Sounding Reference Signal for Precoding for Partial Reciprocity

Abstract

Aspects of the present disclosure generally relate to wireless communication. In some aspects, a user equipment may determine downlink (DL) channel state information; and transmit a first sounding reference signal (SRS) and a second SRS, where the second SRS is precoded at least in part based on the DL channel state information. Many other aspects are provided.

Description

Technical Field

[0001] Aspects of the present disclosure generally relate to wireless communication and techniques and apparatuses for precoding sounding reference signals for partial reciprocity. Background Art

[0002] Wireless communication systems are widely deployed to provide various telecommunication services such as telephony, video, data, messaging, and broadcasting. A typical wireless communication system may employ a multiple access technology capable of supporting communication with multiple user equipments (UEs) by sharing available system resources (e.g., bandwidth, transmit power, etc.). Examples of such multiple access technologies include code division multiple access (CDMA) systems, time division multiple access (TDMA) systems, frequency division multiple access (FDMA) systems, orthogonal frequency division multiple access (OFDMA) systems, single carrier frequency division multiple access (SC-FDMA) systems, time division synchronous code division multiple access (TD-SCDMA) systems, and long term evolution (LTE). LTE / LTE-Advanced is a set of enhancements to the Universal Mobile Telecommunications System (UMTS) mobile standard promulgated by the Third Generation Partnership Project (3GPP).

[0003] A wireless communication network may include multiple base stations (BSs) capable of supporting communication with multiple user equipments (UEs). A user equipment (UE) may communicate with a base station (BS) via a downlink and an uplink. The downlink (or forward link) refers to the communication link from the BS to the UE, and the uplink (or reverse link) refers to the communication link from the UE to the BS. As will be described in more detail herein, a BS may be referred to as a Node B, gNB, access point (AP), radio head, transmit receive point (TRP), New Radio (NR) BS, 5G Node B, etc.

[0004] The above multi-access technologies have been adopted in various telecommunication standards to provide a common protocol that enables different user equipments to communicate at the city, national, regional, or even global level. New Radio (NR), also known as 5G, is a set of enhancements to the LTE mobile standard promulgated by the Third Generation Partnership Project (3GPP). NR aims to better support mobile broadband Internet access by improving spectral efficiency, reducing costs, enhancing services, leveraging new spectrums, and better integrating with other open standards. These open standards use Orthogonal Frequency Division Multiplexing (OFDM) with Cyclic Prefix (CP) (CP-OFDM) on the downlink (DL), CP-OFDM and / or SC-FDM (e.g., also known as Discrete Fourier Transform Spread OFDM (DFT-s-OFDM)) on the uplink (UL), and support beamforming, Multiple-Input Multiple-Output (MIMO) antenna technology, and carrier aggregation. However, as the demand for mobile broadband access continues to grow, further improvements to LTE and NR technologies are needed. Preferably, these improvements should be applicable to other multi-access technologies and the telecommunication standards that employ these technologies. Summary of the Invention

[0005] In some aspects, a method of wireless communication performed by a UE may include determining downlink (DL) channel state information (CSI), and transmitting a first sounding reference signal (SRS) and a second SRS, wherein the second SRS is precoded at least in part based on the DL CSI.

[0006] In some aspects, a UE for wireless communication may include a memory and one or more processors operatively coupled to the memory. The memory and the one or more processors may be configured to determine DL CSI, and transmit a first SRS and a second SRS, wherein the second SRS is precoded at least in part based on the DL CSI.

[0007] In some aspects, a non-transitory computer-readable medium may store one or more instructions for wireless communication. When executed by one or more processors of a UE, the one or more instructions may cause the one or more processors to determine DL CSI, and transmit a first sounding reference signal SRS and a second SRS, wherein the second SRS is precoded at least in part based on the DL CS.

[0008] In some aspects, a component for wireless communication may include a module for determining DL CSI, and a module for transmitting a first SRS and a second SRS, wherein the second SRS is precoded at least in part based on the DL CS.

[0009] Aspects generally include a method, apparatus, system, computer program product, non-transitory computer-readable medium, user equipment, base station, wireless communication device, and / or processing system as generally described herein with reference to the accompanying drawings and shown in the drawings and the specification.

[0010] The features and technical advantages of examples in accordance with the present disclosure have been outlined above rather broadly in order that the detailed description that follows may be better understood. Additional features and advantages will be described hereinafter. The concepts and specific examples disclosed herein may be readily utilized as a basis for modifying or designing other structures for carrying out the same purposes of the present disclosure. Such equivalent constructions do not depart from the scope of the appended claims. The features of the concepts disclosed herein, their organization and method of operation, and related advantages will be better understood from the following description when considered in conjunction with the accompanying drawings. Each of the drawings is provided for purposes of illustration and description and is not to be construed as a definition of the limits of the claims. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] For a more particular description of the features briefly outlined above in accordance with some aspects, reference may be had to the aspects illustrated in the accompanying drawings. It should be noted, however, that the drawings illustrate only certain typical aspects of the present disclosure and are not to be considered limiting of its scope, as the description may admit of other equally effective aspects. The same reference numerals in different drawings may denote the same or similar elements.

[0012] Figure 1 is a block diagram conceptually illustrating an example of a wireless communication network in accordance with various aspects of the present disclosure.

[0013] Figure 2 is a block diagram conceptually illustrating an example of a base station communicating with a UE in a wireless communication network in accordance with various aspects of the present disclosure.

[0014] Figure 3 is a diagram illustrating an example of a DL bandwidth and a UL bandwidth having partial reciprocity in accordance with various aspects of the present disclosure.

[0015] Figure 4 is a diagram illustrating an example of transmitting a CSI report.

[0016] Figure 5A and 5B is a diagram illustrating one or more examples of a precoded sounding reference signal for partial reciprocity in accordance with various aspects of the present disclosure.

[0017] Figure 6 is a diagram illustrating an example of radio resource control (RRC) signaling in accordance with various aspects of the present disclosure.

[0018] Figure 7A diagram showing an example of RRC signaling according to various aspects of the present disclosure.

[0019] Figure 8 A diagram showing an example of RRC signaling according to various aspects of the present disclosure.

