Method and apparatus for transmitting and receiving random access preambles in a wireless communication system
This specification provides 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). Specifically, the UE receives a downlink control channel (Physical Downlink Control Channel (PDCCH)) including downlink control information (DCI) from an eNB and the DCI includes an indicator indicating whether a preamble format of a random access preamble allocated to the UE is format 0/1 or format 2. Then, the UE transmits the random access preamble to the eNB in a subcarrier allocated to the UE according to the preamble format and receives a random access response from the eNB in response to the random access preamble.
1. A method of 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:
receiving, from a base station (BS), Downlink Control Information (DCI) including (i) preamble format indicator and (ii) subcarrier indicator; and
transmitting, to the BS, the random access preamble on an allocated subcarrier based on the DCI,
wherein the preamble format indicator indicates whether a format of the random access preamble is format 0/1 or format 2,
wherein, based on the format being format 0/1, the subcarrier indicator is 6 bits, and
wherein, based on the format being format 2, the subcarrier indicator is 8 bits.
2. The method of claim 1 ,
wherein the format is format 0/1, when a value of the preamble format indicator is ‘0’, and
wherein the format is format 2, when the value of the preamble format indicator is ‘1’.
3. The method of claim 1 , further comprising:
receiving, from the BS, a random access response in response to the random access preamble.
4. The method of claim 1 ,
wherein when the maximum number of IDs of the random access preamble is RAPID max , a bit number of the subcarrier indicator is calculated through the following equation,
[log 2 (RAPID MAX )].
5. The method of claim 1 ,
wherein the bit number of the subcarrier indicator is the same or increases, based on a value of a subcarrier spacing.
6. The method of claim 1 ,
wherein the DCI further includes a flag indicating a format of the DCI, start number information associated with a start number of repetition of a random access procedure, and a carrier indication associated with a carrier for transmitting the random access preamble.
7. The method of claim 6 ,
wherein the remaining bit number of the DCI is set to a value of 1.
8. The method of claim 1 ,
wherein a subcarrier spacing of the format 0/1 is 3.75 kHz and a subcarrier spacing of the format 2 is 1.25 kHz.
9. The method of claim 1 ,
wherein the maximum number of subcarriers allocated for the random access preamble in the format 0/1 is 48, and
wherein the maximum number of subcarriers allocated for the random access preamble in the format 2 is 144.
10. The method of claim 1 , further comprising:
receiving, from the BS, system information associated with the preamble format supported by the BS.
11. A method of receiving a random access preamble, by a base station (BS), in a wireless communication system supporting a narrow band-Internet of things (NB-IoT), the method comprising:
transmitting, to a user equipment (UE), Downlink Control Information (DCI) including (i) preamble format indicator and (ii) subcarrier indicator; and
receiving, from the UE, the random access preamble in an allocated subcarrier based on the DCI,
wherein the preamble format indicator indicates whether a format of the random access preamble is format 0/1 or format 2,
wherein, based on the format being format 0/1, the subcarrier indicator is 6 bits, and
wherein, based on the format being format 2, the subcarrier indicator is 8 bits.
12. A user equipment (UE) transmitting a random access preamble in a wireless communication system supporting a narrow band-Internet of things (NB-IoT), the UE comprising:
at least one transceiver for transmitting and receiving a radio signal; and
at least one processor functionally connected with the at least one transceiver,
wherein the at least one processor is configured to
receive, from a base station (BS), Downlink Control Information (DCI) including (i) preamble format indicator and (ii) subcarrier indicator; and
transmit, to the BS, the random access preamble on an allocated subcarrier based on the DCI,
wherein the preamble format indicator indicates whether a format of the random access preamble is format 0/1 or format 2,
wherein, based on the format being format 0/1, the subcarrier indicator is 6 bits, and
wherein, based on the format being format 2, the subcarrier indicator is 8 bits.