BACKGROUND

The following relates generally to wireless communications, and more specifically to channel quality indicator (CQI) report based on demodulation reference signal (DMRS).

Wireless communications systems are widely deployed to provide various types of communication content such as voice, video, packet data, messaging, broadcast, and so on. These systems may be capable of supporting communication with multiple users by sharing the available system resources (e.g., time, frequency, and power). Examples of such multiple-access systems include fourth generation (4G) systems such as Long Term Evolution (LTE) systems, LTE-Advanced (LTE-A) systems, or LTE-A Pro systems, and fifth generation (5G) systems which may be referred to as New Radio (NR) systems. These systems may employ technologies such as code division multiple access (CDMA), time division multiple access (TDMA), frequency division multiple access (FDMA), orthogonal frequency division multiple access (OFDMA), or discrete Fourier transform-spread-OFDM (DFT-S-OFDM).

A wireless multiple-access communications system may include a number of base stations or network access nodes, each simultaneously supporting communication for multiple communication devices, which may be otherwise known as user equipment (UE). Some wireless communications systems may support ultra-reliable low latency communication (URLLC) between a base station and a UE. However, the low latency requirements of a URLLC system may be incompatible with conventional transmission methods. In particular, conventional techniques for performing channel state information (CSI) reporting for URLLC may be deficient considering the low latency requirements of a URLLC system.

SUMMARY

The described techniques relate to improved methods, systems, devices, or apparatuses that support channel quality indicator (CQI) report based on demodulation reference signal (DMRS). Specifically, the techniques described herein provide procedures at a user equipment (UE) for performing CQI reporting based on a DMRS received from a base station. In some cases, the base station may configure the UE with such DMRS based CQI reporting (e.g., by transmitting a CQI reporting configuration to the UE). The CQI reporting configuration may specify the UE is to report CQI based on DMRS and, in some cases, may configure the UE to report the CQI with hybrid automatic repeat request (HARQ) feedback (e.g., with acknowledgement (ACK)/negative acknowledgement (NACK) reporting from the UE).

For example, a UE may receive a control message (e.g., a physical downlink control channel (PDCCH) transmission) that indicates a resource for reception of a downlink transmission (e.g., a physical downlink shared channel (PDSCH) transmission) and an uplink control resource (e.g., a physical uplink control channel (PUCCH) resource) for transmission of CQI information (e.g., a CQI report, signal to noise ratio (SNR) information, a channel state information (CSI) report, etc.). The UE may identify a DMRS of the downlink transmission, and calculate a CQI based on the DMRS. The UE may then transmit the calculated CQI to the base station via the uplink control resource indicated by the control message received from the base station. In some cases, the CQI information may be transmitted with HARQ feedback using the uplink control resource (e.g., the UE may multiplex the CQI with an ACK/NACK corresponding to the downlink transmission). In other cases, the control message may indicate separate uplink resources for each of the CQI and the HARQ feedback.

In some cases, the reported CQI may include SNR information associated with the DMRS received by the UE. In some cases, the CQI report may include the absolute SNR (e.g., the explicit value of the measured SNR). In other cases, the CQI report may include delta SNR (e.g., a delta SNR value relative to some reference SNR value). For example, CQI reporting of delta SNR may reduce the range of reportable SNR, resulting in less CQI reporting overhead. In some cases, the reference SNR may refer to some radio resource control (RRC) configured SNR for the configured modulation coding scheme (MCS), the SNR of a previous DMRS, the SNR from the previous CQI requested by the base station, etc.

In some cases, multiple downlink transmissions (e.g., multiple PDSCH transmissions) may indicate the same uplink control resource (e.g., the same PUCCH) for CQI reporting based on the DMRS. In such cases where PUCCH for DMRS based CQI observes multiple PDSCHs, the UE may report CQI for a reference PDSCH. In some cases, the reference PDSCH may be configured via RRC signaling, the latest (e.g., most recently received) DMRS, etc. In some cases, downlink control information (DCI) of the PDCCH may indicate which PDSCH are to be associated with CQI reporting (e.g., by adding a bit in DCI for each PDSCH configured by the control message from the base station). The UE may then report CQI for the indicated PDSCH. In other cases where PUCCH for DMRS based CQI observes multiple PDSCHs, the UE may calculate CQI for all, or a subset, of the PDSCHs (e.g., based on the DMRS associated with each PDSCH). In such cases, the UE may report each CQI, an average CQI, a maximum CQI variation, etc., for all PDSCHs within the PUCCH window.

