Method for performing a random access procedure in wireless communication system and a device therefor
The present invention relates to a wireless communication system. More specifically, the present invention relates to a method and a device for transmitting a random access preamble (hereinafter, message 1); receiving a random access response (hereinafter, message 2) including a first uplink grant and a second uplink grant, as a response to the message 1; performing an initial transmission of a message 3 using the first uplink grant; starting a timer at a time when the initial transmission of a message 3 is performed; and performing a retransmission of the message 3 using the second uplink grant when the timer expires.
1. A method for a user equipment to perform a random access procedure in a wireless communication system, the method comprising:
transmitting a random access preamble (hereinafter, message 1);
receiving a random access response (hereinafter, message 2) including a first uplink grant and a second uplink grant, as a response to the message 1;
performing an initial transmission of a message 3 using the first uplink grant;
starting a timer at a time when the initial transmission of a message 3 is performed; and
performing a retransmission of the message 3 using the second uplink grant when the timer expires.
2. The method of claim 1 , wherein the timer stops when a response (hereinafter, message 4) to the message 3 is successfully received.
3. The method of claim 1 , wherein the timer is a contention resolution timer.
4. The method of claim 1 , wherein the first uplink grant is different from the second uplink grant.
5. The method of claim 1 , wherein the second message includes information indicating a maximum retransmission number.
6. The method of claim 1 , wherein the timer is re-started at a time when the first retransmission of the message 3 is performed.
7. The method of claim 1 , wherein the message 3 is no longer retransmitted when a number of retransmissions of the message 3 reaches the maximum retransmission number, even though the time expires.
8. A User Equipment (UE) for operating in a wireless communication system, the UE comprising:
a Radio Frequency (RF) module; and
a processor operably coupled with the RF module and configured to:
transmit a random access preamble (hereinafter, message 1),
receive a random access response (hereinafter, message 2) including a first uplink grant and a second uplink grant, as a response to the message 1,
perform an initial transmission of a message 3 using the first uplink grant,
start a timer at a time when the initial transmission of a message 3 is performed, and
perform a retransmission of the message 3 using the second uplink grant when the timer expires.
9. The UE of claim 8 , wherein the timer stops when a response (hereinafter, message 4) to the message 3 is successfully received.
10. The UE of claim 8 , wherein the timer is a contention resolution timer.
11. The UE of claim 8 , wherein the first uplink grant is different from the second uplink grant.
12. The UE of claim 8 , wherein the second message includes information indicating a maximum retransmission number.
13. The UE of claim 8 , wherein the timer is re-started at a time when the first retransmission of the message 3 is performed.
14. The UE of claim 8 , wherein the message 3 is no longer retransmitted when a number of retransmissions of the message 3 reaches the maximum retransmission number, even though the time expires.