# US 11,909,474 B2 · Rank adapation for MIMO transmissions and retransmissions > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 11,909,474 B2 - Document ID: US11909474B2 - Status: Granted - Kind: B2 - Application number: 17/319,836 - Filed: 2021-05-13 - Published: 2022-11-17 - Granted: 2024-02-20 - Earliest claimed: 2021-05-13 - Assignees: QUALCOMM Incorporated - Applicants: QUALCOMM Incorporated - Inventors: Gideon Shlomo Kutz; Tal Oved; Amit Bar-Or Tillinger; Assaf Touboul - Web page: https://patentgrep.com/patent/US11909474B2 ## CPC - H04L 1/1845: {Combining techniques, e.g. code combining} - H04B 17/336: Signal-to-interference ratio [SIR] or carrier-to-interference ratio [CIR] - H04L 1/0618: {Space-time coding} - H04L 1/1819: {with retransmission of additional or different redundancy} - H04L 5/0051: {of dedicated pilots, i.e. pilots destined for a single user or terminal} - H04L: TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION (arrangements common to telegraphic and telephonic communication H04M) - H04B: TRANSMISSION ## Abstract Certain aspects of the present disclosure provide a technique for wireless communications by a user equipment (UE). The UE implements the technique to detect that a decoding failure of a first multiple input multiple output (MIMO) transmission, sent by a network entity on a first number of layers, is caused by a rank mismatch. The UE then sends a rank correction request to a network entity. The UE then combines samples from the first MIMO transmission and a second MIMO transmission, sent by the network entity using a space-time code (STC) with a second number of layers in response to the rank correction request, to recover data lost due to the decoding failure. ## Claims ### Claim 1 An apparatus for wireless communications by a user equipment (UE), comprising: a memory comprising instructions; and one or more processors configured to execute the instructions and cause the UE to: detect 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; send, to a network entity, a rank correction request; combine 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); rank the first number of layers based on their associated SNR; and include information regarding the ranking with the rank correction request. ### Claim 2 (depends on 1) The apparatus of claim 1, wherein the rank mismatch indicates a mismatch between a previously indicated rank number and a rank number supported by channel conditions experienced by the first MIMO transmission. ### Claim 3 (depends on 1) The apparatus of claim 1, wherein the one or more processors are configured to execute the instructions and cause the UE to send the rank correction request via at least one of: a physical uplink control channel (PUCCH) or a physical uplink shared channel (PUSCH), and wherein the rank correction indicates at least one of: a requested rank number or a difference in rank numbers. ### Claim 4 (depends on 3) The apparatus of claim 3, the one or more processors are configured to execute the instructions and cause the UE to: receive, from the network entity, a demodulation reference signal (DMRS); and determine the requested rank number based on the DMRS. ### Claim 5 (depends on 3) The apparatus of claim 3, wherein the difference in rank numbers indicates a value corresponding to a difference between a previously indicated rank number and a rank number supported by channel conditions experienced by the first MIMO transmission. ### Claim 6 (depends on 1) The apparatus of claim 1, wherein the second MIMO transmission conveys data equivalent of the second number of layers, and wherein the second number of layers comprises at least one of: a number of new layers or the first number of layers. ### Claim 7 (depends on 1) The apparatus of claim 1, wherein layers within the subset of the first number of layers have lowest SNRs among the first number of layers. ### Claim 8 (depends on 6) The apparatus of claim 6, wherein: the first MIMO transmission has a precoding matrix associated with the first number of layers; and the second MIMO transmission has a modified precoding matrix associated with the second number of layers. ### Claim 9 (depends on 1) The apparatus of claim 1, wherein the first and the second MIMO transmissions respectively have different first and second orders of precoding vectors, when channel conditions are same or similar between the first and the second MIMO transmissions. ### Claim 10 (depends on 1) The apparatus of claim 1, the one or more processors are configured to execute the instructions and cause the UE to combine samples from a third MIMO transmission with the first MIMO transmission and the second MIMO transmission to recover the data lost due to the decoding failure. ### Claim 11 (depends on 10) The apparatus of claim 10, wherein the one or more processors are configured to execute the instructions and cause