A station is disclosed that is configured for signal transmission in an Orthogonal Frequency Division Multiple Access (OFDMA) system. The station includes a processor configured to fix a subcarrier spacing to a predetermined value for one or more subframes in all available bandwidths. The station further includes a transmitter configured to transmit a signal having the fixed subcarrier spacing, regardless of a frame structure of the one or more subframes. According to certain embodiments, the predetermined value may be divided evenly by at least one channel raster. The predetermined value may be 12.5 KHz, according to certain embodiments. Alternatively, the predetermined value is 6.25 KHz for one or more low mobility mobile stations, and/or the predetermined value is 25 KHz for one or more high mobility mobile stations. The station may be a mobile station or a base station configured for uplink and downlink transmission.