A method of operation performed by a radio base station operating in a wireless communication network, the method comprising: mapping a nominal carrier frequency to a reference subcarrier frequency according to a mapping function, the nominal carrier frequency among a plurality of nominal carrier frequencies defined by a carrier frequency raster that defines nominal carrier frequency positions within a frequency band of interest, and the mapping function uniquely mapping each nominal carrier frequency to a corresponding reference subcarrier frequency on a subcarrier frequency grid that defines permissible subcarrier frequency positions within the frequency band; defining an Orthogonal Frequency Division Multiplex, OFDM, carrier referenced to the reference subcarrier frequency and comprising a set of subcarriers at respective ones of the permissible subcarrier frequency positions, as defined by the subcarrier frequency grid; and receiving or transmitting on the OFDM carrier; and wherein the nominal carrier frequency F P is given by: F P = F DL _ LOW + Δ ⁢ F ⋅ N DL − N offset _ DL where F DL _ LOW is a starting point of the carrier frequency raster, Δ F is a grid spacing of the carrier frequency raster, N DL is a frequency number corresponding to the nominal carrier frequency F P, and N offset_DL is the frequency number of the starting point of the carrier frequency raster; wherein each subcarrier frequency f SC in the subcarrier frequency grid is given by: f SC = f offset + Δ ⁢ f ⋅ u SC − u offset where f offset defines a starting point of the subcarrier frequency grid, u offset sets a subcarrier number of the starting point of the subcarrier frequency grid, u SC is the position number of the subcarrier frequency in the subcarrier frequency grid, and Δ f is a grid spacing of the subcarrier frequency grid; said method characterised in that the grid spacing of the subcarrier frequency grid is independent of the grid spacing of the carrier frequency raster; and wherein the defined mapping function is given by: f SC 0 = Δ ⁢ f ⋅ floor F P Δ ⁢ f where f SC 0 is the reference subcarrier frequency; Δ f is the subcarrier spacing; F p is the nominal carrier frequency; and floor ( x)= the largest integer not greater than x. mapping a nominal carrier frequency to a reference subcarrier frequency according to a mapping function, the nominal carrier frequency among a plurality of nominal carrier frequencies defined by a carrier frequency raster that defines nominal carrier frequency positions within a frequency band of interest, and the mapping function uniquely mapping each nominal carrier frequency to a corresponding reference subcarrier frequency on a subcarrier frequency grid that defines permissible subcarrier frequency positions within the frequency band; defining an Orthogonal Frequency Division Multiplex, OFDM, carrier referenced to the reference subcarrier frequency and comprising a set of subcarriers at respective ones of the permissible subcarrier frequency positions, as defined by the subcarrier frequency grid; and receiving or transmitting on the OFDM carrier; and wherein the nominal carrier frequency F P is given by: F P = F DL _ LOW + Δ ⁢ F ⋅ N DL − N offset _ DL where F DL _ LOW is a starting point of the carrier frequency raster, Δ F is a grid spacing of the carrier frequency raster, N DL is a frequency number corresponding to the nominal carrier frequency F P, and N offset_DL is the frequency number of the starting point of the carrier frequency raster; wherein each subcarrier frequency f SC in the subcarrier frequency grid is given by: f SC = f offset + Δ ⁢ f ⋅ u SC − u offset where f offset defines a starting point of the subcarrier frequency grid, u offset sets a subcarrier number of the starting point of the subcarrier frequency grid, u SC is the position number of the subcarrier frequency in the subcarrier frequency grid, and Δ f is a grid spacing of the subcarrier frequency grid; said method characterised in that the grid spacing of the subcarrier frequency grid is independent of the grid spacing of the carrier frequency raster; and wherein the defined mapping function is given by: f SC 0 = Δ ⁢ f ⋅ floor F P Δ ⁢ f where f SC 0 is the reference subcarrier frequency; Δ f is the subcarrier spacing; F p is the nominal carrier frequency; and floor ( x)= the largest integer not greater than x. where f SC 0 is the reference subcarrier frequency; Δ f is the subcarrier spacing; F p is the nominal carrier frequency; and floor ( x)= the largest integer not greater than x.