A method performed at a user equipment, UE, (102, 1302), the method comprising: receiving a first physical signal; determining a first physical structure based on information in the first physical signal, wherein the first physical structure includes resource elements; and determining resource elements based on the first physical structure; wherein the resource elements are identified by indices of subcarriers in a frequency domain and indices of orthogonal frequency-division multiplexing, OFDM, symbols in a time domain, first slots with a first subcarrier spacing which is integer multiple or integer submultiple of a second subcarrier spacing are arranged consecutively in the time domain, each of the first slots having a fixed number of OFDM symbols, and second slots with the second subcarrier spacing are arranged consecutively in the time domain, each of the second slots having the fixed number of OFDM symbols, a first set of OFDM symbols is mapped to one of the first slots, a second set of OFDM symbols is mapped to one of the second slots, and one of first slot boundaries for the first slots is aligned with one of second slot boundaries for the second slots at a periodic time position, a starting time position or an ending time position of a first OFDM symbol of the first set of OFDM symbols is aligned with a starting time position or an ending time position of a second OFDM symbol of the second set of OFDM symbols, the starting time position and the ending time position of the first OFDM symbol are different from any of the first and second slot boundaries, the starting time position and the ending time position of the second OFDM symbol are different from any of the first and second slot boundaries, a time length of the first OFDM symbol is different from a time length of the second OFDM symbol, a cyclic prefix length of one OFDM symbol of the first set of the OFDM symbols is different from a cyclic prefix length of another OFDM symbol of the first set of OFDM symbols, and a cyclic prefix length of one OFDM symbol of the second set of the OFDM symbols is different from a cyclic prefix length of another OFDM symbol of the second set of OFDM symbols. receiving a first physical signal; determining a first physical structure based on information in the first physical signal, wherein the first physical structure includes resource elements; and determining resource elements based on the first physical structure; wherein the resource elements are identified by indices of subcarriers in a frequency domain and indices of orthogonal frequency-division multiplexing, OFDM, symbols in a time domain, first slots with a first subcarrier spacing which is integer multiple or integer submultiple of a second subcarrier spacing are arranged consecutively in the time domain, each of the first slots having a fixed number of OFDM symbols, and second slots with the second subcarrier spacing are arranged consecutively in the time domain, each of the second slots having the fixed number of OFDM symbols, a first set of OFDM symbols is mapped to one of the first slots, a second set of OFDM symbols is mapped to one of the second slots, and one of first slot boundaries for the first slots is aligned with one of second slot boundaries for the second slots at a periodic time position, a starting time position or an ending time position of a first OFDM symbol of the first set of OFDM symbols is aligned with a starting time position or an ending time position of a second OFDM symbol of the second set of OFDM symbols, the starting time position and the ending time position of the first OFDM symbol are different from any of the first and second slot boundaries, the starting time position and the ending time position of the second OFDM symbol are different from any of the first and second slot boundaries, a time length of the first OFDM symbol is different from a time length of the second OFDM symbol, a cyclic prefix length of one OFDM symbol of the first set of the OFDM symbols is different from a cyclic prefix length of another OFDM symbol of the first set of OFDM symbols, and a cyclic prefix length of one OFDM symbol of the second set of the OFDM symbols is different from a cyclic prefix length of another OFDM symbol of the second set of OFDM symbols.