Type II CSI port selection codebook enhancement using partial reciprocity

Abstract

A base station and a wireless communication (UE) may perform Type II CSI-RS port selection based at least on partial reciprocity between an uplink path and a downlink path between the base station and the UE. The base station may identify a dominant signal path between the base station and the UE based on measurements performed during uplink transmissions, and may transmit corresponding information to the UE indicating a CSI measurement and reporting configuration that may include a single measurement resource or multiple measurement resources. Each measurement resource may include a multi-port CSI-RS port. When multiple measurement resources are configured, the UE may indicate a selection of the measurement resource to the base station and may also report a layer-independent or layer-common selection of a subset of the CSI-RS ports included in the indicated single measurement resource or multiple measurement resources. Other enhancements include frequency domain compression enhancement and dynamic codebook parameter reconfiguration.

Description

Technical Field

[0001] The present application relates to wireless communications, and more particularly, to channel state information (CSI) port selection codebook enhancement during wireless cellular communications, such as during 5G-NR communications. Background Art

[0002] The use of wireless communication systems is growing rapidly. In recent years, wireless devices such as smartphones and tablets have become increasingly sophisticated. In addition to supporting phone calls, many mobile devices (e.g., user equipment devices or UEs) now also provide access to the Internet, email, text messaging, and navigation using the Global Positioning System (GPS), and are capable of operating sophisticated applications that utilize these capabilities. In addition, there are many different wireless communication technologies and wireless communication standards. Some examples of wireless communication standards include GSM, UMTS (WCDMA, TDS-CDMA), LTE, LTE Advanced (LTE-A), HSPA, 3GPP2 CDMA2000 (e.g., 1xRTT, 1xEV-DO, HRPD, eHRPD), IEEE802.11 (WLAN or Wi-Fi), IEEE 802.16 (WiMAX), BLUETOOTH TM The next telecommunications standard beyond the current International Mobile Telecommunications Advanced (IMT-Advanced) standard is known as the fifth generation mobile network or fifth generation wireless system, referred to as 3GPP NR (also known as 5G-NR for 5G New Radio, or simply NR). NR provides higher capacity for a higher density of mobile broadband users while supporting device-to-device, ultra-reliable, and massive machine-to-machine communications, as well as lower latency and reduced battery consumption than the current LTE standard.

[0003] In general, wireless communication technologies such as cellular communication technologies are generally designed to provide mobile communication capabilities to wireless devices. The introduction of an ever-increasing number of features and functions in wireless communication devices has created a continuous demand for improved wireless communications and improved wireless communication devices. In particular, it is very important to ensure the accuracy of transmitted and received signals. A UE, which may be a mobile phone or smart phone, a portable gaming device, a communication system / device installed in or loaded by a transport vehicle (e.g., a car, bus, train, truck, motorcycle, etc.), a laptop, a wearable device, a PDA, a tablet computer, a portable Internet device, a music player, a data storage device or other handheld device, is typically powered by a portable power source (e.g., a battery) and may have multiple radio interfaces that enable support for various wireless communication standards (LTE, LTE-A, 5G-NR, Wi-Fi, BLUETOOTH, etc.). TMCurrently, efforts are underway to achieve efficient use of wireless communication resources, thereby improving the operating efficiency of systems and devices.

[0004] Many wireless communication standards provide for the use of known signals (e.g., pilot signals or reference signals) for various purposes, such as synchronization, measurement, equalization, and control. For example, in cellular wireless communications, a reference signal (RS) is a special signal that exists only at the physical layer and is not used to convey any specific information, but rather to provide a reference point for downlink power. When a wireless communication device or mobile equipment (UE) attempts to determine downlink power (e.g., the power of a signal from a base station, such as an eNB for LTE and a gNB for NR), the device measures the power of the reference signal and uses it to determine the downlink cell power. Reference signals also assist receivers in demodulating received signals. Because the reference signal includes data known to both the transmitter and the receiver, the receiver can use the reference signal to determine / identify various characteristics of the communication channel. This is often referred to as "channel estimation," a key component of many high-end wireless communications, such as LTE and 5G-NR. The known channel characteristics of a communication link in wireless communications are called channel state information (CSI), which provides information indicating the combined effects of, for example, scattering, fading, and power decay with distance. CSI has the potential to adapt the transmission to the current channel conditions, which is crucial for achieving reliable communication with high data rates in multi-antenna systems.

[0005] Typically, multi-antenna systems use precoding to improve communications. Precoding is an extension of beamforming to support multi-stream (or multi-layer) transmission for multi-antenna wireless communications, and is used to control differences in signal characteristics between corresponding signals transmitted from multiple antennas by modifying the signal transmitted from each antenna according to a precoding matrix. In one sense, precoding can be considered as a process of cross-coupling signals (in a closed-loop operation) before transmission to equalize the demodulation performance of the layers. The precoding matrix is typically selected from a codebook defining a plurality of precoding matrix candidates, and the precoding matrix candidate is typically selected according to the desired performance level based on any of a number of different factors, such as the current system configuration, the communication environment and / or feedback information from a receiver, such as a mobile device (UE) receiving the transmitted signal.

[0006] Feedback information is used to select precoding matrix candidates by defining the same codebook at both the transmitter (which can be a base station) and the receiver (which can be a mobile device or UE), and using the feedback information from the receiver as an indication of the preferred precoding matrix. In this case, the feedback information includes content called a precoding matrix index (PMI), which can be based on the characteristics of the signal received at the receiver. For example, the receiver may determine that the received signal has a relatively low signal-to-noise ratio (SNR) and may therefore transmit a PMI that will replace the current precoding matrix with a new precoding matrix to increase the signal-to-noise ratio (SNR).

[0007] The precoding matrix is based on a specific set of assumed antenna configurations. These antenna configurations are specified by defining the number of rows and columns of cross-polarity antenna elements. For example, a smaller antenna may have 1 row and 2 columns of cross-polarity antenna elements, thereby supporting a total of 4 transceivers. A larger antenna may have 4 rows and 4 columns of cross-polarity antenna elements, thereby supporting a total of 32 transceivers. This z-group antenna configuration does not restrict the use of other configurations in real-time network deployments. The maximum antenna configuration can support a specified total number (e.g., 32) of transceivers and can therefore transmit a specified total number of CSI reference signals. Actual network deployments may use active antennas with more transceivers, but for the purpose of CSI reporting, the actual network deployment may use up to a specified total number of transceivers to transmit CSI reference signals.

[0008] To date, four solutions for PMI reporting have been defined, Type I single panel, Type I multi-panel, Type II single panel, and Type II port selection. Generally speaking, Type II solutions focus on providing more detailed CSI for the purpose of multi-user MIMO. Such Type II solutions support a maximum of two (2) levels, corresponding to a maximum of two (2) layers per UE. The maximum number of layers per cell may be higher to allow multiple UEs to use 2×2 MIMO simultaneously while sharing a common resource block (RB) allocation. Type II reporting is based on selecting a set of beams and then specifying the relative amplitudes and phases to generate a weighted combination of beams for each layer transmission. The Type II port selection solution relies on the base station having some advance information to allow beamforming of the CSI-RS transmission. If channel reciprocity is available, then this advance information can be derived from uplink (UL) measurements. Otherwise, the advance information can be derived from beam management reports, or the advance information can use wideband reports from different PMI reporting solutions (when a combination of PMI reporting solutions is used, it is sometimes called a "hybrid solution"). For more efficient and simplified reporting by the UE, it may be beneficial to exploit even partial reciprocity that may exist between UL and DL transmissions.

[0009] Other corresponding problems associated with the prior art will become apparent to those skilled in the art after comparing such prior art with the disclosed embodiments described herein. Summary of the Invention

[0010] Embodiments of methods and procedures are presented herein for, inter alia, supporting use of a Type II CSI port selection codebook with improved feedback in various devices (e.g., wireless communication devices), the Type II CSI port selection codebook exploiting partial reciprocity between uplink and downlink transmissions, for example, during 5G-NR communications. Embodiments of a wireless communication system are further presented herein, the wireless communication system including a wireless communication device (UE) and / or a base station and an access point (AP) communicating with each other within the wireless communication system.

[0011] In the 3GPP Rel-15 specification, beamformed CSI-RS (Channel State Information - Reference Signal) utilizes Type II port selection based on downlink (DL) and uplink (UL) channel reciprocity. A total of "X" CSI-RS ports can be selected, specifically X / 2 ports for horizontal polarization (HPol) and X / 2 ports for vertical polarization (VPol). From these X / 2 CSI-RS ports, "L" CSI-RS ports can be selected, with the first CSI-RS port selected from every "d" number of ports. Subsequently, wraparound can be utilized to select the consecutive L ports. The 3GPP Rel-16 specification discloses the same port selection design as Rel-15, while adding certain features. For example, when configuring the subband PMI (precoding matrix index), the frequency-domain DFT matrix can be used to compress the linear combination coefficients. For the Type II port selection codebook, the gNB assumes that the CSI-RS is precoded based on channel reciprocity. For example, the downlink channel can be estimated based on the uplink channel. For FDD (frequency division duplex), there may not be exact channel reciprocity, especially when the duplex distance is large. However, even for FDD, there may still be partial reciprocity. For example, the arrival or departure angles between the DL carrier and the UL carrier may be similar, and the channel delay profiles between the DL carrier and the UL carrier may be similar. In some embodiments, the Type II CSI port selection codebook can be enhanced by exploiting partial channel reciprocity, promoting layer-independent CSI-RS port selection, layer-common CSI-RS port selection, frequency domain compression enhancement, and / or dynamic codebook parameter reconfiguration.

[0012] As described above, based on the uplink (UL) sounding reference signal (SRS) transmitted by the UE to the base station (e.g., to the gNB), the base station can estimate the UL channel and assume certain reciprocity of the channel to obtain downlink (DL) channel characteristics, such as a preferred beam. The base station can then transmit the CSI-RS precoded using the preferred beam. The CSI-RS can have multiple CSI-RS ports, and each port can be transmitted from the base station using a different beam, i.e., each CSI-RS port can correspond to a different beam via which the CSI-RS port is transmitted. The UE can indicate the preferred CSI-RS port to the base station via a CSI report, for example, implicitly indicating the preferred beam.

