A base station, BS, in a wireless communication system, the BS being adapted to: - receive a data message and a random access request from at least one UE device, the random access request and the data message having a respective duration with a different time unit and the time unit of the random access request being shorter than the time unit of the data message, - check whether a size of a time misalignment, Δt, between a first data frame located in a first frequency sub-band and a second data frame located in a second frequency sub-band adjacent to the first frequency sub-band is larger than a size of a cyclic prefix, CP; and when the size of the time misalignment, Δt, is larger than the size of the cyclic prefix, CP, the base station is configured to: determine a first size, wG1, of the frequency guard band based on a power spectral density, PSD-1, of a first pulse shape used for a transmission of the first data frame located in the first frequency sub-band; determine a second size, wG2, of the frequency guard band based on a power spectral density, PSD-2, of a second pulse shape used for a transmission of the second data frame located in the second frequency sub-band adjacent to the first frequency sub-band; and select the size, w, of the frequency guard band as being the highest value amongst the first and second sizes,wG1,wG2; - inform the UE device about the determined size, w, of the frequency guard band. - receive a data message and a random access request from at least one UE device, the random access request and the data message having a respective duration with a different time unit and the time unit of the random access request being shorter than the time unit of the data message, - check whether a size of a time misalignment, Δt, between a first data frame located in a first frequency sub-band and a second data frame located in a second frequency sub-band adjacent to the first frequency sub-band is larger than a size of a cyclic prefix, CP; and when the size of the time misalignment, Δt, is larger than the size of the cyclic prefix, CP, the base station is configured to: determine a first size, wG1, of the frequency guard band based on a power spectral density, PSD-1, of a first pulse shape used for a transmission of the first data frame located in the first frequency sub-band; determine a second size, wG2, of the frequency guard band based on a power spectral density, PSD-2, of a second pulse shape used for a transmission of the second data frame located in the second frequency sub-band adjacent to the first frequency sub-band; and select the size, w, of the frequency guard band as being the highest value amongst the first and second sizes,wG1,wG2; determine a first size, wG1, of the frequency guard band based on a power spectral density, PSD-1, of a first pulse shape used for a transmission of the first data frame located in the first frequency sub-band; determine a second size, wG2, of the frequency guard band based on a power spectral density, PSD-2, of a second pulse shape used for a transmission of the second data frame located in the second frequency sub-band adjacent to the first frequency sub-band; and select the size, w, of the frequency guard band as being the highest value amongst the first and second sizes,wG1,wG2; - inform the UE device about the determined size, w, of the frequency guard band.