Method and MTC device for performing random access procedure for coverage enhancement
A disclosure of the present specification provides a method for performing a random access procedure for coverage enhancement. The method may comprise the steps of: transmitting a random access preamble repetitively to a certain cell on the basis of a predetermined repetition level; when a random access response has not received within a random access response window, reconfiguring the repetition level; and retransmitting the random access preamble repetitively on the basis of the reconfigured repetition level.
1. A method of performing a random access procedure, the method performed by a wireless device located in a coverage extension region of a long term evolution (LTE) based cell and comprising:
repeatedly transmitting a random access preamble according to a first repetition level to a cell;
based on that no random access response (RAR) including a random access preamble identifier corresponding to the transmitted random access preamble is received within a RAR window from the cell, performing a repetition level change from the first repetition level to a second repetition level and a power ramping,
wherein the repetition level change is performed firstly and then the power ramping is performed; and
repeatedly retransmitting the random access preamble based on the repetition level change to the second repetition level and based on the power ramping,
wherein based on that the random access preamble is transmitted according to a physical downlink control channel (PDCCH) order, the PDCCH order includes repetition level information.
2. The method of claim 1 , wherein the random access preamble is repeatedly transmitted and retransmitted on a plurality of subframes.
3. The method of claim 1 , further comprising:
transmitting a scheduled message when the RAR is received; and
based on that a message in response to the scheduled message is not received until a contention resolution timer expires, repeatedly retransmitting the random access preamble.
4. The method of claim 1 , wherein the second repetition level is higher than the first repetition level, and
wherein information on the first and second the repetition levels is received via a higher layer signal.
5. The method of claim 3 , wherein the power ramping is performed until reaching a maximum transmission power configured in the wireless device.
6. The method of claim 1 , wherein the change of the repetition level is performed based on a total PRACH power, and
wherein the total PRACH power corresponds to a summation of power on subframes where the random access preamble is repeatedly transmitted.
7. The method of claim 1 , wherein the RAR is repeatedly transmitted from the cell.
8. A wireless device located in a coverage extension region to perform a random access procedure for coverage enhancement of a long term evolution (LTE) based cell, the wireless device comprising:
a transceiver to repeatedly transmit a random access preamble to a cell according to a first repetition level; and
a processor to perform a repetition level change from the first repetition level to a second repetition level and a power ramping, based on that no random access response (RAR) including a random access preamble identifier corresponding to the transmitted random access preamble is received within a RAR window from the cell,
wherein the repetition level change is performed firstly and then the power ramping is performed,
wherein the processor repeatedly retransmits the random access preamble based on the repetition level change to the second repetition level and based on the power ramping, and
wherein based on that the random access preamble is transmitted according to a physical downlink control channel (PDCCH) order, the PDCCH order includes repetition level information.
9. The wireless device of claim 8 , wherein the random access preamble is repeatedly transmitted and retransmitted on a plurality of subframes.
10. The wireless device of claim 8 , wherein the processor transmits a scheduled message when the RAR is received; and
wherein based on that a message in response to the scheduled message is not received until a contention resolution timer expires, the processor repeatedly retransmits the random access preamble.
11. The wireless device of claim 8 , wherein the second repetition level is higher than the first repetition level, and
wherein information on the first and second the repetition levels is received via a higher layer signal.
12. The wireless device of claim 8 , wherein the power ramping is performed until reaching a maximum transmission power configured in the wireless device.
13. The wireless device of claim 8 , wherein the change of the repetition level is performed based on a total PRACH power, and
wherein the total PRACH power corresponds to a summation of power on subframes where the random access preamble is repeatedly transmitted.