[0013] In some embodiments, the UE may receive information from the base station indicating a channel state information (CSI) measurement and reporting configuration that may include a single measurement resource or multiple measurement resources. Each measurement resource may include a multi-port CSI-RS port. When multiple measurement resources are configured, the UE may indicate the selection of the measurement resource to the base station and may report to the base station the selection of a subset of the CSI-RS ports included in the indicated single measurement resource or multiple measurement resources. The selection of the subset of CSI-RS ports may be performed independently for each layer of the multi-layer transmission, or the selection may be performed jointly for each layer of the multi-layer transmission.

[0014] In some embodiments, the base station may identify a dominant signal path between the base station and the device based on a channel estimation performed using uplink communication between the base station and the device. The base station may transmit preferred CSI-RS ports corresponding to the dominant signal paths to the device, wherein for each of the dominant signal paths, the CSI-RS port is transmitted via a corresponding beam independently identified by the base station.

[0015] This summary is intended to provide a brief overview of some of the subject matter described in this document. Therefore, it should be understood that the above-described features are merely examples and should not be construed as narrowing the scope or spirit of the subject matter described herein in any way. Other features, aspects, and advantages of the subject matter described herein will become apparent from the following detailed description, accompanying drawings, and claims. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 An exemplary (and simplified) wireless communication system according to some embodiments is shown;

[0017] Figure 2 illustrates an exemplary base station in communication with an exemplary wireless user equipment (UE) device in accordance with some embodiments;

[0018] Figure 3 is an exemplary block diagram of a UE according to some embodiments;

[0019] Figure 4 shows an exemplary block diagram of a base station according to some embodiments;

[0020] Figure 5 shows an exemplary simplified block diagram of an example cellular communication circuit according to some embodiments;

[0021] Figure 6 presents an exemplary diagram illustrating a precoding structure associated with Type II CSI reporting according to the prior art;

[0022] Figure 7 shows an exemplary diagram illustrating a reporting structure used by a UE to report back to a base station according to the prior art;

[0023] Figure 8 presents an exemplary diagram illustrating a codebook structure with compressed combining coefficients for Type II CSI reporting;

[0024] Figure 9 shows an exemplary diagram illustrating layer independent CSI-RS port selection according to some embodiments;

[0025] Figure 10 shows an exemplary diagram illustrating layer common CSI-RS port selection according to some embodiments;

[0026] Figure 11 showing an exemplary diagram illustrating frequency domain compression for CSI-RS port selection according to some embodiments;

[0027] Figure 12 shows an exemplary diagram illustrating layer common CSI-RS port selection using fully free indication according to some embodiments; and

[0028] Figure 13 An exemplary diagram illustrating antenna group selection for layer-common CSI-RS port selection according to some embodiments is presented.

[0029] While the features described herein are susceptible to various modifications and alternative forms, specific embodiments thereof are shown by way of example in the drawings and are herein described in detail. It should be understood, however, that the drawings and detailed description thereof are not intended to limit this disclosure to the specific forms disclosed, but on the contrary, are intended to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the subject matter as defined by the appended claims. DETAILED DESCRIPTION

[0030] Acronyms

[0031] Various acronyms are used throughout this patent application. The definitions of the most prominent acronyms used that may appear throughout this patent application are as follows:

[0032] AMR: Adaptive Multi-Rate

[0033] AP: Access Point

[0034] APN: Access Point Name

[0035] APR: Application Processor

[0036] AS: Access layer

[0037] BS: Base Station

[0038] BSR: Buffer Size Report

[0039] BSSID: Basic Service Set Identifier

[0040] CBRS: Citizens Broadband Radio Service

[0041] CBSD: Citizens Broadband Radio Service Device

[0042] CBSR: Codebook Subset Restriction

[0043] CCA: Clear Channel Assessment

[0044] CMR: Change Mode Request

[0045] CS: Circuit Switching

[0046] CSI: Channel State Information

[0047] DL: Downlink (from BS to UE)

[0048] DSDS: Dual SIM Dual Standby

[0049] DYN: Dynamic

[0050] EDCF: Enhanced Distributed Coordination Function

[0051] FDD: Frequency Division Duplex

[0052] FO: First-order state

[0053] FT: frame type

[0054] GAA: General Authorization Access

[0055] GPRS: General Packet Radio Service

[0056] GSM: Global System for Mobile Communications

[0057] GTP: GPRS Tunneling Protocol

[0058] IMS: Internet Protocol Multimedia Subsystem

[0059] IP: Internet Protocol

[0060] IR: Initialization and refresh status

[0061] KPI: Key Performance Indicator

[0062] LAN: Local Area Network

[0063] LBT: Listen first, speak later

[0064] LQM: Link Quality Metric

[0065] LTE: Long Term Evolution

[0066] MIMO: Multiple Input Multiple Output

[0067] MNO: Mobile Network Operator

[0068] MU: Multi-User

[0069] NAS: Non-Access Stratum

[0070] NB: Narrowband

[0071] OOS: Out of sync

[0072] PAL: Priority Access Licensee

[0073] PDCP: Packet Data Convergence Protocol

[0074] PDN: Packet Data Network

[0075] PDU: Protocol Data Unit

[0076] PGW: PDN Gateway

[0077] PLMN: Public Land Mobile Network

[0078] PMI: Precoding Matrix Indicator

[0079] PSD: Power Spectral Density

[0080] PSS: Primary Synchronization Signal

[0081] PT: Payload Type

[0082] QBSS: Basic Service Set with enhanced quality of service

[0083] QI: Quality Indicator

[0084] RAN: Radio Access Network

[0085] RAT: Radio Access Technology

[0086] RF: Radio Frequency

[0087] ROHC: Robust Header Compression

[0088] RRC: Radio Resource Control

[0089] RS: Reference signal

[0090] RTP: Real-time Transport Protocol

[0091] RTT: Round Trip Time

[0092] RX: Receive

[0093] SAS: Spectrum Allocation Server

[0094] SI: System Information

[0095] SID: System Identification Number

[0096] SIM: Subscriber Identity Module

[0097] SGW: Serving Gateway

[0098] SMB: Small and medium-sized business

[0099] SRS: Sounding Reference Signal

[0100] SSS: Secondary synchronization signal

[0101] TBS: Transport Block Size

[0102] TCP: Transmission Control Protocol

[0103] TDD: Time Division Duplex

[0104] TX: Transmit

[0105] UE: User Equipment

[0106] UI: User Interface

[0107] UL: Uplink (from UE to BS)

[0108] UMTS: Universal Mobile Telecommunications System

[0109] USIM: UMTS Subscriber Identity Module

[0110] WB: Broadband

[0111] Wi-Fi: Wireless local area network (WLAN) RAT based on the Institute of Electrical and Electronics Engineers (IEEE) 802.11 standard

[0112] WLAN: Wireless LAN

[0113] the term

[0114] The following is a glossary of terms that will appear in this application:

[0115] Memory medium—any of various types of non-transitory memory devices or storage devices. The term "memory medium" is intended to include installation media, such as CD-ROMs, floppy disks, or tape devices; computer system memory or random access memory such as DRAM, DDR RAM, SRAM, EDO RAM, Rambus RAM, etc.; non-volatile memory such as flash, magnetic media, such as hard drives or optical storage devices; registers, or other similar types of memory elements, etc. Memory media may also include other types of memory or combinations thereof. Furthermore, the memory medium may be located in a first computer system executing a program, or may be located in a different second computer system connected to the first computer system via a network, such as the Internet. In the latter case, the second computer system may provide program instructions to the first computer system for execution. The term "memory medium" may include two or more memory media that may reside in different locations in different computer systems connected, for example, via a network. The memory medium may store program instructions (e.g., represented as a computer program) that may be executed by one or more processors.

[0116] Carrier Medium—storage media as described above, and physical transmission media such as a bus, network, and / or other physical transmission media that transport signals such as electrical, electromagnetic, or digital signals.

[0117] Programmable hardware elements—include various hardware devices that include multiple programmable function blocks connected via programmable interconnects. Examples include FPGAs (field programmable gate arrays), PLDs (programmable logic devices), FPOAs (field programmable object arrays), and CPLDs (complex PLDs). Programmable function blocks can range from fine-grained (combinational logic units or lookup tables) to coarse-grained (arithmetic logic units or processor cores). Programmable hardware elements may also be referred to as "configurable logic units."

[0118] Computer system (or computer) – Any of various types of computing or processing systems, including a personal computer system (PC), a mainframe computer system, a workstation, a network appliance, an Internet appliance, a personal digital assistant (PDA), a television system, a grid computing system, or other devices or combinations of devices. In general, the term "computer system" can be broadly defined to encompass any device (or combination of devices) having at least one processor that executes instructions from a memory medium.

[0119] User Equipment (UE) (or "UE device") - any of various types of computer system devices that perform wireless communications. Also known as wireless communication devices, many of which may be mobile and / or portable. Examples of UE devices include mobile phones or smartphones (e.g., iPhones). TM , based on Android TM phones) and tablets such as iPads TM 、Samsung Galaxy TM etc., gaming devices (such as Sony PlayStation TM , Microsoft XBox TM etc.), portable gaming devices (e.g., Nintendo DS TM PlayStation Portable TM 、Gameboy Advance TM iPod TM ), laptops, wearable devices (e.g., Apple Watch TM , Google Glass TM ), PDAs, portable internet devices, music players, data storage devices or other handheld devices, etc. If various other types of devices include Wi-Fi or both cellular and Wi-Fi communication capabilities and / or other wireless communication capabilities (e.g., via short-range radio access technologies (SRATs) such as BLUETOOTH TM Generally speaking, the term "UE" or "UE device" can be broadly defined to cover any electronic device, computing device and / or telecommunication device (or combination of devices) capable of wireless communication and which may also be portable / mobile.

[0120] Wireless device (or wireless communication device)—any of various types of computer system devices that perform wireless communication using WLAN communication, SRAT communication, Wi-Fi communication, etc. As used herein, the term "wireless device" can refer to a UE device as defined above or a fixed device, such as a fixed wireless client or a wireless base station. For example, a wireless device can be a wireless station of any type of 802.11 system, such as an access point (AP) or a client station (UE), or a wireless station of any type of cellular communication system that communicates according to a cellular radio access technology (e.g., LTE, CDMA, GSM), such as, for example, a base station or a cellular phone.