The base station may receive CQI from the UE, and may determine resources and configurations for communications with the UE (e.g., the base station may identify a MCS for a next transmission, or in some cases a retransmission, to the UE). In some cases, the base station may reduce MCS configuration overhead (e.g., MCS bit fields in downlink DCI) once DMRS based CQI is triggered. For example, the base station may indicate a delta MCS (e.g., a delta value from the previous MCS value to the updated MCS value) in DCI, which may reduce the number of bits needed to convey an MCS update to the UE. A method of wireless communication at a UE is described.

The method may include receiving a control message that indicates a resource for reception of a downlink transmission and a first uplink control resource for transmission of a CQI, identifying a DMRS of the downlink transmission based on the control message, calculating the CQI based on the identified DMRS, and transmitting the calculated CQI via the first uplink control resource.

An apparatus for wireless communication at a UE is described. The apparatus may include a processor, memory coupled with the processor, and instructions stored in the memory. The instructions may be executable by the processor to cause the apparatus to receive a control message that indicates a resource for reception of a downlink transmission and a first uplink control resource for transmission of a CQI, identify a DMRS of the downlink transmission based on the control message, calculate the CQI based on the identified DMRS, and transmit the CQI indicator via the first uplink control resource.

Another apparatus for wireless communication at a UE is described. The apparatus may include means for receiving a control message that indicates a resource for reception of a downlink transmission and a first uplink control resource for transmission of a CQI, identifying a DMRS of the downlink transmission based on the control message, calculating the CQI based on the identified DMRS, and transmitting the calculated CQI via the first uplink control resource.

A non-transitory computer-readable medium storing code for wireless communication at a UE is described. The code may include instructions executable by a processor to receive a control message that indicates a resource for reception of a downlink transmission and a first uplink control resource for transmission of a CQI, identify a DMRS of the downlink transmission based on the control message, calculate the CQI based on the identified DMRS, and transmit the calculated CQI via the first uplink control resource.

Some examples of the method, apparatuses, and non-transitory computer-readable medium described herein may further include operations, features, means, or instructions for multiplexing, on the first uplink control resource, the calculated CQI with an ACK or a NACK associated with the downlink transmission.

Some examples of the method, apparatuses, and non-transitory computer-readable medium described herein may further include operations, features, means, or instructions for receiving, with the control message, an indication of a second uplink control resource for transmission of HARQ feedback, where the first uplink control resource and the second uplink control resource may be different and transmitting an ACK or a NACK associated with the downlink transmission via the second uplink control resource. Some examples of the method, apparatuses, and non-transitory computer-readable medium described herein may further include operations, features, means, or instructions for receiving a timing offset and identifying the first uplink control resource based on the timing offset and the second uplink control resource.

In some examples of the method, apparatuses, and non-transitory computer-readable medium described herein the transmitted CQI indicates an ACK (e.g., an early ACK) of the downlink transmission. In some examples of the method, apparatuses, and non-transitory computer-readable medium described herein the transmitted CQI indicates a NACK (e.g., an early NACK) of the downlink transmission. Some examples of the method, apparatuses, and non-transitory computer-readable medium described herein may further include operations, features, means, or instructions for receiving a retransmission of the downlink transmission based at least in part on the transmitted CQI.

In some examples of the method, apparatuses, and non-transitory computer-readable medium described herein, transmitting the calculated CQI further may include operations, features, means, or instructions for measuring a SNR of the identified DMRS and transmitting a delta SNR, where the delta SNR may be based on the measured SNR of the identified DMRS and a reference SNR. In some examples of the method, apparatuses, and non-transitory computer-readable medium described herein, the reference SNR includes an SNR of a configured MCS, an SNR of a previous DMRS, or an SNR of a previous requested CQI.

In some examples of the method, apparatuses, and non-transitory computer-readable medium described herein, transmitting the calculated CQI further may include operations, features, means, or instructions for measuring a SNR of the identified DMRS and transmitting an absolute SNR, where the absolute SNR may be based on the measured SNR of the identified DMRS. In some examples of the method, apparatuses, and non-transitory computer-readable medium described herein, identifying the DMRS of the downlink transmission further may include operations, features, means, or instructions for identifying a reference PDSCH associated with the downlink transmission, where the DMRS may be identified based on the reference PDSCH.

