Uplink subband precoding via sounding reference signal precoded by frequency domain basis

Abstract

Certain aspects of the present disclosure provide techniques for uplink transmission using subband precoding. In some cases, a UE may receive information indicating one or more of a sounding reference signal (SRS) port selected by the network entity and associated linear combination coefficients from a network entity, determine a subband precoding based at least in part on the selected SRS port and the linear combination coefficients, and transmit a physical uplink shared channel (PUSCH) using the subband precoding.

Description

Technical Field

[0001] Aspects of the present disclosure relate to wireless communications and, more particularly, to techniques for performing subband level precoding for uplink transmissions. Background Art

[0002] Wireless communication systems are widely deployed to provide various telecommunication services such as telephony, video, data, messaging, broadcast, etc. These wireless communication systems may employ multiple access technologies capable of supporting communication with multiple users by sharing available system resources (e.g., bandwidth, transmit power, etc.). Examples of such multiple access systems include 3rd Generation Partnership Project (3GPP) Long Term Evolution (LTE) systems, LTE-Advanced (LTE-A) systems, 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, and Time Division Synchronous Code Division Multiple Access (TD-SCDMA) systems, to name a few.

[0003] In some examples, a wireless multiple access communication system may include multiple base stations (BS), each of which is capable of simultaneously supporting communications for multiple communication devices (also referred to as user equipment (UE)). In an LTE or LTE-A network, a set of one or more base stations may define an eNodeB (eNB). In other examples (e.g., in a next generation, new radio (NR) or 5G network), a wireless multiple access communication system may include multiple distributed units (DUs) (e.g., edge units (EUs), edge nodes (ENs), radio heads (RHs), smart radio heads (SRHs), transmit receive points (TRPs), etc.) communicating with multiple central units (CUs) (e.g., central nodes (CNs), access node controllers (ANCs), etc.), wherein a set of one or more DUs communicating with a CU may define an access node (e.g., which may be referred to as a BS, a 5G NB, a next generation Node B (gNB or gNodeB), a transmit receive point (TRP), etc.). A BS or DU may communicate with a set of UEs on downlink channels (eg, for transmissions from the BS or DU to the UEs) and uplink channels (eg, for transmissions from the UEs to the BS or DU).

[0004] These multiple access technologies have been adopted in various telecommunication standards to provide a common protocol that enables different wireless devices to communicate at a city, country, region, and even global level. NR (e.g., New Radio or 5G) is an example of an emerging telecommunication standard. NR is a collection of enhancements to the LTE mobile standard released by 3GPP. NR is designed to better support mobile broadband Internet access by improving spectral efficiency, reducing costs, improving services, utilizing new spectrum, and using OFDMA with cyclic prefix (CP) on the downlink (DL) and on the uplink (UL) to better integrate with other open standards. To this end, NR supports beamforming, multiple-input multiple-output (MIMO) antenna technology, and carrier aggregation.

[0005] However, as the demand for mobile broadband access continues to grow, there is a need for further improvements to NR and LTE technologies. Preferably, these improvements should be applicable to other multiple access technologies and the telecommunication standards that employ them. Summary of the invention

[0006] The systems, methods, and devices of the present disclosure each have several aspects, no single one of which is solely responsible for its desirable attributes. Without limiting the scope of the present disclosure as expressed by the appended claims, some features will now be briefly discussed. After considering this discussion, and particularly after reading the section entitled "Detailed Description of the Invention," one will understand how the features of the present disclosure provide advantages including improved communication between access points and stations in a wireless network.

[0007] Certain aspects of the present disclosure relate to a method for wireless communication by a user equipment (UE). The method generally includes: sending a sounding reference signal (SRS) signal on a SRS resource to a network entity on multiple sounding reference signal (SRS) ports, receiving information indicating one or more of the sounding reference signal (SRS) ports selected by the network entity and associated linear combination coefficients from the network entity, determining a subband precoding based at least in part on the selected SRS ports and the linear combination coefficients; and sending a physical uplink shared channel (PUSCH) using the subband precoding.

[0008] Certain aspects of the present disclosure relate to a method for wireless communication by a network entity. The method generally includes measuring a sounding reference signal (SRS) sent from a user equipment (UE) to the network entity, selecting one or more of the SRS ports and associated linear combination coefficients based on the measurement, sending information indicating the one or more SRS ports and the associated linear combination coefficients to the UE, and receiving from the UE a physical uplink shared channel (PUSCH) sent using subband precoding based on the indicated SRS ports and the associated linear combination coefficients.

[0009] Aspects of the present disclosure also include various devices, components, and computer-readable media having instructions for performing the various operations described herein.

[0010] To achieve the aforementioned and related purposes, one or more aspects include the features fully described below and particularly pointed out in the claims. The following description and the accompanying drawings set forth in detail certain illustrative features of one or more aspects. However, these features are only indicative of a few of the various ways in which the principles of the various aspects can be employed. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] In order to be able to understand in detail the manner in which the above features of the present disclosure are achieved, the above brief overview may be described in more detail by reference to various aspects (some of which are illustrated in the accompanying drawings). However, it should be noted that the accompanying drawings only illustrate certain typical aspects of the present disclosure and are therefore not to be considered as limiting its scope, as the description may allow for other equally effective aspects.

[0012] Figure 1 is a block diagram conceptually illustrating an example telecommunications system in accordance with certain aspects of the present disclosure.

[0013] Figure 2 is a block diagram illustrating an example of a communication protocol stack for implementing an example RAN architecture, in accordance with certain aspects of the present disclosure.

[0014] Figure 3 is a block diagram conceptually illustrating designs of example base stations (BSs) and user equipment (UEs) in accordance with certain aspects of the present disclosure.

[0015] Figure 4 An example of a frame format for a telecommunications system is illustrated in accordance with certain aspects of the present disclosure.

[0016] Figure 5 Illustrated is a conceptual example of a first precoder matrix for transmitting layer 0 and a second precoder matrix for transmitting layer 1 in accordance with certain aspects of the present disclosure.

[0017] Figure 6Illustrated are three tables showing example M values ​​according to rank and layer, in accordance with certain aspects of the present disclosure.

[0018] Figure 7 Various matrices are shown graphically.

[0019] Figure 8 is a call flow diagram illustrating an example of codebook based UL transmission.

[0020] Fig. 9 An example of wideband precoding for codebook-based UL transmission is illustrated.

[0021] Fig.10 is a call flow diagram illustrating an example of wideband precoding for non-codebook based UL transmissions.

[0022] Fig.11 An example of wideband precoding for non-codebook based UL transmission is illustrated.

[0023] Figures 12A-12F The sets of precoder matrices for various layer and antenna port combinations are illustrated.

[0024] Fig.13

[0013] Illustrated are example operations for wireless communications by a UE in accordance with certain aspects of the present disclosure.

[0025] Fig.14

[0013] Illustrated are example operations for wireless communications by a base station in accordance with certain aspects of the present disclosure.

[0026] Fig.15 is a call flow diagram illustrating an example UL transmission with subband precoding in accordance with certain aspects of the present disclosure.

[0027] Fig.16 Example SRS ports with FD-based precoding according to aspects of the present disclosure are illustrated.

[0028] Figure 17A-17B Example scenarios for SRS port selection according to aspects of the present disclosure are illustrated.

[0029] To facilitate understanding, identical reference numerals have been used, where possible, to designate identical elements that are common to the figures. It is contemplated that elements disclosed in one aspect may be beneficially utilized on other aspects without specific recitation. DETAILED DESCRIPTION

[0030] Aspects of the present disclosure relate to wireless communications and, more particularly, to techniques for performing subband level precoding for uplink transmissions.

[0031] The following description provides examples and does not limit the scope, applicability or examples set forth in the claims. Without departing from the scope of the present disclosure, the functions and arrangements of the elements discussed may be changed. Various examples may appropriately omit, replace or add various processes or components. For example, the described method may be performed in a different order than described, and various steps may be added, omitted or combined. In addition, the features described for some examples may be combined in some other examples. For example, any number of aspects set forth herein may be used to implement a device or implement a method. In addition, the scope of the present disclosure is intended to cover such devices or methods that are practiced using other structures, functions, or structures and functions other than or different from the various aspects of the present disclosure set forth herein. It should be understood that any aspect of the present disclosure disclosed herein may be embodied by one or more elements of the claims. The word "exemplary" is used herein to mean "used as an example, instance or illustration". Any aspect described as "exemplary" herein is not necessarily interpreted as preferred or superior to other aspects.