[0020] Figure 9 A diagram showing an example process, such as performed by a user equipment, according to various aspects of the present disclosure. Detailed Description

[0021] Aspects of the present disclosure will now be described more fully hereinafter with reference to the accompanying drawings. However, the present disclosure may be embodied in many different forms and should not be construed as limited to any specific structure or function presented throughout this disclosure. Rather, these aspects are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the present disclosure to those skilled in the art. Based on the teachings herein, those skilled in the art should appreciate that the scope of the present disclosure is intended to cover any aspect disclosed herein, whether implemented independently of any other aspect of the present disclosure or in combination with any other aspect of the present disclosure. For example, any number of the aspects set forth herein may be used to implement a device or practice a method. In addition, the scope of the present disclosure is intended to cover such a device or method that practices using other structures, functions, or a combination of structures and functions in addition to or different from the aspects of the present disclosure set forth herein. It should be understood that any aspect of the disclosure disclosed herein may be embodied by one or more elements of the claims.

[0022] Several aspects of a telecommunications system will now be presented with reference to various devices and techniques. These devices and techniques will be described in the following detailed description and illustrated in the drawings by various blocks, modules, components, circuits, steps, processes, algorithms, etc. (collectively referred to as elements). These elements may be implemented using hardware, software, or a combination thereof. Whether these elements are implemented as hardware or software depends on the particular application and design constraints imposed on the overall system.

[0023] It should be noted that although terms typically associated with 3G and / or 4G wireless technologies may be used herein to describe aspects, aspects of the present disclosure may be applied to other generation-based communication systems, such as 5G and later communication systems, including NR technology.

[0024] Figure 1FIG. 0 is a schematic diagram showing a wireless network 100 in which various aspects of the present disclosure may be practiced. The wireless network 100 may be an LTE network or some other wireless network, such as a 5G or NR network. The wireless network 100 may include a plurality of BSs 110 (shown as BS 110a, BS 110b, BS 110c, and BS 110d) and other network entities. A BS is an entity that communicates with a user equipment (UE) and may also be referred to as a base station, NR BS, Node B, gNB, 5G Node B (NB), access point, transmit receive point (TRP), etc. Each BS may provide communication coverage for a specific geographical area. In 3GPP, the term "cell" may refer to the coverage area of a BS and / or the BS subsystem serving that coverage area, depending on the context in which the term is used.

[0025] A BS may provide communication coverage for a macro cell, a pico cell, a femto cell, and / or another type of cell. A macro cell may cover a relatively large geographical area (e.g., with a radius of several kilometers) and may allow unrestricted access by UEs having a service subscription. A pico cell may cover a relatively small geographical area and may allow unrestricted access by UEs having a service subscription. A femto cell may cover a relatively small geographical area (e.g., a home) and may allow restricted access by UEs associated with the femto cell (e.g., UEs in a closed subscriber group (CSG)). The BS of a macro cell may be referred to as a macro BS. The BS of a pico cell may be referred to as a pico BS. The BS of a femto cell may be referred to as a femto BS or a home BS. In Figure 1 the example shown, BS 110a may be the macro BS of macro cell 102a, BS 110b may be the pico BS of pico cell 102b, and BS 110c may be the femto BS of femto cell 102c. A BS may support one or more (e.g., three) cells. The terms "eNB", "base station", "NR BS", "gNB", "TRP", "AP", "Node B", "5G NB", and "cell" may be used interchangeably herein.

[0026] In some aspects, a cell is not necessarily stationary, and the geographical area of a cell may move according to the location of a mobile BS. In some aspects, BSs may be interconnected with each other and / or with one or more other BSs or network nodes (not shown) in the wireless network 100 using any suitable transport network via various types of backhaul interfaces, such as direct physical connections, virtual networks, etc.

[0027] The wireless network 100 may also include relay stations. A relay station is an entity that can receive data transmissions from an upstream station (e.g., a BS or a UE) and send data transmissions to a downstream station (e.g., a UE or a BS). A relay station can also be a UE capable of relaying transmissions for other UEs. In Figure 1 the example shown, the relay station 110d can communicate with the macro BS 110a and the UE 120d to facilitate communication between the BS 110a and the UE 120d. A relay station may also be referred to as a relay BS, relay base station, relay, etc.

[0028] The wireless network 100 can be a heterogeneous network that includes different types of BSs, such as macro BSs, pico BSs, femto BSs, relay BSs, etc. These different types of BSs can have different transmit power levels, different coverage areas, and different impacts on interference in the wireless network 100. For example, a macro BS can have a high transmit power level (e.g., 5 to 40 watts), while pico BSs, femto BSs, and relay BSs can have lower transmit power levels (e.g., 0.1 to 2 watts).

[0029] The network controller 130 can be coupled to a set of BSs and can provide coordination and control for these BSs. The network controller 130 can communicate with the BSs via a backhaul. The BSs can also communicate with each other, for example, directly or indirectly via a wireless or wired backhaul.

[0030] UEs 120 (e.g., 120a, 120b, 120c) can be dispersed in the wireless network 100, and each UE can be fixed or mobile. A UE may also be referred to as an access terminal, terminal, mobile station, subscriber unit, station, etc. A UE can be a cellular phone (e.g., a smart phone), a personal digital assistant (PDA), a wireless modem, a wireless communication device, a handheld device, a laptop computer, a cordless phone, a wireless local loop (WLL) station, a tablet computer, a camera, a gaming device, a netbook, a smartbook, an ultrabook, a medical device or equipment, a biosensor / device, a wearable device (smart watch, smart clothing, smart glasses, smart wristband, smart jewelry (e.g., smart ring, smart bracelet)), an entertainment device (e.g., a music or video device, or a satellite radio), a vehicle component or sensor, a smart meter / sensor, an industrial manufacturing device, a global positioning system device, or any other suitable device configured to communicate via a wireless or wired medium.

[0031] Some UEs can be considered as Machine Type Communication (MTC) or evolved or enhanced Machine Type Communication (eMTC) UEs. MTC and eMTC UEs include, for example, robots, drones, remote devices, sensors, meters, monitors, location tags, etc., which can communicate with a base station, another device (e.g., a remote device), or some other entity. For example, a wireless node can provide connectivity to a network (e.g., a wide area network such as the Internet or a cellular network) via a wired or wireless communication link or provide connectivity to the network. Some UEs can be considered Internet of Things (IoT) devices, and / or can be implemented as NarrowBand IoT (NB-IoT) devices. Some UEs can be considered Customer Premises Equipment (CPE). UE 120 can be included within a housing that houses components of UE 120 such as a processor component, a memory component, etc.

[0032] In general, any number of wireless networks can be deployed in a given geographical area. Each wireless network can support a specific Radio Access Technology (RAT), and can operate on one or more frequencies. A RAT can also be referred to as a radio technology, an air interface, etc. A frequency can also be referred to as a carrier, a channel, etc. Each frequency can support a single RAT in a given geographical area to avoid interference between wireless networks of different RATs. In some cases, an NR or 5G RAT network can be deployed.

