Method for transmitting and receiving random access preamble in wireless communication system and device therefor

1. A method for transmitting a random access preamble by a user equipment (UE) in a wireless communication system supporting a narrow band-Internet of things (NB-IoT), the method comprising:

transmitting, to a base station, a random access preamble according to a specific preamble structure in a subcarrier allocated by the base station; and

receiving, from the base station, a random access response message in response to the random access preamble,

wherein a gap is inserted for a predetermined time after the random access preamble is repeatedly transmitted 16 times during a predetermined duration, and

wherein the predetermined duration is determined by multiplying a transmission duration transmitted by the random access preamble by the number of repeated transmission times of the random access preamble.

2. The method of claim 1 , wherein the transmission duration is constituted by a symbol group of a Cyclic Prefix (CP) and three symbols according to the specific preamble structure.

3. The method of claim 2 , wherein a subcarrier of the symbol group is hopped on a frequency axis in a specific pattern constituted by a hopping pair symmetric according to the specific preamble structure.

4. The method of claim 3 , wherein subcarrier indexes of second and third symbol groups are values larger than a subcarrier index of a previous symbol group by ‘1’ or smaller than the subcarrier index by ‘1’ based on a start symbol group of the specific pattern,

wherein subcarrier indexes of the third symbol group and a fourth symbol group are values larger than the subcarrier index by ‘3’ or smaller than the subcarrier index ‘3’, and

wherein a subcarrier index of a fifth symbol group is a value larger than the subcarrier index of the previous symbol group by ‘18’.

5. The method of claim 1 , wherein a subcarrier spacing is 1.25 kHz in the specific preamble structure.

6. The method of claim 1 , wherein the gap is ‘40’ ms.

7. The method of claim 1 , wherein the random access response message includes a timing advance command value for adjusting uplink transmission timing of the UE.

8. The method of claim 7 , further comprising:

performing uplink transmission based on the timing advance command value.

9. A method for receiving a random access preamble by a base station in a wireless communication system supporting a narrow band-Internet of things (NB-IoT), the method comprising:

receiving, from a UE, a random access preamble according to a specific preamble structure in an allocated subcarrier; and

transmitting, to the UE, a random access response message in response to the random access preamble,

wherein a gap is inserted for a predetermined time after the random access preamble is repeatedly transmitted 16 times during a predetermined duration, and

wherein the predetermined duration is determined by multiplying a transmission duration transmitted by the random access preamble by the number of repeated transmission times of the random access preamble.

10. A UE transmitting a random access preamble in a wireless communication system supporting a narrow band-Internet of things (NB-IoT), the UE comprising:

a radio frequency (RF) module for transmitting and receiving a radio signal; and

a processor functionally connected with the RF module,

wherein the processor is configured to

transmit, to a base station, a random access preamble according to a specific preamble structure in a subcarrier allocated by the base station, and

receive, from the base station, a random access response message in response to the random access preamble, and

wherein a gap is inserted for a predetermined time after the random access preamble is repeatedly transmitted 16 times during a predetermined duration, and

wherein the predetermined duration is determined by multiplying a transmission duration transmitted by the random access preamble by the number of repeated transmission times of the random access preamble.

11. The UE of claim 10 , wherein the transmission duration is constituted by a symbol group of a Cyclic Prefix (CP) and three symbols according to the specific preamble structure.

12. The UE of claim 11 , wherein a subcarrier of the symbol group is hopped on a frequency axis in a specific pattern constituted by a hopping pair symmetric according to the specific preamble structure.

13. The UE of claim 12 , wherein subcarrier indexes of second and third symbol groups are values larger than a subcarrier index of a previous symbol group by ‘1’ or smaller than the subcarrier index by ‘1’ based on a start symbol group of the specific pattern,

wherein subcarrier indexes of the third symbol group and a fourth symbol group are values larger than the subcarrier index by ‘3’ or smaller than the subcarrier index ‘3’, and

wherein a subcarrier index of a fifth symbol group is a value larger than the subcarrier index of the previous symbol group by ‘18’.

14. The UE of claim 10 , wherein a subcarrier spacing is 1.25 kHz in the specific preamble structure.

15. The UE of claim 10 , wherein the gap is ‘40’ ms.

16. The UE of claim 10 , wherein the random access response message includes a timing advance command value for adjusting uplink transmission timing of the UE.

17. The UE of claim 16 , wherein the processor performs uplink transmission based on the timing advance command value.