CROSS REFERENCES TO RELATED APPLICATIONS

The present application for patent claims priority to International Patent Application No. PCT/CN2019/097207 by Li et al., entitled “CONFIGURATION OF SOUNDING REFERENCE SIGNAL RESOURCE FOR MULTI-PANEL UPLINK TRANSMISSION,” filed Jul. 23, 2019; and to International Patent Application No. PCT/CN2018/096696 by Li et al., entitled “CONFIGURATION OF SOUNDING REFERENCE SIGNAL RESOURCE FOR MULTI-PANEL UPLINK TRANSMISSION,” filed Jul. 23, 2018, each of which is assigned to the assignee hereof and each of which is hereby incorporated by reference in its entirety.

BACKGROUND

The following relates generally to wireless communications, and more specifically to configuration of sounding reference signal (SRS) resource(s) for multi-panel uplink transmission.

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 multiple-input, multiple-output (MIMO) communications (e.g., where communicating devices may be equipped with multiple antennas such that communications may employ multipath signal propagation). In some cases, MIMO communications may rely on transmissions of reference signals (e.g., sounding reference signals (SRSs)) over one or more antenna ports. Further, devices may store codebooks or lookup tables including, for example, uplink transmission parameters (e.g., uplink precoding information, co-phase information, a combination of beams for communication, etc.). For example, to indicate uplink transmission parameters, a base station may receive and evaluate a reference signal from a UE. The base station may then indicate an index associated with the codebook to the UE (e.g., and the UE may lookup uplink parameters accordingly). In some cases, this may result in latency arising from lookup procedures, memory storage burdens, overhead associated with codebook index signaling, etc.

SUMMARY

The described techniques relate to improved methods, systems, devices, and apparatuses that support configuration of sounding reference signal (SRS) resource(s) for multi-panel uplink transmission. Generally, the described techniques provide for SRS configuration in wireless communications systems supporting multi-panel uplink transmissions for determination of uplink precoding and co-phase information.

A user equipment (UE) may transmit a UE capability report to a base station indicating a number of SRS resources the UE is capable of transmitting over, a number of antenna ports the UE is capable of using for each SRS resource (e.g., for each SRS transmission), coherency capabilities between different antenna ports, etc. The base station may configure one or more SRS resources based at least in part on the capabilities of the UE, as indicated in the UE capability report. For example, the base station may configure three SRS resources, and each SRS resource may be associated with (e.g., or configured with) one or more antenna ports. The UE may then transmit SRSs according to the SRS configuration. In the above example, the UE may transmit three SRSs, one over each SRS resource, and each SRS may be transmitted using an antenna port configuration indicated by the SRS resource configuration.

The base station may determine co-phase information and uplink precoding information (e.g., UE precoder information) based on the one or more received SRSs. In some examples, the UE may identify co-phase adjustments for the one or more SRS resources, and may transmit the one or more SRSs according to the identified co-phase adjustments (e.g., where the co-phase may be adjusted from one SRS to the next). In such cases, the base station may indicate co-phase information via an SRS resource indicator (SRI) that indicates an SRS resource corresponding to one of the received SRS transmissions (e.g., as the SRI may implicitly indicate a co-phase adjustment used by the UE for the SRS transmission on the indicated SRS resource). In such cases, the base station may transmit an explicit indication of uplink precoding information (e.g., such as a transmitted precoding matrix indicator (TPMI) or other explicit indication or index of uplink precoding information and number of layers) in addition to the SRI. In other examples, the UE may identify precoder adjustments for the one or more SRS resources, and may transmit the one or more SRSs according to the identified precoder adjustments (e.g., where the precoder may be adjusted from one SRS to the next). In such cases, the base station may indicate uplink precoding information via an SRI that indicates an SRS resource corresponding to one of the received SRS transmissions (e.g., as the SRI may implicitly indicate a co-phase adjustment used by the UE for the SRS transmission on the indicated SRS resource). In such cases, the base station may transmit an explicit indication of co-phase information in addition to the SRI. In yet other examples (e.g., when only a single SRS resource is configured), the base station may transmit explicit indications of uplink precoding information and co-phase information (e.g., the base station may transmit TPMI to convey uplink precoding information, and a separate indication of co-phase may also be transmitted).

The UE may receive the uplink precoding indication and the co-phase information indication (e.g., via SRI and explicit indications), and may adjust SRS transmission parameters accordingly. For example, the UE may determine, based on the uplink precoding information, a precoding matrix, a number of physical uplink shared channel (PUSCH) transmission layers, a selection of a subset of antenna ports for PUSCH transmission, etc. In some cases, uplink precoding information indications and/or co-phase information indications may refer to explicit indications of indices, and the UE may reference a codebook or other lookup table using the index to obtain the uplink precoding information indications and/or co-phase information. According to additional aspects of the present disclosure, explicit uplink precoding information indications (e.g., TPMI) may include a precoder port selection pattern to account for the multiple panels that may be employed. For example, precoder port selection patterns may indicate antenna port indices (e.g., such that certain panels or subsets of the panels may be selected). As such, explicit uplink precoding information indications may be sent for different panels or subsets of the panels.

