

wherein when the S-TTI on a timing of subtracting a minimum processing time from the S-TTI for the V2X UE to perform a transmission corresponds to a Wth S-TTI in the L-TTI having index Z value, the V2X UE measures the CBR in a subchannel unit based on the S-TTI from a timing of subtracting 100 S-TTI lengths from the Wth S-TTI in the L-TTI having index Z value to a timing of subtracting 1 S-TTI length from the Wth S-TTI in the L-TTI having index Z value,

wherein the Z is an integer of 0 or more, and

wherein the W is a positive integer.