A method performed by a terminal for transmitting uplink, UL, data in a wireless communication system, the method comprising: receiving configuration information for a grant-free UL transmission, the configuration information including a number of repetitive transmissions K, information on a redundancy version, RV, sequence, and period information associated with a number of preconfigured resources M for repetitive transmission, wherein the resources for the repetitive transmissions in a period P are associated with the same hybrid automatic repeat request, HARQ, process identifier, ID, and the information on the RV sequence is configured as 0-0-0-0; identifying a resource that is determined available first after generating an UL data signal to be transmitted as a resource for an initial transmission of the UL data; performing the initial transmission of the UL data on the identified resource; and performing a following repeated transmission after the initial transmission of the UL data on each following resource in the period P of the identified resource until K-1 repeated transmissions of the UL data have been performed or, if the period P ends before all K-1 repeated transmissions have been performed, until the period P of the identified resource ends, characterised in that the identified resource is one of F resources counted from the first resource among the M resources that are associated with the HARQ process ID in the period P, wherein F<M, wherein said F resources can be used for initial and repeated transmissions, and wherein the remaining M-F resources associated with the HARQ process ID can be used only for repeated transmissions. receiving configuration information for a grant-free UL transmission, the configuration information including a number of repetitive transmissions K, information on a redundancy version, RV, sequence, and period information associated with a number of preconfigured resources M for repetitive transmission, wherein the resources for the repetitive transmissions in a period P are associated with the same hybrid automatic repeat request, HARQ, process identifier, ID, and the information on the RV sequence is configured as 0-0-0-0; identifying a resource that is determined available first after generating an UL data signal to be transmitted as a resource for an initial transmission of the UL data; performing the initial transmission of the UL data on the identified resource; and performing a following repeated transmission after the initial transmission of the UL data on each following resource in the period P of the identified resource until K-1 repeated transmissions of the UL data have been performed or, if the period P ends before all K-1 repeated transmissions have been performed, until the period P of the identified resource ends, characterised in that the identified resource is one of F resources counted from the first resource among the M resources that are associated with the HARQ process ID in the period P, wherein F<M, wherein said F resources can be used for initial and repeated transmissions, and wherein the remaining M-F resources associated with the HARQ process ID can be used only for repeated transmissions.