[0032] The technology described herein can be used for various wireless communication technologies, such as LTE, CDMA, TDMA, FDMA, OFDMA, SC-FDMA and other networks. The terms "network" and "system" are often used interchangeably. A CDMA network can implement radio technologies such as Universal Terrestrial Radio Access (UTRA), cdma2000, etc. UTRA includes Wideband CDMA (WCDMA) and other variants of CDMA. cdma2000 covers IS-2000, IS-95 and IS-856 standards. A TDMA network can implement radio technologies such as Global System for Mobile Communications (GSM). An OFDMA network can implement radio technologies such as NR (e.g., 5G RA), Evolved UTRA (E-UTRA), Ultra Mobile Broadband (UMB), IEEE 802.11 (Wi-Fi), IEEE 802.16 (WiMAX), IEEE 802.20, Flash-OFDMA, etc. UTRA and E-UTRA are part of Universal Mobile Telecommunications System (UMTS).

[0033] New Radio (NR) is an emerging wireless communication technology developed jointly with the 5G Technology Forum (5GTF). 3GPP Long Term Evolution (LTE) and LTE-Advanced (LTE-A) are versions of UMTS that use E-UTRA. UTRA, E-UTRA, UMTS, LTE, LTE-A, and GSM are described in documents from an organization called "3rd Generation Partnership Project" (3GPP). cdma2000 and UMB are described in documents from an organization called "3rd Generation Partnership Project 2" (3GPP2). The techniques described herein can be used for the above-mentioned wireless networks and radio technologies as well as other wireless networks and radio technologies. For clarity, although terms commonly associated with 3G and / or 4G wireless technologies may be used herein to describe various aspects, various aspects of the present disclosure may be applied to other communication systems based on generations, such as 5G and higher versions including NR technology.

[0034] New Radio (NR) access (e.g., 5G technology) can support various wireless communication services, such as enhanced mobile broadband (eMBB) for wide bandwidth (e.g., 80 MHz or higher), millimeter wave (mmW) for high carrier frequency (e.g., 25 GHz or higher), massive machine type communication MTC (mMTC) for non-backward compatible MTC technology, and / or mission critical ultra-reliable low latency communication (URLLC). These services may include latency and reliability requirements. These services may also have different transmission time intervals (TTIs) to meet corresponding quality of service (QoS) requirements. In addition, these services can coexist in the same subframe.

[0035] Example Wireless Communication System

[0036] Figure 1 An example wireless communication network 100 is illustrated in which aspects of the present disclosure may be performed. For example, a UE 120 in the wireless communication network 100 may include a UL subband precoding module configured to perform (or assist the UE 120 in performing) the following reference Fig.13 Similarly, the base station 120 (e.g., gNB) may include a UL subband precoding module configured to perform (or assist the base station 120 in performing) the following with reference to Fig.14 Operation 1400 is described.

[0037] like Figure 1As shown in , the wireless communication network 100 may include multiple base stations (BS) 110 and other network entities. A BS may be a station that communicates with a user equipment (UE). Each BS 110 may provide communication coverage for a specific geographic area. In 3GPP, the term "cell" may refer to the coverage area of ​​a node B (NB) and / or a NB subsystem serving the coverage area, depending on the context in which the term is used. In NR systems, the terms "cell" and next generation node B (gNB or gNodeB), NRBS, 5G NB, access point (AP) or transmit receive point (TRP) may be interchangeable. In some examples, a cell may not necessarily be stationary, and the geographic area of ​​a cell may move according to the location of a mobile BS. In some examples, base stations may be interconnected and / or connected to one or more other base stations or network nodes (not shown) in the wireless communication network 100 through various types of backhaul interfaces (such as direct physical connections, wireless connections, virtual networks, etc.) using any suitable transport network.

[0038] Generally, any number of wireless networks can be deployed in a given geographic area. Each wireless network can support a specific radio access technology (RAT) and can operate on one or more frequencies. RAT can also be referred to as radio technology, air interface, etc. Frequency can also be referred to as carrier, subcarrier, frequency channel, tone, subband, etc. Each frequency can support a single RAT in a given geographic area to avoid interference between wireless networks of different RATs. In some cases, NR or 5G RAT networks can be deployed.

[0039] A BS may provide communication coverage for macro cells, pico cells, femto cells, and / or other types of cells. A macro cell may cover a relatively large geographic area (e.g., a radius of several kilometers) and may allow unrestricted access by UEs with service subscriptions. A pico cell may cover a relatively small geographic area and may allow unrestricted access by UEs with service subscriptions. A femto cell may cover a relatively small geographic 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), UEs for users in a home, etc.). A BS for a macro cell may be referred to as a macro BS. A BS for a pico cell may be referred to as a pico BS. A BS for a femto cell may be referred to as a femto BS or a home BS. In Figure 1In the example shown, BSs 110a, 110b, and 110c may be macro BSs for macro cells 102a, 102b, and 102c, respectively. BS 110x may be a pico BS for pico cell 102x. BSs 110y and 110z may be femto BSs for femto cells 102y and 102z, respectively. A BS may support one or more (e.g., three) cells.

[0040] The wireless communication network 100 may also include a relay station. A relay station is a station that receives data and / or other information from an upstream station (e.g., a BS or a UE) and transmits the data and / or other information to a downstream station (e.g., a UE or a BS). A relay station may also be a UE that relays transmissions for other UEs. Figure 1 In the illustrated example, a relay station 110r may communicate with a BS 110a and a UE 120r to facilitate communication between the BS 110a and the UE 120r. A relay station may also be referred to as a relay BS, a relay, or the like.

[0041] The wireless communication network 100 may be a heterogeneous network including BSs of different types (e.g., macro BSs, pico BSs, femto BSs, relays, etc.). These different types of BSs may have different transmit power levels, different coverage areas, and different impacts on interference in the wireless communication network 100. For example, a macro BS may have a high transmit power level (e.g., 20 watts), while a pico BS, a femto BS, and a relay may have a lower transmit power level (e.g., 1 watt).

[0042] The wireless communication network 100 may support synchronous or asynchronous operation. For synchronous operation, the BSs may have similar frame timing, and transmissions from different BSs may be approximately aligned in time. For asynchronous operation, the BSs may have different frame timing, and transmissions from different BSs may not be aligned in time. The techniques described herein may be used for both synchronous and asynchronous operation.

[0043] A network controller 130 may couple to a set of BSs and provide coordination and control for these BSs. The network controller 130 may communicate with the BSs 110 via a backhaul. The BSs 110 may also communicate with each other (eg, directly or indirectly) via a wireless or wired backhaul.

[0044] UE 120 (e.g., 120x, 120y, etc.) may be dispersed throughout the wireless communication network 100, and each UE may be stationary or mobile. UE may also be referred to as a mobile station, terminal, access terminal, subscriber unit, station, customer premises equipment (CPE), cellular phone, smart phone, personal digital assistant (PDA), wireless modem, wireless communication device, handheld device, laptop computer, cordless phone, wireless local loop (WLL) station, tablet computer, camera, gaming device, netbook, smartbook, ultrabook, appliance, medical device or medical equipment, biosensor / device, wearable device (such as smart watch, smart clothing, smart glasses, smart wristband, smart jewelry (e.g., smart ring, smart bracelet, etc.)), entertainment device (e.g., music device, video device, satellite radio, etc.), vehicle component or sensor, smart meter / sensor, industrial manufacturing equipment, global positioning system device, or any other suitable device configured to communicate via wireless or wired medium. Some UEs may be considered as machine type communication (MTC) devices or evolved MTC (eMTC) devices. MTC and eMTC UEs include, for example, robots, drones, remote devices, sensors, meters, monitors, location tags, etc. that can communicate with a BS, another device (e.g., a remote device), or some other entity. For example, a wireless node can provide connectivity for or to a network (e.g., a wide area network such as the Internet or a cellular network) via a wired or wireless communication link. Some UEs may be considered Internet of Things (IoT) devices, which may be narrowband IoT (NB-IoT) devices.

