Method and apparatus for conveying precoding information in a MIMO system

A method in a second node of obtaining precoding information in a control message from a first node, the control message containing information that describes properties of an associated wireless data transmission between the first and second nodes employing spatial multiplexing and precoding information for sending codewords corresponding to transport blocks in said wireless data transmission, comprising the steps of:

• receiving said control message including precoding parameters determined by the first node;
• and
• detecting said precoding parameters by decoding control information bits in at least one precoding information field of the control message based on values in payload size related fields in the control message, wherein said values are used to indicate that a first codeword is enabled while a second codeword is disabled, or that two codewords are enabled, whereby an interpretation of said control information bits in the precoding information field(s) is determined based on whether one or two codewords are enabled.

An apparatus in a second node of obtaining precoding information in a control message from a first node, the control message containing information that describes properties of an associated wireless data transmission between the first and second nodes employing spatial multiplexing and precoding information for sending codewords corresponding to transport blocks in said wireless data transmission, comprising:

• a transceiver configured to receive said control message including precoding parameters determined by the first node;
• and
• a decoder configured to detect said precoding parameters by decoding control information bits in at least one precoding information field of the control message based on values in payload size related fields in the control message, wherein said values are used to indicate that a first codeword is enabled while a second codeword is disabled, or that two codewords are enabled, whereby an interpretation of said control information bits in the precoding information field(s) is determined based on whether one or two codewords are enabled.