[0121] Communication Device—Any of various types of computer systems or devices that perform communication, either wired or wireless. A communication device may be portable (or mobile), or stationary or fixed in place. A wireless device is one example of a communication device. A UE is another example of a communication device.

[0122] Base Station (BS)—The term “base station” has the full breadth of its ordinary meaning and includes at least a wireless communication station installed at a fixed location and used to communicate as part of a wireless telephone system or radio system.

[0123] Processor - refers to any element (e.g., circuit) or combination of elements that is capable of performing functions in a device (e.g., in a user equipment device or in a cellular network device). Processors may include, for example, general-purpose processors and associated memory, portions or circuits of individual processor cores, entire processor cores or processing circuit cores, processing circuit arrays or processor arrays, circuits such as ASICs (Application Specific Integrated Circuits), programmable hardware elements such as field programmable gate arrays (FPGAs), and any combination of the foregoing.

[0124] Channel - the medium used to transmit information from a sender (transmitter) to a receiver. It should be noted that because the characteristics of the term "channel" can vary according to different wireless protocols, the term "channel" as used herein may be considered to be used in a manner consistent with the standard of the device type to which the term is referenced. In some standards, the channel width may be variable (e.g., depending on device capabilities, frequency band conditions, etc.). For example, LTE may support scalable channel bandwidths of 1.4 MHz to 20 MHz. In contrast, a WLAN channel may be 22 MHz wide, while a Bluetooth channel may be 1 MHz wide. Other protocols and standards may include different definitions of channels. In addition, some standards may define and use multiple types of channels, such as different channels for uplink or downlink and / or different channels for different purposes such as data, control information, etc.

[0125] Band—The term "band" has the full breadth of its ordinary meaning and includes at least a segment of the spectrum (e.g., radio frequency spectrum) where channels are used for the same purpose or set aside. Furthermore, "band" is used to refer to any interval in the frequency domain bounded by lower and higher frequencies. The term can refer to a radio frequency band or some other interval of the spectrum. A radio communication signal can occupy a frequency range over which the signal is carried (or within which the signal is carried). This frequency range is also referred to as the bandwidth of the signal. Thus, bandwidth refers to the difference between the upper and lower frequencies in a continuous frequency band. A band can represent a single communication channel, or it can be subdivided into multiple communication channels. The allocation of radio frequency ranges for different uses is a primary function of radio spectrum allocation.

[0126] Wi-Fi—The term "Wi-Fi" has the full scope of its ordinary meaning and includes at least wireless communication networks, or RATs, that are served by wireless LAN (WLAN) access points and provide connectivity to the Internet through those access points. Most modern Wi-Fi networks (or WLAN networks) are based on the IEEE 802.11 standard and are marketed under the name "Wi-Fi." Wi-Fi (WLAN) networks are distinct from cellular networks.

[0127] Automatic—refers to an action or operation being performed by a computer system (e.g., software executed by a computer system) or a device (e.g., a circuit, a programmable hardware element, an ASIC, etc.) without requiring user input to directly specify or execute the action or operation. Thus, the term "automatic" is in contrast to manual execution or specification of an action by a user, where the user provides input to directly execute the action. An automated process may be initiated by user-provided input, but the subsequent "automatically" performed actions are not specified by the user, e.g., not "manually" performed, where the user specifies each action to be performed. For example, a user filling out an electronic form by selecting each field and providing input specifying information (e.g., by typing information, selecting checkboxes, radio selections, etc.) is not manually filling out the form, even though the computer system must update the form in response to the user's actions. The form may be automatically filled out by a computer system, where the computer system (e.g., software executing on the computer system) analyzes the fields of the form and fills it out without requiring any user input to specify the answers to the fields. As indicated above, a user may invoke automatic filling of a form without participating in the actual filling out of the form (e.g., the user does not manually specify the answers to the fields, but rather they are automatically completed). This specification provides various examples of operations that are automatically performed in response to actions that a user has taken.

[0128] About—refers to a value that is close to the correct or exact value. For example, about can refer to a value that is within 1% to 10% of the exact (or desired) value. However, it should be noted that the actual threshold value (or tolerance) may depend on the application. For example, in some embodiments, "about" may mean within 0.1% of some specified or desired value, while in various other embodiments, the threshold value may be, for example, 2%, 3%, 5%, etc., depending on the desires or requirements of the particular application.

[0129] Concurrency—refers to parallel execution or implementation, where tasks, processes, or programs are executed in an at least partially overlapping manner. For example, concurrency can be implemented using "strong" or strict parallelism, where tasks are executed (at least partially) in parallel on respective computing elements, or using "weak parallelism," where tasks are executed in an interleaved manner (e.g., by time-multiplexing of execution threads).

[0130] Station (STA)—The term "station" herein refers to any device capable of communicating wirelessly (e.g., using the 802.11 protocol). A station can be a laptop, desktop PC, PDA, access point, or Wi-Fi phone, or any other type of device similar to a UE. A STA can be fixed, mobile, portable, or wearable. Generally speaking, in wireless networking terminology, a station (STA) broadly encompasses any device capable of wireless communication, and the terms station (STA), wireless client (UE), and node (BS) are often used interchangeably.

[0131] Configured to - Various components may be described as being "configured to" perform one or more tasks. In such contexts, "configured to" is a broad statement that generally means "having the structure" to perform one or more tasks during operation. Thus, a component can be configured to perform a task even when the component is not currently performing the task (e.g., a set of electrical conductors can be configured to electrically connect a module to another module even when the two modules are not connected). In some contexts, "configured to" can be a broad statement that generally means "having the circuitry" to carry out one or more tasks during operation. Thus, a component can be configured to perform a task even when the component is not currently turned on. Generally, the circuitry that forms the structure corresponding to "configured to" may include hardware circuitry.

[0132] Transmission scheduling - refers to the scheduling of transmissions (such as wireless transmissions). In cellular radio communications, signal transmissions and data transmissions can be organized according to designated time units of a specific duration for the transmission. For example, in LTE, transmissions are divided into radio frames, each of which has an equal (time) duration (for example, each radio frame can be 10ms). Radio frames in LTE can be further divided into ten subframes, each of which has an equal duration, and subframes are designated as the minimum (shortest) scheduling unit, or a designated time unit for transmission. Similarly, the minimum (or shortest) scheduling unit for 5G NR (or simply NR) transmission is called a time slot. Therefore, as used herein, the term "time slot" is used to refer to the minimum (or shortest) scheduling time unit of wireless communications described as performing NR communications. However, as mentioned above, in different communication protocols, such scheduling time units may be named differently, for example, it is a "subframe" in LTE, etc.

[0133] For ease of description, various components may be described as performing tasks. Such descriptions should be interpreted as including the phrase "configured to." Representing a component as being configured to perform one or more tasks expressly does not invoke the sixth paragraph of Section 112 of Title 35 of the United States Code for that component.

[0134] Figure 1 and Figure 2 -Exemplary Communication System

[0135] Figure 1 An exemplary (and simplified) wireless communication system according to some embodiments is shown. Note that Figure 1 The system is only one example of a possible system, and embodiments may be implemented in any of a variety of systems as desired.

[0136] As shown, the exemplary wireless communication system includes base stations 102A through 102N, also collectively referred to as base stations 102. Figure 1 As shown, base station 102A communicates with one or more user equipment 106A, 106B, etc. through 106N via a transmission medium. Each of the user equipment may be referred to herein as a "user equipment" (UE) or a UE device. Thus, user equipment 106A through 106N are referred to as UEs or UE devices, and are also collectively referred to as UE 106. According to various embodiments disclosed herein, various of the UE devices may use an enhanced Type II CSI port selection codebook based at least on partial reciprocity.

[0137] Base station 102A may be a base transceiver station (BTS) or cell site and may include hardware that enables wireless communication with UEs 106A to 106N. Base station 102A may also be configured to communicate with network 100, such as a cellular service provider's core network, a telecommunications network such as the Public Switched Telephone Network (PSTN) and / or the Internet, a neutral host, or various CBRS (Citizens Broadband Radio Service) deployments, among other possibilities. Thus, base station 102A may facilitate communication between user devices and / or between user devices and network 100. The communication area (or coverage area) of a base station may be referred to as a "cell." It should also be noted that a "cell" may also refer to a logical identity for a given coverage area at a given frequency. Generally, any independent cellular wireless coverage area may be referred to as a "cell." In such a case, a base station may be located at a specific intersection of three cells. In this uniform topology, a base station may serve three 120-degree beamwidth areas, referred to as cells. Furthermore, for carrier aggregation, small cells, relays, etc. may all represent cells. Thus, particularly in carrier aggregation, there may be primary cells and secondary cells that may serve at least partially overlapping coverage areas but on different respective frequencies. For example, a base station may serve any number of cells, and the cells served by a base station may or may not be collocated (e.g., remote radio heads). Also as used herein, with respect to a UE, a base station may sometimes be considered to represent a network in light of the UE's uplink and downlink communications. Thus, a UE communicating with one or more base stations in a network may also be interpreted as a UE communicating with the network, and may also be considered to be at least a portion of a UE communicating on or through a network.