[0045] Some wireless networks (e.g., LTE) use orthogonal frequency division multiplexing (OFDM) on the downlink and single carrier frequency division multiplexing (SC-FDM) on the uplink. OFDM and SC-FDM divide the system bandwidth into multiple (K) orthogonal subcarriers, which are also commonly referred to as tones, bins, etc. Each subcarrier can be modulated with data. Typically, modulation symbols are sent in the frequency domain with OFDM and in the time domain with SC-FDM. The spacing between adjacent subcarriers can be fixed, and the total number of subcarriers (K) can depend on the system bandwidth. For example, the spacing of the subcarriers can be 15kHz, and the minimum resource allocation (called a "resource block" (RB)) can be 12 subcarriers (or 180kHz). Therefore, for system bandwidths of 1.25, 2.5, 5, 10, or 20 megahertz (MHz), the nominal fast Fourier transform (FFT) size can be equal to 128, 256, 512, 1024, or 2048, respectively. The system bandwidth may also be divided into subbands. For example, a subband may cover 1.08 MHz (ie, 6 resource blocks), and there may be 1, 2, 4, 8, or 16 subbands for system bandwidths of 1.25, 2.5, 5, 10, or 20 MHz, respectively.

[0046] Communication systems such as NR can utilize OFDM with cyclic prefix (CP) on uplink and downlink, and include support for half-duplex operation using time division duplex (TDD). Beamforming can be supported and the beam direction can be dynamically configured. MIMO transmission with precoding can also be supported. MIMO configuration in DL can support up to 8 transmit antennas, with multi-layer DL transmission of up to 8 streams and up to 4 streams per UE. Multi-layer transmission of up to 4 streams per UE can be supported. Aggregation of multiple cells up to 8 serving cells can be supported.

[0047] In some examples, access to the air interface can be scheduled. A scheduling entity (e.g., BS) allocates resources for communications between some or all devices and equipment within its service area or cell. A scheduling entity may be responsible for scheduling, allocating, reconfiguring, and releasing resources for one or more subordinate entities. That is, for scheduled communications, subordinate entities utilize resources allocated by the scheduling entity. The base station is not the only entity that can act as a scheduling entity. In some examples, a UE may act as a scheduling entity and may schedule resources for one or more subordinate entities (e.g., one or more other UEs), and other UEs may utilize resources scheduled by the UE for wireless communications. In some examples, a UE may act as a scheduling entity in a peer-to-peer (P2P) network and / or a mesh network. In a mesh network example, in addition to communicating with a scheduling entity, UEs may also communicate directly with each other.

[0048] exist Figure 1 In FIG. 1 , a solid line with double arrows indicates desired transmission between a UE and a serving BS, which is a BS designated to serve the UE on a downlink and / or uplink. A thin dashed line with double arrows indicates interfering transmission between a UE and a BS.

[0049] Figure 2 A diagram illustrating an example of a communication protocol stack for implementing in a RAN (e.g., such as RAN 100) according to various aspects of the present disclosure is illustrated. The illustrated communication protocol stack 200 may be implemented by a device operating in a wireless communication system such as a 5G NR system (e.g., wireless communication network 100). In various examples, the layers of the protocol stack 200 may be implemented as separate software modules, portions of a processor or ASIC, portions of non-collocated devices connected by a communication link, or various combinations thereof. For example, collocated and non-collocated implementations may be used in a protocol stack of a network access device or UE. As shown in FIG. Figure 2 As shown in , the system can support various services through one or more protocols. One or more protocol layers of the protocol stack 200 can be implemented by AN and / or UE.

[0050] like Figure 2 As shown in FIG. , the protocol stack 200 is implemented in an AN (eg, Figure 1 The RRC layer 205, the PDCP layer 210, the RLC layer 215, the MAC layer 220, the PHY layer 225, and the RF layer 230 may be implemented by the AN. For example, the CU-CP may implement the RRC layer 205 and the PDCP layer 210. The DU may implement the RLC layer 215 and the MAC layer 220. The AU / RRU may implement (multiple) PHY layers 225 and (multiple) RF layers 230. The PHY layer 225 may include a high PHY layer and a low PHY layer.

[0051] The UE may implement the entire protocol stack 200 (eg, the RRC layer 205, the PDCP layer 210, the RLC layer 215, the MAC layer 220, the PHY layer(s) 225, and the RF layer 230).

[0052] Figure 3 The diagram shows (such as Figure 1 1 and 120, which may be used to implement various aspects of the present disclosure. For example, antenna 352, processors 366, 358, 364, and / or controller / processor 380 of UE 120 may be configured to (or used to) perform Fig.13Operation 1300 of BS 110, and / or antenna 334, processor 320, 330, 338 and / or controller / processor 340 of BS 110 may be configured to (or used to) perform the following reference Fig.14 Operation 1400 is described.

[0053] At BS 110, a transmit processor 320 may receive data from a data source 312 and control information from a controller / processor 340. The control information may be for a physical broadcast channel (PBCH), a physical control format indicator channel (PCFICH), a physical hybrid ARQ indicator channel (PHICH), a physical downlink control channel (PDCCH), a group common PDCCH (GC PDCCH), etc. The data may be for a physical downlink shared channel (PDSCH), etc. The processor 320 may process (e.g., encode and symbol map) the data and the control information to obtain data symbols and control symbols, respectively. The processor 320 may also generate reference symbols, e.g., for a primary synchronization signal (PSS), a secondary synchronization signal (SSS), and a cell-specific reference signal (CRS). A transmit (TX) multiple-input multiple-output (MIMO) processor 330 may perform spatial processing (e.g., precoding) on ​​data symbols, control symbols, and / or reference symbols (if applicable), and may provide output symbol streams to modulators (MODs) 332a to 332t. Each modulator 332 may process a respective output symbol stream (e.g., for OFDM, etc.) to obtain an output sample stream. Each modulator may further process (e.g., convert to analog, amplify, filter, and upconvert) the output sample stream to obtain a downlink signal. The downlink signals from modulators 332a through 332t may be transmitted via antennas 334a through 334t, respectively.

[0054] At the UE 120, antennas 352a to 352r may receive downlink signals from the base station 110 and may provide received signals to demodulators (DEMODs) 354a to 354r in the transceiver, respectively. Each demodulator 354 may condition (e.g., filter, amplify, downconvert, and digitize) a respective received signal to obtain input samples. Each demodulator may further process the input samples (e.g., for OFDM, etc.) to obtain received symbols. A MIMO detector 356 may obtain received symbols from all demodulators 354a to 354r, perform MIMO detection on the received symbols (if applicable), and provide detected symbols. A receive processor 358 may process (e.g., demodulate, deinterleave, and decode) the detected symbols, provide decoded data for the UE 120 to a data sink 360, and provide decoded control information to a controller / processor 380.

[0055] In a MIMO system, a transmitter (e.g., BS 120) includes multiple transmit antennas 354a to 354r, and a receiver (e.g., UE 110) includes multiple receive antennas 352a to 352r. Therefore, there are multiple signal paths 394 from the transmit antennas 354a to 354r to the receive antennas 352a to 352r. Each of the transmitter and the receiver may be implemented, for example, within UE 110, BS 120, or any other suitable wireless communication device.

[0056] The use of such multi-antenna techniques enables wireless communication systems to exploit the spatial domain to support spatial multiplexing, beamforming, and transmit diversity. Spatial multiplexing can be used to simultaneously send different data streams, also known as layers, on the same time-frequency resources. Data streams can be sent to a single UE to increase the data rate, or to multiple UEs to increase the overall system capacity, the latter of which is called multi-user MIMO (MU-MIMO). This is achieved by spatially precoding each data stream (i.e., multiplying the data stream by different weights and phase shifts) and then sending each spatially precoded stream through multiple transmit antennas on the downlink. The spatially precoded data streams arrive at (multiple) UEs with different spatial signatures, which enables each UE to recover one or more data streams destined for that UE. On the uplink, each UE sends a spatially precoded data stream, which enables the base station to identify the source of each spatially precoded data stream.

[0057] The number of data streams or layers corresponds to the rank of transmission. Typically, the rank of a MIMO system is limited by the number of transmit or receive antennas, whichever is lower. In addition, channel conditions at the UE and other considerations such as available resources at the base station may also affect the transmission rank. For example, the rank (and therefore the number of transmission layers) assigned to a particular UE on the downlink can be determined based on a rank indicator (RI) sent from the UE to the base station. The RI can be determined based on the antenna configuration (e.g., the number of transmit and receive antennas) and the signal to interference and noise ratio (SINR) measured on each receive antenna. The RI can indicate, for example, the number of layers that can be supported under current channel conditions. The base station can use the RI as well as resource information (e.g., the available resources and amount of data to be scheduled for the UE) to assign a transmission rank to the UE.