[0033] In some aspects, two or more UEs 120 (e.g., shown as UE 120a and UE 120e) can communicate directly using one or more sidelink channels (e.g., without using the base station 110 as a medium for communicating with each other). For example, UE 120 can communicate using peer-to-peer (P2P) communication, device-to-device (D2D) communication, vehicle-to-everything (V2X) protocols (e.g., which can include vehicle-to-vehicle (V2V) protocols, vehicle-to-infrastructure (V2I) protocols, etc.), a mesh network, etc. In such cases, UE120 can perform scheduling operations, resource selection operations, and / or other operations performed by the base station 110 described elsewhere herein.

[0034] As described above, Figure 1 is provided as an example. Other examples may be different from those regarding Figure 1 described.

[0035] Figure 2 FIG. 200 shows a block diagram of a design of a base station 110 and a UE 120, which can be one of the base stations and one of the UEs in Figure 1 . The base station 110 can be equipped with T antennas 234a to 234t, and the UE 120 can be equipped with R antennas 252a to 252r, where generally T≥1 and R≥1.

[0036] At base station 110, a transmit processor 220 may receive data for one or more UEs from a data source 212, select one or more modulation and coding schemes (MCSs) for each UE based at least in part on a channel quality indicator (CQI) received from the UE, process (e.g., encode and modulate) the data for the UE based at least in part on the MCS selected for each UE, and provide data symbols for all UEs. The transmit processor 220 may also process system information (e.g., for semi-static resource partitioning information (SRPI), etc.) and control information (e.g., CQI requests, grants, upper layer signaling, etc.), and provide overhead symbols and control symbols. The transmit processor 220 may also generate reference symbols for reference signals (e.g., cell-specific reference signals (CRS)) and synchronization signals (e.g., primary synchronization signal (PSS) and secondary synchronization signal (SSS)). A transmit (TX) multiple-input multiple-output (MIMO) processor 230 may perform spatial processing (e.g., precoding) on the data symbols, control symbols, overhead symbols, and / or reference symbols (if applicable), and may provide T output symbol streams to T modulators (MOD) 232a through 232t. Each modulator 232 may process its respective output symbol stream (e.g., for OFDM, etc.) to obtain an output sample stream. Each modulator 232 may further process (e.g., convert to analog, amplify, filter, and up-convert) the output sample stream to obtain a downlink signal. The T downlink signals from modulators 232a through 232t may be transmitted via T antennas 234a through 234t, respectively. According to various aspects described in more detail below, position coding may be utilized to generate synchronization signals to convey additional information.

[0037] At the UE 120, antennas 252a through 252r may receive downlink signals from the base station 110 and / or other base stations, and may provide the received signals to demodulators (DEMOD) 254a through 254r, respectively. Each demodulator 254 may condition (e.g., filter, amplify, down-convert, and digitize) the received signal to obtain input samples. Each demodulator 254 may further process the input samples (e.g., for OFDM, etc.) to obtain received symbols. The MIMO detector 256 may obtain the received symbols from all R demodulators 254a through 254r, perform MIMO detection on the received symbols if applicable, and provide the detected symbols. The receive processor 258 may process (e.g., demodulate and decode) the detected symbols, provide the decoded data of the UE 120 to the data sink 260, and provide the decoded control information and system information to the controller / processor 280. The channel processor may determine the reference signal received power (RSRP), received signal strength indicator (RSSI), reference signal received quality (RSRQ), channel quality indicator (CQI), etc. In some aspects, one or more components of the UE 120 may be included in a housing.

[0038] On the uplink, at the UE 120, the transmit processor 264 may receive and process data from the data source 262 and control information from the controller / processor 280 (e.g., for reports including RSRP, RSSI, RSRQ, CQI, etc.). The transmit processor 264 may also generate reference symbols for one or more reference signals. If applicable, the symbols from the transmit processor 264 may be precoded by the TX MIMO processor 266, further processed by the modulators 254a through 254r (e.g., for DFT-s-OFDM, CP-OFDM, etc.), and transmitted to the base station 110. At the base station 110, the uplink signals from the UE 120 and other UEs may be received by the antennas 234, processed by the demodulator 232, detected by the MIMO detector 236 (if applicable), and further processed by the receive processor 238 to obtain the decoded data and control information transmitted by the UE 120. The receive processor 238 may provide the decoded data to the data sink 239 and provide the decoded control information to the controller / processor 240. The base station 110 may include a communication unit 244 and communicate with the network controller 130 via the communication unit 244. The network controller 130 may include a communication unit 294, a controller / processor 290, and a memory 292.

[0039] The controller / processor 240 of the base station 110, the controller / processor 280 of the UE 120, and / or Figure 2Any other component may perform one or more techniques associated with precoding the sounding reference signal for partial reciprocity, as described in more detail elsewhere herein. For example, the controller / processor 240 of the base station 110, the controller / processor 280 of the UE 120, and / or Figure 2 Any other component may perform or direct the operation of, for example, Figure 9 Process 900 and / or other processes described herein. The memories 242 and 282 may store data and program codes for the base station 110 and the UE 120, respectively. In some aspects, the memories 242 and / or the memory 282 may include non-transitory computer-readable media storing one or more instructions for wireless communication. For example, when executed by one or more processors of the base station 110 and / or the UE 120, the one or more instructions may perform or direct the operation of, for example, Figure 9 Process 900 and / or other processes described herein. The scheduler 246 may schedule the UE for data transmission on the downlink and / or the uplink.

[0040] In some aspects, the UE 120 may include components for determining downlink CSI, components for transmitting a first sounding reference signal (SRS) and a second SRS, where the second SRS is precoded at least in part based on the downlink CSI, and so on. In some aspects, these components may include one or more components of the UE 120 described in connection with Figure 2 For example, the controller / processor 280, the transmit processor 264, the TX MIMO processor 266, the MOD 254, the antenna 252, the DEMOD 254, the MIMO detector 256, the receive processor 258, etc.

[0041] As described above, Figure 2 is provided as an example. Other examples may be different from those described with respect to Figure 2

[0042] Figure 3 is a diagram illustrating an example of a DL bandwidth and a UL bandwidth having partial reciprocity in accordance with various aspects of the present disclosure.

