Method and device for transmitting discovery reference signal in wireless access system supporting unlicensed band
The present invention relates to a wireless access system supporting an unlicensed band, methods for configuring a discovery reference signal (DRS), methods for re-configuring subframes for same, methods for transmitting a DRS, and devices for supporting same. A method for a base station transmitting a discovery reference signal (DRS), according to one embodiment of the present invention, comprises: a step of configuring a DRS transmitted from an unlicensed band cell (Ucell) configured in an unlicensed band; and transmitting the configured DRS during a DRS opportunity, wherein the DRS includes a primary synchronization signal (PSS), a secondary synchronization signal (SSS), and a cell-specific reference signal (CRS), wherein the SSS is generated on the basis of a subframe (SF) number of a subframe in which the DRS opportunity has occurred, wherein the SSS is generated on the basis of a sequence corresponding to SF number 0 when the SF number is between SF numbers 0 to 4, and the SSS is generated on the basis of a sequence corresponding to SF number 5 when the SF number is between SF numbers 5 to 9.
1. A method of transmitting a discovery reference signal (DRS) by a base station in a wireless access system supporting an unlicensed band, the method comprising:
generating the DRS for the unlicensed band; and
transmitting the DRS in a DRS occasion via the unlicensed band,
wherein the DRS includes a primary synchronization signal (PSS), a secondary synchronization signal (SSS), and a cell-specific reference signal (CRS),
wherein the DRS is transmitted in a subframe (SF) among SF #1, SF #2, SF #3, SF #4, SF #6, SF #7, SF #8, and SF #9,
wherein the SSS is generated based on a SSS sequence related to a SF number where the DRS occasion occurs,
wherein the SSS sequence related to the SF number comprises (i) a first SSS sequence related to one SF number of a first SF number group including SF #1, SF #2, SF #3, and SF #4, and (ii) a second sequence related to one SF number of a second SF number group including SF #6, SF #7, SF #8, and SF #9, and
wherein the first SSS sequence is different from the second SSS sequence.
2. The method of claim 1 , further comprising:
performing a channel sensing procedure to determine whether the unlicensed band is idle, before transmitting the DRS.
3. The method of claim 1 , wherein the CRS is generated based on a CRS sequence related to the SF number where the DRS occasion occurs,
wherein the CRS sequence related to one SF number comprises (i) a first CRS sequence related to the first SF number group, and (ii) a second CRS sequence related to one SF number of the second SF number group, and
wherein the first CRS sequence is different from the second CRS sequence.
4. The method of claim 1 , wherein the DRS further includes a channel status information-reference signal (CSI-RS).
5. The method of claim 4 , wherein the CSI-RS is generated based on a CSI-RS sequence related to the SF number where the DRS occasion occurs,
wherein the CSI-RS sequence related to one SF number comprises (i) a first CSI-RS sequence related to the first SF number group, and (ii) a second CSI-RS sequence related to one SF number of the second SF number group, and
wherein the first CSI-RS sequence is different from the second CSI-RS sequence.
6. The method of claim 1 , wherein, based on determination that the DRS is transmitted without a physical downlink shared channel (PDSCH), the base station transmits the DRS without the PDSCH based on a channel sensing procedure to determine whether the unlicensed band is idle for a predetermined interval.
7. The method of claim 1 , wherein the SF number where the DRS occasion occurs is determined as one SF included in a discovery measurement timing configuration (DMTC) based on a result of a channel sensing procedure for transmitting the DRS.
8. The method of claim 1 , wherein the first SSS sequence related to the first SF number group is identical to a sequence configured for generation of the SSS transmitted in SF #0, and
wherein the second SSS sequence related to the second SF number group is identical to a sequence configured for generation of the SSS transmitted in SF #5.
9. A base station for transmitting a discovery reference signal (DRS) in a wireless access system supporting an unlicensed band, the base station comprising:
a transmitter; and
a processor coupled with the transmitter and configured to:
generate the DRS for the unlicensed band; and
transmit the DRS in a DRS occasion via the unlicensed band,
wherein the DRS includes a primary synchronization signal (PSS), a secondary synchronization signal (SSS), and a cell-specific reference signal (CRS),
wherein the DRS is transmitted in a subframe (SF) among SF #1, SF #2, SF #3, SF #4, SF #6, SF #7, SF #8, and SF #9,
wherein the SSS is generated based on a SSS sequence related to a SF number where the DRS occasion occurs,
wherein the SSS sequence related to the SF number comprises (i) a first SSS sequence related to one SF number of a first SF number group including SF #1, SF #2, SF #3, and SF #4, and (ii) a second sequence related to one SF number of a second SF number group including SF #6, SF #7, SF #8, and SF #9, and
wherein the first SSS sequence is different from the second SSS sequence.
10. The base station of claim 9 , wherein the processor is configured to perform a channel sensing procedure to determine whether the unlicensed band is idle, before transmitting the DRS.
11. The base station of claim 9 , wherein the CRS is generated based on a CRS sequence related to the SF number where the DRS occasion occurs,
wherein the CRS sequence related to one SF number comprises (i) a first CRS sequence related to the first SF number group, and (ii) a second CRS sequence related to one SF number of the second SF number group, and
wherein the first CRS sequence is different from the second CRS sequence.
12. The base station of claim 9 , wherein the DRS further includes a channel status information-reference signal (CSI-RS).
13. The base station of claim 12 , wherein the CSI-RS is generated based on a CSI-RS sequence related to the SF number where the DRS occasion occurs,
wherein the CSI-RS sequence related to one SF number comprises (i) a first CSI-RS sequence related to the first SF number group, and (ii) a second CSI-RS sequence related to one SF number of the second SF number group, and
wherein the first CSI-RS sequence is different from the second CSI-RS sequence.
14. The base station of claim 9 , wherein, based on determination that the DRS is transmitted without a physical downlink shared channel (PDSCH), the processor is configured to transmit the DRS without the PDSCH based on a channel sensing procedure to determine whether the unlicensed band is idle for a predetermined interval.
15. The base station of claim 9 , wherein the SF number where the DRS occasion occurs is determined as one SF included in a discovery measurement timing configuration (DMTC) based on a result of a channel sensing procedure for transmitting the DRS.
16. The base station of claim 9 , wherein the first SSS sequence related to the first SF number group is identical to a sequence configured for generation of the SSS transmitted in SF #0, and
wherein the second SSS sequence related to the second SF number group is identical to a sequence configured for generation of the SSS transmitted in SF #5.