[0058] On the uplink, at the UE 120, a transmit processor 364 may receive and process data from a data source 362 (e.g., for a physical uplink shared channel (PUSCH)) and control information from a controller / processor 380 (e.g., for a physical uplink control channel (PUCCH)). The transmit processor 364 may also generate reference symbols for reference signals (e.g., for a sounding reference signal (SRS)). The symbols from the transmit processor 364 may be precoded by a TX MIMO processor 366 (if applicable), further processed by a demodulator 354a-354r (e.g., for SC-FDM, etc.) in the transceiver, and transmitted to the base station 110. At the BS 110, the uplink signal from the UE 120 may be received by the antenna 334, processed by the modulator 332, detected by the MIMO detector 336 (if applicable), and further processed by the receive processor 338 to obtain decoded data and control information transmitted by the UE 120. The receive processor 338 may provide the decoded data to a data sink 339 and the decoded control information to a controller / processor 340 .

[0059] Controllers / processors 340 and 380 may direct the operation at BS 110 and UE 120, respectively. Processor 340 and / or other processors and modules at BS 110 may perform or direct the execution of processes for the techniques described herein. Memories 342 and 382 may store data and program codes for BS 110 and UE 120, respectively. Scheduler 344 may schedule UEs for data transmission on the downlink and / or uplink.

[0060] Figure 4 4 is a diagram showing an example of a frame format 400 for NR. The transmission timeline for each of the downlink and uplink may be divided into units of radio frames. Each radio frame may have a predetermined duration (e.g., 10 ms) and may be divided into 10 subframes with indices 0 to 9, each subframe being 1 ms. Depending on the subcarrier spacing, each subframe may include a variable number of slots. Depending on the subcarrier spacing, each slot may include a variable number of symbol periods (e.g., 7 or 14 symbols). The symbol periods in each slot may be assigned an index. A mini slot, which may be referred to as a subslot structure, refers to a transmission time interval (e.g., 2, 3, or 4 symbols) having a duration less than a slot. Each symbol in a slot may indicate a link direction (e.g., DL, UL, or flexible) for data transmission, and the link direction for each subframe may be dynamically switched. The link direction may be based on a slot format. Each slot may include DL / UL data and DL / UL control information.

[0061] In NR, a synchronization signal (SS) block is transmitted. The SS block includes PSS, SSS, and two symbols PBCH. The SS block can be transmitted at a fixed time slot position, such as Figure 4 Symbols 0-3 shown in . The UE can use PSS and SSS for cell search and acquisition. PSS can provide half-frame timing, and SS can provide CP length and frame timing. PSS and SSS can provide cell identification. PBCH carries some basic system information, such as downlink system bandwidth, timing information within a radio frame, SS burst set period, system frame number, etc. SS blocks can be organized into SS bursts to support beam scanning. Additional system information (such as remaining minimum system information (RMSI), system information block (SIB), other system information (OSI)) can be sent on the physical downlink shared channel (PDSCH) in certain subframes. SS blocks can be sent up to sixty-four times, for example, for mmW, there can be up to sixty-four different beam directions. Up to sixty-four transmissions of SS blocks are called SS burst sets. SS blocks in an SS burst set are sent in the same frequency region, while SS blocks in different SS burst sets can be sent at different frequency locations.

[0062] The UE may operate in various radio resource configurations including a configuration associated with sending a pilot using a dedicated resource set (e.g., a radio resource control (RRC) dedicated state, etc.) or a configuration associated with sending a pilot using a common resource set (e.g., an RRC common state, etc.). When operating in the RRC dedicated state, the UE may select a dedicated resource set for sending a pilot signal to the network. When operating in the RRC common state, the UE may select a common resource set for sending a pilot signal to the network. In either case, the pilot signal sent by the UE may be received by one or more network access devices (such as an AN or DU, or a portion thereof). Each receiving network access device may be configured to receive and measure the pilot signal sent on the common resource set, and also receive and measure the pilot signal sent on the dedicated resource set allocated to the UE (the network access device is a member of a set of network access devices for monitoring the UE). One or more of the receiving network access devices, or the CU to which the receiving network access device sends the measurement of the pilot signal, may use these measurements to identify a serving cell for the UE, or to initiate a change in a serving cell for one or more of the UEs.

[0063] Example CSI Report Configuration

[0064] Channel state information (CSI) may refer to channel characteristics of a communication link. CSI may represent, for example, the combined effects of scattering, fading, and power attenuation with distance between the transmitter and the receiver. Channel estimation using a pilot such as a CSI reference signal (CSI-RS) may be performed to determine these effects on the channel. CSI may be used to adjust transmission based on current channel conditions, which is useful for achieving reliable communications, particularly high data rates in multi-antenna systems. CSI is typically estimated, quantized, and fed back to the transmitter at the receiver.

[0065] The time and frequency resources that can be used by the UE to report CSI are controlled by the base station (e.g., gNB). The CSI may include a channel quality indicator (CQI), a precoding matrix indicator (PMI), a CSI-RS resource indicator (CRI), a SS / PBCH block resource indicator (SSBRI), a layer indicator (LI), a rank indicator (RI), and / or L1-RSRP. However, as described below, additional or other information may be included in the report.

[0066] The base station may configure the UE for CSI reporting. For example, the BS configures one CSI reporting configuration or multiple CSI reporting configurations for the UE. The CSI reporting configuration may be provided to the UE via higher layer signaling such as radio resource control (RRC) signaling (e.g., CSI-ReportConfig). The CSI reporting configuration may be associated with CSI-RS resources for channel measurement (CM), interference measurement (IM), or both. The CSI reporting configuration configures CSI-RS resources (e.g., CSI-ResourceConfig) for measurement. The CSI-RS resources provide the UE with a configuration of a CSI-RS port or a CSI-RS port group mapped to time and frequency resources (e.g., resource elements (REs)). The CSI-RS resources may be zero power (ZP) or non-zero power (NZP) resources. At least one NZP CSI-RS resource may be configured for CM.

[0067] For Type II single-panel codebooks, the PMI is a linear combination of beams; it has a subset of orthogonal beams to be used for the linear combination, and it has per-layer, per-polarization, amplitude, and phase for each beam. For any type of PMI, there can be a configured wideband (WB) PMI and / or subband (SB) PMI.

[0068] The CSI report configuration can configure aperiodic, periodic or semi-persistent CSI reports for the UE. For periodic CSI, the UE can be configured with periodic CSI-RS resources. Periodic CSI and semi-persistent CSI reports on the physical uplink control channel (PUCCH) can be triggered via RRC or medium access control (MAC) control elements (CE). For aperiodic and semi-persistent CSI on the physical uplink shared channel (PUSCH), the BS can signal the UE with a CSI reporting trigger, which indicates that the UE sends a CSI report for one or more CSI-RS resources, or configures the CSI-RS report trigger state (e.g., CSI-AperiodicTriggerStateList and CSI-SemiPersistentOnPUSCH-TriggerStateList). CSI reporting triggers for aperiodic CSI and semi-persistent CSI on PUSCH can be provided via downlink control information (DCI). The CSI-RS trigger can be a signaling to the UE indicating that a CSI-RS will be sent for a CSI-RS resource.

[0069] The UE may report CSI feedback based on the CSI reporting configuration and the CSI reporting trigger. For example, the UE may measure a channel associated with the CSI for a triggered CSI-RS resource. Based on the measurement, the UE may select a preferred CSI-RS resource. The UE reports CSI feedback for the selected CSI-RS resource. The LI may be calculated based on the reported CQI, PMI, RI, and CRI; the CQI may be calculated based on the reported PMI, RI, and CRI; the PMI may be calculated based on the reported RI and CRI; and the RI may be calculated based on the reported CRI.

[0070] Each CSI reporting configuration may be associated with a single downlink bandwidth part (BWP). A CSI reporting setting configuration may define a CSI reporting band as a subset of a subband of a BWP. The associated DL BWP may be indicated by a higher layer parameter (e.g., bwp-Id) in a CSI reporting configuration for channel measurement and contain (multiple) parameters for one CSI reporting band, such as codebook configuration, time domain behavior, frequency granularity for CSI, measurement restriction configuration, and CSI-related quantities reported by the UE. Each CSI resource setting may be located in a DL BWP identified by a higher layer parameter, and all CSI resource settings may be linked to a CSI reporting setting with the same DL BWP.