[0043] Reference numeral 305 indicates the DL channel bandwidth, and reference numeral 310 indicates the UL channel bandwidth. As indicated by reference numeral 315, a portion of the DL channel bandwidth and a portion of the UL channel bandwidth may overlap. In other words, a portion of the UL channel bandwidth and a portion of the DL channel bandwidth may use a shared bandwidth. Based at least in part on the overlap of the DL channel bandwidth portion and the UL channel bandwidth portion, the DL channel and the UL channel have partial reciprocity.

[0044] ​In some aspects, all of the UL channel bandwidth can be within a portion of the DL channel bandwidth, or all of the DL channel bandwidth can be within a portion of the UL channel bandwidth. In some aspects, if all of the UL channel bandwidth overlaps with all of the DL channel bandwidth, then the UL channel and the DL channel have full reciprocity. In other words, full reciprocity occurs when the UL channel and the DL channel have the same bandwidth.

[0045] In a full reciprocity scenario, the UE can send SRS to the base station. The base station can use the SRS to determine the CSI of the UL channel. Because the UL channel and the DL channel have reciprocity, the base station can estimate the DL CSI at least partially based on the CSI of the UL channel.

[0046] However, in a partial reciprocity scenario, the base station cannot correctly estimate the DL CSI at least partially based on the CSI of the UL channel. Therefore, the base station can send a CSI reference signal (CSI-RS), a physical downlink control channel (PDCCH) trigger, and / or a media access control control element activation so that the UE sends a CSI report separately from any SRS transmission.

[0047] As described above, Figure 3 is provided as an example. Other examples may be different from those regarding Figure 3 described.

[0048] Figure 4 FIG. 400 is a diagram illustrating an example of transmitting a CSI report. As shown, the base station and the UE communicate to provide information to the base station to determine the CSI of the DL channel. In some aspects, example 400 can be used in a scenario where there is no full reciprocity between the UL channel and the DL channel. Example 400 can be used in a partial reciprocity scenario.

[0049] As indicated by reference numeral 405, the UE can receive a synchronization signal physical broadcast channel block (SSB), a CSI-RS, etc. from the base station. The SSB, CSI-RS, etc. can provide the UE with an opportunity to measure the signal from the base station using the DL channel.

[0050] As indicated by reference numeral 410, the UE can determine the DL CSI of the downlink channel. In some aspects, the UE can determine the DL CSI at least partially based on measuring the SSB or the CSI-RS.

[0051] As shown by reference numeral 415, the UE may receive a PDCCH message that triggers a CSI report. In some aspects, the PDCCH message may include downlink control information (DCI) that may trigger a transmission of a CSI report. The DCI may identify resources (e.g., including one or more resource elements) for sending the CSI report via a physical uplink shared channel (PUSCH) or via a physical uplink control channel (PUCCH).

[0052] As shown by reference numeral 420, the UE may send a PUSCH message with a CSI report. The base station may use the CSI report to determine the CSI of the DL channel. In some aspects, the UE may be configured to send a sounding reference signal (SRS) separately for the base station to separately determine the CSI of the UL channel. At least partially based on sending the CSI report separately from the SRS, the base station may consume computing, communication, and / or network resources to separately determine the CSI of the DL and the CSI of the UL.

[0053] In some aspects described herein, the UE may determine the CSI of the DL channel (e.g., at least partially based on measuring SSB, CSI-RS, etc.). The UE may be configured to send a pair of SRSs to the base station. The first SRS in the pair of SRSs (e.g., an SRS without information about the DL CSI) may be sent to the base station. The second SRS of the pair of SRSs may be precoded with information about the DL CSI. The BS may be able to determine the DL CSI at least partially based on the pair of SRSs. For example, the base station may decode the second SRS at least partially based on receiving the pair of SRSs and determine the DL CSI. In this way, the DL CSI may be sent to the network without separately sending and scheduling a CSI transmission. This may save computing, communication, and / or network resources that may otherwise have been used to schedule and send a CSI report via a PUSCH message.

[0054] Figure 5A and 5B FIGS. 500 and 550 are diagrams illustrating one or more examples of precoding a sounding reference signal for partial reciprocity in accordance with various aspects of the present disclosure. As shown, a base station (e.g., base station 110) and a UE (e.g., UE 120) communicate to provide information to the base station to determine the CSI of the DL channel. In some aspects, these one or more examples may be used in scenarios where there is not full reciprocity between the UL channel and the DL channel. These one or more examples may be used in partial reciprocity scenarios.

[0055] As Figure 5AAs shown with reference numeral 505, the UE may receive RRC signaling (e.g., from a base station). In some aspects, the RRC signaling may be used to schedule a resource set (e.g., an SRS resource set) for transmitting a first SRS and a second SRS. The resource set may include a first resource for transmitting the first SRS and a second resource for transmitting the second SRS. The first resource and the second resource may be scheduled during the same symbol or different symbols.

[0056] In some aspects, the RRC signaling may include an indication of a resource set of one or more non-zero power (NZP) CSI-RS associated with the first SRS and / or the second SRS. In some aspects, the RRC signaling may include an indication of a resource set of one NZP CSI-RS associated with the first SRS and the second SRS. For example, the RRC signaling may be used to configure the UE to use a periodic and / or semi-persistent SRS resource set to transmit the first SRS and / or the second SRS. In some aspects, the RRC signaling may include an indication of one or more resource identifiers (e.g., NZP-CSI-RS-ResourceId) to identify one or more resources for the NZP CSI-RS. For example, the RRC signaling may identify one or more resource identifiers with parameters of the CSI-RS associated with the resource set for transmitting the SRS (e.g., associatedCSI-RS). In some aspects, the order of the SRS resources in the resource set for transmitting the SRS corresponds to the order of the NZP CSI-RS resources.

[0057] In some aspects, the RRC signaling may indicate that the UE is to transmit a first SRS and a second SRS. The RRC signaling (e.g., a CSI report configuration (e.g., CSI-ReportConfig)) may indicate whether, with what information, and / or how to precode the first SRS and / or the second SRS. For example, the RRC signaling may indicate that the UE precodes the second SRS at least partially based on DL CSI. The RRC signaling may further indicate whether the first SRS and / or the second SRS will be precoded (e.g., srsPrecoded), the bandwidth of the resource set for transmitting the SRS, whether to use wideband precoding or subband precoding to precode the first SRS and / or the second SRS (e.g., Precoding-FormatIndicator), a codebook configuration indicating a precoder for precoding the first SRS and / or the second SRS (e.g., codebookConfig), a subband size indicating the size of the subband if subband precoding is indicated, and so on.

