1. A method for a base station in a cell of a multi-cell wireless system using a transmission frame structure, each frame comprising a plurality of subframes, each subframe comprising a plurality of time slots, each time slot comprising a plurality of orthogonal frequency division multiplexing (OFDM) symbols, the method comprising:broadcasting a control signal containing a cell identity associated with the cell;
forming a subchannel by selecting a plurality of OFDM subcarriers within a frequency channel in a time slot; and
transmitting data over the subchannel to a mobile station in the cell, wherein:
the data are scrambled before modulation based on the cell identity;
the scrambled data are modulated to produce modulated data symbols; and
the modulated data symbols are mapped to the plurality of OFDM subcarriers in the subchannel.