[0138] Base station 102 and user equipment can be configured to communicate over a transmission medium using any of a variety of radio access technologies (RATs), also known as wireless communication technologies or telecommunication standards, such as GSM, UMTS (WCDMA), LTE, LTE-Advanced (LTE-A), LAA / LTE-U, 5G-NR (abbreviated as NR), 3GPP2 CDMA2000 (e.g., 1xRTT, 1xEV-DO, HRPD, eHRPD), Wi-Fi, WiMAX, etc. It is noted that if base station 102A is implemented in the context of LTE, it may alternatively be referred to as an "eNodeB" or "eNB." It is noted that if base station 102A is implemented in the context of 5G NR, it may alternatively be referred to as a "gNodeB" or "gNB." In some embodiments, base station 102 can communicate with a UE that uses an enhanced Type II CSI port selection codebook based at least on partial reciprocity, as described herein. Depending on a given application or specific considerations, some of the various different RATs may be functionally grouped according to overall defining characteristics for convenience. For example, all cellular RATs may be collectively considered to represent a first (form / type) RAT, while Wi-Fi communications may be considered to represent a second RAT. In other cases, each cellular RAT may be individually considered a distinct RAT. For example, when distinguishing between cellular and Wi-Fi communications, "first RAT" may collectively refer to all considered cellular RATs, while "second RAT" may refer to Wi-Fi. Similarly, different forms of Wi-Fi communications (e.g., above 2.4 GHz versus above 5 GHz) may be considered to correspond to different RATs, where applicable. Furthermore, cellular communications performed according to a given RAT (e.g., LTE or NR) may be distinguished from one another based on the spectrum in which those communications occur. For example, LTE or NR communications may be performed on both a primary licensed spectrum and a secondary spectrum, such as an unlicensed spectrum. Overall, the use of various terms and expressions will always be clearly noted in relation to and within the context of the various applications / implementations being considered.

[0139] As shown, base station 102A may also be configured to communicate with network 100 (e.g., a cellular service provider's core network, a telecommunications network such as a public switched telephone network (PSTN), and / or the Internet), as well as various other possibilities. Thus, base station 102A may facilitate communications between user devices and / or between user devices and network 100. In particular, cellular base station 102A may provide UE 106 with various communication capabilities, such as voice, SMS, and / or data services.

[0140] Thus, base station 102A and other similar base stations (such as base stations 102B...102N) operating according to the same or different cellular communication standards can be provided as a network of cells that can provide continuous or nearly continuous overlapping service to 106A-106N and similar devices within a geographic area via one or more cellular communication standards.

[0141] Thus, although base station 102A may function as Figure 1 106N, each UE 106 may also be capable of receiving signals from (and potentially within communication range of) one or more other cells (which may be provided by base stations 102B-N and / or any other base stations), which may be referred to as "neighboring cells." Such cells may also be capable of facilitating communications between user devices and / or between user devices and network 100. Such cells may include "macro" cells, "micro" cells, "pico" cells, and / or cells of any other variety of granularities of service area size. For example, in Figure 1 The base stations 102A-102B shown in FIG may be macro cells, while the base station 102N may be a micro cell. Other configurations are also possible.

[0142] In some embodiments, base station 102A may be a next-generation base station, such as a 5G New Radio (5G NR) base station or "gNB." In some embodiments, a gNB may be connected to a legacy evolved packet core (EPC) network and / or to a new radio communications core (NRC) network. Furthermore, a gNB cell may include one or more transmission and reception points (TRPs). Furthermore, a UE capable of operating in accordance with 5G NR may connect to one or more TRPs within one or more gNBs.

[0143] As described above, the UE 106 may be capable of communicating using multiple wireless communication standards. For example, the UE 106 may be configured to communicate using any or all of a 3GPP cellular communication standard (such as LTE or NR) or a 3GPP2 cellular communication standard (such as a cellular communication standard in the CDMA2000 family of cellular communication standards). Thus, the base station 102 and other similar base stations operating according to the same or different cellular communication standards may be provided as one or more cell networks that may provide continuous or nearly continuous overlapping service to the UE 106 and similar devices over a wide geographic area via one or more cellular communication standards.

[0144] UE 106 may also or alternatively be configured to use WLAN, BLUETOOTH TM 、BLUETOOTH TMThe system may communicate using one or more global navigation satellite systems (GNSS, such as GPS or GLONASS), one or more mobile television broadcast standards (e.g., ATSC-M / H or DVB-H), etc. Other combinations of wireless communication standards (including more than two wireless communication standards) are also possible.

[0145] Furthermore, the UE 106 may also be in communication with the network 100 via one or more base stations or via other devices, stations, or any apparatus not explicitly shown but considered to be part of the network 100. Thus, a UE 106 in communication with the network may be interpreted as the UE 106 in communication with one or more network nodes that are considered to be part of the network and that may interact with the UE 106 to communicate with the UE 106 and, in some cases, influence at least some of the communication parameters and / or usage of communication resources of the UE 106.

[0146] In addition, for example Figure 1 As shown in FIG, at least some UEs (e.g., UE 106D and 106E) may represent vehicles that communicate with each other and with base station 102, for example, via cellular communications such as 3GPP LTE and / or 5G-NR communications. Additionally, UE 106F may represent a pedestrian that is communicating and / or interacting in a similar manner with the vehicles represented by UEs 106D and 106E. Figure 1 Other aspects of vehicles communicating in the network exemplified in , for example in the context of vehicle-to-everything (V2X) communications, such as specified by 3GPP TS 22.185 V.14.3.0.

[0147] Figure 2 An exemplary user equipment 106 (e.g., one of devices 106A through 106N) is shown communicating with a base station 102 and an access point 112 according to some embodiments. The UE 106 may be a device having cellular communication capabilities and non-cellular communication capabilities (e.g., BLUETOOTH TM, Wi-Fi, etc.), such as a mobile phone, a handheld device, a computer or a tablet computer, or almost any type of wireless device. UE 106 may include a processor configured to execute program instructions stored in a memory. UE 106 may execute any of the method embodiments described in the present invention by executing such stored instructions. Alternatively or in addition, UE 106 may include a programmable hardware element, such as an FPGA (field programmable gate array) configured to execute any of the method embodiments described herein or any part of any of the method embodiments described herein. UE 106 may be configured to communicate using any one of a plurality of wireless communication protocols. For example, UE 106 may be configured to communicate using two or more of CDMA 2000, LTE, LTE-A, NR, WLAN, or GNSS. Other combinations of wireless communication standards are also possible.

[0148] UE 106 may include one or more antennas for communicating using one or more wireless communication protocols according to one or more RAT standards. In some embodiments, UE 106 may share one or more portions of a receive chain and / or transmit chain between multiple wireless communication standards. The shared radio component may include a single antenna, or may include multiple antennas (e.g., for MIMO) for performing wireless communication. Alternatively, UE 106 may include an independent transmit chain and / or receive chain (e.g., including independent antennas and other radio components) for each wireless communication protocol with which it is configured to communicate. As another alternative, UE 106 may include one or more radio components shared between multiple wireless communication protocols, and one or more radio components used exclusively by a single wireless communication protocol. For example, UE 106 may include a shared radio component for communicating using one of LTE or CDMA2000 1xRTT or NR, and a shared radio component for communicating using Wi-Fi and BLUETOOTH. TM Independent radio components for each of the communications. Other configurations are also possible.

[0149] Figure 3 —Exemplary UE

[0150] Figure 3A block diagram of an exemplary UE 106 according to some embodiments is shown. As shown, the UE 106 may include a system on a chip (SOC) 300, which may include components for various purposes. For example, as shown, the SOC 300 may include a processor 302 that can execute program instructions for the UE 106, and a display circuit 304 that can perform graphics processing and provide display signals to a display 360. The processor 302 may also be coupled to a memory management unit (MMU) 340 and / or other circuits or devices (such as the display circuit 304, the radio circuit 330, the connector I / F 320, and / or the display 360). The MMU 340 may be configured to receive addresses from the processor 302 and convert those addresses to locations in a memory (e.g., the memory 306, the read-only memory (ROM) 350, the NAND flash memory 310). The MMU 340 may be configured to perform memory protection and page table translation or setup. In some embodiments, the MMU 340 may be included as part of the processor 302.

[0151] As shown, the SOC 300 may be coupled to various other circuits of the UE 106. For example, the UE 106 may include various types of memory (e.g., including NAND flash 310), a connector interface 320 (e.g., for coupling to a computer system), a display 360, and wireless communication circuitry (e.g., for LTE, LTE-A, NR, CDMA2000, BLUETOOTH, etc.). TM , Wi-Fi, GPS, etc.). The UE device 106 may include at least one antenna (e.g., 335a), and may include multiple antennas (e.g., as shown by antennas 335a and 335b), for performing wireless communications with base stations and / or other devices. Antennas 335a and 335b are shown by way of example, and the UE device 106 may include fewer or more antennas. Generally speaking, one or more antennas are collectively referred to as antennas 335. For example, the UE device 106 may use antennas 335 to perform wireless communications with the radio circuit 330. As described above, in some embodiments, the UE may be configured to perform wireless communications using multiple wireless communication standards.

[0152] As further described herein, the UE 106 (and / or the base station 102) may include hardware and software components for implementing a method for at least the UE 106 to use an enhanced Type II CSI port selection codebook based at least on partial reciprocity during wireless communications, such as during 5G-NR communications, as further detailed herein. The processor 302 of the UE device 106 may be configured to implement a portion or all of the methods described herein, for example, by executing program instructions stored on a memory medium (e.g., a non-transitory computer-readable memory medium). In other embodiments, the processor 302 may be configured as a programmable hardware element, such as an FPGA (field programmable gate array) or as an ASIC (application-specific integrated circuit). Furthermore, according to various embodiments, the processor 302 may be coupled to a processor such as a processor 106. Figure 3 Other components shown and / or interoperable with other components may be used to utilize the enhanced Type II CSI port selection codebook based at least on partial reciprocity during wireless communications, such as during 5G-NR communications, to implement various other applications and / or end-user applications running on UE 106.

[0153] In some embodiments, the radio circuitry 330 may include separate controllers dedicated to controlling communications for various corresponding RAT standards. Figure 3 As shown, the radio circuit 330 may include a Wi-Fi controller 356, a cellular controller (e.g., an LTE and / or NR controller) 352, and a BLUETOOTH controller. TM Controller 354, and in at least some embodiments, one or more or all of these controllers may be implemented as respective integrated circuits (ICs or chips) that communicate with each other and with SOC 300 (more specifically, with processor 302). For example, Wi-Fi controller 356 may communicate with cellular controller 352 via a cell-ISM link or WCI interface, and / or BLUETOOTH TM The controller 354 may communicate with the cellular controller 352 via a cell-ISM link, etc. Although three separate controllers are shown within the radio circuit 330, other embodiments have fewer or more similar controllers for various different RATs that may be implemented in the UE device 106. For example, at least one exemplary block diagram illustrating some embodiments of the cellular controller 352 is provided in Figure 5 , as further described below.