the UE to receive the third MIMO transmission with a third number of layers different than the second number of layers. ### Claim 12 (depends on 1) The apparatus of claim 1, the one or more processors are configured to execute the instructions and cause the UE to: participate in coding rate adaptation after sending the rank correction request. ### Claim 13 (depends on 1) The apparatus of claim 1, the one or more processors are configured to execute the instructions and cause the UE to: receive one or more retransmissions of the first MIMO transmission and the second MIMO transmission at least in response to the decoding failure of the second MIMO transmission. ### Claim 14 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. ### Claim 15 (depends on 14) The apparatus of claim 14, wherein the rank mismatch indicates a mismatch between a previously indicated rank number and a rank number supported by channel conditions experienced by the first MIMO transmission. ### Claim 16 (depends on 14) The apparatus of claim 14, wherein the one or more processors are configured to execute the instructions and cause the UE to receive the rank correction request via at least one of: a physical uplink control channel (PUCCH) or a physical uplink shared channel (PUSCH), and wherein the rank correction indicates at least one of: a requested rank number or a difference in rank numbers. ### Claim 17 (depends on 16) The apparatus of claim 16, wherein the one or more processors are configured to execute the instructions and cause the UE to: send, to the UE, a demodulation reference signal (DMRS) for use in determination of the requested rank number. ### Claim 18 (depends on 16) The apparatus of claim 16, wherein the difference in rank numbers indicates a value corresponding to a difference between a previously indicated rank number and a rank number supported by channel conditions experienced by the first MIMO transmission. ### Claim 19 (depends on 14) The apparatus of claim 14, wherein: the second MIMO transmission conveys data equivalent of the second number of layers, and wherein the second number of layers comprises at least one of: a number of new layers or the first number of layers; layers within the subset of the first number of layers have lowest SNRs among the first number of layers; and the first MIMO transmission has a precoding matrix associated with the first number of layers and the second MIMO transmission has a modified precoding matrix associated with the second number of layers. ### Claim 20 (depends on 14) The apparatus of claim 14, wherein the first and the second MIMO transmissions respectively have different first and second orders of precoding vectors, when channel conditions are same or similar between the first and the second MIMO transmissions. ### Claim 21 (depends on 14) The apparatus of claim 14, wherein samples from a third MIMO transmission are a combination of the first MIMO transmission and the second MIMO transmission. ### Claim 22 (depends on 21) The apparatus of claim 21, wherein the third MIMO transmission has a third number of layers different than the second number of layers. ### Claim 23 (depends on 14) The apparatus of claim 14, the one or more processors are configured to execute the instructions and cause the UE to: send one or more retransmissions of the first MIMO transmission and the second MIMO transmission at least in response to the decoding failure of the second MIMO transmission. ### Claim 24 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. ### Claim 25 (depends on 24) The method of claim 24, wherein the rank mismatch indicates a mismatch between a previously indicated rank number and a rank number supported by channel conditions experienced by the first MIMO transmission. ### Claim 26 (depends on 24) The method of claim 24, wherein the rank correction request is sent via at least one of: a physical uplink control channel (PUCCH) or a physical uplink shared channel (PUSCH), and wherein the rank correction indicates at least one of: a requested rank number or a difference in rank numbers. ### Claim 27 (depends on 24) The method of claim 24, wherein the second MIMO transmission conveys data equivalent of the second number of layers, and wherein the second number of layers comprises at least one of: a number of new layers or the first number of layers. ### Claim 28 (depends on 24) The method of claim 24, further comprising combining samples from a third MIMO transmission with the first MIMO transmission and the second MIMO transmission to recover the data lost due to the decoding failure. ### Claim 29 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. ### Claim 30 (depends on 29) The method of claim 29, wherein the rank mismatch indicates a mismatch between a previously indicated rank number and a rank number supported by channel conditions experienced by the first MIMO transmission.