[0071] In some systems, the UE may be configured via higher layer signaling (e.g., in the CSI reporting configuration) with one of two possible subband sizes indicating the frequency granularity of the CSI report (e.g., reportFreqConfiguration contained in CSI-ReportConfig), where a subband may be defined as The UE may further receive an indication of the subbands for which CSI feedback is requested. In some examples, a subband mask is configured for the requested subbands for CSI reporting. The UE calculates a precoder for each requested subband and finds a PMI that matches the calculated precoder on each subband.

[0072] Compressed CSI feedback coefficient report

[0073] As discussed above, a user equipment (UE) may be configured for channel state information (CSI) reporting, for example, by receiving a CSI configuration message from a base station. In certain systems (e.g., Release 15 5G NR), the UE may be configured to report at least a type II precoder across configured frequency domain (FD) units. For example, the precoder matrix W for layer r is r The W1 matrix includes a W2 matrix that reports a subset of the selected beams using spatial compression and a W matrix that reports the linear combination coefficients of the selected beams (2L) across the configured FD elements (for cross-polarization). 2,r matrix:

[0074]

[0075] where b i is the selected beam, c i is the linear combination coefficient (i.e., W 2,r The entry of the matrix), L is the number of selected spatial beams, and N3 corresponds to the number of frequency units (e.g., subbands, resource blocks (RBs), etc.). In some configurations, L is RRC configured. The precoder is based on a linear combination of DFT beams. Type II codebooks can improve MU-MIMO performance. In some configurations where two polarizations are considered, W 2,r The matrix size is 2L X N3.

[0076] In some systems (e.g., Release 16 5G NR), the UE may be configured to report FD compressed precoder feedback to reduce the overhead of CSI reporting. Figure 5 As shown in , the precoder matrix (W) of layer i (i=0,1) 2,i ) can use FD compression The matrix compresses the precoder matrix into A matrix, of size 2L X M (where M is the network configured and signaled in the CSI configuration message via RRC or DCI, and M < N3), is given as follows:

[0077]

[0078] where the precoder matrix W i (not shown) has P = 2N1N2 rows (spatial domain, number of ports) and N3 columns (the frequency domain compression unit includes RBs or reporting subbands), and where M bases are selected for each of layer 0 and layer 1. Matrix 520 consists of linear combination coefficients (amplitudes and co-phases), where each element represents the coefficient of a tap of a beam. As shown Matrix 520 is defined to be of size 2L X M, where one row corresponds to one spatial beam in W1 (not shown) of size P X 2L (where L is the network configured via RRC), and where one entry represents the coefficient of a tap of that spatial beam. The UE may be configured to report (e.g., CSI report) a subset K0 < 2LM of the linear combination coefficients of matrix 520. For example, the UE may report K NZ,i < K0 coefficients (where K NZ,i corresponds to the maximum number of non-zero coefficients for layer i (i = 0 or 1), and K0 is the network configured via RRC), which are illustrated as shaded boxes (the unreported coefficients are set to zero). In some configurations, the entries of matrix 520 correspond to the rows of matrix 530. In the example shown, at layer 0 matrix 520 and at layer 1 matrix 550 are both of size 2L X M.

[0079] Matrix 530 consists of basis vectors (each row is a basis vector) for performing compression in the frequency domain. In the example shown, at layer 0 matrix 530 and at layer 1 matrix 560 both include M = 4 FD bases (illustrated as shaded rows) from among N3 candidate DFT bases. In some configurations, the UE may report via CSI report a subset of the bases of the selected matrix. The M bases are specifically selected at layer 0 and layer 1. That is, the bases selected at layer 0 may be the same / partially overlapping / non-overlapping with the bases selected at layer 1.

[0080] Frequency domain compression for high rank indication

[0081] Figure 6Three alternative examples for determining the FD basis for a particular RI are illustrated. Each example is illustrated with a left column indicating the RI (e.g., RI={1,2,3,4}) and a bottom row indicating the transmission layer (e.g., layer 0, layer 1, layer 2, layer 3). That is, the number of layers indicates the transmission rank, where RI=1 is limited to a single spatial layer, RI=2 corresponds to two spatial layers, RI=3 corresponds to three spatial layers, and RI=4 corresponds to four spatial layers. Therefore, Type II CSI may relate to UEs with up to four spatial layers.

[0082] In some configurations using FD compression, each layer reports up to K0 non-zero coefficients (NZCs), regardless of rank, and the total number of NZCs across all layers is constrained to 2K0. That is, for ranks 1 and 2, only the per-layer constraint needs to be considered, since the total NZC constraint across layers becomes redundant (since the total NZC of two layers, each of which is constrained to K0, will not exceed 2K0). On the other hand, for ranks 3 and 4, both the per-layer constraint and the total constraint will be considered.

[0083] Similarly, for the FD base (M i ) is equivalent to RI=2. In one example, each layer of RI=2 (layer 0 and layer 1) uses M number of FD bases, so that the FD bases across all four layers of RI=4 are equivalent to 2M. That is, for a given RI of M i can be described as:

[0084]

[0085] exist Figure 5 In the example shown in Matrix 530 includes an FD basis M=4 (M0=4), and Matrix 560 includes M = 4 FD bases (M1 = 4), resulting in a total of 8 FD bases for RI = 2. Therefore, for RI = {3, 4}, the total number of FD bases across all four layers should be comparable to M0 + M1 or 2M (e.g., between 6 and 10 FD bases for RI {3, 4}).

[0086] like Figure 6 As shown in , table 610 illustrates an example for making the total number of FD bases for RI={3,4} comparable to RI=2. In this example, the FD base for RI={3,4} for each layer of layers 0-3 is M2. In some examples, M2 may be set equal to M / 2 or 2 / 3*M in the standard specification. The M value may be determined, for example, by the following equation:

[0087] M=ceil(p*N3)

[0088] And M2 can be determined by the following equation:

[0089] M2=ceil(v0*N3)

[0090] where p and v0 are jointly configured, for example according to:

[0091] (p,v0) = (1 / 2,1 / 4), (1 / 4,1 / 4) and (1 / 4,1 / 8)

[0092] In various aspects of the techniques described herein, a UE may be configured for CSI reporting, for example, by receiving a CSI configuration message from a base station. In some systems, a UE may be configured to report a type II precoder across at least a configured frequency domain (FD) unit. For example, a precoder for a layer l on a N3 subband may be represented as a matrix W of size P×N3. l :

[0093]

[0094] In this equation, L is the number of spatial domain (SD) basis (or basis) (e.g., spatial beams) configured through RRC signaling of the CSI report configuration, yes The SD basis is based on DFT and has index and The SD base can be written as:

[0095]

[0096]

[0097] In this equation, N1 and N2 represent the first and second dimensions of the configured codebook, respectively. In some cases, these parameters may refer to the number of antenna elements in the vertical and horizontal dimensions at the base station, respectively. The oversampling factor is represented by O1 and O2.

[0098] also, (m=0,1,…M l ) is an N3×1 FD basis (i.e., is a 1×N3 row vector), which is also called the transitive domain basis. l is the number of FD bases selected for layer 1 and is derived based on the RRC configuration. In some cases, for each layer of rank 1 and rank 2, there are M bases and the value is is determined by the ratio p configured by RRC, and R is the number of precoding matrix indicator (PMI) subbands within a CQI subband. The FD basis can be a DFT basis and has an index The FD basis is expressed as:

[0099]

[0100] As mentioned above, the linear combination coefficients can include three parts: parameter represents the amplitude reference of the first polarization, and represents the amplitude reference of the second polarization. These values ​​are for the corresponding polarization (e.g. and All coefficients associated are common. Parameters Indicates that the coefficients and indices in the first polarization are and The SD basis is associated with the index The (differential) magnitude of the FD basis is associated with The coefficients and indices in the second polarization are and The SD basis is associated with the index The (differential) magnitude associated with the FD basis of . Similarly, the parameter Indicates that the coefficients and indices in the first polarization are and The SD basis is associated with the index The (differential) magnitude of the FD basis is associated with The coefficients and indices in the second polarization are and The SD basis is associated with the index The (differential) magnitude associated with the FD basis.