[0154] Figure 4 —Exemplary Base Station

[0155] Figure 4 1 shows a block diagram of an exemplary base station 102 according to some embodiments. Note that Figure 4The base station 102 is only one example of a possible base station. As shown, the base station 102 may include a processor 404 that may execute program instructions for the base station 102. The processor 404 may also be coupled to a memory management unit (MMU) 440 or other circuit or device that may be configured to receive addresses from the processor 404 and translate those addresses into locations in memory (e.g., memory 460 and read-only memory (ROM) 450).

[0156] The base station 102 may include at least one network port 470. The network port 470 may be configured to couple to a telephone network and provide access to the telephone network as described above. Figure 1 and Figure 2 The network port 470 may be configured to couple to a plurality of devices such as the UE device 106 to the telephone network described in the embodiment of the present invention. The network port 470 (or an additional network port) may also or alternatively be configured to couple to a cellular network, such as a core network of a cellular service provider. The core network may provide mobility-related services and / or other services to a plurality of devices such as the UE device 106. In some cases, the network port 470 may be coupled to the telephone network via the core network, and / or the core network may provide the telephone network (e.g., in other UE devices served by the cellular service provider).

[0157] Base station 102 may include at least one antenna 434, and possibly multiple antennas. The at least one antenna 434 may be configured to function as a wireless transceiver and may be further configured to communicate with UE device 106 via radio 430. Antenna 434 communicates with radio 430 via a communication chain 432. Communication chain 432 may be a receive chain, a transmit chain, or both. Radio 430 may be designed to communicate via various wireless telecommunication standards, including, but not limited to, LTE, LTE-A, 5G-NR (or simply NR), WCDMA, CDMA2000, and the like. The processor 404 of base station 102 may be configured to implement some or all of the methods described herein, for example, by executing program instructions stored on a memory medium (e.g., a non-transitory computer-readable memory medium) on base station 102, to communicate with a UE device. The UE device may utilize an enhanced Type II CSI port selection codebook based at least on partial reciprocity during wireless communications, such as 5G-NR communications. Alternatively, processor 404 may be configured as a programmable hardware element such as an FPGA (field programmable gate array) or as an ASIC (application-specific integrated circuit), or a combination thereof. In the case of certain RATs (e.g., Wi-Fi), base station 102 may be designed as an access point (AP), in which case network port 470 may be implemented to provide access to a wide area network and / or one or more local area networks, for example, it may include at least one Ethernet port, and radio 430 may be designed to communicate in accordance with the Wi-Fi standard. Base station 102 may operate in accordance with various methods and embodiments disclosed herein for communicating with UE devices that utilize enhanced Type II CSI port selection codebooks for enhanced channel state information reporting, as disclosed herein, during wireless communications, such as during 5G-NR communications, at least based on partial reciprocity.

[0158] Figure 5 —Exemplary Cellular Communications Circuit

[0159] Figure 5 1 shows an exemplary simplified block diagram of an exemplary cellular controller 352 according to some embodiments. Note that Figure 5The block diagram of the cellular communication circuitry is only one example of possible cellular communication circuitry; other circuitry, such as circuitry that includes or is coupled to sufficient antennas for different RATs to perform uplink activities using separate antennas, or circuitry that includes or is coupled to fewer antennas, such as circuitry that can be shared between multiple RATs, is also possible. According to some embodiments, the cellular communication circuitry 352 may be included in a communication device such as the communication device 106 described above. As described above, the communication device 106 may be a user equipment (UE) device, a mobile device or mobile station, a wireless device or wireless station, a desktop computer or computing device, a mobile computing device (e.g., a laptop, notebook, or portable computing device), a tablet and / or device, among other devices.

[0160] The cellular communication circuitry 352 may be (e.g., communicatively; directly or indirectly) coupled to one or more antennas, such as antennas 335a-b and 336 as shown. In some embodiments, the cellular communication circuitry 352 may include dedicated receive chains for multiple RATs (including and / or coupled to (e.g., communicatively; directly or indirectly) dedicated processors and / or radio components (e.g., a first receive chain for LTE and a second receive chain for 5G NR). For example, Figure 5 As shown, the cellular communication circuitry 352 may include a first modem 510 and a second modem 520. The first modem 510 may be configured to communicate according to a first RAT (e.g., such as LTE or LTE-A), and the second modem 520 may be configured to communicate according to a second RAT (e.g., such as 5G NR).

[0161] As shown, the first modem 510 may include one or more processors 512 and a memory 516 in communication with the processor 512. The modem 510 may communicate with a radio frequency (RF) front end 530. The RF front end 530 may include circuitry for transmitting and receiving radio signals. For example, the RF front end 530 may include receive circuitry (RX) 532 and transmit circuitry (TX) 534. In some embodiments, the receive circuitry 532 may communicate with a downlink (DL) front end 550, which may include circuitry for receiving radio signals via antenna 335a.

[0162] Similarly, the second modem 520 may include one or more processors 522 and a memory 526 in communication with the processor 522. The modem 520 may communicate with an RF front end 540. The RF front end 540 may include circuitry for transmitting and receiving radio signals. For example, the RF front end 540 may include receive circuitry 542 and transmit circuitry 544. In some embodiments, the receive circuitry 542 may communicate with a DL front end 560, which may include circuitry for receiving radio signals via the antenna 335b.

[0163] In some embodiments, the switch 570 can couple the transmit circuitry 534 to an uplink (UL) front end 572. Furthermore, the switch 570 can couple the transmit circuitry 544 to the UL front end 572. The UL front end 572 can include circuitry for transmitting radio signals via the antenna 336. Thus, when the cellular communication circuitry 352 receives an instruction to transmit according to a first RAT (e.g., via a transmit chain including the transmit circuitry 534 and the UL front end 572), the switch 570 can be switched to a first state that allows the first modem 510 to transmit signals according to the first RAT (e.g., via a transmit chain including the transmit circuitry 534 and the UL front end 572). Similarly, when the cellular communication circuitry 352 receives an instruction to transmit according to a second RAT (e.g., via a transmit chain including the transmit circuitry 544 and the UL front end 572), the switch 570 can be switched to a second state that allows the second modem 520 to transmit signals according to the second RAT (e.g., via a transmit chain including the transmit circuitry 544 and the UL front end 572).

[0164] As described herein, the first modem 510 and / or the second modem 520 may include hardware and software components for implementing any of the various features and techniques described herein. For example, by executing program instructions stored on a memory medium (e.g., a non-transitory computer-readable memory medium), the processors 512, 522 may be configured to implement some or all of the features described herein. Alternatively (or additionally), the processors 512, 522 may be configured as programmable hardware elements, such as an FPGA (field programmable gate array) or as an ASIC (application-specific integrated circuit). Alternatively (or in addition), in combination with one or more of the other components 530, 532, 534, 540, 542, 544, 550, 570, 572, 335, and 336, the processors 512, 522 may be configured to implement some or all of the features described herein.

[0165] Furthermore, as described herein, processors 512, 522 may include one or more processing elements. Thus, processors 512, 522 may include one or more integrated circuits (ICs) configured to perform the functions of processors 512, 522. Furthermore, each integrated circuit may include circuits (e.g., a first circuit, a second circuit, etc.) configured to perform the functions of processors 512, 522.

[0166] In some embodiments, the cellular communication circuitry 352 may include only one transmit / receive chain. For example, the cellular communication circuitry 352 may not include the modem 520, the RF front end 540, the DL front end 560, and / or the antenna 335b. As another example, the cellular communication circuitry 352 may not include the modem 510, the RF front end 530, the DL front end 550, and / or the antenna 335a. In some embodiments, the cellular communication circuitry 352 may also not include the switch 570, and the RF front end 530 or the RF front end 540 may communicate with the UL front end 572, for example, directly.

[0167] Type II Channel State Information (CSI) reporting

[0168] In 3GPP New Radio (NR or 5G-NR) systems, two types of codebooks, Type I codebook and Type II codebook, have been standardized to support CSI feedback for advanced MIMO operations. Both types of codebooks are constructed from a beam grid based on a two-dimensional (2D) discrete Fourier transform (DFT), enabling beam-selected CSI feedback and in-phase combining between the two polarizations. CSI feedback based on Type II codebook also reports the wideband and subband polarization information of the selected beam, resulting in more accurate CSI. This in turn provides improved precoded MIMO transmission through the network.

[0169] Figure 6 An exemplary diagram is shown showing a precoding structure associated with Type II CSI reporting according to the prior art. CSI may be reported to a base station (gNB) to indicate which precoding is preferred by the UE. As described above, there are two types of codebooks for CSI reporting, or in other words, there are two types of CSI reports, Type I and Type II. In Type II reporting, the precoding matrix is reported for each PMI subband and is represented by a linear combination of a set of a specified number (L) of DFT vectors representing each column. Figure 6 As shown, there may be a specified number (N3) of subbands, each with a corresponding precoding matrix W. Each precoding matrix includes two columns, w 1 and w 2. Each column corresponds to a precoding vector for a layer. For each layer, the precoding vector can be further divided into two parts, the first polarization and the second polarization. The L DFT vectors are common to all subbands and are used for subband-specific combinations. Specifically, each column vector is a weighted sum of a specified number (L) of vectors. The weighted (or combined) coefficients of the combination weights are in Figure 6 Indicated by c0, c1 and c2. Figure 6 As indicated in the example of , v0, v1, and v2 represent three DFT vectors. The UE reports to the gNB which three DFT vectors are preferred.

[0170] Figure 7 An exemplary diagram is shown showing a reporting structure used by a UE to report back to a base station (e.g., to a gNB) according to the prior art. Each subband has its own corresponding set of combining coefficients, and ultimately the UE needs to report all combining coefficients. When considering reporting by the UE, the Type II overhead is dominated by the subband combining coefficients. Figure 7 The total number of entries is 2L×N3, the amplitude is one (1) bit, and the phase is three (3) bits. In the worst case, there may be 19 subbands, 32 transmit (TX) ports, and a CSI payload size of over 1000 bits.