In some examples of the method, apparatuses, and non-transitory computer-readable medium described herein, identifying the DMRS of the downlink transmission further may include operations, features, means, or instructions for identifying a most recent DMRS. Some examples of the method, apparatuses, and non-transitory computer-readable medium described herein may further include operations, features, means, or instructions for identifying a reference PDSCH associated with the downlink transmission based on the received control message, where the DMRS may be identified based on the reference PDSCH.

Some examples of the method, apparatuses, and non-transitory computer-readable medium described herein may further include operations, features, means, or instructions for identifying a set of PDSCHs associated with the downlink transmission, selecting a PDSCH of the set of PDSCHs, calculating the CQI based on a DMRS associated with the selected PDSCH and transmitting an indication of the selected PDSCH and the calculated CQI based on the first uplink control resource.

Some examples of the method, apparatuses, and non-transitory computer-readable medium described herein may further include operations, features, means, or instructions for identifying a set of PDSCHs associated with the downlink transmission, calculating a set of CQI, each CQI based on a DMRS associated with each PDSCH of the set of PDSCHs, identifying an average CQI based on the set of calculated CQI and transmitting the average CQI based on the first uplink control resource. In some examples of the method, apparatuses, and non-transitory computer-readable medium described herein, the set of PDSCHs may be within a window of the first uplink control resource.

Some examples of the method, apparatuses, and non-transitory computer-readable medium described herein may further include operations, features, means, or instructions for identifying a set of PDSCHs associated with the downlink transmission, calculating a set of CQI, each CQI based on a DMRS associated with each PDSCH of the set of PDSCHs, identifying a maximum CQI variation based on the set of calculated CQI and transmitting the maximum CQI variation based on the first uplink control resource.

Some examples of the method, apparatuses, and non-transitory computer-readable medium described herein may further include operations, features, means, or instructions for identifying a set of PDSCHs associated with the downlink transmission, calculating a set of CQI, each CQI based on a DMRS associated with each PDSCH of the set of PDSCHs and transmitting each of the calculated set of CQIs with a corresponding ACK or a NACK associated with each PDSCH, based on the first uplink control resource.

Some examples of the method, apparatuses, and non-transitory computer-readable medium described herein may further include operations, features, means, or instructions for determining a NACK to be sent based on the downlink transmission and transmitting the calculated CQI based on the determination. In some examples of the method, apparatuses, and non-transitory computer-readable medium described herein, the calculated CQI includes the determined NACK.

Some examples of the method, apparatuses, and non-transitory computer-readable medium described herein may further include operations, features, means, or instructions for receiving a CQI reporting configuration for calculating the CQI based on DMRS measurement and transmitting the CQI with HARQ feedback, where the CQI may be calculated based on the CQI reporting configuration.

In some examples of the method, apparatuses, and non-transitory computer-readable medium described herein, transmitting the calculated CQI further may include operations, features, means, or instructions for transmitting the calculated CQI with HARQ feedback based on the CQI reporting configuration. In some examples of the method, apparatuses, and non-transitory computer-readable medium described herein, the CQI reporting configuration may be received via RRC signaling.

In some examples of the method, apparatuses, and non-transitory computer-readable medium described herein, identifying the DMRS further may include operations, features, means, or instructions for identifying a CQI report indication based on the control message, where the CQI report indication may be associated with a PDSCH transmission and identifying the DMRS based on the PDSCH transmission. In some examples of the method, apparatuses, and non-transitory computer-readable medium described herein, the transmitted CQI corresponds to the PDSCH transmission. In some examples of the method, apparatuses, and non-transitory computer-readable medium described herein, the CQI report indication includes a DCI bit in the received control message.

A method of wireless communication at a base station is described. The method may include transmitting a control message that indicates a resource for a downlink transmission and a first uplink control resource for reception of a CQI, transmitting the downlink transmission, where the downlink transmission includes a DMRS, and receiving the CQI via the first uplink control resource, where the CQI is based on the DMRS.

An apparatus for wireless communication at a base station is described. The apparatus may include a processor, memory coupled with the processor, and instructions stored in the memory. The instructions may be executable by the processor to cause the apparatus to transmit a control message that indicates a resource for a downlink transmission and a first uplink control resource for reception of a CQI, transmit the downlink transmission, where the downlink transmission includes a DMRS, and receive the CQI via the first uplink control resource, where the CQI is based on the DMRS.