[0058] In some aspects, a first RRC signaling (e.g., a first part of the RRC signaling, a first instance of the RRC signaling, etc.) can be used to configure a first SRS, and a second RRC signaling (e.g., a second part of the RRC signaling, a second instance of the RRC signaling, etc.) can be used to configure a second SRS. In some aspects, the first RRC signaling and the second RRC signaling can be received separately. In some aspects, the first RRC signaling can configure transmission, activation, triggering, etc. for the first SRS separately from the second RRC signaling that can configure transmission, activation trigger, etc. for the second SRS. The first RRC signaling and / or the second RRC signaling can indicate that the UE is to transmit the first SRS separately from the second SRS (e.g., using different resource sets). In some aspects, the RRC signaling can configure the UE for SRS handover, where the UE transmits the first SRS without precoding or with a precoding different from that of the second SRS, and transmits the second SRS with precoding.

[0059] In some aspects, the UE can receive a third RRC signaling and / or a first DCI to trigger the first SRS. The UE can also receive a fourth RRC signaling and / or a second DCI to trigger the second SRS. In some aspects, the third RRC signaling and / or the fourth RRC signaling can indicate the periodic or semi-persistent scheduling of one or more resource sets for transmitting the first SRS and / or the second SRS. In some aspects, the third RRC signaling and / or the first DCI can indicate that the UE is to transmit the first SRS without precoding at least partially based on DL CSI (e.g., without an indication of srsPrecoded). In some aspects, the fourth RRC signaling and / or the second DCI can indicate that the UE is to transmit the second SRS with precoding at least partially based on DL CSI (e.g., with an indication of srsPrecoded).

[0060] As shown by reference numeral 510, the UE can receive an SSB and / or a CSI-RS (e.g., from a base station). The SSB and / or the CSI-RS can provide the UE with an opportunity to measure signals from the base station using the DL channel. The DL CSI can be at least partially based on measurements (e.g., made by the UE) of the CSI-RS (e.g., NZP CSI-RS). In some aspects, a single SSB and / or a single CSI-RS can be associated with the first SRS and the second SRS.

[0061] In some aspects, the UE may be configured to transmit a first SRS and a second SRS based at least in part on a single SSB and / or a single CSI-RS. For example, the UE may be configured to transmit the first SRS and / or the second SRS based at least in part on RRC signaling, where the CSI-RS index is configured by the RRC signaling. In some aspects, the first SRS and / or the second SRS may be activated based at least in part on a Media Access Control (MAC) control element (CE), and / or the first SRS and / or the second SRS may be triggered by DCI.

[0062] As shown by reference numeral 515, the UE may determine DL CSI. In some aspects, the DL CSI may include indications of reference signal received power (RSRP), received signal strength indicator (RSSI), reference signal received quality (RSRQ), channel quality indicator (CQI), etc.

[0063] As shown by reference numeral 520, the UE may precode one or more SRSs (e.g., the first SRS and / or the second SRS) with the DL CSI. In other words, the UE may precode the second SRS based at least in part on the DL CS. The UE may calculate a precoder for precoding the second SRS based at least in part on measurements of an SSB, CSI-RS, etc. associated with the second SRS.

[0064] In some aspects, the UE may precode the first SRS based at least in part on a precoding matrix. The UE may precode the second SRS based at least in part on the precoding matrix and the DL CSI. In some aspects, the precoding matrix may be independent of the DL CSI. In some aspects, the precoding matrix may be based at least in part on the configuration of the UE.

[0065] To precode the second SRS with the DL CSI, the UE may perform an initial step of the precoding process to determine an intermediate quantity based at least in part on Function 1:

[0066]

[0067] Function 1

[0068] In Function 1, is a low peak-to-average power ratio sequence, N ap is the number of antenna ports of the UE, is the length of the sounding reference signal sequence, is consecutive OFDM symbols, K TC is the transmission comb number, is the starting position in the frequency domain, and l0 is the starting position in the time domain.

[0069] The intermediate quantity can be precoded and multiplied by an amplitude scaling factor β SRS to meet the transmit power requirement and / or be mapped to physical resources according to function 2:

[0070]

[0071] function 2

[0072] As shown by reference label 525, the UE may transmit a first SRS (e.g., a first periodic or semi-persistent SRS). In some aspects, the SRS may be an unprecoded SRS or may be precoded with a precoder different from that of the second SRS.

[0073] As shown by reference label 530, the UE may transmit a second SRS (e.g., a second periodic or semi-persistent SRS) that is at least partially precoded based on DL CSI. In some aspects, the period of the first SRS may be different from the period of the second SRS.

[0074] In some aspects, the first SRS and / or the second SRS may be triggered or activated at least partially based on RRC signaling, MAC-CE, DCI, etc. that receive and activate the first SRS. In some aspects, the first SRS may be triggered or activated separately from the triggering or activation of the second SRS.

[0075] Although described with reference to a first SRS and a second SRS, additional SRSs may be used within the scope of this description. For example, the UE may transmit a first SRS, a second SRS, a third SRS, and a fourth SRS. In some aspects, one or more of the third SRS or the fourth SRS may be precoded at least partially based on DL CSI.

[0076] In some aspects, the UE may transmit all four SRSs in the same resource set. In some aspects, the UE may transmit the first SRS, the second SRS, the third SRS, and the fourth SRS via a single SRS port (e.g., at least partially based on the UE being configured as a 1 transmitter 2 receiver UE). In some aspects, the UE may transmit the first SRS and the second SRS via a first SRS port and may transmit the third SRS and the fourth SRS via a second SRS port (e.g., at least partially based on the UE being configured as a 2 transmitter 4 receiver UE).

[0077] As shown by reference numeral 535, the base station may determine UL CSI and DL CSI at least in part based on a first SRS and a second SRS. For example, the base station may use the first SRS to determine UL CSI and may compare the first SRS and the second SRS to determine the DL CSI precoded into the second SRS. In this way, computational, communication, and / or network resources may be saved that would otherwise be used to schedule and transmit CSI reports independently of the SRS.

[0078] As described above, Figure 5A is provided as an example. Other examples may be different from those Figure 5A described with respect to

[0079] As Figure 5B and shown by reference numeral 555, the UE may receive RRC signaling from the base station. The RRC signaling may have one or more attributes described with respect to the RRC signaling described with reference numeral 505. The RRC signaling may provide configuration information to the UE.