A method of wireless communication at a UE is described. The method may include receiving, from a base station, an SRS resource configuration for one or more SRS resources and transmitting, to the base station, one or more SRSs based on the SRS resource configuration. The method may further include receiving, from a base station, an SRS resource indication (SRI) indicating a selected SRS resource of the one or more SRS resources based at least in part on the one or more transmitted SRSs. The method may further include receiving, from the base station, at least one of an uplink precoding information indication and a co-phase information indication based on the one or more transmitted SRSs, the uplink precoding information indication and the co-phase information indication being included with the SRI or with a transmitted precoding matrix indicator (TPMI). The method may further include adjusting SRS transmission parameters based at least on the uplink precoding information indication and the co-phase information indication.

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, from a base station, an SRS resource configuration for one or more SRS resources, and transmit, to the base station, one or more SRSs based on the SRS resource configuration. The instructions may be executable by the processor to further cause the apparatus to receive, from a base station, an SRS resource indication (SRI) indicating a selected SRS resource of the one or more SRS resources based at least in part on the one or more transmitted SRSs. The instructions may be executable by the processor to further cause the apparatus to receive, from the base station, at least one of an uplink precoding information indication and a co-phase information indication based on the one or more transmitted SRSs, the uplink precoding information indication and the co-phase information indication being included with the SRI or with a transmitted precoding matrix indicator (TPMI), and adjust SRS transmission parameters based at least on the uplink precoding information indication and the co-phase information indication.

Another apparatus for wireless communication at a UE is described. The apparatus may include means for receiving, from a base station, an SRS resource configuration for one or more SRS resources, and transmitting, to the base station, one or more SRSs based on the SRS resource configuration. The apparatus may further include means for receiving, from the base station, an SRS resource indication (SRI) indicating a selected SRS resource of the one or more SRS resources based at least in part on the one or more transmitted SRSs. The apparatus may include further means for receiving, from the base station, at least one of an uplink precoding information indication and a co-phase information indication based on the one or more transmitted SRSs, the uplink precoding information indication and the co-phase information indication being included with the SRI or with a transmitted precoding matrix indicator (TPMI), and adjusting SRS transmission parameters based at least on the uplink precoding information indication and the co-phase information indication.

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, from a base station, an SRS resource configuration for one or more SRS resources, and transmit, to the base station, one or more SRSs based on the SRS resource configuration. The code may include instructions further executable by a processor to receive, from the base station, an SRS resource indication (SRI) indicating a selected SRS resource of the one or more SRS resources based at least in part on the one or more transmitted SRSs. The code may include instructions further executable by a processor to receive, from the base station, at least one of an uplink precoding information indication and a co-phase information indication based on the one or more transmitted SRSs, the uplink precoding information indication and the co-phase information indication being included with the SRI or with a transmitted precoding matrix indicator (TPMI), and adjust SRS transmission parameters based at least on the uplink precoding information indication and the co-phase information indication.

In some examples of the method, apparatuses, and non-transitory computer-readable medium described herein, transmitting the one or more SRSs based on the SRS resource configuration further may include operations, features, means, or instructions for identifying a co-phase adjustment for each of the one or more SRS resources and transmitting the one or more SRSs based on the identified co-phase adjustments.

In some examples of the method, apparatuses, and non-transitory computer-readable medium described herein, receiving the co-phase information indication may include operations, features, means, or instructions for receiving an SRI indicating a selected SRS resource of the one or more SRS resources based on the one or more transmitted SRSs, where the co-phase information indication includes the co-phase adjustment associated with the selected SRS resource indicated by the SRI.

Some examples of the method, apparatuses, and non-transitory computer-readable medium described herein may further include operations, features, means, or instructions for determining, based on the uplink precoding information indication, a precoding matrix, a number of PUSCH transmission layers, a selection of a subset of antenna ports for PUSCH transmission, or some combination thereof. In some examples of the method, apparatuses, and non-transitory computer-readable medium described herein, the uplink precoding information indication includes a precoder port selection pattern indicating the selection of the subset of antenna ports for PUSCH transmission.

In some examples of the method, apparatuses, and non-transitory computer-readable medium described herein, transmitting the one or more SRSs based on the SRS resource configuration further may include operations, features, means, or instructions for identifying a precoder adjustment for each of the one or more SRS resources and transmitting the one or more SRSs based on the identified precoder adjustments.

In some examples of the method, apparatuses, and non-transitory computer-readable medium described herein, receiving the uplink precoding information indication may include operations, features, means, or instructions for receiving an SRI indicating a selected SRS resource of the one or more SRS resources based on the one or more transmitted SRSs, where the uplink precoding information indication includes the precoder adjustment associated with the selected SRS resource indicated by the SRI.

