In an OFDM system, multiple (M) interlaces are defined for M non-overlapping sets of frequency subbands, and M slots with fixed indices are also defined. Data streams and pilot are mapped to slots, which are in turn mapped to interlaces based on a slot-to-interlace mapping scheme that can achieve frequency diversity and good performance for all slots. At a transmitter, a slot-to-interlace converter maps the slots to the interlaces. The slot-to-interlace converter includes multiple multiplexers and a control unit. The multiplexers map the M slots to the M interlaces based on the slot-to-interlace mapping scheme. The control unit generates at least one control signal for the multiplexers. The multiplexers may be arranged and controlled in various manners depending on the slot-to-interlace mapping scheme. At a receiver, a complementary interlace-to-slot converter maps the interlaces to the slots.