[0171] Enhanced codebook for channel state information (CSI) port selection

[0172] As previously indicated, in the 3GPP Rel-15 specification, beamformed CSI-RS (Channel State Information - Reference Signal) utilizes Type II port selection based on downlink (DL) and uplink (UL) channel reciprocity. A total of "X" CSI-RS ports can be selected, specifically X / 2 ports for horizontal polarization (HPol) and X / 2 ports for vertical polarization (VPol). From these X / 2 CSI-RS ports, a number "L" of CSI-RS ports can be selected, where the first CSI-RS port is selected from every "d" number of ports. Subsequently, wraparound can be utilized to select the consecutive L ports. The 3GPP Rel-16 specification discloses the same port selection design as Rel-15, while adding certain features. For example, when configuring the subband PMI (precoding matrix index), the frequency-domain DFT matrix can be used to compress the linear combination coefficients. For the Type II port selection codebook, the gNB is assumed to precode the CSI-RS based on channel reciprocity. For example, the downlink channel can be estimated based on the uplink channel. For FDD (Frequency Division Duplex), exact channel reciprocity may not exist, especially when the duplex distance is large.

[0173] As indicated above, the use of channel reciprocity helps to simplify the design of Type II CSI-RS port selection. UL and DL channels can exhibit very similar channel characteristics, so the channel estimation performed for UL or DL can be used for the complementary direction (DL or UL). Instead of transmitting only non-precoded CSI-RS and querying the UE to report what the preferred beamforming vector is, the base station can perform port selection, so the base station can beamform the CSI-RS and query the UE to indicate which CSI-RS is preferred by the UE. The UE is allowed to indicate "L" CSI-RS ports, such as 2 or 4 ports. Only L consecutive ports can be indicated to keep signaling manageable. Indicate that a "window" contains L consecutive CSI-RS ports. The starting point of the window can be flexible, but is subject to another parameter "d", because the starting point must be separated by the number "d" CSI-RS ports. "d" itself can be configurable (e.g., 1, 2, 3, or 4). In the worst case, only every four CSI-RS ports can represent the starting point of the window. Once the start of the window has been indicated, the next L CSI-RS ports may be reported.

[0174] There are obvious restrictions on how CSI ports are reported. The enhancements in 3GPP Rel-16 are limited to, for example, compressing the linear combination coefficients of the frequency domain DFT matrix, such as Figure 8 As indicated in ). As mentioned previously, the assumption about reciprocity is that the UL channel and the DL channel are likely to be similar, and only the channel in one direction (UL or DL) needs to be estimated, while the same estimate is used for the other complementary channel. For FDD, there may be paired UL / DL carriers with a duplex distance, which is introduced to minimize interference between the UL channel and the DL channel. Therefore, there may be no channel reciprocity between UL and DL, especially when the duplex distance is large. However, despite this, the channels may still not be completely uncorrelated, and there may be some reciprocity. In other words, even for FDD, there may still be partial reciprocity. Two characteristics have been identified as being highly correlated between UL and DL, namely the arrival or departure angle and the channel delay profile. The arrival or departure angle is related to the angle of signal reflection, and the channel delay profile itself is related to signal reflection, so similar reflected signals will experience similar delays. Potentially, even the delay power profiles may be similar. Type II port selection can be enhanced by adapting to this partial reciprocity of FDD design. For example, compression can be performed more efficiently by exploiting knowledge of channel delay and power profiles, which can lead to simpler compression configuration for UEs, particularly from the perspective of a base station (e.g., gNB). In general, Type II CSI port selection can be enhanced by exploiting partial channel reciprocity, facilitating layer-independent CSI-RS port selection, layer-common CSI-RS port selection, frequency domain compression enhancement, and / or dynamic codebook parameter reconfiguration.

[0175] For improved CSI-RS transmission and CSI feedback or reporting, in some embodiments, based on the UL SRS transmitted by the UE to the base station (e.g., to the gNB), the gNB can estimate the UL channel and assume certain reciprocity of the channel to obtain downlink (DL) channel characteristics, such as a preferred beam. The base station can then transmit the CSI-RS precoded using the preferred beam. The CSI-RS can have multiple CSI-RS ports, and each port can be transmitted from the base station using a different beam, i.e., each CSI-RS port can correspond to a different beam used to transmit the CSI-RS port. The UE can indicate the preferred CSI-RS port to the base station via the CSI report, for example, implicitly indicating the preferred beam.

[0176] The base station can configure multiple frequency and time resources for CSI-RS resources. For example, a CSI-RS resource can span up to four OFDM symbols and occupy different resource elements (REs) in the frequency domain. A CSI-RS resource can have up to 32 ports, i.e., a pattern of up to 32 ports can exist within the same CSI-RS resource. These patterns can be orthogonal to allow the UE to correctly identify individual ports, for example, to separate each port. When the gNB transmits CSI-RS ports, it can transmit up to 32 CSI-RS ports, and each CSI-RS port can be transmitted using a different beam (or precoder). In one sense, when the gNB transmits CSI-RS resources, it can transmit up to 32 ports, each of which may be individually beamformed. The UE can separate the different CSI-RS ports according to a specified orthogonal pattern, allowing the UE to measure the quality of each CSI-RS port and determine which CSI-RS port has the highest relative quality.

[0177] It should be noted that, as used herein, a port is understood as a logical concept established in the 3GPP specification. Thus, each port is configured to have or be associated with certain resource allocations and certain patterns, which are about how to transmit certain signals, such as how to transmit CSI-RS. Resources can be configured or allocated for a CSI-RS port, for example, the first 2 REs of every 6 REs in the frequency domain (RE is the unit of subcarrier or tone in OFDM, with 4 consecutive symbols in the time domain). Then, the pattern and how to generate the sequence for that particular port can be defined. For example, a specific orthogonal pattern can be specified. Thus, the transmission of a CSI-RS port can be interpreted as the transmission of a CSI-RS according to a specific frequency domain and time domain resource configuration and an orthogonal pattern. The UE can also have an indication of the same configuration of frequency resources and time resources and orthogonal patterns, thereby allowing the UE to extract the corresponding signal and measure the quality of each CSI-RS port. For example, for every 4 REs in the frequency domain, the gNB may transmit CSI-RS port 0 on the first RE, CSI-RS port 1 on the second RE, CSI-RS port 2 on the third RE, and CSI-RS port 3 on the fourth RE. Each CSI-RS port can be transmitted using a different corresponding beam, i.e., using a different corresponding precoding. In simple terms, "transmitting a CSI-RS port" can be interpreted as transmitting CSI-RS according to a specific resource configuration, which may include frequency resources, time resources, and additional possible resource configurations, such as using orthogonal cover codes corresponding to orthogonal patterns.

[0178] Layer-independent CSI-RS port selection

[0179] Figure 9 An exemplary diagram illustrating layer-independent CSI-RS port selection is shown. Figure 9, the signal between the transmitter 908 and the receiver 902 may travel through three different signal paths. A line-of-sight signal path (920) and two reflected signal paths (922 and 924, respectively). The corresponding signals on the three signal paths may arrive at the receiver at the same time or at different times. The reflectors (904 and 906) may typically be the same for UL and DL (e.g., representing a stationary element / structure). The base station 908 may detect the three paths during UL, e.g., the base station may detect that the strongest signal is received on paths 920, 922, and 924, and may also continue to transmit across / along those same three paths (DL). It may be assumed that the angle of the strongest beam is the same for UL and DL. Therefore, there may be three channel directions with multiple beams (CSI-RS ports) associated with each direction. CSI-RS0 and CSI-RS 1 correspond to signal path 922, CSI-RS 2 and CSI-RS 3 correspond to signal path 920, and CSI-RS 4 and CSI-RS 5 correspond to signal path 924. In Figure 9 In the example shown, the base station (e.g., gNB) 908 can identify two separate (candidate) beams (CSI-RS ports) and can select a preferred beam of the two beams.

[0180] Considering the spatial basis, beams can be common to all layers. That is, when reporting multi-layer (e.g., four-layer) transmission, each layer can share the same spatial basis. For example, when CSI-RS 0 is selected for layer 0, CSI-RS 0 can also be applied to (or selected for) layers 1, 2, and 3. However, when the direction of the signal path is clearly known, it can be beneficial to indicate which specific CSI port is preferred independently of the layer. For example, when the UE and gNB support three-layer transmission, there may be a dominant path, and path 922 may be selected for (or used for) layer 1, while path 924 may be selected for layer 2. In short, CSI-RS port selection can be performed independently for each layer.

[0181] According to one proposal, only one CSI-RS port may be selected for each layer. A CSI-RS port may be indicated for one polarization, and the same index may be automatically used for the other polarization. A first number "X / 2" of CSI-RS ports may correspond to horizontal polarization (HPol), and a second number "X / 2" of CSI-RS ports may correspond to vertical polarization (VPol). CSI-RS ports with the same relative index may be selected for both HPol and VPol.

[0182] According to another proposal, only one linear combination coefficient is required for each layer and for each PMI subband before compression. For HPol, no coefficient may be required; for example, HPol can be assumed to have a specific value. For VPol, both phase and amplitude may be required. In other words, two CSI-RS ports can be selected for each layer, the first for HPol and the second for VPol. The gNB can indicate not only the ports it intends to use but also the phase offset it intends to use to ensure that multiple ports are coherently combined on the UE side.

[0183] According to yet another proposal, the CSI-RS port selected from among the X / 2 CSI-RS ports may be indicated according to multiple options, still in a layer-independent manner.

[0184] According to the first option, the UE is free to indicate which port to select. Figure 9 In the example, there are six ports and any of those six ports can be indicated. Three bits are required to indicate one of the six possible ports. This represents the most flexible design, essentially completely free indication, where each layer may require Units digit.

[0185] According to the second option, X / 2 CSI-RS ports can be divided into e groups, each group having d CSI-RS ports. Figure 9 The six ports shown in are divided into three groups, where each group corresponds to one of the signal paths as indicated (and previously noted above). Beam refinement (final selection) can be performed within each respective group, where the corresponding path is identified in the UL. The group can therefore be indicated, and a specific beam within the group can then be selected. That is, a preferred group and an offset within the group can be indicated to identify the port. The offsets may be the same for all layers, and only the groups may need to be indicated independently per layer. There is a tradeoff between overhead (flexibility decreases as overhead decreases) and flexibility (flexibility increases as overhead increases). The offsets within a group may be common among all layers, using Each layer independently signals which group's index can be used For example, if e1 and e2 are signaled for layers 1 and 2 respectively, and d_c is used for all layers, then e1*d+d_c CSI-RS ports are selected for layer 1, and e2*d+d_c CSI-RS ports are selected for layer 2. The digits are used to jointly encode the group index across different layers to save overhead, where C e RI is the number of possible RI choices in e, where RI is the number of layers.