[0101] For RI = {1, 2}, for each layer, the number of FD bases M = M 1,2 , where the value is determined by the ratio p configured by RRC, and R is the number of precoding matrix indicator (PMI) subbands within one CQI subband. For RI={3,4}, the number of FD bases M=M 3,4 , where the value Determined by the ratio v0 configured via RRC. Possible combinations of p and v0 include In addition, for each layer of RI={1,2,3,4}, the UE is configured to report a total of 2LM 1,2 or a total of 2LM 3,4 The maximum number of coefficients to be reported per layer is K0, and the maximum total number of coefficients to be reported across all layers is 2K0, where and It is configured by RRC. It should be noted that M is used regardless of the rank. 1,2 To calculate K0.

[0102] Using codebook operation with FD compression, for layer 1, the precoder across N3 FD units (also called PMI subbands) is t ×N3 matrix W l Given, as follows:

[0103]

[0104] Among them, W1, and W f as follows:

[0105]

[0106]

[0107] Figure 7 The three matrices are graphically illustrated in Figure 7 Only two layers are shown, but in reality it can be 3 or 4 layers using the same structure, only the number of FD bases and the number of non-zero coefficients or NZCs are different) can be written as:

[0108]

[0109]

[0110]

[0111] The SD basis is based on the DFT and is indexed by and The SD base is written as:

[0112]

[0113]

[0114] The FD basis can be a DFT basis and the index is The FD basis of is expressed as:

[0115]

[0116] coefficient and can be described as follows:

[0117]

[0118] Given these definitions, more precisely, the linear combination representation can be expressed as:

[0119]

[0120] Example UL subband precoding via SRS using FD-based precoding

[0121] Some deployments (e.g., NR Release 15 and 16 systems) support codebook-based transmission and non-codebook-based transmission schemes for uplink transmission with wideband precoder. Codebook-based UL transmission is based on BS configuration and can be used in situations where reciprocity does not hold.

[0122] Figure 8 is a call flow diagram illustrating an example of a conventional codebook-based UL transmission using a wideband precoder. As illustrated, the UE transmits (non-precoded) SRS using up to 2 SRS resources (each resource having 1, 2, or 4 ports). The gNB measures the SRS and selects an SRS resource and wideband precoder to apply to the SRS ports within the selected resource based on the measurement results.

[0123] As illustrated, the gNB configures the selected SRS resources for the UE via the SRS Resource Indicator (SRI) and the wideband precoder for the UE via the Transmit Precoder Matrix Indicator (TPMI). For dynamic grants, the SRI and TPMI may be configured via DCI format 0_1. For configured grants (e.g., for semi-persistent uplink), the SRI and TPMI may be configured via RRC or DCI.

[0124] The UE determines the selected SRS resources from the SRI and the precoding from the TPMI and sends the PUSCH accordingly. Fig. 9 It illustrates how the wideband precoder (indicated via TPMI) can map transmit layers to PUSCH ports. Figures 12A-12F An example set of precoder matrices that may be selected via the TPMI index for various layer and antenna port combinations are illustrated.

[0125] Fig.10is a call flow diagram illustrating an example of non-codebook based UL transmission. As illustrated, the UE transmits a (precoded) SRS. Although the example shows 2 SRS resources, the UE can transmit using up to 4 SRS resources (each with 1 port). The gNB measures the SRS and selects one or more SRS resources based on the measurement results. In this case, since the UE transmits precoded SRS, by selecting the SRS resource, the gNB also effectively selects the precoder. For non-codebook based UL transmission, each SRS resource corresponds to a layer. The precoder for this layer is actually the precoder of the SRS simulated by the UE. Selecting N SRS resources means a rank of N. The UE will use the same precoder as the SRS to transmit the PUSCH.

[0126] As illustrated, the gNB configures the selected SRS resources for the UE via an SRS Resource Indicator (SRI). For dynamic grants, SRI may be configured via DCI format 0_1. For configured grants, SRI may be configured via RRC or DCI.

[0127] In this case, the UE determines the selected SRS resource from the SRI, selects the same precoder used when transmitting the selected SRS resource, and transmits the PUSCH accordingly. Fig.11 It illustrates how a PUSCH port is effectively selected via SRS ports spanning selected SRS resource(s).

[0128] As mentioned above, wideband precoding is commonly used in legacy (e.g., Release 15 and Release 16) systems. However, in some cases, subband precoding can provide gains, especially when the number of Tx layers is greater than or equal to 4. One challenge of subband precoding for UL transmission is how to define the transmission scheme of subband precoding and the related signaling (e.g., TPMI from gNB to UE).

[0129] Various aspects of the present disclosure propose an UL transmission scheme that implements subband precoding via SRS port selection. As will be described in more detail below, each SRS port can be transmitted from a specific antenna port and based on a specific frequency domain basis. The frequency domain basis applied to the SRS port can be obtained by the UE via DL channel measurement (e.g., assuming DL / UL reciprocity). The gNB measures the UL channel (e.g., based on the precoded SRS) and determines one or more optimal SRS ports to be used for the PUSCH. In addition, the gNB also determines the optimal coefficients associated with each port.

[0130] In addition, the gNB may further configure / signal the port selection and coefficients to the UE. Possible advantages of the UL subband precoding described herein include enhanced performance gain, relaxed UE implementation complexity, and DL / UL reciprocity can be exploited in terms of latency.

[0131] Fig.13 1300 for wireless communications by a UE for UL subband precoding in accordance with certain aspects of the present disclosure. Operations 1300 may be performed, for example, by Figure 1 or Figure 3 UE 120 executes.

[0132] Operations 1300 begin at 1302 by transmitting a sounding reference signal (SRS) signal on a SRS resource to a network entity on a plurality of SRS ports. At 1304, the UE receives information from the network entity indicating one or more of the sounding reference signal (SRS) ports selected by the network entity and associated linear combination coefficients. At 1306, the UE determines a subband precoding based at least in part on the selected SRS ports. At 1308, the UE transmits a physical uplink shared channel (PUSCH) using the subband precoding.

[0133] Fig.14 1 is a flow diagram illustrating example operations 1400 for wireless communications by a network entity (e.g., a base station such as an eNB or gNB), in accordance with certain aspects of the present disclosure. Operations 1400 may be performed, for example, by Figure 1 or Figure 3 BS 110 performs to configure UE 120 for UL subband precoding (according to Fig.13 Operation 1300).

[0134] Operations 1400 begin at 1402 by measuring a sounding reference signal (SRS) sent from a user equipment (UE) to a network entity. At 1404, the network entity selects one or more of the SRS ports and associated linear combination coefficients based on the measurements. At 1406, the network entity sends information indicating the one or more SRS ports and associated linear combination coefficients to the UE. At 1408, the network entity receives a physical uplink shared channel (PUSCH) from the UE, the physical uplink shared channel (PUSCH) being sent using subband precoding based on the indicated SRS ports and associated linear combination coefficients.

[0135] Fig.15 is a call flow diagram illustrating an example UL transmission using subband precoding, which may help understand Fig.13 and Fig.14Operations 1300 and 1400. As illustrated, the UE may determine an SRS precoder based on DL reference signal measurements and transmit a precoded SRS on one or more SRS ports. Based on the SRS measurements, the base station (gNB) selects one or more SRS ports and associated linear combination coefficients.

[0136] The gNB then signals the selected SRS ports and the associated linear combination coefficients to the UE (via SRI). The gNB may send the selected SRS ports and the linear combination coefficients to the UE via DCI or RRC or MAC CE. The UE then transmits the PUSCH using subband precoding based on the selected SRS ports and the associated linear combination coefficients.

[0137] The SRS transmitted by the UE may be precoded by the FD basis. In some cases, each SRS port may be simulated via a combination of a specific antenna port and a specific FD basis. For example, SRS ports 0 and 1 may be associated with different antenna ports but the same FD basis. Alternatively, SRS ports 0 and 1 may be associated with different FD basis but the same antenna port. Fig.16 An example of precoding is graphically illustrated where the FD basis is applied to 4 SRS ports (ports 0-3) across N3 FD units.

[0138] As described herein, with UL subband precoding selected via SRS ports, the precoder for layer l∈{0,…,v-1} across N3 FD units can be expressed as:

[0139]

[0140] in The size is p×1, in row i k There is only one "1" in the ith k ports are selected on all N3 FD units. Alternatively, the precoder of layer 1 can be expressed as:

[0141]

[0142] Some of the coefficients may be equal to zero if the corresponding SRS port is not selected.

