Method of handling random access in wireless communication system

1. A method of handling random access for a user equipment (UE) of a wireless communication system, the method comprising:

transmitting a plurality of repetitions of a random access preamble in a repetition window; and

monitoring a physical downlink control channel (PDCCH) for at least one random access response identified by a random access radio network temporary identifier (RA-RNTI);

wherein the RA-RNTI is determined based on a specific subframe within the repetition window and the RA-RNTI is computed as:

RA-RNTI=1+ t _id+10× f _id+delta_shift;

wherein the t_id is an index of the specific subframe in a radio frame within the repetition window, the f_id is an index of a specific PRB pair for transmitting one of the plurality of repetitions of the random access preamble within a PRACH within the specific subframe in an ascending order of a frequency domain, and the delta_shift is a shift parameter to prevent overlap of the RA-RNTI with an RA-RNTI for another PRACH in which a legacy random access preamble without repetitions is transmitted.

2. The method of claim 1 , wherein the index of the specific PRB pair is determined based on comparison with other PRB pairs of other PRACHs within the specific subframe in the ascending order of the frequency domain.

3. The method of claim 1 , wherein the delta_shift is a maximum RA-RNTI used by another UE which transmits another random access preamble without repetitions.

4. The method of claim 1 , wherein the delta_shift is 60 for a frequency division duplex system.

5. The method of claim 1 , wherein the PRB pair within the PRACH within the specific subframe is a PRB pair with the lowest order in the frequency domain within the PRACH within the specific subframe.

6. The method of claim 1 , wherein the repetition window is within a radio frame or spreads across a plurality of radio frames.

7. The method of claim 1 , wherein the step of monitoring the PDCCH for the at least one random access response identified by the RA-RNTI is performed in a random access response window;

wherein the random access response window starts at the first subframe that contains an end of a repetition among the plurality of repetitions of the random access preamble within the repetition window plus three subframes, and has a length equal to the repetition window plus ra-ResponseWindowSize subframes.

8. A method of handling random access for a network of a wireless communication system, the method comprising:

receiving a plurality of repetitions of a random access preamble transmitted in a repetition window by a user equipment (UE) of the wireless communication system; and

determining a random access radio network temporary identifier (RA-RNTI) based on a specific subframe within the repetition window; and

transmitting at least one random access response identified by the RA-RNTI to allow the UE to monitor a physical downlink control channel (PDCCH) for the at least one random access response;

wherein the RA-RNTI is determined based on a specific subframe within the repetition window and the RA-RNTI is computed as:

RA-RNTI=1+ t _id+10× f _id+delta_shift;

wherein the t_id is an index of the specific subframe in a radio frame within the repetition window, the f_id is an index of a specific PRB pair for transmitting one of the plurality of repetitions of the random access preamble within a PRACH within the specific subframe in an ascending order of a frequency domain, and the delta_shift is a shift parameter to prevent overlap of the RA-RNTI with an RA-RNTI for another PRACH in which a legacy random access preamble without repetitions is transmitted.

9. The method of claim 8 , wherein the specific subframe is the first subframe of the repetition window, and the repetition window is within a radio frame or spreads across a plurality of radio frames.

10. The method of claim 8 , further comprising:

transmitting to the UE a configuration for the repetition window indicating a start position and a length of the repetition window via broadcast or a dedicated signaling.

11. The method of claim 8 , wherein the delta_shift is 60 for a frequency division duplex system.

12. A user equipment (UE) handling random access in a wireless communication system, the UE comprising:

a communication interfacing unit transmitting a plurality of repetitions of a random access preamble in a repetition window; and

a processing means monitoring a physical downlink control channel (PDCCH) for at least one random access response identified by a random access radio network temporary identifier (RA-RNTI);

wherein the RA-RNTI is determined based on a specific subframe within the repetition window and the RA-RNTI is computed as:

RA-RNTI=1+ t _id+10× f _id+delta_shift;

wherein the t_id is an index of the specific subframe in a radio frame within the repetition window, the f_id is an index of a specific PRB pair for transmitting one of the plurality of repetitions of the random access preamble within a PRACH within the specific subframe in an ascending order of a frequency domain, and the delta_shift is a shift parameter to prevent overlap of the RA-RNTI with an RA-RNTI for another PRACH in which a legacy random access preamble without repetitions is transmitted.

13. The UE of claim 12 , wherein the index of the specific PRB pair is determined based on comparison with other PRB pairs of other PRACHs within the specific subframe in the ascending order of the frequency domain.

14. The UE of claim 12 , wherein the delta_shift is a maximum RA-RNTI used by another UE which transmits another random access preamble without repetitions.

15. The UE of claim 12 , wherein the delta_shift is 60 for a frequency division duplex system.

16. The UE of claim 12 , wherein the PRB pair within the PRACH within the specific subframe is a PRB pair with the lowest order in the frequency domain within the PRACH within the specific subframe.

17. The UE of claim 12 , wherein the repetition window is within a radio frame or spreads across a plurality of radio frames.

18. The UE of claim 12 , wherein the processing means monitoring the PDCCH for the at least one random access response identified by the RA-RNTI is performed in a random access response window;

wherein the random access response window starts at the first subframe that contains an end of a repetition among the plurality of repetitions of the random access preamble within the repetition window plus three subframes, and has a length equal to the repetition window plus ra-ResponseWindowSize subframes.

19. A network handling random access in a wireless communication system, the network comprising:

a receiving means receiving a plurality of repetitions of a random access preamble transmitted in a repetition window by a user equipment (UE) of the wireless communication system; and

a processing means determining a random access radio network temporary identifier (RA-RNTI) based on a specific subframe within the repetition window; and

a transmitting means transmitting at least one random access response identified by the RA-RNTI to allow the UE to monitor a physical downlink control channel (PDCCH) for the at least one random access response;

wherein the RA-RNTI is determined based on a specific subframe within the repetition window and the RA-RNTI is computed as:

RA-RNTI=1+ t _id+10× f _id+delta_shift;

wherein the t_id is an index of the specific subframe in a radio frame within the repetition window, the f_id is an index of a specific PRB pair for transmitting one of the plurality of repetitions of the random access preamble within a PRACH within the specific subframe in an ascending order of a frequency domain, and the delta_shift is a shift parameter to prevent overlap of the RA-RNTI with an RA-RNTI for another PRACH in which a legacy random access preamble without repetitions is transmitted.

20. The network of claim 19 , wherein the specific subframe is the first subframe of the repetition window, and the repetition window is within a radio frame or spreads across a plurality of radio frames.

21. The network of claim 19 , wherein the transmitting means transmits to the UE a configuration for the repetition window indicating a start position and a length of the repetition window via broadcast or a dedicated signaling.

22. The network of claim 19 , wherein the delta_shift is 60 for a frequency division duplex system.