however as shown in fig7 it can be understood that all dft input positions are available in the mapping relationship between the forward data resource channels corresponding to two layers used for forward data stream transmission and the dft input positions for reverse ack nack bit transmission for the data streams received over the two layers proposed by the present invention therefore for interference measurement with the mapping relationship it should be ensured that at least 8 of the 16 input positions are always unused and this means that there is a need for some restriction on the forward resource allocation a detailed description will now be made of a reverse ack nack bit transmission method according to an embodiment of the present invention under the assumption that resource channels are bound on a two by two basis for forward resource allocation for convenience it is assumed that there are a total of 8 forward data resource channels that is in this case only one dft is needed for reverse ack nack bit transmission for example let 39 s assume that a base station transmits data streams to mobile stations a and b over forward data resource channels 0 and 1 and their associated two layers transmits data streams to mobile stations c and d over forward data resource channels 2 and 3 and their associated two layers transmits data streams to mobile stations e and f over forward data resource channels 4 and 5 and their associated two layers and transmits data streams to mobile stations g and h over forward data resource channels 6 and 7 and their associated two layers that is in this.