Feedback channel transmission and detection in multi antenna wireless communication systems

A method by a user equipment in a communications system, the method comprising:

• determining a codebook subset restriction indicating a reduced set of precoding matrices out of an original set of precoding matrices in an original codebook, wherein a full set of Precoding Matrix Indicator, PMI, bits is used to identify the original set of precoding matrices in the original codebook;
• and
• generating a mapping rule based on the codebook subset restriction;
• and
• determining a reduced set of PMI bits based on a set of entries in the reduced set of precoding matrices wherein the reduced set of PMI bits has fewer bits than the full set of PMI bits.

A network node comprising:

• a transceiver configured to provide communication between the network node and a user equipment;
• and
• a processor coupled with the transceiver, wherein the processor is configured to perform operations comprising:
• determining a codebook subset restriction indicating a reduced set of precoding matrices out of an original set of precoding matrices in an original codebook, wherein a full set of Precoding Matrix Indicator, PMI, bits is used to identify the original set of precoding matrices in the original codebook;
• determining a reduced set of PMI bits for use in a feedback channel based on a number of entries in the reduced set of precoding matrices, wherein the reduced set of PMI bits has fewer bits than the full set of PMI bits;
• determining a mapping of the entries in the reduced set of precoding matrices to entries in the original set of precoding matrices;
• and
• receiving on the feedback channel, from the user equipment, a feedback message having the reduced set of PMI bits.

A user equipment comprising:

• a transceiver configured to provide communication between user equipment and a network node;
• and
• a processor coupled with the transceiver, wherein the processor is configured to perform operations comprising:
• determining a codebook subset restriction indicating a reduced set of precoding matrices out of an original set of precoding matrices in an original codebook, wherein a full set of Precoding Matrix Indicator, PMI, bits is used to identify the original set of precoding matrices in the original codebook;
• generating a mapping rule based on the codebook subset restriction;
• and
• determining a reduced set of PMI bits based on a set of entries in the reduced set of precoding matrices wherein the reduced set of PMI bits has fewer bits than the full set of PMI bits.