A method for selecting transport formats in a wireless transmitting device which has transmission modes including a single-stream transmission mode and a multiple-stream transmission mode, the wireless transmitting device comprising a transmit buffer to buffer data before the transport formats being selected for transmitting said data to a wireless receiving device, the method comprising: acquiring radio qualities associated with each stream being transmitted to the wireless receiving device; setting the transmission mode according to the acquired radio qualities detecting whether there is buffer limitation for said transmit buffer when said multiple-stream transmission mode is set, and when buffer limitation is detected and said multiple-stream transmission mode is selected for stream transmission: resetting said transmission mode to said single-stream transmission mode; selecting a single preliminary transport format for a single stream in said single-stream transmission mode; comparing a transport block size indicated in said single preliminary transport format with a number of buffered data bits in said transmit buffer; if said transport block size is larger than or equal to the number of buffered data bits, using said single preliminary transport format as selected transport format for said single stream; and if said transport block size is lower than the number of buffered data bits, selecting the transmission mode to said multiple-stream transmission mode, and allocating the buffered data bits to multiple streams in said multiple-stream transmission mode based on the received radio qualities associated with respective streams and selecting transport formats for respective streams of the multiple streams based on respective allocated buffered data bits of said multiple streams, wherein the buffered data bits are represented by the number of bits buffered in the transmit buffer, and said detecting step comprises selecting preliminary transport formats for said multiple-stream transmission mode assuming there is no buffer limitation and obtaining transport block sizes indicated in the preliminary transport formats; comparing a sum of all said transport block sizes for the multiple streams with the number of buffered data bits; and determining that buffer limitation is detected if the sum exceeds the number of buffered data bits. acquiring radio qualities associated with each stream being transmitted to the wireless receiving device; setting the transmission mode according to the acquired radio qualities detecting whether there is buffer limitation for said transmit buffer when said multiple-stream transmission mode is set, and when buffer limitation is detected and said multiple-stream transmission mode is selected for stream transmission: resetting said transmission mode to said single-stream transmission mode; selecting a single preliminary transport format for a single stream in said single-stream transmission mode; comparing a transport block size indicated in said single preliminary transport format with a number of buffered data bits in said transmit buffer; if said transport block size is larger than or equal to the number of buffered data bits, using said single preliminary transport format as selected transport format for said single stream; and if said transport block size is lower than the number of buffered data bits, selecting the transmission mode to said multiple-stream transmission mode, and allocating the buffered data bits to multiple streams in said multiple-stream transmission mode based on the received radio qualities associated with respective streams and selecting transport formats for respective streams of the multiple streams based on respective allocated buffered data bits of said multiple streams, wherein the buffered data bits are represented by the number of bits buffered in the transmit buffer, and said detecting step comprises resetting said transmission mode to said single-stream transmission mode; selecting a single preliminary transport format for a single stream in said single-stream transmission mode; comparing a transport block size indicated in said single preliminary transport format with a number of buffered data bits in said transmit buffer; if said transport block size is larger than or equal to the number of buffered data bits, using said single preliminary transport format as selected transport format for said single stream; and if said transport block size is lower than the number of buffered data bits, selecting the transmission mode to said multiple-stream transmission mode, and allocating the buffered data bits to multiple streams in said multiple-stream transmission mode based on the received radio qualities associated with respective streams and selecting transport formats for respective streams of the multiple streams based on respective allocated buffered data bits of said multiple streams, wherein the buffered data bits are represented by the number of bits buffered in the transmit buffer, and said detecting step comprises selecting preliminary transport formats for said multiple-stream transmission mode assuming there is no buffer limitation and obtaining transport block sizes indicated in the preliminary transport formats; comparing a sum of all said transport block sizes for the multiple streams with the number of buffered data bits; and determining that buffer limitation is detected if the sum exceeds the number of buffered data bits.