Rank adapation for MIMO transmissions and retransmissions

An apparatus for wireless communications by a network entity, comprising:

• a memory comprising instructions;
• and
• one or more processors configured to execute the instructions and cause the UE to:
• send, to a user equipment (UE), a first multiple input multiple output (MIMO) transmission on a first number of layers;
• receive, from the UE, a rank correction request indicating a decoding failure of the first MIMO transmission caused by a rank mismatch, wherein the rank mismatch indicates that the first number of layers is different than a rank number of a current channel;
• and
• send a second MIMO transmission with a second number of layers, using a space-time code (STC), in response to the rank correction request, to the UE to recover data lost due to the decoding failure, wherein the second number of layers comprises a subset of the first number of layers selected based on their associated signal to noise ratio (SNR),
• wherein the rank correction request includes information regarding a ranking of the first number of layers based on their associated SNR.

A method for wireless communications by a user equipment (UE), comprising:

• detecting that a decoding failure of a first multiple input multiple output (MIMO) transmission received on a first number of layers is caused by a rank mismatch, wherein the rank mismatch indicates that the first number of layers is different than a rank number of a current channel;
• sending, to a network entity, a rank correction request;
• combining samples from the first MIMO transmission and a second MIMO transmission received on a second number of layers in response to the rank correction request, to recover data lost due to the decoding failure, wherein the second number of layers comprises a subset of the first number of layers selected based on their associated signal to noise ratio (SNR);
• ranking the first number of layers based on their associated SNR;
• and
• including information regarding the ranking with the rank correction request.

A method for wireless communications by a network entity, comprising:

• sending, to a user equipment (UE), a first multiple input multiple output (MIMO) transmission on a first number of layers;
• receiving, from the UE, a rank correction request indicating a decoding failure of the first MIMO transmission due to a rank mismatch, wherein the rank mismatch indicates that the first number of layers is different than a rank number of a current channel;
• and
• sending a second MIMO transmission with a second number of layers, using a space-time code (STC), in response to the rank correction request, to the UE to recover data lost due to the decoding failure, wherein the second number of layers comprises a subset of the first number of layers selected based on their associated signal to noise ratio (SNR),
• wherein the rank correction request includes information regarding a ranking of the first number of layers based on their associated SNR.