[0143] In some cases, SRS port organization and precoding may be based on restrictions. According to one option, the gNB may configure restrictions on FD basis emulation. For example, the restriction may be on the maximum FD basis index (or delay or phase offset) that the UE may use to transmit an SRS port. In some cases, each SRS resource may have only one SRS port and the maximum number of SRS resources may be greater than 4.

[0144] According to another option, the gNB may configure restrictions for FD basis emulation. In this case, each SRS resource may have more than one SRS port. Ports within each SRS resource may be associated with the same antenna port but different FD basis. For improvement of channel estimation, the gNB may jointly estimate the channels associated with SRS ports within the same group.

[0145] like Figure 17A-17B As shown, there are various options for configuring SRS port selection. Fig.17A As illustrated in , in a "layer common" approach, each layer can have the same SRS port selection. Fig. 17B As illustrated in , in a "layer-specific" approach, different layers may have different port selections (e.g. Indicated by layer index l in

[0146] There are various methods for configuring linear coefficients. In some cases, according to the total ∑ l K 0,l SRS ports (K 0,l represents the number of non-zero ports selected for layer l), the gNB may further indicate K NZ ≤∑ l K 0,l non-zero coefficients (assuming that the coefficients of unindicated ports are set to zero).

[0147] In some cases, the configuration of the coefficients may depend on which of the (described above) SRS port selection configurations is used. For example, for layer common, K may be indicated NZ ≤v×K0 non-zero coefficients, where K0 represents the number of non-zero ports selected at each layer.

[0148] The format and content of the coefficients may also vary according to various options. For example, according to a first option, quantization of each coefficient may be used. In this case, an A-bit amplitude quantization is used (e.g., |c k,l |), and can indicate B-bit phase quantization (e.g., |c k,l |).

[0149] According to a second option, the coefficients may be indicated via joint coefficient quantization. In such a case, the non-zero coefficients may be jointly selected from the candidate set Such as: Examples are Figures 12A-12F middle.

[0150] In some cases, the gNB may configure the FD basis and coefficients for the UE via two-stage DCI signaling (involving a first DCI transmission and a second DCI transmission). In such a case, the first DCI may provide sufficient information for a complete precoder. For example, the first DCI may indicate at least one (may be more or all) SRS ports per layer.

[0151] The second DCI may provide the remaining information for subband precoding. For example, the second DCI may indicate the remaining SRS ports (if all SRS ports are not included in the first DCI). The second DCI may also indicate the associated coefficients of the indicated SRS ports.

[0152] The methods disclosed herein include one or more steps or actions for implementing these methods. Without departing from the scope of the claims, the method steps and / or actions may be interchangeable with each other. In other words, unless a specific order of steps or actions is specified, the order and / or use of specific steps and / or actions may be modified without departing from the scope of the claims.

[0153] As used herein, a phrase referring to "at least one" of a list of items refers to any combination of those items, including single members. For example, "at least one of a, b, or c" is intended to cover a, b, c, ab, ac, bc, and abc, as well as any combination with multiples of the same elements (e.g., aa, aaa, aab, aac, abb, acc, bb, bbb, bbc, cc, and ccc or any other order of a, b, and c).

[0154] As used herein, the term "determining" includes a wide variety of actions. For example, "determining" may include calculating, computing, processing, deriving, investigating, searching (e.g., searching in a table, a database, or another data structure), ascertaining, etc. In addition, "determining" may include receiving (e.g., receiving information), accessing (e.g., accessing data in a memory), etc. In addition, "determining" may include solving, selecting, choosing, establishing, etc.

[0155] The foregoing description is provided to enable any person skilled in the art to practice the various aspects described herein. Various modifications to these aspects will be apparent to those skilled in the art, and the general principles defined herein may be applied to other aspects. Therefore, the claims are not intended to be limited to the various aspects shown herein, but to conform to the full scope consistent with the language of the claims, wherein, unless otherwise specified, the elements mentioned in the singular are not intended to mean "one and only one", but "one or more". Unless otherwise explicitly stated, the term "some" refers to one or more. All structural and functional equivalents of the elements of the various aspects described throughout this disclosure are known or will be known later to those of ordinary skill in the art, and are expressly incorporated herein by reference and are intended to be covered by the claims. In addition, anything disclosed herein is not intended to be dedicated to the public, regardless of whether such disclosures are explicitly described in the claims.

[0156] The various operations of the methods described above may be performed by any suitable components capable of performing the corresponding functions. These components may include various hardware and / or (multiple) software components and / or (multiple) modules, including but not limited to circuits, application specific integrated circuits (ASICs) or processors. For example, Figure 3 The various processors shown in FIG. 1 may be configured to perform Figure 8 and Fig. 9 Operations 800 and 900.

[0157] The various illustrative logic blocks, modules, and circuits described in conjunction with the present disclosure may be implemented or executed with a general purpose processor, a digital signal processor (DSP), an application specific integrated circuit (ASIC), a field programmable gate array (FPGA) or other programmable logic device (PLD), discrete gate or transistor logic, discrete hardware components, or any combination thereof designed to perform the functions described herein. The general purpose processor may be a microprocessor, but as an alternative, the processor may be any commercially available processor, controller, microcontroller, or state machine. The processor may also be implemented as a combination of computing devices, for example, a combination of a DSP and a microprocessor, a plurality of microprocessors, one or more microprocessors combined with a DSP core, or any other such configuration.

[0158] If implemented in hardware, an example hardware configuration may include a processing system in a wireless node. The processing system may be implemented using a bus architecture. Depending on the specific application and overall design constraints of the processing system, the bus may include any number of interconnecting buses and bridges. The bus may link together various circuits including a processor, a machine-readable medium, and a bus interface. Among other things, the bus interface may be used to connect a network adapter to the processing system via the bus. The network adapter may be used to implement signal processing functions at the PHY layer. In the user terminal 120 (see Figure 1 ), a user interface (e.g., a keypad, display, mouse, joystick, etc.) may also be connected to the bus. The bus may also link various other circuits such as timing sources, peripherals, voltage regulators, power management circuits, etc., which are well known in the art and therefore will not be described further. The processor may be implemented using one or more general purpose and / or special purpose processors. Examples include microprocessors, microcontrollers, DSP processors, and other circuits that can execute software. Those skilled in the art will recognize how to best implement the functionality described for the processing system depending on the specific application and the overall design constraints imposed on the entire system.

[0159] If implemented in software, these functions can be stored on or sent through a computer-readable medium as one or more instructions or codes. Whether it is referred to as software, firmware, middleware, microcode, hardware description language or other, software should be broadly interpreted as meaning instructions, data or any combination thereof. Computer-readable media include both computer storage media and communication media, and communication media include any media that helps to transfer a computer program from one place to another. The processor can be responsible for managing the bus and general processing, including the execution of software modules stored on a machine-readable storage medium. A computer-readable storage medium can be coupled to a processor so that the processor can read information from the storage medium and write information to the storage medium. Alternatively, a storage medium can be integrated into a processor. For example, a machine-readable medium can include a transmission line, a carrier modulated by data, and / or a computer-readable storage medium on which instructions separated from a wireless node are stored, all of which can be accessed by a processor through a bus interface. Alternatively or additionally, a machine-readable medium or any part thereof can be integrated into a processor, such as a cache and / or a general register file. By way of example, examples of machine-readable storage media may include, for example, RAM (random access memory), flash memory, ROM (read only memory), PROM (programmable read only memory), EPROM (erasable programmable read only memory), EEPROM (electrically erasable programmable read only memory), registers, magnetic disks, optical disks, hard drives, or any other suitable storage media, or any combination thereof. The machine-readable medium may be embodied in a computer program product.

[0160] A software module may include a single instruction or many instructions, and may be distributed over several different code segments, between different programs, and across multiple storage media. A computer-readable medium may include multiple software modules. A software module includes instructions that, when executed by a device such as a processor, cause a processing system to perform various functions. A software module may include a sending module and a receiving module. Each software module may reside in a single storage device, or may be distributed across multiple storage devices. By way of example, when a triggering event occurs, a software module may be loaded from a hard drive into a RAM. During the execution of a software module, a processor may load some of the instructions into a cache to increase access speed. Subsequently, one or more cache lines may be loaded into a general register file to be executed by a processor. When the function of a software module is mentioned below, it should be understood that this function is implemented by a processor when executing instructions from the software module.