[0080] As shown by reference numeral 560, the UE may receive an SSB and / or CSI-RS (e.g., from the base station). The SSB and / or CSI-RS may have one or more attributes described with respect to the SSB and / or CSI-RS described with reference numeral 510. As described in connection with reference numeral 510, the SSB and / or CSI-RS may provide the UE with an opportunity to measure signals from the base station using the DL channel.

[0081] As shown by reference numeral 565, the UE may determine DL CSI. In some aspects, the DL CSI may include indications of RSRP, RSSI, RSRQ, CQI, etc.

[0082] As shown by reference numeral 570, the UE may receive one or more PDCCH messages and / or one or more DCI messages that trigger the first SRS and / or the second SRS. In some aspects, the UE may receive DCI associated with the first SRS and / or the second SRS to identify one or more resources associated with one or more NZP CSI-RS, and / or to indicate one or more resources for transmitting the first SRS and the second SRS.

[0083] In some aspects, one or more PDCCH messages and / or one or more DCI messages may indicate that the first SRS is associated with a first resource set and is configured not to be precoded or to use a different precoding than that for the second SRS. In some aspects, one or more PDCCH messages and / or one or more DCI messages may indicate that the second SRS is associated with a second resource set and / or is configured with precoding (e.g., associated with DL CSI).

[0084] As shown by reference numeral 575, the UE may precode one or more SRSs (e.g., a second SRS) with DL CSI. In some aspects, the UE may precode one or more SRSs in the manner described herein (e.g., as described by reference numeral 520).

[0085] As shown by reference numeral 580, the UE may transmit a first SRS (e.g., a first priority SRS). In some aspects, the first SRS may be an unprecoded SRS or may be precoded with a precoder different from that of the second SRS.

[0086] As shown by reference numeral 585, the UE may transmit a second SRS (e.g., a second priority SRS) precoded at least in part based on DL CSI. In some aspects, the period of the first SRS may be different from the period of the second SRS.

[0087] In some aspects, triggering or activating the first SRS and / or the second SRS may be at least in part based on receiving RRC signaling, MAC-CE, DCI, etc. that activates or triggers the first SRS. In some aspects, the first SRS may be triggered or activated separately from the triggering or activation of the second SRS.

[0088] Although described with reference to a first SRS and a second SRS, additional SRSs may be used within the scope of this description. For example, the UE may transmit a first SRS, a second SRS, a third SRS, and a fourth SRS. In some aspects, one of the third SRS or the fourth SRS may be precoded at least in part based on DL CSI.

[0089] In some aspects, the UE may transmit all four SRSs in the same resource set. In some aspects, the UE may transmit the first SRS, the second SRS, the third SRS, and the fourth SRS via a single SRS port (e.g., at least in part based on the UE being configured as a 1 transmitter 2 receiver UE). In some aspects, the UE may transmit the first SRS and the second SRS via a first SRS port and may transmit the third SRS and the fourth SRS via a second SRS port (e.g., at least in part based on the UE being configured as a 2 transmitter 4 receiver UE).

[0090] As described above, Figure 5B is provided as an example. Other examples may be different from those described with respect to Figure 5B as described.

[0091] Figure 6FIG. 600 is a diagram illustrating an example 600 of RRC signaling in accordance with various aspects of the present disclosure. As shown, the RRC signaling may include an indication of a resource set for one or more SRSs (e.g., SRS-ResourceSet), and the indication may include a field indicating whether the UE is to use precoding for the associated SRS (e.g., precoding at least partially based on DL CSI). As shown, an indication of "precoding" may be added to the "ENUMERATED" field (e.g., shown as the last indication in the "ENUMERATED" field).

[0092] As described above, Figure 6 is provided as an example. Other examples may differ from those Figure 6 described with respect to

[0093] Figure 7 FIG. 700 is a diagram illustrating an example 700 of RRC signaling in accordance with various aspects of the present disclosure. As shown, the RRC signaling may include an indication of a configuration of a precoder. In some aspects, the configuration of the precoder may be at least partially based on RRC signaling indicating a configuration of a CSI report (e.g., CSI-ReportConfig). The configuration may include one or more of an indication of whether the SRS is precoded (e.g., srsPrecoded), an indication of whether to use a wideband or subband precoder for precoding (e.g., Precoding-FormatIndicator), an indication of the corresponding precoder to be used for the SRS (e.g., codebookConfig), an indication of the subband size if a subband precoder is used (e.g., subbandSize), etc.

[0094] As described above, Figure 7 is provided as an example. Other examples may differ from those Figure 7 described with reference to

[0095] Figure 8FIG. 800 is a diagram illustrating an example 800 of RRC signaling in accordance with various aspects of the present disclosure. The illustrated RRC signaling may be used to configure an SRS set. As shown, the RRC signaling may include an indication of a configuration of a precoder. In some aspects, the configuration of the precoder may be at least partially based on RRC signaling indicating a configuration of CSI reporting (e.g., CSI-ReportConfig). The configuration may include one or more of an indication of whether the SRS in the set is precoded (e.g., srsPrecoded), an indication of whether to precode with a wideband or subband precoder (e.g., Precoding-FormatIndicator), an indication of the corresponding precoder to be used for the SRS set in the set (e.g., codebookConfig), an indication of the subband size if a subband precoder is used (e.g., subbandSize), etc.

[0096] As described above, Figure 8 is provided as an example. Other examples may be different from those Figure 8 described with respect to

[0097] Figure 9 FIG. 900 is a diagram illustrating an example process 900, such as may be performed by a UE, in accordance with various aspects of the present disclosure. Example process 900 is an example in which a UE (e.g., UE 120, etc.) performs operations associated with precoding a sounding reference signal for partial reciprocity with a sounding reference signal precoded for partial reciprocity.

[0098] As Figure 9 shown, in some aspects, process 900 may include determining DL CSI (block 910). For example, as described above, a UE (e.g., using controller / processor 280, etc.) may determine DL CSI.

[0099] As Figure 9 further shown, in some aspects, process 900 may include transmitting a first SRS and a second SRS, where the second SRS is precoded at least in part based on the DL CS (block 920). For example, as described above, a UE (e.g., using controller / processor 280, transmit processor 264, TX MIMO processor 266, MOD 254, antenna 252, etc.) may transmit the first SRS and the second SRS. In some aspects, the second SRS is precoded at least in part based on the DL CSI.

[0100] Process 900 may include additional aspects, such as any single aspect or any combination of aspects described below, and / or in combination with one or more other processes described elsewhere herein.

[0101] In a first aspect, transmitting the first SRS and the second SRS includes transmitting the first SRS and the second SRS at least in part based on a single DL CSI reference signal.

