A method performed by a wireless device in a wireless communication system, the method comprising: receiving a first physical random access channel, PRACH, configuration for a new radio uplink, NR UL, carrier and a second PRACH configuration for a supplemental uplink, SUL, carrier, wherein the NR UL carrier and a DL carrier linked to the NR UL carrier belong to a first frequency band, and wherein the SUL carrier for NR belongs to a second frequency band; selecting a UL carrier for a random access procedure among the NR UL carrier and the SUL carrier based on a result of a reference signal received power, RSRP, measurement on the DL carrier; and performing the random access procedure on the selected UL carrier based on a PRACH configuration for the selected UL carrier, wherein, based on the result of the RSRP measurement on the DL carrier being less than a threshold, the SUL carrier is selected as the UL carrier for the random access procedure, wherein, based on the result of the RSRP measurement on the DL carrier being not less than the threshold, the NR UL carrier is selected as the UL carrier for the random access procedure, wherein the method further comprises receiving a UL grant informing a UL carrier for a physical uplink shared channel, PUSCH, transmission among the NR UL carrier and the SUL carrier, characterized in that: based on i) the SUL carrier being selected as the UL carrier for the random access procedure and ii) the UL grant informing the NR UL carrier, the wireless device stays on the SUL carrier without carrier switching from the SUL carrier to the NR UL carrier until the UL carrier is changed by another random access procedure. receiving a first physical random access channel, PRACH, configuration for a new radio uplink, NR UL, carrier and a second PRACH configuration for a supplemental uplink, SUL, carrier, wherein the NR UL carrier and a DL carrier linked to the NR UL carrier belong to a first frequency band, and wherein the SUL carrier for NR belongs to a second frequency band; selecting a UL carrier for a random access procedure among the NR UL carrier and the SUL carrier based on a result of a reference signal received power, RSRP, measurement on the DL carrier; and performing the random access procedure on the selected UL carrier based on a PRACH configuration for the selected UL carrier, wherein, based on the result of the RSRP measurement on the DL carrier being less than a threshold, the SUL carrier is selected as the UL carrier for the random access procedure, wherein, based on the result of the RSRP measurement on the DL carrier being not less than the threshold, the NR UL carrier is selected as the UL carrier for the random access procedure, wherein the method further comprises receiving a UL grant informing a UL carrier for a physical uplink shared channel, PUSCH, transmission among the NR UL carrier and the SUL carrier, characterized in that: based on i) the SUL carrier being selected as the UL carrier for the random access procedure and ii) the UL grant informing the NR UL carrier, the wireless device stays on the SUL carrier without carrier switching from the SUL carrier to the NR UL carrier until the UL carrier is changed by another random access procedure.