A user traffic multiplexing scheme for the downlink of an OFDM cellular system is proposed and evaluated. The scheme is based on the set of orthogonal time-frequency (T-F) patterns obtained from a generic Costas sequence. An inter-cell interference averaging method, based on randomly variable cyclic time offsetting of the whole set of orthogonal T-F patterns, is also part of the scheme. The time offset is changed for each transmission time interval, according to a cell-specific multi-level pseudo-random sequence. In such a way the inter-cell OFDM interference becomes limited and noise-like, while no resource planning on the system level is required