A method for assigning a single frequency sub-channel to a plurality of
MSs (Mobile Stations) in an OFDM (Orthogonal Frequency Division
Multiplexing) system utilizing SDM (Spatial Division Multiplexing) with
multiple transmit/receive antennas. In the method, a BS (Base Station)
can effectively assign a pilot channel to estimate a downlink channel.
The BS divides the single frequency sub-channel into a plurality of
spatial channels, and sequentially assigns the plurality of spatial
channels to the MSs having the maximum communication capacity, thereby
transmitting signals of the MSs through the single frequency sub-channel.