A method for reporting channel state information, CSI, in a wireless communication system, the method comprising: receiving, by a wireless device, a configuration for an extended physical uplink control channel, PUCCH, format, the configuration including information regarding a first number of resource blocks, RBs, allocated to the extended PUCCH format and a second number of RBs allocated to the extended PUCCH format, the first number of RBs being smaller than the second number of RBs, wherein an RB is a resource allocation unit and includes a plurality of subcarriers in one slot; determining, by the wireless device, a payload size of periodic CSI reports in a CSI triggering subframe in which the periodic CSI reports are triggered; selecting, by the wireless device, one of the first and second number of RBs allocated to the extended PUCCH format by comparing the payload size of the periodic CSI reports with a payload size of the extended PUCCH format for the first and second number of RBs; and transmitting, by the wireless device, the periodic CSI reports through the extended PUCCH format for the selected number of RBs in the CSI triggering subframe, wherein: if the payload size of periodic CSI reports is equal to or less than a payload size of the extended PUCCH format for the first number of RBs, the first number of RBs is selected, and, if the payload size of periodic CSI reports is greater than a payload size of the extended PUCCH format for the first number of RBs, the second number of RBs is selected. receiving, by a wireless device, a configuration for an extended physical uplink control channel, PUCCH, format, the configuration including information regarding a first number of resource blocks, RBs, allocated to the extended PUCCH format and a second number of RBs allocated to the extended PUCCH format, the first number of RBs being smaller than the second number of RBs, wherein an RB is a resource allocation unit and includes a plurality of subcarriers in one slot; determining, by the wireless device, a payload size of periodic CSI reports in a CSI triggering subframe in which the periodic CSI reports are triggered; selecting, by the wireless device, one of the first and second number of RBs allocated to the extended PUCCH format by comparing the payload size of the periodic CSI reports with a payload size of the extended PUCCH format for the first and second number of RBs; and transmitting, by the wireless device, the periodic CSI reports through the extended PUCCH format for the selected number of RBs in the CSI triggering subframe, wherein: if the payload size of periodic CSI reports is equal to or less than a payload size of the extended PUCCH format for the first number of RBs, the first number of RBs is selected, and, if the payload size of periodic CSI reports is greater than a payload size of the extended PUCCH format for the first number of RBs, the second number of RBs is selected. if the payload size of periodic CSI reports is equal to or less than a payload size of the extended PUCCH format for the first number of RBs, the first number of RBs is selected, and, if the payload size of periodic CSI reports is greater than a payload size of the extended PUCCH format for the first number of RBs, the second number of RBs is selected.