[0102] In a second aspect, alone or in combination with the first aspect, process 900 includes receiving radio resource control signaling scheduling a resource set that includes a first resource for transmitting the first SRS and a second resource for transmitting the second SRS.

[0103] In a third aspect, alone or in combination with one or more of the first and second aspects, process 900 includes determining measurements of NZP CSI-RS associated with the second SRS and calculating a precoder for precoding the second SRS at least in part based on the measurements of NZP CSI-RS associated with the second SRS.

[0104] In a fourth aspect, alone or in combination with one or more of the first to third aspects, the radio resource control signaling further includes an indication of a resource set of one or more NZP CSI-RS associated with one or more of the first SRS or the second SRS.

[0105] In a fifth aspect, alone or in combination with one or more of the first to fourth aspects, process 900 includes receiving DCI associated with one or more of the first SRS and the second SRS, where the DCI identifies one or more resources associated with one or more NZP CSI-RS and where the DCI indicates one or more resources for transmitting the first SRS and the second SRS.

[0106] In a sixth aspect, alone or in combination with one or more of the first to fifth aspects, process 900 includes receiving RRC signaling that indicates that the UE is to transmit the first SRS and the second SRS, where the second SRS is precoded at least in part based on DL CSI.

[0107] In a seventh aspect, alone or in combination with one or more of the first to sixth aspects, the first SRS is an unprecoded SRS.

[0108] In an eighth aspect, alone or in combination with one or more of the first to seventh aspects, process 900 includes receiving RRC signaling indicating one or more of the following: whether the first SRS is to be precoded, whether wideband precoding or subband precoding is to be used to precode one or more of the first SRS or the second SRS, a codebook configuration indicating a precoder for precoding at least one of the first SRS or the second SRS, or a subband size for using subband precoding.

[0109] In a ninth aspect, either alone or in combination with one or more of the first to eighth aspects, the first SRS has a first period that is different from the second period of the second SRS.

[0110] In a tenth aspect, either alone or in combination with one or more of the first to ninth aspects, the uplink channels associated with the first SRS and the second SRS and the DL channels associated with the DL CSI have partial reciprocity.

[0111] In an eleventh aspect, either alone or in combination with one or more of the first to tenth aspects, the first SRS is precoded at least in part based on a precoding matrix, and the second SRS is precoded at least in part based on the precoding matrix and the DL CSI.

[0112] In a twelfth aspect, either alone or in combination with one or more of the first to eleventh aspects, the precoding matrix is independent of the DL CSI.

[0113] In a thirteenth aspect, either alone or in combination with one or more of the first to twelfth aspects, the first SRS and the second SRS are associated with a single NZP CSI-RS, and the DL CSI is at least in part based on measurements of the NZP CSI-RS.

[0114] In a fourteenth aspect, either alone or in combination with one or more of the first to thirteenth aspects, procedure 900 includes transmitting the first SRS, the second SRS, the third SRS, and the fourth SRS during different symbols of the same resource set.

[0115] In a fifteenth aspect, either alone or in combination with one or more of the first to fourteenth aspects, transmitting the first SRS, the second SRS, the third SRS, and the fourth SRS includes transmitting the first SRS, the second SRS, the third SRS, and the fourth SRS via a single SRS port.

[0116] In a sixteenth aspect, either alone or in combination with one or more of the first to fifteenth aspects, the fourth SRS is precoded at least in part based on the DL CSI.

[0117] In a seventeenth aspect, either alone or in combination with one or more of the first to sixteenth aspects, transmitting the first SRS, the second SRS, the third SRS, and the fourth SRS includes: transmitting the first SRS and the second SRS via a first SRS port, and transmitting the third SRS and the fourth SRS via a second SRS port.

[0118] In an eighteenth aspect, either alone or in combination with one or more of the first to seventeenth aspects, procedure 900 includes receiving first RRC signaling to configure the first SRS, and receiving second RRC signaling to configure the second SRS.

[0119] In a nineteenth aspect, either alone or in combination with one or more of the first to eighteenth aspects, transmitting a first SRS and a second SRS includes transmitting the first SRS separately from the second SRS.

[0120] Although Figure 9 example boxes of process 900 are shown, in some aspects, process 900 may include more boxes, fewer boxes, different boxes, or boxes in a different arrangement than those depicted Figure 9 herein. Additionally or alternatively, two or more boxes of process 900 may be executed in parallel.

[0121] The foregoing disclosure provides illustration and description, but is not intended to be exhaustive or to limit these aspects to the precise forms disclosed. Modifications and variations may be made in light of the above disclosure, or may be obtained from practice of these aspects.

[0122] As used herein, the term "component" is intended to be broadly construed as hardware, firmware, and / or a combination of hardware and software. As used herein, a processor is implemented as hardware, firmware, and / or a combination of hardware and software.

[0123] As used herein, depending on the context, meeting a threshold may refer to a value greater than the threshold, greater than or equal to the threshold, less than the threshold, less than or equal to the threshold, equal to the threshold, not equal to the threshold, etc.

[0124] It is apparent that the systems and / or methods described herein may be implemented in different forms of hardware, firmware, and / or a combination of hardware and software. The actual specific control hardware or software code used to implement these systems and / or methods does not limit these aspects. Thus, the operations and behaviors of the systems and / or methods are described herein without reference to specific software code, and it should be understood that software and hardware may be designed at least in part based on the description herein to implement the systems and / or methods.

[0125] Even if particular combinations of features are recited in the claims and / or disclosed in the specification, these combinations are not intended to limit the disclosure of the various aspects. In fact, many of these features may be combined in ways not specifically recited in the claims and / or not disclosed in the specification. Although each dependent claim listed below may directly depend on only one claim, the disclosure of the various aspects includes the combination of each dependent claim with every other claim in the claim set. A phrase referring to "at least one" of a list of items refers to any combination of those items, including a single member. For example, "at least one of a, b, or c" is intended to cover a, b, c, a-b, a-c, b-c, and a-b-c, as well as any combination having multiple of the same element (e.g., a-a, a-a-a, a-a-b, a-a-c, a-b-b, a-c-c, b-b, b-b-b, b-b-b, b-b-c, c-c, and c-c-c-c or any other order of a, b, and c).

