A method performed by a terminal (1401,1402,1403) in a wireless communication system, the method comprising: receiving, from a base station (1501,1502,1503), on a physical downlink control channel, PDCCH, downlink control information, DCI, including a frequency domain resource allocation field; identifying an allocated resource for transmitting or receiving data in a second bandwidth part based on the frequency domain resource allocation field; and transmitting or receiving the data on the allocated resource, the method characterized in that: a size of the frequency domain resource allocation field, for the second bandwidth part, is based on a size of a first bandwidth part being an initial bandwidth part, and the frequency domain resource allocation field indicates a first starting resource block RB start and a first number of contiguously allocated resource blocks L RB, the second bandwidth part is activated, and has a size that is different from the size of the first bandwidth part, a scaling factor Z is determined based on the size of the first bandwidth part and the size of the second bandwidth part, and a second starting resource block of the allocated resource is based on RB start and Z, and a second number of contiguously allocated resource blocks of the allocated resource is based on L RB and Z. receiving, from a base station (1501,1502,1503), on a physical downlink control channel, PDCCH, downlink control information, DCI, including a frequency domain resource allocation field; identifying an allocated resource for transmitting or receiving data in a second bandwidth part based on the frequency domain resource allocation field; and transmitting or receiving the data on the allocated resource, the method characterized in that: a size of the frequency domain resource allocation field, for the second bandwidth part, is based on a size of a first bandwidth part being an initial bandwidth part, and the frequency domain resource allocation field indicates a first starting resource block RB start and a first number of contiguously allocated resource blocks L RB, the second bandwidth part is activated, and has a size that is different from the size of the first bandwidth part, a scaling factor Z is determined based on the size of the first bandwidth part and the size of the second bandwidth part, and a second starting resource block of the allocated resource is based on RB start and Z, and a second number of contiguously allocated resource blocks of the allocated resource is based on L RB and Z. a size of the frequency domain resource allocation field, for the second bandwidth part, is based on a size of a first bandwidth part being an initial bandwidth part, and the frequency domain resource allocation field indicates a first starting resource block RB start and a first number of contiguously allocated resource blocks L RB, the second bandwidth part is activated, and has a size that is different from the size of the first bandwidth part, a scaling factor Z is determined based on the size of the first bandwidth part and the size of the second bandwidth part, and a second starting resource block of the allocated resource is based on RB start and Z, and a second number of contiguously allocated resource blocks of the allocated resource is based on L RB and Z.