[0186] Layer common CSI-RS port selection

[0187] Figure 10 An exemplary diagram illustrating layer-common CSI-RS port selection is shown. For simplicity, only two signal paths 1022 and 1024 are shown (lines for line-of-sight signal paths are not considered). Signal path 1022 reflects from reflector 1004 between base station 1008 and UE 1002, while signal path 1024 reflects from reflector 1006 between base station 1008 and UE 1002. In this case, there are two groups of four possible ports, each corresponding to two different (reflected) signal paths 1022 and 1024. In this case, the port selection can be common for each layer. A corresponding beam can be selected from each group, with the first group including CSI-RS 0, CSI-RS 1, CSI-RS 2, and CSI-RS 3 and the second group including CSI-RS 4, CSI-RS 5, CSI-RS 6, and CSI-RS 7. For example, two CSI-RS ports can be selected from two groups, and the beam can be used for any single layer. Each single layer may be transmitted using any one of the selected beams or using a linear combination of the selected beams.

[0188] In some embodiments, non-consecutive ports may be selected. Figure 10 In the example shown, CSI-RS ports 1 and 5 are selected. This provides the UE with flexibility in pairing beams, without being restricted by the order of ports, such as the order of gNB transmit ports. CSI-RS port selection can be performed jointly and can be common for each layer. L of the X / 2 CSI-RS ports can be selected for HPol and VPol, and CSI-RS ports with the same relative index can be selected for HPol and VPol.

[0189] The CSI-RS port may be indicated according to a number of options.

[0190] According to the first option 1, the ports can be divided into groups, for example, two groups can be selected. Within these groups, a CSI-RS port can be selected and the offset can also be indicated. Figure 10 In the example shown, the offset is 1, so CSI-RS (port) 1 is selected from the top group (corresponding to signal path 1022), and CSI-RS (port) 5 is selected from the bottom group (corresponding to signal path 1024). More generally, the number "X / 2" CSI-RS ports can be divided into a number "e" groups, each with a number "d" CSI-RS ports. The offset within a group can be common across all layers, for example, e = 2 and d = 4. The number of "L" groups out of "e" groups can be selected using the bits. For each selected group, a CSI-RS can be selected. The relative index of the CSI-RS groups can be the same, e.g. for all groups, or the relative index can be independent, e.g. For each group.

[0191] According to the second option, you can use The ones digit provides complete freedom of indication.

[0192] According to a third option, multiple ports may be reported within a group. For example, instead of reporting one port from a group (such as CSI-RS 1 in the top group in the previous example), multiple ports from the group may be reported. Thus, the X / 2 CSI-RS may be divided into a number "e" groups, each group having a number "d" CSI-RS ports. The offset within a group may be common among all layers, e.g., e=2 and d=4. A subset of the groups may be selected, where a total number "L" of the X / 2 CSI-RS ports are selected. One or more CSI-RS ports may be selected for each group, and the number of CSI-RS ports selected per group may be restricted to be the same.

[0193] According to a fourth option, a subset of a group may be selected, which may be one group or more than one group. When a group is selected, all CSI-RS ports within the group may be selected.

[0194] Frequency domain compression enhancement

[0195] In 3GPP Release 16, N3 refers to the number of subbands used for PMI reporting. DFT compression is used to compress frequency-domain coefficients. Only M DFT bases are used from the N3 DFT bases. When N3 <= 19, M DFT bases are freely selected from the N3 DFT bases. When N3 > 19, M windows are selected from the 2M windows. The positions of the 2M windows can be offset by up to 2M around the DC component.

[0196] Figure 11 An exemplary diagram is shown illustrating frequency domain compression for CSI-RS port selection according to some embodiments. The number of rows in matrix 1100 represents the spatial basis. For example, for L spatial bases, there are 2L rows (L per polarization). The number of columns represents the subband, e.g., up to 19 or 38 subbands may be reported. The example shows an 8×19 matrix (1100). Each column for this particular subband is a preferred linear combination of the 8 spatial bases. The matrix is reported back to the gNB along with the spatial basis. The gNB then multiplies the matrix by the spatial basis to reconstruct the beam that the gNB will use for DL transmissions.

[0197] One issue that can arise is that the channel exhibits a flat frequency characteristic. If the channel has a shorter time span, then the channel may be quite flat in frequency. If there is no multipath in the time domain, then the channel delay spread may be very short and there may not be much frequency selectivity, for example, each individual frequency domain may contain identical / similar channels. If there is more multipath in the time domain, then there may be more selectivity in the frequency domain.

[0198] Delay reciprocity can be exploited by considering the number of multipaths of the UL channel and how the delay profile of the UL channel is. The delay profiles can be very similar for UL and DL. The base station can be able to determine the frequency selectivity on the DL based on the UL delay profile. The DFT (of the matrix) from the frequency domain to the time domain allows compression. Figure 11 In the example shown in FIG1 , only columns 1, 3, 4, and 6 correspond to frequency bases with high energy (e.g., worthy of consideration for transmission), so other frequency bases do not need to be considered. Therefore, to provide further improvement, in some embodiments, the base station may not request information for the entire time domain. Once the base station knows the time domain pattern of the channel, the base station can help reduce overhead by instructing the UE to report a subset of frequency bases that, after undergoing DFT, represent different time domain taps.

[0199] In some embodiments, the base station may pre-configure a subset of the DFT basis for coefficient compression according to a plurality of options. That is, the base station may indicate which taps (each tap represented by a column in the matrix 1150) it prefers.

[0200] According to a first option, the base station may provide a bitmap to indicate the DFT basis (or basis) that can be used for compression. For each enabled DFT basis, the base station may further configure limits on the amplitudes that can be used. The same amplitude limits may apply to all spatial bases and layers. The amplitude limits may apply to the amplitude average of all spatial bases within the same layer and / or the amplitude average of all spatial bases across all layers. Each coefficient may correspond to a spatial basis. The base station may indicate in a bitmap whether the UE is to provide an indication corresponding to a given tap. The base station may provide the UE with indications about limits on a given tap, such as, for example, limiting the energy to within a certain threshold. The bitmap may represent which taps are to be turned on and off. For "on", additional limits may be indicated. For example, the total energy corresponding to a given (selected / active) column may not exceed a specified threshold.

[0201] According to a second option, the base station can provide a window size, such as a maximum delay spread, for the DFT basis (or basis). The window can have an initial offset relative to the DC component. The base station can further restrict the basis selection within the window. Generally, once the base station determines / obtains the delay profile of the channel and the method for selecting the column (selecting the frequency basis), the base station can help the UE further reduce overhead.

[0202] Dynamic codebook parameter reconfiguration

[0203] Codebook resolution and overhead depend on many factors for Type II CSI reporting. According to the current 3GPP Rel-15 and Rel-16 standards, this configuration is mostly semi-statically configured in RRC. When the sounding reference signal (SRS) can provide partial reciprocity, parameters can be dynamically configured to perform further basic CSI reporting enhancements. SRS is a reference signal transmitted by the UE in the uplink direction and is used by the base station to estimate the uplink channel quality of a wider bandwidth. The base station can use this information for uplink frequency selection scheduling. When SRS provides CSI reporting enhancement based on partial reciprocity, dynamic configuration of parameters can provide additional advantages. Therefore, in contrast to semi-statically configuring parameters via RRC, parameters can be dynamically configured in response to an indication received by the UE from the base station. For example, the base station may determine that the channel has become very directional and may instruct the UE to report a reduced number of spatial bases relative to the possible available spatial bases. Dynamic configuration can be achieved through MAC-CE or L1DCI. The configured parameters may include angle-related parameters, such as the number of selected spatial bases. The parameters may further include delay-related parameters such as the number of selected frequency bases, the number of non-zero coefficients and / or a PMI oversampling factor (eg, 1 or 2).

[0204] Example of selecting a common CSI-RS port for each layer

[0205] In some embodiments, downlink CSI can be derived from uplink transmissions, for example, using the SRS for FDD systems. For FDD systems, due to the duplex separation between DL and UL, many parameters for the propagation channels (DL and UL) can be considered independent, but some other parameters can be considered correlated, such as the skew angle and delay profile at the base station (e.g., gNB). This can provide the gNB with an opportunity to derive useful information about the DL from the received UL signal, such as the SRS or DMRS for PUSCH / PUCCH or PRACH, or even UL channels such as PUSCH or PUCCH. Similar to the case for TDD, for various reasons such as power consumption, form factor, etc., a UE may have more DL antennas than UL antennas. Therefore, for FDD systems, in addition to the duplex separation, the inequality between the number of DL antennas and the number of UL antennas may cause other obstacles when deriving DL CSI from UL transmissions.

[0206] One possible approach is for the gNB to derive the departure angle and delay profile from UL observations of the UL signal, for example, thereby identifying orthogonal DFT beams at the UL frequency with significant power, and then applying the necessary carrier frequency adjustments to the orthogonal DFT beams at the DL frequency. The gNB may also be configured to implement a proprietary algorithm that can be applied to the UL observations to derive the DL precoding vector for the CSI-RS. Therefore, if a solution that does not depend on any particular structure in the precoder for the CSI-RS is available, then the solution may be applicable to a wide range of scenarios.

[00109] In 3GPP Rel-15 and 3GPP Rel-16, for a Type II port selection codebook design, port selection is by multiple adjacent CSI-RS ports and is wideband. Considering the above, and further considering that the overhead due to wideband signaling may present a less severe problem than the overhead due to subband signaling in CSI feedback, free antenna port selection may be used.