[0161] In addition, any connection is appropriately defined as a computer-readable medium. For example, if the software is transmitted from a website, server or other remote source using a coaxial cable, fiber optic cable, twisted pair, digital subscriber line (DSL), or wireless technology (such as infrared (IR), radio and microwave), then the coaxial cable, fiber optic cable, twisted pair, DSL, or wireless technology (such as infrared, radio, microwave) are all included in the definition of medium. As used herein, disk and disc include compact disk (CD), laser disk, optical disk, digital versatile disk (DVD), floppy disk and (Blu- ) disk, where magnetic disks typically reproduce data magnetically, while optical disks reproduce data optically. Thus, in some aspects, computer-readable media may include non-transitory computer-readable media (e.g., tangible media). Additionally, for other aspects, computer-readable media may include transient computer-readable media (e.g., signals). Combinations of the above should also be included within the scope of computer-readable media.

[0162] Thus, certain aspects may include a computer program product for performing the operations presented herein. For example, such a computer program product may include a computer-readable medium having instructions stored (and / or encoded) thereon, which instructions may be executed by one or more processors to perform the operations described herein (e.g., for performing the operations described herein and Fig.13 and Fig.14 ).

[0163] In addition, it should be understood that, if applicable, the modules and / or other suitable components for performing the methods and techniques described herein can be downloaded and / or otherwise obtained by the user terminal and / or base station. For example, such a device can be coupled to a server to facilitate the transmission of the components for performing the methods described herein. Alternatively, the various methods described herein can be provided via a storage component (e.g., RAM, ROM, a physical storage medium such as a compact disk (CD) or a floppy disk), so that the user terminal and / or base station can obtain various methods when the storage component is coupled to or provided to the device. In addition, any other suitable technology for providing the methods and techniques described herein to the device can be utilized.

[0164] It is to be understood that the claims are not limited to the precise configuration and components illustrated above. Various modifications, changes and variations may be made in the arrangement, operation and details of the methods and apparatus described above without departing from the scope of the claims.

Claims

1. A method for wireless communication by a user equipment UE, comprising: transmitting a sounding reference signal (SRS) to a network entity on a SRS resource on a plurality of sounding reference signal (SRS) ports, wherein each SRS resource has a port associated with a specific frequency domain FD basis or FD transmit filter and a specific antenna port or spatial domain transmit filter; receiving, from the network entity, information indicating one or more of the sounding reference signal (SRS) ports selected by the network entity and associated linear combination coefficients; determining a subband precoding based at least in part on the selected SRS ports and the linear combination coefficients; and A physical uplink shared channel PUSCH is sent using the subband precoding.

2. The method according to claim 1, wherein the information is signaled via at least one of downlink control information (DCI), radio resource control (RRC) signaling, or medium access control (MAC) control element (MAC-CE).

3. The method according to claim 1, further comprising: measuring one or more downlink signals sent from the network entity; selecting at least one of a set of one or more frequency-domain FD bases or a set of one or more FD transmit filters based on the measuring; as well as The SRS signal is precoded based at least in part on at least one of the set of FD bases or the set of FD transmit filters.

4. The method according to claim 1, wherein: Each SRS port within the SRS resource is associated with a different antenna port or spatial domain transmit filter; and Each SRS port within an SRS resource is associated with the same FD basis or FD transmit filter.

5. The method according to claim 1, wherein: Each SRS port within the SRS resource is associated with the same antenna port or spatial domain transmit filter; and Each SRS port within an SRS resource is associated with a different FD basis or FD transmit filter.

6. The method of claim 1, wherein the SRS is sent based at least in part on a restriction signaled by the network entity, wherein the restriction implies a maximum FD base index or a maximum phase / delay offset to be applied in sending the SRS.

7. The method of claim 6, wherein the restriction indicates: Each SRS resource has only one SRS port; an SRI is received to enable port selection.

8. The method according to claim 6, wherein: The restriction indicates that each SRS resource has one or more SRS ports; and The method includes receiving an SRI and a port indicator within each resource to enable port selection.

9. The method of claim 1, wherein the same SRS port is used for each transmission layer for the subband precoding.

10. The method of claim 1, wherein a transmission layer specific SRS port is used for the subband precoding.

11. The method according to claim 1, wherein the linear combination coefficients include: a first set of coefficients representing quantized amplitude values; as well as A second set of coefficients representing quantized phase values.

12. The method according to claim 11, further comprising: receiving an indication of a number of non-zero coefficients; in quantization of only non-zero coefficients is indicated; and The coefficients of unindicated SRS ports are set to zero.

13. The method of claim 1, wherein the linear combination coefficients comprise linear combination coefficients jointly selected from a candidate set of linear combination coefficients.

14. The method according to claim 11, further comprising: receiving an indication of a number of non-zero coefficients; in Only non-zero coefficients are jointly selected and indicated; and The coefficients of unindicated SRS ports are set to zero.

15. The method of claim 1, wherein the information is signaled via at least a first downlink control information (DCI) transmission and a second DCI transmission.

16. The method of claim 15, wherein the first DCI indicates: One or more SRS ports per transmit layer.

17. The method of claim 16, wherein the second DCI indicates: remaining SRS ports of the plurality of SRS ports not indicated in the first DCI; and The linear combination coefficients associated with at least the remaining SRS ports.

18. A method for wireless communication by a network entity, comprising: measuring a sounding reference signal SRS transmitted from a user equipment UE to a network entity on an SRS resource on a plurality of sounding reference signal SRS ports, wherein each SRS resource has one port associated with a specific frequency domain FD basis or FD transmit filter and a specific antenna port or spatial domain transmit filter; selecting one or more of the SRS ports and associated linear combination coefficients based on the measurements; sending information indicating the one or more SRS ports and associated linear combination coefficients to the UE; as well as A physical uplink shared channel (PUSCH) transmitted with subband precoding based on the indicated SRS ports and associated linear combination coefficients is received from the UE.

19. The method of claim 18, wherein the information is signaled via at least one of downlink control information (DCI), radio resource control (RRC) signaling, or medium access control (MAC) control element (MAC-CE).

20. The method of claim 18, wherein: Each SRS port within the SRS resource is associated with a different antenna port or spatial domain transmit filter; and Each SRS port within an SRS resource is associated with the same FD basis or FD transmit filter.

21. The method of claim 18, wherein: Each SRS port within the SRS resource is associated with the same antenna port or spatial domain transmit filter; and Each SRS port within an SRS resource is associated with a different FD basis or FD transmit filter.

22. The method of claim 18, further comprising signaling to the UE a restriction implying a maximum frequency domain FD base index or a maximum phase / delay offset to be applied in transmitting the SRS.

23. The method of claim 22, wherein the restriction indicates: Each SRS resource has only one SRS port; an SRI is received to enable port selection.

24. The method of claim 22, wherein the restriction indicates: Each SRS resource has one or more SRS ports; and The SRI and the port indicator within each resource are received to implement port selection.

25. The method of claim 18, wherein the same SRS port is used for each transmission layer for the subband precoding.

26. The method of claim 18, wherein a transmission layer specific SRS port is used for the subband precoding.

27. The method of claim 18, wherein the linear combination coefficients include: a first set of coefficients representing quantized amplitude values; as well as A second set of coefficients representing quantized phase values.

28. The method according to claim 27, further comprising: signaling an indication of the number of non-zero coefficients; in quantization of only non-zero coefficients is indicated; and The coefficients of unindicated SRS ports are set to zero.

29. The method of claim 18, wherein the linear combination coefficients comprise linear combination coefficients jointly selected from a candidate set of linear combination coefficients.

30. The method of claim 29, further comprising: signaling an indication of the number of non-zero coefficients; in Only non-zero coefficients are jointly selected and indicated; and The coefficients of unindicated SRS ports are set to zero.

31. The method of claim 18, wherein the information is signaled via at least a first downlink control information (DCI) transmission and a second DCI transmission.

32. The method of claim 31 , wherein the first DCI indicates: One or more SRS ports per transmit layer.

33. The method of claim 32, wherein remaining SRS ports of the plurality of SRS ports not indicated in the first DCI; and The linear combination coefficients associated with at least the remaining SRS ports.

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