[0126] Unless expressly described otherwise, any element, act, or instruction used herein should not be construed as critical or essential. Additionally, as used herein, the articles "a" and "an" are intended to include one or more items and may be used interchangeably with "one or more". Additionally, as used herein, the terms "set" and "group" are intended to include one or more items (e.g., related items, unrelated items, combinations of related and unrelated items, etc.) and may be used interchangeably with "one or more". If referring to only one item, the phrase "only one" or similar language is used. Additionally, as used herein, the terms "has", "have", and / or similar terms are intended to be open-ended terms. Additionally, the phrase "based on" is intended to mean "at least partially based on" unless expressly stated otherwise.

Claims

1. A method for wireless communication performed by a user equipment UE, comprising: Receiving first radio resource control signaling to activate or trigger a first sounding reference signal SRS; Receiving second radio resource control signaling to activate or trigger a second SRS; Determining downlink DL channel state information; And Transmitting the first SRS and the second SRS, wherein the second SRS is precoded at least in part based on the DL channel state information, and wherein an uplink UL channel associated with the first SRS and the second SRS and a downlink DL channel associated with the DL channel state information have partial reciprocity.

2. The method according to claim 1, wherein, Transmitting the first SRS and the second SRS includes: Transmitting the first SRS and the second SRS at least in part based on a single DL channel state information reference signal.

3. The method according to claim 1, further comprising: Receiving radio resource control signaling for a scheduled resource set, the resource set including a first resource for transmitting a first SRS and a second resource for transmitting a second SRS.

4. The method according to claim 3, further comprising: Determining measurements of non-zero power channel state information reference signals NZP CSI-RS associated with the second SRS; And Calculating a precoder for precoding the second SRS at least in part based on measurements of NZP CSI-RS associated with the second SRS.

5. The method according to claim 3, wherein, The radio resource control signaling further includes an indication of a resource set of one or more non-zero power channel state information reference signals associated with one or more of the first SRS or the second SRS.

6. The method according to claim 1, further comprising: Receiving downlink channel information DCI associated with one or more of the first SRS and the second SRS, Wherein the DCI identifies one or more resources associated with one or more non-zero power channel state information reference signals, and Wherein the DCI indicates one or more resources for transmitting the first SRS and the second SRS.

7. The method according to claim 1, further comprising: Receiving radio resource control signaling that indicates the UE is to transmit the first SRS and the second SRS, wherein the second SRS is precoded at least in part based on the DL channel state information.

8. The method according to claim 1, wherein The first SRS is an unprecoded SRS.

9. The method according to claim 1, further comprising: Receiving radio resource control signaling indicating one or more of the following: Whether to precode the first SRS, Whether to use wideband precoding or subband precoding to precode one or more of the first SRS or the second SRS, A codebook configuration for indicating a precoder for precoding at least one of the first SRS or the second SRS, or A subband size for using subband precoding.

10. The method according to claim 1, wherein The first SRS has a first period different from a second period of the second SRS.

11. The method according to claim 1, wherein, The first SRS is precoded at least in part based on a precoding matrix, and Wherein the second SRS is precoded at least in part based on a precoding matrix and DL channel state information.

12. The method according to claim 11, wherein, The precoding matrix is independent of the DL channel state information.

13. The method according to claim 11, wherein The first SRS and the second SRS are associated with a single non-zero power channel state information reference signal NZP CSI-RS, and wherein the DL channel state information is at least in part based on measurements of the NZP CSI-RS.

14. The method according to claim 1, further comprising: Transmitting a first SRS, a second SRS, a third SRS, and a fourth SRS during different symbols of the same resource set.

15. The method according to claim 14, wherein Transmitting the first SRS, the second SRS, the third SRS, and the fourth SRS includes: Transmitting the first SRS, the second SRS, the third SRS, and the fourth SRS via a single SRS port.

16. The method according to claim 14, wherein, The fourth SRS is precoded at least in part based on the DL channel state information.

17. The method according to claim 14, wherein, Transmitting the first SRS, the second SRS, the third SRS, and the fourth SRS includes: Transmitting the first SRS and the second SRS via a first SRS port, and Transmitting the third SRS and the fourth SRS via a second SRS port.

18. The method according to claim 1, wherein, The first radio resource control signaling is further configured to configure the first SRS, and the second radio resource control signaling is further configured to configure the second SRS.

19. The method according to claim 18, wherein, Transmitting the first SRS and the second SRS includes: Transmitting the first SRS separately from the second SRS.

20. The method according to claim 18, further comprising: Receiving one or more of a first media access control control element MAC-CE, or first downlink control information, that activates or triggers the first SRS; and Receiving one or more of a second MAC-CE, or second downlink control information, that activates or triggers the second SRS.

21. The method according to claim 18, wherein The first radio resource control signaling indicates that the first SRS is associated with a first resource set and is configured without precoding or with a precoding different from that for the second SRS, and wherein the second radio resource control signaling indicates that the second SRS is associated with a second resource set and is configured with precoding.

22. A user equipment UE for wireless communication, comprising: A memory; and One or more processors operatively coupled to the memory, the memory and the one or more processors being configured to: Receive first radio resource control signaling to activate or trigger a first sounding reference signal SRS; Receive second radio resource control signaling to activate or trigger a second SRS; Determine downlink DL channel state information; and Transmit the first SRS and the second SRS, wherein the second SRS is precoded at least in part based on the DL channel state information, and wherein the uplink UL channel associated with the first SRS and the second SRS and the downlink DL channel associated with the DL channel state information have partial reciprocity.

23. A non - transitory computer - readable medium storing one or more instructions for wireless communication, the one or more instructions comprising: One or more instructions that, when executed by one or more processors of a user equipment (UE), cause the one or more processors to: Receive first radio resource control signaling to activate or trigger a first sounding reference signal (SRS); Receive second radio resource control signaling to activate or trigger a second SRS; Determine downlink (DL) channel state information; And Transmit the first SRS and the second SRS, wherein the second SRS is precoded at least in part based on the DL channel state information, and wherein the uplink (UL) channel associated with the first SRS and the second SRS and the downlink (DL) channel associated with the DL channel state information have partial reciprocity.

24. An apparatus for wireless communication, comprising: Means for receiving first radio resource control signaling to activate or trigger a first sounding reference signal (SRS); Means for receiving second radio resource control signaling to activate or trigger a second SRS; Means for determining downlink (DL) channel state information; And Means for transmitting the first SRS and the second SRS, wherein the second SRS is precoded at least in part based on the DL channel state information, and wherein the uplink (UL) channel associated with the first SRS and the second SRS and the downlink (DL) channel associated with the DL channel state information have partial reciprocity.

25. A computer program product comprising computer - readable instructions that are executable by a processor to cause the processor to perform the method according to any one of claims 1 to 21.

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