[0207] Instead of using i 1,1 To select port {i 1,1 ×d+0,i 1,1 ×d+1,…,i 1,1 ×dL-1} and {P CSI-RS / 2+i 1,1 ×d+0,P CSI-RS / 2+i 1,1 ×d+1,…,P CSI-RS / 2+i 1,1 ×dL-1}, where d is a parameter configured by the gNB, and P CSI-RS is the number of CSI-RS ports configured for the port selection codebook, which can be obtained from P CSI-RS / 2 ports, L ports are selected, presumably for polarization 0. The selected ports are indexed by {S 0,0, S 0,1 ,…,S 0,L-1} and S 0,0 0,1 <… 0,L-1 Given, and the same port selection applies to polarization 1 (approximately): {S 1,0, S 1,1 ,…,S 1,L-1}={P CSI-RS / 2+S 0,0, P CSI-RS / 2+S0,1,…,P CSI-RS / 2+S 0,L-1}.

[0208] ​​Depending on the precoder applied to the CSI-RS, the gNB can select different numbers of CSI-RS ports for different polarizations: for example, three ports for +45° polarization and five ports for -45° polarization, and thus can also select ports from among all CSI-RS ports.

[0209] In some embodiments, all P CSI-RS You can freely select ports on each port, for example, you can select P CSI-RS 2L ports out of 1 ports. A combined index (as also defined in 3GPP Rel-15 and 3GPP Rel-16) may be used. Alternatively, P CSI-RS bitmap or P CSI-RS A 2-bit bitmap can be used to indicate the selection of a port, for example, where P CSI-RS =8, the 8-bit bitmap [0011 10 01] indicates the selection of ports 2, 3, 4, and 7, and the 4-bit bitmap [01 01] indicates the selection of ports 1, 3, 5, and 7.

[0210] It is also possible that the DL channel information derived from the UL channel may not match the actual DL channel information due to the difference in UL channel propagation versus DL channel propagation. To address this issue, the gNB may select one or more beam groups that are neighbors of the beam group derived from the UL channel, and precode all beam groups for the UE to test. In this case, the UE may feed back both the beam group index and the port selection using the selected beam group. Assuming that beam groups are mapped to Q CSI-RS ports, and there are a total of G beam groups—e.g., the first Q CSI-RS ports for beam group 1, and the second Q CSI-RS ports for beam group 2—the UE may feed back the beam group index (1 or 2 in this example) and a bitmap of the selected ports in the selected beam group. Figure 13 In FIG, two beam groups (1302 and 1304) are shown, so G = 2, Q = 4. Within each beam group, there are Q beams. For example, if the UE selects beam 1302, then the bitmap

[1001] can select beams 1 and 4 from the beam group 1302.

[0211] Reference again Figure 10 , CSI-RS port selection can be done jointly and can be common for each layer. A number "L" of the X / 2 CSI-RS ports can be selected for HPol and VPol. CSI-RS ports with the same relative index can be selected for HPol and V-Pol. The signaling overhead can be Units place. Figure 10In the example shown in , X=8, and port 0 selected from the top group may be coupled with port 5 selected from the bottom group, and port 1 selected from the top group may be coupled with port 6 selected from the bottom group.

[0212] Figure 12 An exemplary diagram illustrating layer-common CSI-RS port selection using completely free indication is shown. For simplicity, only two signal paths 1222 and 1224 are shown (line-of-sight signal paths are not considered). Signal path 1222 reflects from reflector 1204 between base station 1208 and UE 1202, while signal path 1224 reflects from reflector 1206 between base station 1208 and UE 1202. In this case, there are two groups of four possible ports, each corresponding to two different (reflected) signal paths 1222 and 1224. In this case, the port selection can be common for each layer. A corresponding beam can be selected from each group, with the first group including CSI-RS 0, CSI-RS 1, CSI-RS 2, and CSI-RS 3 and the second group including CSI-RS 4, CSI-RS 5, CSI-RS 6, and CSI-RS 7. For example, two CSI-RS ports can be selected from two groups, and the beam can be used for any single layer. Each single layer may be transmitted using any one of the selected beams or using a linear combination of the selected beams. Figure 12 In the example shown, CSI-RS 1 is selected from the top group and CSI-RS 7 is selected from the bottom group, which shows that the selection of CSI-RS ports is completely free and can be used The ones digit indicates the ports to the UE.

[0213] Antenna group selection can be combined with any of the above methods. Figure 13 An exemplary diagram illustrating antenna group selection for layer common CSI-RS port selection as mentioned above is shown. Figure 13 In the example shown, X=32, X'=8, e=4. The number "X" CSI-RSs may be divided into a number "e" of groups, each group having X' CSI-RS ports. One of the groups may be selected, wherein a total number "L" of the X' CSI-RS ports are selected. One or more CSI-RS ports may be selected for each group. The number of CSI-RS ports selected for each group may be determined according to the method discussed above. If the gNB makes a decision based on the observed beam (1304-DL), there may be a mismatch between UL and DL under certain conditions. As a safety measure, the gNB may configure two beam groups. A first beam group (1302) and a second beam group (1304). The UE may select a beam group, such as 1302, and may take necessary steps to select a port. In Figure 13In the example of , if X is the total number of antenna ports, e is the number of beam groups, and X' is the number of CSI ports per beam group, then e=2 and X'=4.

[0214] It is understood that the use of personally identifiable information should be subject to privacy policies and practices that are generally recognized to meet or exceed industry or government requirements for maintaining user privacy. Specifically, personally identifiable information data should be managed and processed to minimize the risk of unintentional or unauthorized access or use, and the nature of authorized use should be clearly stated to users.

[0215] Embodiments of the present invention may be implemented in any of a variety of forms. For example, in some embodiments, the present invention may be implemented as a computer-implemented method, a computer-readable storage medium, or a computer system. In other embodiments, one or more custom-designed hardware devices such as ASICs may be used to implement the present invention. In other embodiments, one or more programmable hardware elements such as FPGAs may be used to implement the present invention.

[0216] In some embodiments, a non-transitory computer-readable storage medium (e.g., a non-transitory memory element) may be configured to store program instructions and / or data, where the program instructions, if executed by a computer system, cause the computer system to perform a method, such as any one of the method embodiments described herein, or any combination of the method embodiments described herein, or any subset of any one of the method embodiments described herein, or any combination of such subsets.

[0217] In some embodiments, a device (e.g., a UE) may be configured to include a processor (or a group of processors) and a memory medium (or a memory element), wherein the memory medium stores program instructions, wherein the processor is configured to read and execute the program instructions from the memory medium, wherein the program instructions are executable to implement any of the various method implementations described herein (or any combination of the method implementations described herein, or any subset of any of the method implementations described herein, or any combination of such subsets). The device may be implemented in any of various forms.

[0218] Although the above embodiments have been described in considerable detail, numerous variations and modifications will become apparent to those skilled in the art once the above disclosure is fully appreciated. It is intended that the following claims be interpreted to encompass all such variations and modifications.

Claims

1. A method for wireless communication, the method comprising: identifying, by a base station, a dominant signal path between the base station and a device based on channel estimation, the channel estimation being performed using uplink communication between the base station and the device; transmitting, by the base station, to the device, channel state information reference signal (CSI-RS) ports corresponding to the dominant signal paths, wherein for each of the dominant signal paths, the CSI-RS port is transmitted through a corresponding beam independently identified by the base station; and An indication of selection of a subset of the CSI-RS ports to be used for each layer in a multi-layer transmission is received from the device by the base station.

2. The method according to claim 1, wherein The selection is for a single corresponding CSI-RS port for each layer of the multi-layer transmission.

3. The method according to claim 2, wherein: The single corresponding CSI-RS port is used for the first polarization, and the same index corresponding to the single CSI-RS port is automatically used for the second polarization.

4. The method according to claim 1, wherein The selection is for two corresponding CSI-RS ports for each layer of the multi-layer transmission.

5. The method according to claim 4, wherein A first CSI-RS port of the two corresponding CSI-RS ports is for a first polarization, and a second CSI-RS port of the two corresponding CSI-RS ports is for a second polarization.

6. An apparatus for wireless communication, the apparatus comprising: a processor configured to cause the device to: receiving, from a base station, channel state information reference signal (CSI-RS) ports corresponding to dominant signal paths between the base station and the device, wherein the dominant signal paths are identified based on channel estimation performed using uplink communication between the base station and the device, wherein for each of the dominant signal paths, the CSI-RS port is transmitted via a corresponding beam independently identified by the base station; selecting a subset of the CSI-RS ports, the subset of the CSI-RS ports to be used for each layer in a multi-layer transmission; as well as An indication of the selection of the subset of CSI-RS ports is provided to the base station.

7. The device according to claim 6, wherein The selection is for a single corresponding CSI-RS port for each layer of the multi-layer transmission.

8. The device according to claim 7, wherein The single corresponding CSI-RS port is used for the first polarization, and the same index corresponding to the single CSI-RS port is automatically used for the second polarization.

9. The device according to claim 6, wherein The selection is for two corresponding CSI-RS ports for each layer of the multi-layer transmission.

10. The device according to claim 9, wherein A first CSI-RS port of the two corresponding CSI-RS ports is for a first polarization, and a second CSI-RS port of the two corresponding CSI-RS ports is for a second polarization.

11. An apparatus for wireless communication, the apparatus comprising: a processor configured to cause the base station to: identifying a dominant signal path between the base station and the device based on a channel estimate performed using uplink communications between the base station and the device; transmitting, to the device, channel state information reference signal (CSI) ports corresponding to the dominant signal paths, wherein for each of the dominant signal paths, the CSI-RS port is transmitted through a corresponding beam independently identified by the base station; as well as receiving an indication of selection of a subset of the CSI-RS ports from the device, A subset of the CSI-RS ports is to be used for each layer in a multi-layer transmission.

12. The device according to claim 11, wherein The selection is for a single corresponding CSI-RS port for each layer of the multi-layer transmission.

13. The device according to claim 12, wherein The single corresponding CSI-RS port is used for the first polarization, and the same index corresponding to the single CSI-RS port is automatically used for the second polarization.

14. The device according to claim 11, wherein The selection is for two corresponding CSI-RS ports for each layer of the multi-layer transmission.

15. The device according to claim 14, wherein A first one of the two corresponding CSI-RS ports is for a first polarization, and a second one of the two corresponding CSI-RS ports is for a second polarization.

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