Another apparatus for wireless communication at a base station is described. The apparatus may include means for transmitting a control message that indicates a resource for a downlink transmission and a first uplink control resource for reception of a CQI, transmitting the downlink transmission, where the downlink transmission includes a DMRS, and receiving the CQI via the first uplink control resource, where the CQI is based on the DMRS.

A non-transitory computer-readable medium storing code for wireless communication at a base station is described. The code may include instructions executable by a processor to transmit a control message that indicates a resource for a downlink transmission and a first uplink control resource for reception of a CQI, transmit the downlink transmission, where the downlink transmission includes a DMRS, and receive the CQI via the first uplink control resource, where the CQI is based on the DMRS.

Some examples of the method, apparatuses, and non-transitory computer-readable medium described herein may further include operations, features, means, or instructions for transmitting a CQI reporting configuration for CQI calculation based on DMRS measurement and CQI reporting with HARQ feedback, where the CQI may be received based on the CQI reporting configuration. In some examples of the method, apparatuses, and non-transitory computer-readable medium described herein, the CQI reporting configuration may be transmitted via RRC signaling.

Some examples of the method, apparatuses, and non-transitory computer-readable medium described herein may further include operations, features, means, or instructions for transmitting a CQI report indication, where the CQI report indication may be associated with a PDSCH transmission and receiving the CQI based on the CQI report indication, where the CQI corresponds to the PDSCH transmission.

In some examples of the method, apparatuses, and non-transitory computer-readable medium described herein, the CQI report indication includes a DCI bit in the transmitted control message. Some examples of the method, apparatuses, and non-transitory computer-readable medium described herein may further include operations, features, means, or instructions for receiving an ACK or a NACK associated with the downlink transmission via the first uplink control resource. In some examples of the method, apparatuses, and non-transitory computer-readable medium described herein, the ACK or the NACK associated with the downlink transmission may be multiplexed with the calculated CQI.

Some examples of the method, apparatuses, and non-transitory computer-readable medium described herein may further include operations, features, means, or instructions for transmitting, with the control message, an indication of a second uplink control resource for transmission of HARQ feedback and receiving an ACK or a NACK associated with the downlink transmission via the second uplink control resource.

Some examples of the method, apparatuses, and non-transitory computer-readable medium described herein may further include operations, features, means, or instructions for identifying a timing offset between the first uplink control resource and the second uplink control resource and transmitting the timing offset, where the ACK or the NACK associated with the downlink transmission may be received via the second uplink control resource indicated by the timing offset.

In some examples of the method, apparatuses, and non-transitory computer-readable medium described herein the received CQI indicates an ACK (e.g., an early ACK) of the downlink transmission. In some examples of the method, apparatuses, and non-transitory computer-readable medium described herein the received CQI indicates a NACK (e.g., an early NACK) of the downlink transmission. Some examples of the method, apparatuses, and non-transitory computer-readable medium described herein may further include operations, features, means, or instructions for transmitting a retransmission of the downlink transmission based at least in part on the received CQI.

In some examples of the method, apparatuses, and non-transitory computer-readable medium described herein, receiving the CQI may include operations, features, means, or instructions for receiving an absolute SNR associated with the DMRS or a delta SNR associated with the DMRS and a reference SNR. In some examples of the method, apparatuses, and non-transitory computer-readable medium described herein, the reference SNR includes an SNR of a configured MCS, an SNR of a previous DMRS, or an SNR of a previous requested CQI. Some examples of the method, apparatuses, and non-transitory computer-readable medium described herein may further include operations, features, means, or instructions for identifying a MCS offset based on the received CQI and transmitting an indication of the MCS offset.

Some examples of the method, apparatuses, and non-transitory computer-readable medium described herein may further include operations, features, means, or instructions for identifying an outer loop link adaptation based on CQIs received based on SRSs or CSI-RSs and identifying an internal loop link adaptation based on CQIs received based on DMRS. Some examples of the method, apparatuses, and non-transitory computer-readable medium described herein may further include operations, features, means, or instructions for identifying a MCS update based on the identified internal loop link adaptation and transmitting an indication of the MCS update. Some examples of the method, apparatuses, and non-transitory computer-readable medium described herein may further include operations, features, means, or instructions for identifying a bursty interference condition based on the identified inter loop link adaptation.

