23. A device for multiplexing data words, comprising: a) an encoder for generating a plurality of data blocks, each block comprising data words and each data word containing data symbols derived from a data signal; b) a control unit for determining for one or more data blocks in dependence on at least one transmission constraint if the data words of said one or more data blocks are to be multiplexed in space-time or in space-frequency, wherein the transmission constraint comprises a data-related transmission constraint relating to a preservation of one or more periodic structures in the data signal; and c) a multiplexer for multiplexing the data words of the data blocks in accordance with the determination made by the control unit.
23. A device for multiplexing data words, comprising: a) an encoder for generating a plurality of data blocks, each block comprising data words and each data word containing data symbols derived from a data signal; b) a control unit for determining for one or more data blocks in dependence on at least one transmission constraint if the data words of said one or more data blocks are to be multiplexed in space-time or in space-frequency, wherein the transmission constraint comprises a data-related transmission constraint relating to a preservation of one or more periodic structures in the data signal; and c) a multiplexer for multiplexing the data words of the data blocks in accordance with the determination made by the control unit. 25. The device according to claim 23 , wherein at least the data words of data blocks relating to the periodic structures are multiplexed in space-frequency, and wherein the data words of data blocks relating to the user data section are multiplexed in space-time.