Some examples of the method, apparatuses, and non-transitory computer-readable medium described herein may further include operations, features, means, or instructions for determining, based on the SRI, a number of PUSCH transmission layers, where the number of PUSCH transmission layers may be equal to the number of SRS resources indicated in the SRI.

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 UE capability report indicating a number of SRS resources capability, a number of SRS ports supported per SRS resource capability, an antenna port coherency capability, or some combination thereof, where the SRS resource configuration may be based on the transmitted UE capability report.

In some examples of the method, apparatuses, and non-transitory computer-readable medium described herein, the uplink precoding information indication includes an index of uplink precoding information and number of layers. In some examples of the method, apparatuses, and non-transitory computer-readable medium described herein, each SRS resource of the one or more SRS resources includes a set of antenna ports. In some examples of the method, apparatuses, and non-transitory computer-readable medium described herein, the uplink precoding information indication further indicates a number of layers.

A method of wireless communication at a base station is described. The method may include transmitting, to a UE, an SRS resource configuration for one or more SRS resources, and receiving, from the UE, one or more SRSs based on the SRS resource configuration. The method may further include transmitting an SRS resource indication (SRI) indicating a selected SRS resource of the one or more SRS resources based at least in part on the one or more transmitted SRSs. The method may further include transmitting, to the UE, at least one of an uplink precoding information indication and a co-phase information indication based on the one or more SRSs, the uplink precoding information indication and the co-phase information indication being included with the SRI or whit a transmitted precoding matrix indicator (TPMI).

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, to a UE, an SRS resource configuration for one or more SRS resources, and receive, from the UE, one or more SRSs based on the SRS resource configuration. The instructions may be executable by the processor to further cause the apparatus to transmit an SRS resource indication (SRI) indicating a selected SRS resource of the one or more SRS resources based at least in part on the one or more transmitted SRSs. The instructions may be executable by the processor to further cause the apparatus to transmit, to the UE, at least one of an uplink precoding information indication and a co-phase information indication based on the one or more SRSs, the uplink precoding information indication and the co-phase information indication being included with the SRI or whit a transmitted precoding matrix indicator (TPMI).

Another apparatus for wireless communication at a base station is described. The apparatus may include means for transmitting, to a UE, an SRS resource configuration for one or more SRS resources, receiving, from the UE, one or more SRSs based on the SRS resource configuration, transmitting an SRS resource indication (SRI) indicating a selected SRS resource of the one or more SRS resources based at least in part on the one or more transmitted SRSs, and transmitting, to the UE, at least one of an uplink precoding information indication and a co-phase information indication based on the one or more SRSs, the uplink precoding information indication and the co-phase information indication being included with the SRI or whit a transmitted precoding matrix indicator (TPMI).

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, to a UE, an SRS resource configuration for one or more SRS resources, receive, from the UE, one or more SRSs based on the SRS resource configuration, transmit an SRS resource indication (SRI) indicating a selected SRS resource of the one or more SRS resources based at least in part on the one or more transmitted SRSs, and transmit, to the UE, at least one of an uplink precoding information indication and a co-phase information indication based on the one or more SRSs, the uplink precoding information indication and the co-phase information indication being included with the SRI or whit a transmitted precoding matrix indicator (TPMI).

In some examples of the method, apparatuses, and non-transitory computer-readable medium described herein, transmitting the co-phase information indication further may include operations, features, means, or instructions for determining a co-phase for each of the SRS resources based on the one or more received SRSs, selecting an SRS resource based on the co-phase associated with the selected SRS resource and transmitting an SRI indicating the selected SRS resource, where the co-phase information indication includes the SRI.

In some examples of the method, apparatuses, and non-transitory computer-readable medium described herein, transmitting the uplink precoding information indication further may include operations, features, means, or instructions for selecting a group of UE antenna ports based on the one or more received SRSs, identifying a precoder port selection pattern based on the selecting and transmitting the uplink precoding information indication, where the uplink precoding information indication includes the identified precoder port selection pattern.

In some examples of the method, apparatuses, and non-transitory computer-readable medium described herein, transmitting the uplink precoding information indication further may include operations, features, means, or instructions for selecting an SRS resource based on the one or more received SRS and transmitting an SRI indicating the selected SRS resource, where the uplink precoding information indication includes the SRI.

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 UE capability report indicating a number of SRS resources capability, a number of SRS ports supported per SRS resource capability, an antenna port coherency capability, or some combination thereof and identifying the SRS resource configuration based on the received UE capability report.

In some examples of the method, apparatuses, and non-transitory computer-readable medium described herein, the uplink precoding information indication includes an index of uplink precoding information and number of layers. In some examples of the method, apparatuses, and non-transitory computer-readable medium described herein, each SRS resource of the one or more SRS resources includes a set of antenna ports. In some examples of the method, apparatuses, and non-transitory computer-readable medium described herein, the uplink precoding information indication further indicates a number of layers.

